Sample records for aldol condensation reactions

  1. A green route to methyl acrylate and acrylic acid by an aldol condensation reaction over H-ZSM-35 zeolite catalysts.

    PubMed

    Ma, Zhanling; Ma, Xiangang; Liu, Hongchao; He, Yanli; Zhu, Wenliang; Guo, Xinwen; Liu, Zhongmin

    2017-08-10

    A one-step aldol condensation reaction to produce MA and AA is a green and promising strategy. Here, the aldol condensation reaction was first conducted with DMM and MAc over different types of zeolite catalysts. The H-ZSM-35 zeolite demonstrates excellent catalytic performance with a DMM conversion of 100% and a MA + AA selectivity of up to 86.2% and superior regeneration ability, with great potential for industrial operation.

  2. Boehmite-An Efficient and Recyclable Acid-Base Bifunctional Catalyst for Aldol Condensation Reaction.

    PubMed

    Reshma, P C Rajan; Vikneshvaran, Sekar; Velmathi, Sivan

    2018-06-01

    In this work boehmite was used as an acid-base bifunctional catalyst for aldol condensation reactions of aromatic aldehydes and ketones. The catalyst was prepared by simple sol-gel method using Al(NO3)3·9H2O and NH4OH as precursors. The catalyst has been characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), UV-visible spectroscopy (DRS), BET surface area analyses. Boehmite is successfully applied as catalyst for the condensation reaction between 4-nitrobenzaldehyde and acetone as a model substrate giving α, β-unsaturated ketones without any side product. The scope of the reaction is extended for various substituted aldehydes. A probable mechanism has been suggested to explain the cooperative behavior of the acidic and basic sites. The catalyst is environmentally friendly and easily recovered from the reaction mixture. Also the catalyst is reusable up to 3 catalytic cycles.

  3. Sequential aldol condensation-transition metal-catalyzed addition reactions of aldehydes, methyl ketones, and arylboronic acids.

    PubMed

    Liao, Yuan-Xi; Xing, Chun-Hui; Israel, Matthew; Hu, Qiao-Sheng

    2011-04-15

    Sequential aldol condensation of aldehydes with methyl ketones followed by transition metal-catalyzed addition reactions of arylboronic acids to form β-substituted ketones is described. By using the 1,1'-spirobiindane-7,7'-diol (SPINOL)-based phosphite, an asymmetric version of this type of sequential reaction, with up to 92% ee, was also realized. Our study provided an efficient method to access β-substituted ketones and might lead to the development of other sequential/tandem reactions with transition metal-catalyzed addition reactions as the key step. © 2011 American Chemical Society

  4. Sequential Aldol Condensation – Transition Metal-Catalyzed Addition Reactions of Aldehydes, Methyl Ketones and Arylboronic Acids

    PubMed Central

    Liao, Yuan-Xi; Xing, Chun-Hui; Israel, Matthew; Hu, Qiao-Sheng

    2011-01-01

    Sequential aldol condensation of aldehydes with methyl ketones followed by transition metal-catalyzed addition reactions of arylboronic acids to form β-substituted ketones is described. By using the 1,1′-spirobiindane-7,7′-diol (SPINOL)-based phosphite, an asymmetric version of this type of sequential reaction, with up to 92% ee, was also realized. Our study provided an efficient method to access β-substituted ketones and might lead to the development of other sequential/tandem reactions with transition metal-catalyzed addition reactions as the key step. PMID:21417359

  5. Theoretical insights into the sites and mechanisms for base catalyzed esterification and aldol condensation reactions over Cu.

    PubMed

    Neurock, Matthew; Tao, Zhiyuan; Chemburkar, Ashwin; Hibbitts, David D; Iglesia, Enrique

    2017-04-28

    Condensation and esterification are important catalytic routes in the conversion of polyols and oxygenates derived from biomass to fuels and chemical intermediates. Previous experimental studies show that alkanal, alkanol and hydrogen mixtures equilibrate over Cu/SiO 2 and form surface alkoxides and alkanals that subsequently promote condensation and esterification reactions. First-principle density functional theory (DFT) calculations were carried out herein to elucidate the elementary paths and the corresponding energetics for the interconversion of propanal + H 2 to propanol and the subsequent C-C and C-O bond formation paths involved in aldol condensation and esterification of these mixtures over model Cu surfaces. Propanal and hydrogen readily equilibrate with propanol via C-H and O-H addition steps to form surface propoxide intermediates and equilibrated propanal/propanol mixtures. Surface propoxides readily form via low energy paths involving a hydrogen addition to the electrophilic carbon center of the carbonyl of propanal or via a proton transfer from an adsorbed propanol to a vicinal propanal. The resulting propoxide withdraws electron density from the surface and behaves as a base catalyzing the activation of propanal and subsequent esterification and condensation reactions. These basic propoxides can readily abstract the acidic C α -H of propanal to produce the CH 3 CH (-) CH 2 O* enolate, thus initiating aldol condensation. The enolate can subsequently react with a second adsorbed propanal to form a C-C bond and a β-alkoxide alkanal intermediate. The β-alkoxide alkanal can subsequently undergo facile hydride transfer to form the 2-formyl-3-pentanone intermediate that decarbonylates to give the 3-pentanone product. Cu is unique in that it rapidly catalyzes the decarbonylation of the C 2n intermediates to form C 2n-1 3-pentanone as the major product with very small yields of C 2n products. This is likely due to the absence of Brønsted acid sites

  6. Kinetic and Mechanistic Examination of Acid–Base Bifunctional Aminosilica Catalysts in Aldol and Nitroaldol Condensations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Collier, Virginia E.; Ellebracht, Nathan C.; Lindy, George I.

    The kinetic and mechanistic understanding of cooperatively catalyzed aldol and nitroaldol condensations is probed using a series of mesoporous silicas functionalized with aminosilanes to provide bifunctional acid–base character. Mechanistically, a Hammett analysis is performed to determine the effects of electron-donating and electron-withdrawing groups of para-substituted benzaldehyde derivatives on the catalytic activity of each condensation reaction. This information is also used to discuss the validity of previously proposed catalytic mechanisms and to propose a revised mechanism with plausible reaction intermediates. For both reactions, electron-withdrawing groups increase the observed rates of reaction, though resonance effects play an important, yet subtle, role inmore » the nitroaldol condensation, in which a p-methoxy electron-donating group is also able to stabilize the proposed carbocation intermediate. Additionally, activation energies and pre-exponential factors are calculated via the Arrhenius analysis of two catalysts with similar amine loadings: one catalyst had silanols available for cooperative interactions (acid–base catalysis), while the other was treated with a silanol-capping reagent to prevent such cooperativity (base-only catalysis). The values obtained for activation energies and pre-exponential factors in each reaction are discussed in the context of the proposed mechanisms and the importance of cooperative interactions in each reaction. The catalytic activity decreases for all reactions when the silanols are capped with trimethylsilyl groups, and higher temperatures are required to make accurate rate measurements, emphasizing the vital role the weakly acidic silanols play in the catalytic cycles. The results indicate that loss of acid sites is more detrimental to the catalytic activity of the aldol condensation than the nitroaldol condensation, as evidenced by the significant decrease in the pre-exponential factor for the aldol

  7. Kinetic and Mechanistic Examination of Acid–Base Bifunctional Aminosilica Catalysts in Aldol and Nitroaldol Condensations

    DOE PAGES

    Collier, Virginia E.; Ellebracht, Nathan C.; Lindy, George I.; ...

    2015-12-09

    The kinetic and mechanistic understanding of cooperatively catalyzed aldol and nitroaldol condensations is probed using a series of mesoporous silicas functionalized with aminosilanes to provide bifunctional acid–base character. Mechanistically, a Hammett analysis is performed to determine the effects of electron-donating and electron-withdrawing groups of para-substituted benzaldehyde derivatives on the catalytic activity of each condensation reaction. This information is also used to discuss the validity of previously proposed catalytic mechanisms and to propose a revised mechanism with plausible reaction intermediates. For both reactions, electron-withdrawing groups increase the observed rates of reaction, though resonance effects play an important, yet subtle, role inmore » the nitroaldol condensation, in which a p-methoxy electron-donating group is also able to stabilize the proposed carbocation intermediate. Additionally, activation energies and pre-exponential factors are calculated via the Arrhenius analysis of two catalysts with similar amine loadings: one catalyst had silanols available for cooperative interactions (acid–base catalysis), while the other was treated with a silanol-capping reagent to prevent such cooperativity (base-only catalysis). The values obtained for activation energies and pre-exponential factors in each reaction are discussed in the context of the proposed mechanisms and the importance of cooperative interactions in each reaction. The catalytic activity decreases for all reactions when the silanols are capped with trimethylsilyl groups, and higher temperatures are required to make accurate rate measurements, emphasizing the vital role the weakly acidic silanols play in the catalytic cycles. The results indicate that loss of acid sites is more detrimental to the catalytic activity of the aldol condensation than the nitroaldol condensation, as evidenced by the significant decrease in the pre-exponential factor for the aldol

  8. Direct catalytic asymmetric aldol-Tishchenko reaction.

    PubMed

    Gnanadesikan, Vijay; Horiuchi, Yoshihiro; Ohshima, Takashi; Shibasaki, Masakatsu

    2004-06-30

    A direct catalytic asymmetric aldol reaction of propionate equivalent was achieved via the aldol-Tishchenko reaction. Coupling an irreversible Tishchenko reaction to a reversible aldol reaction overcame the retro-aldol reaction problem and thereby afforded the products in high enantio and diastereoselectivity using 10 mol % of the asymmetric catalyst. A variety of ketones and aldehydes, including propyl and butyl ketones, were coupled efficiently, yielding the corresponding aldol-Tishchenko products in up to 96% yield and 95% ee. Diastereoselectivity was generally below the detection limit of 1H NMR (>98:2). Preliminary studies performed to clarify the mechanism revealed that the aldol products were racemic with no diastereoselectivity. On the other hand, the Tishchenko products were obtained in a highly enantiocontrolled manner.

  9. Iron-catalyzed vinylogous aldol condensation of Biginelli products and its application toward pyrido[4,3-d]pyrimidinones.

    PubMed

    Zhang, Lianqiang; Zhang, Zhiguo; Liu, Qingfeng; Liu, Tongxin; Zhang, Guisheng

    2014-03-07

    A novel iron-catalyzed vinylogous aldol condensation of Biginelli products with aryl aldehydes has been developed for the syntheses of potential bioactive (E)-6-arylvinyl-dihydropyrimidin-2(1H)-ones. These materials are valuable synthetic precursors to drug-like pyrido[4,3-d]pyrimidine derivatives. The amide group at the 5-position of the dihydropyrimidin-2(1H)-ones played an important role in the vinylogous aldol condensation reaction.

  10. Natural Occurrence of Aldol Condensation Products in Valencia Orange Oil.

    PubMed

    Abreu, Ingo; Da Costa, Neil C; van Es, Alfred; Kim, Jung-A; Parasar, Uma; Poulsen, Mauricio L

    2017-12-01

    Cold pressed orange oils contain predominantly d-limonene (approximately 95%) and various other lower concentration monoterpenes, sesquiterpenes, sinensals plus 3 key aliphatic aldehydes: hexanal, octanal. and decanal. The aldol self-condensation products or "dimers" for each aldehyde have been postulated as being present at low concentrations in the oil. However, to date only the hexanal dimer has been previously reported. In this paper, cold pressed Valencia orange oil was fractionally distilled/folded and analyzed by GC and high resolution GC-MS to detect these compounds on 2 different capillary column phases. Subsequently the hexanal, octanal, and decanal self-aldol condensation products, 2-butyl-2-octenal, 2-hexyl-2-decenal, and 2-octyl-2-dodecenal, respectively, were detected in the folded oil. These predominantly trans configuration isomeric compounds were synthesized, to confirm them as being present in nature and evaluated organoleptically by a panel of evaluators. To further confirm the mechanism of their formation, the enriched oil was made into a simple beverage to show the effect on the formation of these aldol compounds under acidic conditions. Finally aliphatic aldehydes from hexanal to undecanal were reacted together in various combinatorial pairs to give an additional 33 self and mixed aldol condensation products, some of which were also detected in the folded oil. This paper discloses the structural elucidation and synthesis of 8 novel aldol condensation products found at trace concentrations in citrus and leading to a further 31 mass spectrally determined aldol products. Sensory evaluations and application of some of these components were demonstrated in a model citrus beverage. © 2017 Institute of Food Technologists®.

  11. Enantioselective aldol reactions with masked fluoroacetates

    NASA Astrophysics Data System (ADS)

    Saadi, Jakub; Wennemers, Helma

    2016-03-01

    Despite the growing importance of organofluorines as pharmaceuticals and agrochemicals, the stereoselective introduction of fluorine into many prominent classes of natural products and chemotherapeutic agents is difficult. One long-standing unsolved challenge is the enantioselective aldol reaction of fluoroacetate to enable access to fluorinated analogues of medicinally relevant acetate-derived compounds, such as polyketides and statins. Herein we present fluoromalonic acid halfthioesters as biomimetic surrogates of fluoroacetate and demonstrate their use in highly stereoselective aldol reactions that proceed under mild organocatalytic conditions. We also show that the methodology can be extended to formal aldol reactions with fluoroacetaldehyde and consecutive aldol reactions. The synthetic utility of the fluorinated aldol products is illustrated by the synthesis of a fluorinated derivative of the top-selling drug atorvastatin. The results show the prospects of the method for the enantioselective introduction of fluoroacetate to access a wide variety of highly functionalized fluorinated compounds.

  12. A Green Enantioselective Aldol Condensation for the Undergraduate Organic Laboratory

    ERIC Educational Resources Information Center

    Bennett, George D.

    2006-01-01

    A number of laboratory exercises for the organic chemistry curriculum that emphasize enantioselective synthesis of the aldol condensation which involves the proline-catalyzed condensation between acetone and isobutyraldehyde are explored. The experiment illustrates some of the trade-offs involved in green chemistry like the use of acetone in large…

  13. Unraveling the role of water in the stereoselective step of aqueous proline-catalyzed aldol reactions.

    PubMed

    Ribas-Arino, Jordi; Carvajal, Maria Angels; Chaumont, Alain; Masia, Marco

    2012-12-03

    A multiscale computational study was performed with the aim of tracing the source of stereoselectivity and disclosing the role of water in the stereoselective step of propionaldehyde aldol self-condensation catalyzed by proline amide in water, a reaction that serves as a model for aqueous organocatalytic aldol condensations. Solvent mixing and hydration behavior were assessed by classical molecular dynamics simulations, which show that the reaction between propanal and the corresponding enamine takes place in a fully hydrated environment. First-principles molecular dynamics simulations were used to study the free-energy profile of four possible reaction paths, each of which yields a different stereoisomer, and high-level static first-principles calculations were employed to characterize the transition states for microsolvated species. The first solvation shell of the oxygen atom of the electrophilic aldehyde at the transition states contains two water molecules, each of which donates one hydrogen bond to the nascent alkoxide and thereby largely stabilizes its excess electron density. The stereoselectivity originates in an extra hydrogen bond donated by the amido group of proline amide in two reaction paths. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Effects of Schiff Base Formation and Aldol Condensation on the Determination of Aldehydes in Rice Wine Using GC-MS.

    PubMed

    Han, Ji Hye; Lee, Sang Mi; Kim, Young-Suk

    2017-04-11

    The Schiff base reaction and aldol condensation that occur during sample preparation can lead to the reduction of aldehyde content in the analysis of traditional Korean rice wine, makgeolli. The contents of aldehydes were decreased, whereas those of hydroxy carbonyl compounds were increased by increasing the pH. In the presence of added amino acids, the levels of aldehydes in makgeolli were reduced as the amount of the amino acid alanine increased. Also, the contents of hydroxyl carbonyl compounds were reduced by alanine addition as compared to the control. Therefore, the determination of aldehydes can be affected by pH and the amount of amino acids, which can vary during fermentation and storage of alcoholic beverages because pH and amino acids affect Schiff base formation and aldol condensation.

  15. One-pot aldol condensation and hydrodeoxygenation of biomass-derived carbonyl compounds for biodiesel synthesis.

    PubMed

    Faba, Laura; Díaz, Eva; Ordóñez, Salvador

    2014-10-01

    Integrating reaction steps is of key interest in the development of processes for transforming lignocellulosic materials into drop-in fuels. We propose a procedure for performing the aldol condensation (reaction between furfural and acetone is taken as model reaction) and the total hydrodeoxygenation of the resulting condensation adducts in one step, yielding n-alkanes. Different combinations of catalysts (bifunctional catalysts or mechanical mixtures), reaction conditions, and solvents (aqueous and organic) have been tested for performing these reactions in an isothermal batch reactor. The results suggest that the use of bifunctional catalysts and aqueous phase lead to an effective integration of both reactions. Therefore, selectivities to n-alkanes higher than 50% were obtained using this catalyst at typical hydrogenation conditions (T=493 K, P=4.5 MPa, 24 h reaction time). The use of organic solvent, carbonaceous supports, or mechanical mixtures of monofunctional catalysts leads to poorer results owing to side effects; mainly, hydrogenation of reactants and adsorption processes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Functionalized multi-walled carbon nanotubes in an aldol reaction

    NASA Astrophysics Data System (ADS)

    Chronopoulos, D. D.; Kokotos, C. G.; Karousis, N.; Kokotos, G.; Tagmatarchis, N.

    2015-01-01

    The covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with a proline-based derivative is reported. Initially, MWCNTs were oxidized in order to introduce a large number of carboxylic units on their tips followed by N-tert-butoxycarbonyl-2,2'(ethylenedioxy)bis-(ethylamine) conjugation through an amide bond. Then, a proline derivative bearing a carboxylic terminal moiety at the 4-position was coupled furnishing proline-modified MWCNTs. This new hybrid material was fully characterized by spectroscopic and microscopy means and its catalytic activity in the asymmetric aldol reaction between acetone and 4-nitrobenzaldehyde was evaluated for the first time, showing to proceed almost quantitatively in aqueous media. Furthermore, several amino-modified MWCNTs were prepared and examined in the particular aldol reaction. These new hybrid materials exhibited an enhanced catalytic activity in water, contrasting with the pristine MWCNTs as well as the parent organic molecule, which failed to catalyze the reaction efficiently. Furthermore, the modified MWCNTs proved to catalyze the aldol reaction even after three repetitive cycles. Overall, a green approach for the aldol reaction is presented, where water can be employed as the solvent and modified MWCNTs can be used as catalysts, which can be successfully recovered and reused, while their catalytic activity is retained.The covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with a proline-based derivative is reported. Initially, MWCNTs were oxidized in order to introduce a large number of carboxylic units on their tips followed by N-tert-butoxycarbonyl-2,2'(ethylenedioxy)bis-(ethylamine) conjugation through an amide bond. Then, a proline derivative bearing a carboxylic terminal moiety at the 4-position was coupled furnishing proline-modified MWCNTs. This new hybrid material was fully characterized by spectroscopic and microscopy means and its catalytic activity in the asymmetric aldol reaction

  17. Mineral catalysis of a potentially prebiotic aldol condensation

    NASA Technical Reports Server (NTRS)

    De Graaf, R. M.; Visscher, J.; Xu, Y.; Arrhenius, G.; Schwartz, A. W.

    1998-01-01

    Minerals may have played a significant role in chemical evolution. In the course of investigating the chemistry of phosphonoacetaldehyde (PAL), an analogue of glycolaldehyde phosphate, we have observed a striking case of catalysis by the layered hydroxide mineral hydrotalcite ([Mg2Al(OH)6][Cl.nH2O]). In neutral or moderately basic aqueous solutions, PAL is unreactive even at a concentration of 0.1 M. In the presence of a large excess of NaOH (2 M), the compound undergoes aldol condensation to produce a dimer containing a C3-C4 double-bond. In dilute neutral solutions and in the presence of the mineral, however, condensation takes place rapidly, to produce a dimer which is almost exclusively the C2-C3 unsaturated product.

  18. Regio- and Stereoselective Cascades via Aldol Condensation and 1,3-Dipolar Cycloaddition for Construction of Functional Pyrrolizidine Derivatives.

    PubMed

    Mao, Zhuo-Ya; Liu, Yi-Wen; Han, Pan; Dong, Han-Qing; Si, Chang-Mei; Wei, Bang-Guo; Lin, Guo-Qiang

    2018-02-16

    An efficient and step-economical approach to access functionalized pyrrolizidine derivatives by a one-pot tandem sequence, including an aldol condensation and subsequent 1,3-dipolar cycloaddition process, has been developed, starting from acetone, aldehyde, and proline. A number of substituted aromatic aldehydes were amenable to this transformation, and the desired products, racemic 7a-7w and chiral 9a-9m, were obtained with excellent regioselectivities and outstanding diastereoselectivities. Moreover, in situ NMR studies revealed MgSO 4 could effectively promote the aldol condensation pathway in this tandem process.

  19. Spontaneous Mirror Symmetry Breaking in the Aldol Reaction and its Potential Relevance in Prebiotic Chemistry

    NASA Astrophysics Data System (ADS)

    Mauksch, Michael; Wei, Shengwei; Freund, Matthias; Zamfir, Alexandru; Tsogoeva, Svetlana B.

    2010-02-01

    The origin of the single chirality of most biomolecules is still a great puzzle. Carbohydrates could form in the formose reaction, which is proposed to be autocatalytic and contains aldol reaction steps. Based on our earlier observation of organoautocatalysis and spontaneous enantioenrichment in absence of deliberate chiral influences in the aldol reaction of acetone and p-nitrobenzaldehyde we suggest that a similar effect might be present also in the aldol reactions involved in gluconeogenesis. Herein we show that reactant precipitation observed in our earlier reported experiments does not affect the asymmetric autocatalysis in the aldol reaction we studied. We explain the phenomenon of spontaneous mirror symmetry breaking in such organocatalytic homogenous systems qualitatively by non-linear reaction network kinetics and classical transition state theory.

  20. Enantioselective organocatalytic one-pot amination/aza-Michael/aldol condensation reaction sequence: synthesis of 3-pyrrolines with a quaternary stereocenter.

    PubMed

    Desmarchelier, Alaric; Coeffard, Vincent; Moreau, Xavier; Greck, Christine

    2012-10-08

    Primary amine-catalyzed direct conversion of α,α-disubstituted aldehydes into 3-pyrrolines with a quaternary stereocenter is reported. The one-pot enantioselective sequence is based on a α-amination, an aza-Michael addition of hydrazine, an aldol condensation dehydratation and proceeds with good yields and excellent levels of enantioselectivity. Synthetically attractive applications including the formation of aziridinopyrrolidine or epoxypyrrolidine derivatives with good yields and selectivities are also described. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Domino-hydroformylation/aldol condensation catalysis: highly selective synthesis of α,β-unsaturated aldehydes from olefins.

    PubMed

    Fang, Xianjie; Jackstell, Ralf; Franke, Robert; Beller, Matthias

    2014-10-06

    A general and highly chemo-, regio-, and stereoselective synthesis of α,β-unsaturated aldehydes by a domino hydroformylation/aldol condensation reaction has been developed. A variety of olefins and aromatic aldehydes were efficiently converted into various substituted α,β-unsaturated aldehydes in good to excellent yields in the presence of a rhodium phosphine/acid-base catalyst system. In view of the easy availability of the substrates, the high atom-efficiency, the excellent selectivity, and the mild conditions, this method is expected to complement current methodologies for the preparation of α,β-unsaturated aldehydes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Peculiar behavior of MWW materials in aldol condensation of furfural and acetone.

    PubMed

    Kikhtyanin, Oleg; Chlubná, Pavla; Jindrová, Tereza; Kubička, David

    2014-07-21

    MWW family of different structural types (MCM-22, MCM-49, MCM-56 and MCM-36) was used as catalysts for aldol condensation of furfural and acetone studied in a batch reactor at 100 °C, autogenous pressure and a reaction time of 0-4 h. To establish a relation between physico-chemical and catalytic properties of microporous materials, the samples were characterized by XRD, SEM, N2 adsorption, FTIR and TGA. It was found that the acidic solids possessed appreciable activity in the reaction and resulted in the formation of products of aldehyde-ketone interaction. Surprisingly, MCM-22 and MCM-49, i.e. three-dimensional materials containing internal supercages, exhibited higher activity than two MCM-36 catalysts with two-dimensional character having larger accessible external surface area due to expansion of the interlayer space by swelling and pillaring treatments. Moreover, all MWW family catalysts gave higher conversion than the large-pore zeolite BEA. Nevertheless, furfural conversion decreased rapidly for all the studied materials due to coke formation. Unexpectedly, the deactivation was found to be more severe for MCM-36 catalysts than for MCM-22 and MCM-49, which was attributed to the reaction taking place also in supercages that are protected by 10-ring channels from severe coking. In contrast the cups located on the external surface were coked rapidly.

  3. N-triflylthiophosphoramide catalyzed enantioselective Mukaiyama aldol reaction of aldehydes with silyl enol ethers of ketones.

    PubMed

    Cheon, Cheol Hong; Yamamoto, Hisashi

    2010-06-04

    The first Brønsted acid catalyzed asymmetric Mukaiyama aldol reaction of aldehydes using silyl enol ethers of ketones as nucleophiles has been reported. A variety of aldehydes and silyl enol ethers of ketones afforded the aldol products in excellent yields and good to excellent enantioselectivities. Mechanistic studies revealed that the actual catalyst may be changed from the silylated Brønsted acid to the Brønsted acid itself depending on the reaction temperature.

  4. N-Triflylthiophosphoramide Catalyzed Enantioselective Mukaiyama Aldol Reaction of Aldehydes with Silyl Enol Ethers of Ketones

    PubMed Central

    Cheon, Cheol Hong; Yamamoto, Hisashi

    2010-01-01

    The first Brønsted acid catalyzed asymmetric Mukaiyama aldol reaction of aldehydes using silyl enol ethers of ketones as nucleophiles has been reported. A variety of aldehydes and silyl enol ethers of ketones afforded the aldol products in excellent yields and good to excellent enantioselectivities. Mechanistic studies revealed that the actual catalyst may be changed from the silylated Brønsted acid to Brønsted acid itself depending on the reaction temperature. PMID:20465277

  5. EncM, a versatile enterocin biosynthetic enzyme involved in Favorskii oxidative rearrangement, aldol condensation, and heterocycle-forming reactions

    PubMed Central

    Xiang, Longkuan; Kalaitzis, John A.; Moore, Bradley S.

    2004-01-01

    The bacteriostatic natural product enterocin from the marine microbe “Streptomyces maritimus” has an unprecedented carbon skeleton that is derived from an aromatic polyketide biosynthetic pathway. Its caged tricyclic, nonaromatic core is derived from a linear poly-β-ketide precursor that formally undergoes a Favorskii-like oxidative rearrangement. In vivo characterization of the gene encM through mutagenesis and heterologous biosynthesis demonstrated that its protein product not only is solely responsible for the oxidative C—C rearrangement, but also facilitates two aldol condensations plus two heterocycle forming reactions. In total, at least five chiral centers and four rings are generated by this multifaceted flavoprotein. Heterologous expression of the enterocin biosynthesis genes encABCDLMN in Streptomyces lividans resulted in the formation of the rearranged metabolite desmethyl-5-deoxyenterocin and the shunt products wailupemycins D-G. Addition of the methyltransferase gene encK, which was previously proposed through mutagenesis to additionally assist EncM in the Favorskii rearrangement, shifted the production to the O-methyl derivative 5-deoxyenterocin. The O-methyltransferase EncK seems to be specific for the pyrone ring of enterocin, because bicyclic polyketides bearing pyrone rings are not methylated in vivo. Expression of encM with different combinations of homologous actinorhodin biosynthesis genes did not result in the production of oxidatively rearranged enterocin-actinorhodin hybrid compounds as anticipated, suggesting that wild-type EncM may be specific for its endogenous type II polyketide synthase or for benzoyl-primed polyketide precursors. PMID:15505225

  6. Decarboxylative aldol reactions of allyl beta-keto esters via heterobimetallic catalysis.

    PubMed

    Lou, Sha; Westbrook, John A; Schaus, Scott E

    2004-09-22

    Mild and selective heterobimetallic-catalyzed decarboxylative aldol reactions involving allyl beta-keto esters have been developed. The reaction is promoted by Pd(0)- and Yb(III)-DIOP complexes at room temperature and involves the in situ formation of a ketone enolate from allyl beta-keto esters followed by addition of the enolate to aldehydes. The reaction is a new example of heterobimetallic catalysis in which the optimized reaction conditions require the addition of both metals.

  7. Doubly Vinylogous Aldol Reaction of Furoate Esters with Aldehydes and Ketones.

    PubMed

    Hartwig, William T; Sammakia, Tarek

    2017-01-06

    The use of bulky Lewis acids, aluminum tris(2,6-diphenylphenoxide) (ATPH) and aluminum tris(2,6-di-2-naphthylphenoxide) (ATNP), in the doubly vinylogous aldol reaction between methyl-5-methyl-2-furoate and aldehydes or ketones is described. These reactions proceed smoothly and in high yields with both enolizable and non-enolizable substrates. This C-C bond-forming reaction enables a new bond construction for the synthesis of functionalized furans.

  8. Method of carbon chain extension using novel aldol reaction

    DOEpatents

    Silks, Louis A; Gordon, John C; Wu, Ruilan; Hanson, Susan Kloek

    2013-07-30

    Method of producing C.sub.8-C.sub.15 hydrocarbons. comprising providing a ketone starting material; providing an aldol starting material comprising chloromethylfurfural; mixing the ketone starting material and the aldol starting material in a reaction in the presence of a proline-containing catalyst selected from the group consisting of Zn(Pro).sub.2, Yb(Pro).sub.3, and combinations thereof, or a catalyst having one of the structures (I), (II) or (III), and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, where (I), (II) and (III) respectively are: ##STR00001## where R.sub.1 is a C.sub.1-C.sub.6 alkyl moiety, X=(OH) and n=2. ##STR00002## In (III), X may be CH.sub.2, sulfur or selenium, M may be Zn, Mg, or a lanthanide, and R.sub.1 and R.sub.2 each independently may be a methyl, ethyl, phenyl moiety.

  9. Method of carbon chain extension using novel aldol reaction

    DOEpatents

    Silks, Louis A; Gordon, John C; Wu, Ruilan; Hangson, Susan Kloek

    2013-08-13

    Method of producing C.sub.8-C.sub.15 hydrocarbons comprising providing a ketone starting material; providing an aldol starting material comprising hydroxymethylfurfural; mixing the ketone starting material and the aldol starting material in a reaction in the presence of a proline-containing catalyst selected from the group consisting of Zn(Pro).sub.2, Yb(Pro).sub.2, and combinations thereof, or a catalyst having one of the structures (I), (II) or (III), and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, where (I), (II) and (III) respectively are: ##STR00001## where R.sub.1 is a C.sub.1-C.sub.6 alkyl moiety, X=(OH) and n=2. ##STR00002## In (III), X may be CH.sub.2, sulfur or selenium, M may be Zn, Mg, or a lanthanide, and R.sub.1 and R.sub.2 each independently may be a methyl, ethyl, phenyl moiety.

  10. Stereoregulations of pyrimidinone based chiral auxiliary in aldol and alkylation reactions: a convenient route to oxyneolignans.

    PubMed

    Chouhan, Mangilal; Sharma, Ratnesh; Nair, Vipin A

    2012-11-16

    (S)-4-Isopropyl-1-phenyltetrahydropyrimidin-2(1H)-one was synthesized and evaluated as a chiral auxiliary for asymmetric acetate and propionate aldol reactions, by generation of titanium and lithium enolates, affording excellent yields and stereoselectivities for syn and anti aldol diastereomers, respectively. High stereoselectivities were also obtained in lithium mediated alkylation reactions. The application of the auxiliary was exemplified in the asymmetric synthesis of a natural oxyneolignan, (+)-(7S,8S)-4-hydroxy-3,3',5'-trimethoxy-8',9'-dinor-8,4'-oxyneoligna-7,9-diol-7'-oic acid.

  11. A General Diastereoselective Catalytic Vinylogous Aldol Reaction Among Tetramic Acid-Derived Pyrroles

    PubMed Central

    2015-01-01

    A catalytic diastereoselective aldol reaction has been developed for N1-arylated/C2-O-silylated/C3-methylated and brominated/C4-O-methylated pyrroles in its reactions with various aldehydes. Syn adducts emerge with regard to the vicinal nitrogen and oxygen heteroatom substituents. The N1-aryl residue undergoes oxidative cleavage, and the C3-bromine atom undergoes palladium-mediated coupling reactions, both without disturbing the newly created stereocenters. PMID:25119431

  12. Synthesis and Characterization of Aldol Condensation Products from Unknown Aldehydes and Ketones: An Inquiry-Based Experiment in the Undergraduate Laboratory

    ERIC Educational Resources Information Center

    Angelo, Nicholas G.; Henchey, Laura K.; Waxman, Adam J.; Canary, James W.; Arora, Paramjit S.; Wink, Donald

    2007-01-01

    An experiment for the undergraduate chemistry laboratory in which students perform the aldol condensation on an unknown aldehyde and an unknown ketone is described. The experiment involves the use of techniques such as TLC, column chromatography, and recrystallization, and compounds are characterized by [to the first power]H NMR, GC-MS, and FTIR.…

  13. Lewis base activation of Lewis acids: catalytic, enantioselective vinylogous aldol addition reactions.

    PubMed

    Denmark, Scott E; Heemstra, John R

    2007-07-20

    The generality of Lewis base catalyzed, Lewis acid mediated, enantioselective vinylogous aldol addition reactions has been investigated. The combination of silicon tetrachloride and chiral phosphoramides is a competent catalyst for highly selective additions of a variety of alpha,beta-unsaturated ketone-, 1,3-diketone-, and alpha,beta-unsaturated amide-derived dienolates to aldehydes. These reactions provided high levels of gamma-site selectivity for a variety of substitution patterns on the dienyl unit. Both ketone- and morpholine amide-derived dienol ethers afforded high enantio- and diastereoselectivity in the addition to conjugated aldehydes. Although alpha,beta-unsaturated ketone-derived dienolate did not react with aliphatic aldehydes, alpha,beta-unsaturated amide-derived dienolates underwent addition at reasonable rates affording high yields of vinylogous aldol product. The enantioselectivities achieved with the morpholine derived-dienolate in the addition to aliphatic aldehydes was the highest afforded to date with the silicon tetrachloride-chiral phosphoramide system. Furthermore, the ability to cleanly convert the morpholine amide to a methyl ketone was demonstrated.

  14. The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation

    NASA Astrophysics Data System (ADS)

    Yu, Xiaofang; Yu, Xiaobo; Wu, Shujie; Liu, Bo; Liu, Heng; Guan, Jingqi; Kan, Qiubin

    2011-02-01

    Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N 2 adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization.

  15. Cooperative Effects Between Arginine and Glutamic Acid in the Amino Acid-Catalyzed Aldol Reaction.

    PubMed

    Valero, Guillem; Moyano, Albert

    2016-08-01

    Catalysis of the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde by mixtures of L-Arg and of L-Glu in wet dimethyl sulfoxide (DMSO) takes place with higher enantioselectivity (up to a 7-fold enhancement in the anti-aldol for the 1:1 mixture) than that observed when either L-Glu or L-Arg alone are used as the catalysts. These results can be explained by the formation of a catalytically active hydrogen-bonded complex between both amino acids, and demonstrate the possibility of positive cooperative effects in catalysis by two different α-amino acids. Chirality 28:599-605, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  16. ALDOL- AND MANNICH-TYPE REACTIONS VIA IN SITU OLEFIN MIGRATION IN IONIC LIQUID

    EPA Science Inventory


    An aldol-type and a Mannich-type reaction via the cross-coupling of aldehydes and imines with allylic alcohols catalyzed by RuCl2(PPh3)3 was developed with ionic liquid as the solvent. The solvent/catalyst system could be reused for at least five times with no loss of reactiv...

  17. Direct asymmetric aldol reaction of aryl ketones with aryl aldehydes catalyzed by chiral BINOL-derived zincate catalyst.

    PubMed

    Li, Hong; Da, Chao-Shan; Xiao, Yu-Hua; Li, Xiao; Su, Ya-Ning

    2008-09-19

    Direct asymmetric aldol reaction of aryl ketones with aryl aldehydes catalyzed by chiral metal complex is reported for the first time herein. Two novel semicrown chiral ligands 1a and 1b were synthesized from (S)- and (R)-BINOL, respectively, and then employed to catalyze the direct asymmetric aldol addition of aryl ketones to aryl aldehydes. Introduced with 2.0 equiv of diethylzinc, 1b had higher enantioselectivity than 1a. Up to 97% yield and up to 80% enantioselectivity were achieved.

  18. Dynamic structural change of the self-assembled lanthanum complex induced by lithium triflate for direct catalytic asymmetric aldol-Tishchenko reaction.

    PubMed

    Horiuchi, Yoshihiro; Gnanadesikan, Vijay; Ohshima, Takashi; Masu, Hyuma; Katagiri, Kosuke; Sei, Yoshihisa; Yamaguchi, Kentaro; Shibasaki, Masakatsu

    2005-09-05

    The development of a direct catalytic asymmetric aldol-Tishchenko reaction and the nature of its catalyst are described. An aldol-Tishchenko reaction of various propiophenone derivatives with aromatic aldehydes was promoted by [LaLi3(binol)3] (LLB), and reactivity and enantioselectivity were dramatically enhanced by the addition of lithium trifluoromethanesulfonate (LiOTf). First, we observed a dynamic structural change of LLB by the addition of LiOTf using 13C NMR spectroscopy, electronspray ionization mass spectrometry (ESI-MS), and cold-spray ionization mass spectrometry (CSI-MS). X-ray crystallography revealed that the structure of the newly generated self-assembled complex was a binuclear [La2Li4(binaphthoxide)5] complex 6. A reverse structural change of complex 6 to LLB by the addition of one equivalent of Li2(binol) was also confirmed by ESI-MS and experimental results. The drastic concentration effects on the direct catalytic asymmetric aldol-Tishchenko reaction suggested that the addition of LiOTf to LLB generated an active oligomeric catalyst species.

  19. RUTHENIUM-CATALYZED TANDEM OLEFIN MIGRATION-ALDOL AND MANNICH-TYPE REACTIONS IN IONIC LIQUID.

    EPA Science Inventory

    In the presence of a catalytic amount of RuCl2(PPh3)3, a cross-coupling of 3-buten-2-ol with aldehydes and imines was developed via a tandem olefin migration--aldol--Mannich reaction in bmim[PF6]. With In(OAc)3 as a co-catalyst, a-vinylbenzyl alcohol and aldehydes underwent sim...

  20. Preparation of immobilized L-prolinamide via enzymatic polymerization of phenolic L-prolinamide and evaluation of its catalytic performance for direct asymmetric aldol reaction.

    PubMed

    Qu, Chengke; Zhao, Wenshan; Zhang, Lei; Cui, Yuanchen

    2014-04-01

    Phenolic L-prolinamide was allowed to participate in enzymatic polymerization with horseradish peroxidase as the catalyst, generating immobilized L-prolinamide. The catalytic performance of the resultant polymer-supported L-prolinamide for direct asymmetric aldol reaction between aromatic aldehyde and cyclohexanone was studied. The results show that as prepared L-prolinamide can catalyze the aldol reaction at room temperature in the presence of H2O. Relevant aldol addition products are obtained with good yields (up to 91%), high diastereoselectivities (up to 6:94 dr), and medium enantioselectivities (up to 87% ee). Moreover, the title polymer-supported catalyst can be recovered and reused for at least five cycles while the activity remains almost unchanged. Copyright © 2014 Wiley Periodicals, Inc.

  1. Synthesis of Chiral 1,2-Oxazinanes and Isoxazolidines via Nitroso Aldol Reaction of Distal Dialdehydes.

    PubMed

    Ramakrishna, Isai; Ramaraju, Panduga; Baidya, Mahiuddin

    2018-02-16

    The first catalytic enantioselective nitroso aldol reaction of distal dialdehydes is reported. The reaction is catalyzed by simple l-proline at room temperature and subsequent reduction delivered biologically potent and synthetically versatile N-O bond containing five- and six-membered heterocycles, 1,2-oxazinanes, and isoxazolidines in high yields and excellent enantioselectivities (up to >99% ee). The method was further exploited to prepare chiral 3-hydroxypiperidines and -pyrrolidines that are otherwise difficult to access.

  2. Physico-Chemical Properties of MgGa Mixed Oxides and Reconstructed Layered Double Hydroxides and Their Performance in Aldol Condensation of Furfural and Acetone

    PubMed Central

    Kikhtyanin, Oleg; Čapek, Libor; Tišler, Zdeněk; Velvarská, Romana; Panasewicz, Adriana; Diblíková, Petra; Kubička, David

    2018-01-01

    MgGa layered double hydroxides (Mg/Ga = 2–4) were synthesized and used for the preparation of MgGa mixed oxides and reconstructed hydrotalcites. The properties of the prepared materials were examined by physico-chemical methods (XRD, TGA, NH3-TPD, CO2-TPD, SEM, and DRIFT) and tested in aldol condensation of furfural and acetone. The as-prepared phase-pure MgGa samples possessed hydrotalcite structure, and their calcination resulted in mixed oxides with MgO structure with a small admixture phase characterized by a reflection at 2θ ≈ 36.0°. The interaction of MgGa mixed oxides with pure water resulted in reconstruction of the HTC structure already after 15 s of the rehydration with maximum crystallinity achieved after 60 s. TGA-MS experiments proved a substantial decrease in carbonates in all rehydrated samples compared with their as-prepared counterparts. This allowed suggesting presence of interlayer hydroxyls in the samples. Acido-basic properties of MgGa mixed oxides determined by TPD technique did not correlate with Mg/Ga ratio which was explained by the specific distribution of Ga atoms on the external surface of the samples. CO2-TPD method was also used to evaluate the basic properties of the reconstructed MgGa samples. In these experiments, an intensive peak at T = 450°C on CO2-TPD curve was attributed to the decomposition of carbonates newly formed by CO2 interaction with interlayer carbonates rather than to CO2 desorption from basic sites. Accordingly, CO2-TPD method quantitatively characterized the interlayer hydroxyls only indirectly. Furfural conversion on reconstructed MgGa materials was much larger compared with MgGa mixed oxides confirming that Brønsted basic sites in MgGa catalysts, like MgAl catalysts, were active in the reaction. Mg/Ga ratio in mixed oxides influenced product selectivity which was explained by the difference in textural properties of the samples. In contrast, Mg/Ga ratio in reconstructed catalysts had practically no effect

  3. Physico-Chemical Properties of MgGa Mixed Oxides and Reconstructed Layered Double Hydroxides and Their Performance in Aldol Condensation of Furfural and Acetone.

    PubMed

    Kikhtyanin, Oleg; Čapek, Libor; Tišler, Zdeněk; Velvarská, Romana; Panasewicz, Adriana; Diblíková, Petra; Kubička, David

    2018-01-01

    MgGa layered double hydroxides (Mg/Ga = 2-4) were synthesized and used for the preparation of MgGa mixed oxides and reconstructed hydrotalcites. The properties of the prepared materials were examined by physico-chemical methods (XRD, TGA, NH 3 -TPD, CO 2 -TPD, SEM, and DRIFT) and tested in aldol condensation of furfural and acetone. The as-prepared phase-pure MgGa samples possessed hydrotalcite structure, and their calcination resulted in mixed oxides with MgO structure with a small admixture phase characterized by a reflection at 2θ ≈ 36.0°. The interaction of MgGa mixed oxides with pure water resulted in reconstruction of the HTC structure already after 15 s of the rehydration with maximum crystallinity achieved after 60 s. TGA-MS experiments proved a substantial decrease in carbonates in all rehydrated samples compared with their as-prepared counterparts. This allowed suggesting presence of interlayer hydroxyls in the samples. Acido-basic properties of MgGa mixed oxides determined by TPD technique did not correlate with Mg/Ga ratio which was explained by the specific distribution of Ga atoms on the external surface of the samples. CO 2 -TPD method was also used to evaluate the basic properties of the reconstructed MgGa samples. In these experiments, an intensive peak at T = 450°C on CO 2 -TPD curve was attributed to the decomposition of carbonates newly formed by CO 2 interaction with interlayer carbonates rather than to CO 2 desorption from basic sites. Accordingly, CO 2 -TPD method quantitatively characterized the interlayer hydroxyls only indirectly. Furfural conversion on reconstructed MgGa materials was much larger compared with MgGa mixed oxides confirming that Brønsted basic sites in MgGa catalysts, like MgAl catalysts, were active in the reaction. Mg/Ga ratio in mixed oxides influenced product selectivity which was explained by the difference in textural properties of the samples. In contrast, Mg/Ga ratio in reconstructed catalysts had practically

  4. Physico-chemical properties of MgGa mixed oxides and reconstructed layered double hydroxides and their performance in aldol condensation of furfural and acetone

    NASA Astrophysics Data System (ADS)

    Kikhtyanin, Oleg; Čapek, Libor; Tišler, Zdeněk; Velvarská, Romana; Panasewicz, Adriana; Diblíková, Petra; Kubička, David

    2018-05-01

    MgGa layered double hydroxides (Mg/Ga=2-4) were synthesized and used for the preparation of MgGa mixed oxides and reconstructed hydrotalcites. The properties of the prepared materials were examined by physico-chemical methods (XRD, TGA, NH3-TPD, CO2-TPD, SEM and DRIFT) and tested in aldol condensation of furfural and acetone. The as-prepared phase-pure MgGa samples possessed hydrotalcite structure, and their calcination resulted in mixed oxides with MgO structure with a small admixture phase characterized by a reflection at 2θ ≈ 36.0°. The interaction of MgGa mixed oxides with pure water resulted in reconstruction of the HTC structure already after 15 s of the rehydration with maximum crystallinity achieved after 60 s. TGA-MS experiments proved a substantial decrease in carbonates in all rehydrated samples compared with their as-prepared counterparts. This allowed suggesting presence of interlayer hydroxyls in the samples. Acido-basic properties of MgGa mixed oxides determined by TPD technique did not correlate with Mg/Ga ratio which was explained by the specific distribution of Ga atoms on the external surface of the samples. CO2-TPD method was also used to evaluate the basic properties of the reconstructed MgGa samples. In these experiments, an intensive peak at T=450 °C on CO2-TPD curve was attributed to the decomposition of carbonates newly formed by CO2 interaction with interlayer carbonates rather than to CO2 desorption from basic sites. Accordingly, CO2-TPD method quantitatively characterized the interlayer hydroxyls only indirectly. Furfural conversion on reconstructed MgGa materials was much larger compared with MgGa mixed oxides confirming that Brønsted basic sites in MgGa catalysts, like MgAl catalysts, were active in the reaction. Mg/Ga ratio in mixed oxides influenced product selectivity which was explained by the difference in textural properties of the samples. In contrast, Mg/Ga ratio in reconstructed catalysts had practically no effect on the

  5. Direct asymmetric aldol reactions between aldehydes and ketones catalyzed by L-tryptophan in the presence of water.

    PubMed

    Jiang, Zhaoqin; Yang, Hui; Han, Xiao; Luo, Jie; Wong, Ming Wah; Lu, Yixin

    2010-03-21

    Primary amino acids and their derivatives were investigated as catalysts for the direct asymmetric aldol reactions between ketones and aldehydes in the presence of water, and L-tryptophan was shown to be the best catalyst. Solvent effects, substrate scope and the influence of water on the reactions were investigated. Quantum chemical calculations were performed to understand the origin of the observed stereoselectivity.

  6. Highly enantioselective asymmetric direct aldol reaction promoted by aziridine amides constructed on chiral terpene scaffold.

    PubMed

    Wujkowska, Zuzanna; Strojewska, Aleksandra; Pieczonka, Adam M; Leśniak, Stanisław; Rachwalski, Michał

    2017-05-01

    Optically pure, diastereomeric aziridine amides built on the chiral skeletons of camphor, fenchone, and menthone have proven to be highly efficient ligands for enantioselective asymmetric direct aldol reaction in the presence of water and zinc triflate. Desired products were formed in moderate to high chemical yields (up to 95%) and with enantiomeric excess up to 99%. The influence of the stereogenic centers located at the aziridine subunit on the stereochemical course of the reaction is discussed. © 2017 Wiley Periodicals, Inc.

  7. Dinuclear Zinc-Prophenol-Catalyzed Enantioselective α-Hydroxyacetate Aldol Reaction with Activated Ester Equivalents

    PubMed Central

    Trost, Barry M.; Michaelis, David J.; Truica, Mihai I.

    2013-01-01

    An enantioselective α-hydroxyacetate aldol reaction that employs N-acetyl pyrroles as activated ester equivalents and generates syn 1,2-diols in good yield and diastereoselectivity is reported. This dinuclear zinc Prophenol-catalyzed transformation proceeds with high enantioselectivity with a wide variety of substrates including aryl, alyl, and alkenyl aldehydes. The resulting α,β-dihydroxy activated esters are versatile intermediates for the synthesis of a variety of carboxylic acid derivatives including amides, esters, and unsymmetrical ketones. PMID:23947595

  8. On the asymmetric autocatalysis of aldol reactions: The case of 4-nitrobenzaldehyde and acetone. A critical appraisal with a focus on theory.

    PubMed

    Romero-Fernández, M Pilar; Babiano, Reyes; Cintas, Pedro

    2018-04-01

    Under neutral conditions, spontaneous mirror symmetry breaking has been occasionally reported for aldol reactions starting from achiral reagents and conditions. Chiral induction might be interpreted in terms of autocatalysis exerted by chiral mono-aldol or bis-aldol products as source of initial enantiomeric excesses, which may account for such experimental observations. We describe here a thorough Density Functional Theory (DFT) study on this complex and otherwise difficult problem, which provides some insights into this phenomenon. The picture adds further rationale to an in-depth analysis by Moyano et al, who showed the isolation and characterization of bis-aldol adducts and their participation in a complex network of reversible steps. However, the lack of enantiodiscrimination (ees vanish rapidly in solution) suggests, according to the present results, a weak association in complexes formed by the catalysts and substrates. The latter would also be consistent with almost flat transition states having similar heights for competitive catalyst-bound transition structures (actually, we were unable to locate them at the level explored). Overall, neither autocatalysis as once conjectured nor mutual inhibition of enantiomers appears to be operating mechanisms. Asymmetric amplification in early stages harnessing unavoidable enantiomeric imbalances in reaction mixtures of chiral products represents a plausible interpretation. © 2018 Wiley Periodicals, Inc.

  9. TANDEM BIS-ALDOL REACTION OF KETONES: A FACILE ONE-POT SYNTHESIS OF 1,3-DIOXANES IN AQUEOUS MEDIUM

    EPA Science Inventory

    A novel tandem bis-aldol reaction of ketone with paraformaldehyde catalyzed by polystyrenesulfonic acid in aqueous medium delivers 1,3-dioxanes in high yield. This one pot, operationally simple microwave-assisted synthetic protocol proceeds efficiently in water in the absence of ...

  10. Tandem Aldol-Michael Reactions in Aqueous Diethylamine Medium: A Greener and Efficient Approach to Bis-Pyrimidine Derivatives

    PubMed Central

    Al-Majid, Abdullah M.; Barakat, Assem; AL-Najjar, Hany J.; Mabkhot, Yahia N.; Ghabbour, Hazem A.; Fun, Hoong-Kun

    2013-01-01

    A simple protocol, involving the green synthesis for the construction of novel bis-pyrimidine derivatives, 3a–i and 4a–e are accomplished by the aqueous diethylamine media promoted tandem Aldol-Michael reaction between two molecules of barbituric acid derivatives 1a,b with various aldehydes. This efficient synthetic protocol using an economic and environmentally friendly reaction media with versatility and shorter reaction time provides bis-pyrimidine derivatives with high yields (88%–99%). PMID:24317435

  11. A Simple Organic Microscale Experiment Illustrating the Equilibrium Aspect of the Aldol Condensation

    NASA Astrophysics Data System (ADS)

    Harrison, Ernest A., Jr.

    1998-05-01

    A simple microscale experiment has been developed that illustrates the equilibrium aspect of the aldol condensation by using two versions of the standard preparation of tetraphenylcyclopentadienone (5) from benzil (1) and 1,3-diphenyl-2-propanone (2). In version (high base concentration) a mixture of 5 and the diastereomeric 4-hydroxy-2,3,4,5-tetraphenyl-2-cyclopenten-1-ones 3 and 4 are produced, while in the other (low base concentration) a mixture of 1, 2, 3, and 4 results. The experiment is typically carried out in conjunction with the previously reported preparation/dehydration of 3, thus the students provide themselves with authentic samples of 3 and 5. Using these, plus authentic samples of 1 and 2 which are made available, students are able to identify all of the components in the equilibrium mixtures, except 4, by TLC analysis. In the case of 4, students are expected to propose a reasonable structure for this compound based on the observed chemistry and the spectroscopic evidence which is provided (i.e., NMR, IR and mass spectra). The experiment lends itself nicely to either the traditional or problem-solving approach, and it also opens up opportunities for collaborative learning.

  12. A One-Pot Tandem Strategy in Catalytic Asymmetric Vinylogous Aldol Reaction of Homoallylic Alcohols.

    PubMed

    Hou, Xufeng; Jing, Zhenzhong; Bai, Xiangbin; Jiang, Zhiyong

    2016-06-27

    Reported is a rationally-designed one-pot sequential strategy that allows homoallylic alcohols to be employed in a catalytic, asymmetric, direct vinylogous aldol reaction with a series of activated acyclic ketones, including trifluoromethyl ketones, γ-ketoesters, and α-keto phosphonates, in high yields (up to 95%) with excellent regio- and enantio-selectivity (up to 99% ee). This modular combination, including Jones oxidation and asymmetric organocatalysis, has satisfactory compatibility and reliability even at a 20 mmol scale, albeit without intermediary purification.

  13. On the adsorption/reaction of acetone on pure and sulfate-modified zirconias.

    PubMed

    Crocellà, Valentina; Cerrato, Giuseppina; Morterra, Claudio

    2013-08-28

    In situ FTIR spectroscopy was employed to investigate some aspects of the ambient temperature (actually, IR-beam temperature) adsorption of acetone on various pure and sulfate-doped zirconia specimens. Acetone uptake yields, on all examined systems and to a variable extent, different types of specific molecular adsorption, depending on the kind/population of available surface sites: relatively weak H-bonding interaction(s) with surface hydroxyls, medium-strong coordinative interaction with Lewis acidic sites, and strong H-bonding interaction with Brønsted acidic centres. Moreover acetone, readily and abundantly adsorbed in molecular form, is able to undergo the aldol condensation reaction (yielding, as the main reaction product, adsorbed mesityl oxide) only if the adsorbing material possesses some specific surface features. The occurrence/non-occurrence of the acetone self-condensation reaction is discussed, and leads to conclusions concerning the sites that catalyze the condensation reaction that do not agree with either of two conflicting interpretations present in the literature of acetone uptake/reaction on, mainly, zeolitic systems. In particular, what turns out to be actually necessary for the acetone aldol condensation reaction to occur on the examined zirconia systems is the presence of coordinatively unsaturated O(2-) surface sites of basicity sufficient to lead to the extraction of a proton from one of the CH3 groups of adsorbed acetone.

  14. Asymmetric vinylogous Mukaiyama aldol reaction of isatins under bifunctional organocatalysis: enantioselective synthesis of substituted 3-hydroxy-2-oxindoles.

    PubMed

    Laina-Martín, Víctor; Humbrías-Martín, Jorge; Fernández-Salas, José A; Alemán, José

    2018-03-13

    A highly enantioselective organocatalytic vinylogous Mukaiyama aldol reaction of silyloxy dienes and isatins under bifunctional organocatalysis is presented. Substituted 3-hydroxy-2-oxindoles are synthesised in good yields and enantioselectivities. These synthetic intermediates are used for the construction of more complex molecules with biological properties such as the formal synthesis of a CB2 agonist presented.

  15. Dynamic Kinetic Asymmetric Transformations of β-Stereogenic-α-Keto Esters via Direct Aldolization

    PubMed Central

    Corbett, Michael T.; Johnson, Jeffrey S.

    2014-01-01

    Dynamic kinetic asymmetric transformations (DyKAT) of racemic β-bromo-α-keto esters via direct aldolization of nitromethane and acetone provide access to fully substituted α-glycolic acid derivatives bearing a β-stereocenter. The aldol adducts are obtained in excellent yield with high relative and absolute stereocontrol under mild reaction conditions. Mechanistic studies determined that the reactions proceed through a facile catalyst-mediated racemization of the β-bromo-α-keto esters under a DyKAT Type I manifold. PMID:24222195

  16. Preparation and characterization of Mg-Zr mixed oxide aerogels and their application as aldol condensation catalysts.

    PubMed

    Sádaba, Irantzu; Ojeda, Manuel; Mariscal, Rafael; Richards, Ryan; López Granados, Manuel

    2012-10-08

    A series of Mg-Zr mixed oxides with different nominal Mg/(Mg+Zr) atomic ratios, namely 0, 0.1, 0.2, 0.4, 0.85, and 1, is prepared by alcogel methodology and fundamental insights into the phases obtained and resulting active sites are studied. Characterization is performed by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N(2) adsorption-desorption isotherms, and thermal and chemical analysis. Cubic Mg(x)Zr(1-x)O(2-x) solid solution, which results from the dissolution of Mg(2+) cations within the cubic ZrO(2) structure, is the main phase detected for the solids with theoretical Mg/(Mg+Zr) atomic ratio ≤0.4. In contrast, the cubic periclase (c-MgO) phase derived from hydroxynitrates or hydroxy precursors predominates in the solid with Mg/(Mg+Zr)=0.85. c-MgO is also incipiently detected in samples with Mg/(Mg+Zr)=0.2 and 0.4, but in these solids the c-MgO phase mostly arises from the segregation of Mg atoms out of the alcogel-derived c-Mg(x)Zr(1-x)O(2-x) phase during the calcination process, and therefore the species c-MgO and c-Mg(x)Zr(1-x)O(2-x) are in close contact. Regarding the intrinsic activity in furfural-acetone aldol condensation in the aqueous phase, these Mg-O-Zr sites located at the interface between c-Mg(x)Zr(1-x)O(2-x) and segregated c-MgO display a much larger intrinsic activity than the other noninterface sites that are present in these catalysts: Mg-O-Mg sites on c-MgO and Mg-O-Zr sites on c-Mg(x)Zr(1-x)O(2-x). The very active Mg-O-Zr sites rapidly deactivate in the furfural-acetone condensation due to the leaching of active phases, deposition of heavy hydrocarbonaceous compounds, and hydration of the c-MgO phase. Nonetheless, these Mg-Zr materials with very high specific surface areas would be suitable solid catalysts for other relevant reactions catalyzed by strong basic sites in nonaqueous environments. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities.

    PubMed

    Van Wyngarden, A L; Pérez-Montaño, S; Bui, J V H; Li, E S W; Nelson, T E; Ha, K T; Leong, L; Iraci, L T

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H 2 SO 4 ) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and 1 H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal

  18. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities

    PubMed Central

    Van Wyngarden, A. L.; Pérez-Montaño, S.; Bui, J. V. H.; Li, E. S. W.; Nelson, T. E.; Ha, K. T.; Leong, L.; Iraci, L. T.

    2016-01-01

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40–80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance–Fourier transform infrared (ATR-FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and

  19. An Unconventional Redox Cross Claisen Condensation-Aromatization of 4-Hydroxyprolines with Ketones.

    PubMed

    Tang, Mi; Sun, Rengwei; Li, Hao; Yu, Xinhong; Wang, Wei

    2017-08-18

    Reaction of α-amino acids, particularly prolines and their derivatives with carbonyl compounds via decarboxylative redox process, is a viable strategy for synthesis of structurally diverse nitrogen centered heterocyclics. In these processes, the decarboxylation is the essential driving force for the processes. The realization of the redox process without decarboxylation may offer an opportunity to explore new reactions. Herein, we report the discovery of an unprecedented redox Claisen-type condensation aromatization cascade reaction of 4-substituted 4-hydroxyproline and its esters with unreactive ketones. We found that the use of propionic acid as a catalyst and a co-solvent can change the reaction course. The commonly observed redox decarboxylation and aldol condensation reactions are significantly minimized. Moreover, unreactive ketones can effectively participate in the Claisen condensation reaction. The new reactivity enables a redox cyclization via an unconventional Claisen-type condensation reaction of in situ formed enamine intermediates from ketone precursors with 4-substituted 4-hydroxyproline and its esters as electrophilic acylation partners. Under the reaction conditions, the cascade process proceeds highly regio- and stereoselectively to afford highly synthetically and biologically valued cis-2,3-dihydro-1H-pyrrolizin-1-ones with a broad substrate scope in efficient 'one-pot' operation, whereas such structures generally require multiple steps.

  20. Structural identification of Zn xZr yO z catalysts for Cascade aldolization and self-deoxygenation reactions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Baylon, Rebecca A. L.; Sun, Junming; Kovarik, Libor

    Complementary characterizations, such as nitrogen sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), visible Raman, scanning transmission electron microscopy (STEM) coupled with elemental mapping, NH3/CO2 temperature programmed desorption (NH3/CO2-TPD), infrared spectroscopic analysis of adsorbed pyridine (Py-IR), and CO2-IR, have been employed to identify the structure and surface chemistry (i.e., acid-base) of mixed Zn xZr yO z oxide catalysts of varied ratios of Zn/Zr. Atomically dispersed Zn2+ species are present in the framework within a thin surface shell (1.5-2.0 nm) of ZrO2 particles when the Zn/Zr ratio is smaller than 1/10; when the ratio is above this, both atomically dispersed Zn2+more » and ZnO clusters coexist in mixed Zn xZr yO z oxide catalysts. The presence of ZnO clusters shows no significant side effect but only a slight increase of selectivity to CO2, caused by steam reforming. The incorporation of atomic Zn2+ into the ZrO2 framework was found to not only passivate strong Lewis acid sites (i.e., Zr-O-Zr) on ZrO2, but to also generate new Lewis acid-base site pairs with enhanced Lewis basicity on the bridged O (i.e., ). In the mixed ketone (i.e., acetone and methyl ethyl ketone (MEK)) reactions, while the passivation of strong acid sites can be correlated to the inhibition of side reactions, such as ketone decomposition and coking, the new Lewis acid-base pairs introduced enhance the cascade aldolization and self-deoxygenation reactions involved in olefin (C3=-C6=) production. More importantly, the surface acid-base properties change with varying Zn/Zr ratios, which in turn affect the cross- and self-condensation reactivity and subsequent distribution of olefins.« less

  1. Lewis base catalyzed aldol additions of chiral trichlorosilyl enolates and silyl enol ethers.

    PubMed

    Denmark, Scott E; Fujimori, Shinji; Pham, Son M

    2005-12-23

    [structures: see text] The consequences of double diastereodifferentiation in chiral Lewis base catalyzed aldol additions using chiral enoxysilanes derived from lactate, 3-hydroxyisobutyrate, and 3-hydroxybutyrate have been investigated. Trichlorosilyl enolates derived from the chiral methyl and ethyl ketones were subjected to aldolization in the presence of phosphoramides, and the intrinsic selectivity of these enolates and the external stereoinduction from chiral catalyst were studied. In the reactions with the lactate derived enolate, the strong internal stereoinduction dominated the stereochemical outcome of the aldol addition. For the 3-hydroxyisobutyrate- and 3-hydroxybutyrate derived enolates, the catalyst-controlled diastereoselectivities were observed, and the resident stereogenic centers exerted marginal influence. The corresponding trimethylsilyl enol ethers were employed in SiCl4/bisphosphoramide catalyzed aldol additions, and the effect of double diastereodifferentiation was also investigated. The overall diastereoselection of the process was again controlled by the strong external influence of the catalyst.

  2. Cross-Aldol Reaction of Activated Carbonyls with Nitrosocarbonyl Intermediates: Stereoselective Synthesis toward α-Hydroxy-β-amino Esters and Amides.

    PubMed

    Mallik, Sumitava; Bhajammanavar, Vinod; Ramakrishna, Isai; Baidya, Mahiuddin

    2017-07-21

    A practical and flexible strategy toward α-hydroxy-β-amino esters and amides, which are important biological motifs, based on an organocatalytic cross-aldol reaction of in situ-generated nitrosocarbonyl intermediates followed by hydrogenation is presented. The protocol features operational simplicity, high yields, a wide substrate scope, and high regio- and diastereoselectivity profiles. The utility of this method was showcased through the synthesis of bestatin analogues and indole formation.

  3. Hydroxyapatite catalyzed aldol condensation: Synthesis, spectral linearity, antimicrobial and insect antifeedant activities of some 2,5-dimethyl-3-furyl chalcones

    NASA Astrophysics Data System (ADS)

    Subramanian, M.; Vanangamudi, G.; Thirunarayanan, G.

    2013-06-01

    A series of 2,5-dimethyl-3-furyl chalcones [2E-1-(2,5-dimethyl-3-furyl)-3-(substituted phenyl)-2-propen-1-ones] have been synthesized by Hydrotalcite catalyzed aldol condensation between 3-acetyl-2,5-dimethylfuron and substituted benzaldehydes. Yields of chalcones are more than 80%. These chalcones were characterized by their physical constants and spectral data. The group frequencies of infrared ν(cm-1) of CO s-cis and s-trans, CH in-plane and out of plane, CHdbnd CH out of plane, lbond2 Cdbnd Crbond2 out of plane modes, NMR chemical shifts δ(ppm) of Hα, Hβ, CO, Cα and Cβ of these chalcones were correlated with Hammett substituent constants, F and R parameters using single and multi-regression analyses. From the results of statistical analyses, the effects of substituents on the group frequencies are explained. Antibacterial, antifungal and insect antifeedant activities of these chalcones have been studied.

  4. Structural Identification of Zn xZr yO z Catalysts for Cascade Aldolization and Self-Deoxygenation Reactions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Baylon, Rebecca A. L.; Sun, Junming; Kovarik, Libor

    Here, complementary characterizations, such as nitrogen sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), visible Raman, scanning transmission electron microscopy (STEM) coupled with elemental mapping, NH 3/CO 2 temperature programmed desorption (NH 3/CO 2-TPD), infrared spectroscopic analysis of adsorbed pyridine (Py-IR), and CO 2-IR, have been employed to identify the structure and surface chemistry (i.e., acid-base) of mixed Zn xZr yO z oxide catalysts of varied ratios of Zn/Zr. Atomically dispersed Zn 2+ species are present in the framework within a thin surface shell (1.5-2.0 nm) of ZrO 2 particles when the Zn/Zr ratio is smaller than 1/10; when the ratio is above this, both atomically dispersed Zn 2+ and ZnO clusters coexist in mixed Zn xZr yO z oxide catalysts. The presence of ZnO clusters shows no significant side effect but only a slight increase of selectivity to CO 2, caused by steam reforming. The incorporation of atomic Zn 2+ into the ZrO 2 framework was found to not only passivate strong Lewis acid sites (i.e., Zr-O-Zr) on ZrO 2, but to also generate new Lewis acid-base site pairs with enhanced Lewis basicity on the bridged O (i.e., Zr—omore » $$\\curvearrowleft\\atop{e\\atop—}$$Zn). In the mixed ketone (i.e., acetone and methyl ethyl ketone (MEK)) reactions, while the passivation of strong acid sites can be correlated to the inhibition of side reactions, such as ketone decomposition and coking, the new Lewis acid-base pairs introduced enhance the cascade aldolization and self-deoxygenation reactions involved in olefin (C 3 =-C 6 =) production. More importantly, the surface acid-base properties change with varying Zn/Zr ratios, which in turn affect the cross- and self-condensation reactivity and subsequent distribution of olefins.« less

  5. Structural Identification of Zn xZr yO z Catalysts for Cascade Aldolization and Self-Deoxygenation Reactions

    DOE PAGES

    Baylon, Rebecca A. L.; Sun, Junming; Kovarik, Libor; ...

    2018-04-22

    Here, complementary characterizations, such as nitrogen sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), visible Raman, scanning transmission electron microscopy (STEM) coupled with elemental mapping, NH 3/CO 2 temperature programmed desorption (NH 3/CO 2-TPD), infrared spectroscopic analysis of adsorbed pyridine (Py-IR), and CO 2-IR, have been employed to identify the structure and surface chemistry (i.e., acid-base) of mixed Zn xZr yO z oxide catalysts of varied ratios of Zn/Zr. Atomically dispersed Zn 2+ species are present in the framework within a thin surface shell (1.5-2.0 nm) of ZrO 2 particles when the Zn/Zr ratio is smaller than 1/10; when the ratio is above this, both atomically dispersed Zn 2+ and ZnO clusters coexist in mixed Zn xZr yO z oxide catalysts. The presence of ZnO clusters shows no significant side effect but only a slight increase of selectivity to CO 2, caused by steam reforming. The incorporation of atomic Zn 2+ into the ZrO 2 framework was found to not only passivate strong Lewis acid sites (i.e., Zr-O-Zr) on ZrO 2, but to also generate new Lewis acid-base site pairs with enhanced Lewis basicity on the bridged O (i.e., Zr—omore » $$\\curvearrowleft\\atop{e\\atop—}$$Zn). In the mixed ketone (i.e., acetone and methyl ethyl ketone (MEK)) reactions, while the passivation of strong acid sites can be correlated to the inhibition of side reactions, such as ketone decomposition and coking, the new Lewis acid-base pairs introduced enhance the cascade aldolization and self-deoxygenation reactions involved in olefin (C 3 =-C 6 =) production. More importantly, the surface acid-base properties change with varying Zn/Zr ratios, which in turn affect the cross- and self-condensation reactivity and subsequent distribution of olefins.« less

  6. New insights into aldol reactions of methyl isocyanoacetate catalyzed by heterogenized homogeneous catalysts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ye, Rong; Zhao, Jie; Yuan, Bing

    The Hayashi–Ito aldol reaction of methyl isocyanoacetate (MI) and benzaldehydes, a classic homogeneous Au(I)-catalyzed reaction, was studied with heterogenized homogeneous catalysts. Among dendrimer encapsulated nanoparticles (NPs) of Au, Pd, Rh, or Pt loaded in mesoporous supports and the homogeneous analogues, the Au NPs led to the highest yield and highest diastereoselectivity of products in toluene at room temperature. The Au catalyst was stable and was recycled for at least six runs without substantial deactivation. Moreover, larger pore sizes of the support and the use of a hydrophobic solvent led to a high selectivity for the trans diastereomer of the product.more » The activation energy is sensitive to neither the size of Au NPs nor the support. A linear Hammett plot was obtained with a positive slope, suggesting an increased electron density on the carbonyl carbon atom in the rate-limiting step. As a result, IR studies revealed a strong interaction between MI and the gold catalyst, supporting the proposed mechanism, in which rate-limiting step involves an electrophilic attack of the aldehyde on the enolate formed from the deprotonated MI.« less

  7. Expedient synthesis of C-aryl carbohydrates by consecutive biocatalytic benzoin and aldol reactions.

    PubMed

    Hernández, Karel; Parella, Teodor; Joglar, Jesús; Bujons, Jordi; Pohl, Martina; Clapés, Pere

    2015-02-16

    The introduction of aromatic residues connected by a C-C bond into the non-reducing end of carbohydrates is highly significant for the development of innovative structures with improved binding affinity and selectivity (e.g., C-aril-sLex). In this work, an expedient asymmetric "de novo" synthetic route to new aryl carbohydrate derivatives based on two sequential stereoselectively biocatalytic carboligation reactions is presented. First, the benzoin reaction of aromatic aldehydes to dimethoxyacetaldehyde is conducted, catalyzed by benzaldehyde lyase from Pseudomonas fluorescens biovar I. Then, the α-hydroxyketones formed are reduced by using NaBH4 yielding the anti diol. After acetal hydrolysis, the aldol addition of dihydroxyacetone, hydroxyacetone, or glycolaldehyde catalyzed by the stereocomplementary D-fructose-6-phosphate aldolase and L-rhamnulose-1-phosphate aldolase is performed. Both aldolases accept unphosphorylated donor substrates, avoiding the need of handling the phosphate group that the dihydroxyacetone phosphate-dependent aldolases require. In this way, 6-C-aryl-L-sorbose, 6-C-aryl-L-fructose, 6-C-aryl-L-tagatose, and 5-C-aryl-L-xylose derivatives are prepared by using this methodology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. New insights into aldol reactions of methyl isocyanoacetate catalyzed by heterogenized homogeneous catalysts

    DOE PAGES

    Ye, Rong; Zhao, Jie; Yuan, Bing; ...

    2016-12-14

    The Hayashi–Ito aldol reaction of methyl isocyanoacetate (MI) and benzaldehydes, a classic homogeneous Au(I)-catalyzed reaction, was studied with heterogenized homogeneous catalysts. Among dendrimer encapsulated nanoparticles (NPs) of Au, Pd, Rh, or Pt loaded in mesoporous supports and the homogeneous analogues, the Au NPs led to the highest yield and highest diastereoselectivity of products in toluene at room temperature. The Au catalyst was stable and was recycled for at least six runs without substantial deactivation. Moreover, larger pore sizes of the support and the use of a hydrophobic solvent led to a high selectivity for the trans diastereomer of the product.more » The activation energy is sensitive to neither the size of Au NPs nor the support. A linear Hammett plot was obtained with a positive slope, suggesting an increased electron density on the carbonyl carbon atom in the rate-limiting step. As a result, IR studies revealed a strong interaction between MI and the gold catalyst, supporting the proposed mechanism, in which rate-limiting step involves an electrophilic attack of the aldehyde on the enolate formed from the deprotonated MI.« less

  9. Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 2: aldol, Mannich addition reactions, deracemization and (S) to (R) interconversion of α-amino acids.

    PubMed

    Sorochinsky, Alexander E; Aceña, José Luis; Moriwaki, Hiroki; Sato, Tatsunori; Soloshonok, Vadim

    2013-11-01

    This review provides a comprehensive treatment of literature data dealing with asymmetric synthesis of α-amino-β-hydroxy and α,β-diamino acids via homologation of chiral Ni(II) complexes of glycine Schiff bases using aldol and Mannich-type reactions. These reactions proceed with synthetically useful chemical yields and thermodynamically controlled stereoselectivity and allow direct introduction of two stereogenic centers in a single operation with predictable stereochemical outcome. Furthermore, new application of Ni(II) complexes of α-amino acids Schiff bases for deracemization of racemic α-amino acids and (S) to (R) interconversion providing additional synthetic opportunities for preparation of enantiomerically pure α-amino acids, is also reviewed. Origin of observed diastereo-/enantioselectivity in the aldol, Mannich-type and deracemization reactions, generality and limitations of these methodologies are critically discussed.

  10. The Aldol Addition and Condensation: The Effect of Conditions on Reaction Pathway

    ERIC Educational Resources Information Center

    Crouch, R. David; Richardson, Amie; Howard, Jessica L.; Harker, Rebecca L.; Barker, Kathryn H.

    2007-01-01

    The reaction of a ketone and an aldehyde in aqueous Na[subscript 2]CO[subscript 2] is described. This experiment is performed in the absence of strong bases or organic solvents and offers the opportunity for students to observe the critical role that reaction temperature and base strength have in determining the product of the base-mediated…

  11. Lewis base activation of Lewis acids. Vinylogous aldol addition reactions of conjugated N,O-silyl ketene acetals to aldehydes.

    PubMed

    Denmark, Scott E; Heemstra, John R

    2006-02-01

    N,O-Silyl dienyl ketene acetals derived from unsaturated morpholine amides have been developed as highly useful reagents for vinylogous aldol addition reactions. In the presence of SiCl4 and the catalytic action of chiral phosphoramide (R,R)-3, N,O-silyl dienyl ketene acetal 8 undergoes high-yielding and highly site-selective addition to a wide variety of aldehydes with excellent enantioselectivity. Of particular note is the high yields and selectivities obtained from aliphatic aldehydes. Low catalyst loadings (2-5 mol %) can be employed. The morpholine amide serves as a useful precursor for further synthetic manipulation.

  12. Free energy landscape for glucose condensation reactions.

    PubMed

    Liu, Dajiang; Nimlos, Mark R; Johnson, David K; Himmel, Michael E; Qian, Xianghong

    2010-12-16

    Ab initio molecular dynamics and metadynamics simulations were used to determine the free energy surfaces (FES) for the acid catalyzed β-D-glucose condensation reaction. Protonation of C1-OH on the β-D-glucose, breakage of the C1-O1 bond, and the formation of C1 carbocation is the rate-limiting step. The effects of solvent on the reaction were investigated by determining the FES both in the absence and presence of solvent water. It was found that water played a critical role in these reactions. The reaction barrier for the proton-catalyzed glucose condensation reaction is solvent induced because of proton's high affinity for water. During these simulations, β-D-glucose conversion to α-d-glucose process via the C1 carbocation was also observed. The associated free energy change and activation barrier for this reaction were determined.

  13. Advances in chemoselective intermolecular cross-benzoin-type condensation reactions.

    PubMed

    Gaggero, Nicoletta; Pandini, Stefano

    2017-08-23

    The intermolecular cross-benzoin and acyloin condensation reactions are powerful approaches to α-hydroxy carbonyls in a single step. However, their potentiality suffers from the occurrence of side reactions including self-condensation and the formation of the undesired cross-acyloin. The broad range of azolium salt precatalysts available confers high tunability to NHC mediated benzoin condensation, assuring a good level of selectivity to the direct coupling between two non-equivalent aldehydes. Many efforts have also been devoted to the design of strategies that expand the range of suitable reaction partners beyond the traditional aldehydes and to the discovery of novel umpolung catalytic systems. The synthesis of both racemic and enantiomerically enriched acyloins is reviewed.

  14. Forging Fluorine‐Containing Quaternary Stereocenters by a Light‐Driven Organocatalytic Aldol Desymmetrization Process

    PubMed Central

    Cuadros, Sara; Dell'Amico, Luca

    2017-01-01

    Abstract Reported herein is a light‐triggered organocatalytic strategy for the desymmetrization of achiral 2‐fluoro‐substituted cyclopentane‐1,3‐diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy‐o‐quinodimethanes and simultaneously forges two adjacent fully substituted carbon stereocenters, with one bearing a stereogenic carbon–fluorine unit. The method uses readily available substrates, a simple chiral organocatalyst, and mild reaction conditions to afford an array of highly functionalized chiral 2‐fluoro‐3‐hydroxycyclopentanones. PMID:28746742

  15. Forging Fluorine-Containing Quaternary Stereocenters by a Light-Driven Organocatalytic Aldol Desymmetrization Process.

    PubMed

    Cuadros, Sara; Dell'Amico, Luca; Melchiorre, Paolo

    2017-09-18

    Reported herein is a light-triggered organocatalytic strategy for the desymmetrization of achiral 2-fluoro-substituted cyclopentane-1,3-diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy-o-quinodimethanes and simultaneously forges two adjacent fully substituted carbon stereocenters, with one bearing a stereogenic carbon-fluorine unit. The method uses readily available substrates, a simple chiral organocatalyst, and mild reaction conditions to afford an array of highly functionalized chiral 2-fluoro-3-hydroxycyclopentanones. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  16. Linked strategy for the production of fuels via formose reaction

    PubMed Central

    Deng, Jin; Pan, Tao; Xu, Qing; Chen, Meng-Yuan; Zhang, Ying; Guo, Qing-Xiang; Fu, Yao

    2013-01-01

    Formose reaction converts formaldehyde to carbohydrates. We found that formose reaction can be used linking the biomass gasification with the aqueous-phase processing (APP) to produce liquid transportation fuel in three steps. First, formaldehyde from syn-gas was converted to triose. This was followed by aldol condensation and dehydration to 4-hydroxymethylfurfural (4-HMF). Finally, 4-HMF was hydrogenated to produce 2,4-dimethylfuran (2,4-DMF) or C9-C15 branched-chain alkanes as liquid transportation fuels. In the linked strategy, high energy-consuming pretreatment as well as expensive and polluting hydrolysis of biomass were omitted, but the high energy recovery of APP was inherited. In addition, the hexoketoses via formose reaction could be converted to HMFs directly without isomerization. A potential platform molecule 4-HMF was formed simultaneously in APP. PMID:23393625

  17. Engineering the donor selectivity of D-fructose-6-phosphate aldolase for biocatalytic asymmetric cross-aldol additions of glycolaldehyde.

    PubMed

    Szekrenyi, Anna; Soler, Anna; Garrabou, Xavier; Guérard-Hélaine, Christine; Parella, Teodor; Joglar, Jesús; Lemaire, Marielle; Bujons, Jordi; Clapés, Pere

    2014-09-22

    D-Fructose-6-phosphate aldolase (FSA) is a unique catalyst for asymmetric cross-aldol additions of glycolaldehyde. A combination of a structure-guided approach of saturation mutagenesis, site-directed mutagenesis, and computational modeling was applied to construct a set of FSA variants that improved the catalytic efficiency towards glycolaldehyde dimerization up to 1800-fold. A combination of mutations in positions L107, A129, and A165 provided a toolbox of FSA variants that expand the synthetic possibilities towards the preparation of aldose-like carbohydrate compounds. The new FSA variants were applied as highly efficient catalysts for cross-aldol additions of glycolaldehyde to N-carbobenzyloxyaminoaldehydes to furnish between 80-98 % aldol adduct under optimized reaction conditions. Donor competition experiments showed high selectivity for glycolaldehyde relative to dihydroxyacetone or hydroxyacetone. These results demonstrate the exceptional malleability of the active site in FSA, which can be remodeled to accept a wide spectrum of donor and acceptor substrates with high efficiency and selectivity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Stereoselective Synthesis of Highly Functionalized α-Diazo-β-ketoalkanoates via Catalytic Onepot Mukaiyama-Aldol Reactions

    PubMed Central

    Zhou, Lei; Doyle, Michael P.

    2010-01-01

    Methyl diazoacetoacetate undergoes zinc triflate catalyzed condensation with a broad selection of aldehydes to produce δ-siloxy-α-diazo-β-ketoalkanoates in good yield, and δ-hydroxy-α-diazo-β-ketoalkanoates are formed with high diastereoselectivity in reactions with α-diazo-β-ketopentanoate promoted by dibutylboron triflate. PMID:20102172

  19. Engineering a Promiscuous Tautomerase into a More Efficient Aldolase for Self-Condensations of Linear Aliphatic Aldehydes.

    PubMed

    Rahimi, Mehran; van der Meer, Jan-Ytzen; Geertsema, Edzard M; Poelarends, Gerrit J

    2017-07-18

    The enzyme 4-oxalocrotonate tautomerase (4-OT) from Pseudomonas putida mt-2 takes part in a catabolic pathway for aromatic hydrocarbons, where it catalyzes the conversion of 2hydroxyhexa-2,4-dienedioate into 2-oxohexa-3-enedioate. This tautomerase can also promiscuously catalyze carbon-carbon bond-forming reactions, including various types of aldol reactions, by using its amino-terminal proline as a key catalytic residue. Here, we used systematic mutagenesis to identify two hotspots in 4-OT (Met45 and Phe50) at which single mutations give marked improvements in aldolase activity for the self-condensation of propanal. Activity screening of a focused library in which these two hotspots were varied led to the discovery of a 4-OT variant (M45Y/F50V) with strongly enhanced aldolase activity in the self-condensation of linear aliphatic aldehydes, such as acetaldehyde, propanal, and butanal, to yield α,β-unsaturated aldehydes. With both propanal and benzaldehyde, this double mutant, unlike the previously constructed single mutant F50A, mainly catalyzes the self-condensation of propanal rather than the cross-condensation of propanal and benzaldehyde, thus indicating that it indeed has altered substrate specificity. This variant could serve as a template to create new biocatalysts that lack dehydration activity and possess further enhanced aldolase activity, thus enabling the efficient enzymatic self-coupling of aliphatic aldehydes. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  20. Recent advances in heterocycle generation using the efficient Ugi multiple-component condensation reaction.

    PubMed

    Tempest, Paul A

    2005-11-01

    The current trend of rising research spending and falling numbers of novel chemical entities continues to drive efforts aimed at increasing efficiency in the drug discovery process. Strategic issues, such as assigning resources to poorly validated targets have been implicated in the declining productivity of recent years. Tactical approaches employed to improve this situation include attempts to speed the discovery process toward decision points in a timely manner. Accelerating the optimization of high-throughput screening hits is a goal in streamlining the discovery process, and the use of multiple-component condensation (MCC) reactions have proved useful toward this end. MCC reactions are powerful and efficient tools for the generation of diverse compound sets. Collections of compounds can be synthesized with all of the required diversity elements included in a single synthetic step. One of the most widely investigated MCC reactions is the Ugi four-component condensation. This review highlights disclosures of the Ugi reaction published over the past two years (2003 to 2005) in three areas: (i) Ugi reaction in conjunction with post-condensation cyclization; (ii) bifunctional condensations leading to heterocyclic cores; and (iii) general findings relating to linear products or interesting improvements in the basic Ugi reaction.

  1. Prebiotic condensation reactions using cyanamide

    NASA Technical Reports Server (NTRS)

    Sherwood, E.; Nooner, D. W.; Eichberg, J.; Epps, D. E.; Oro, J.

    1978-01-01

    Condensation reactions in cyanamide, 4-amino-5-imidazole-carboxamide and cyanamide, imidazole systems under dehydrating conditions at moderate temperatures (60 to 100 deg C) were investigated. The cyanamide, imidazole system was used for synthesis of palmitoylglycerols from ammonium palmitate and glycerol. With the addition of deoxythymidine to the former system, P1, P2-dideoxythymidine 5 prime-phosphate was obtained; the same cyanamide, 4-amino-5-imidazole-carboxamide system was used to synthesize deoxythymidine oligonucleotides using deoxythymidine 5 prime-phosphate and deoxythymidine 5 prime-triphosphate, and peptides using glycine, phenylalanine or isoleucine with adenosine 5 prime-triphosphate. The pH requirements for these reactions make their prebiotic significance questionable; however, it is conceivable that they could occur in stable pockets of low interlayer acidity in a clay such as montmorillonite.

  2. Ion-molecule condensation reactions: a mechanism for organic synthesis in ionized reducing atmospheres.

    PubMed

    Meot-Ner, M

    1978-12-01

    The CH3+ ion, formed in ionized methane, undergoes consecutive eliminative condensation reactions with methane to form the carbonium ions C2H5+, i-C3H7+ and t-C4H9+. At T smaller than 500 degrees K, NCH4 greater than 10(16) cm-3 these ions react with NH3 in competitive condensation -- H+ transfer reactions, e.g. C2H5 + NH3 M leads to C2H5NH3+ leads to NH4+ + C2H4 At particle densities of NCH4 smaller than 10(16) cm-3 proton transfer is the only significant reaction channel. At NCH4 greater than 10(17) cm-3 condensation constitutes 5--20% of the overall reactions. The product of the condensation reaction further associates with CO2 to form C2H5NH3+ . CO2; the atomic composition of this cluster ion is identical with the protonated amino acid alanine. The carbonium ions i-C3H7+ and t-C4H9+ condense also with HCN to yield protonated isocyanides. HCNH% also appears to condense with HCN at T greater than 570 degrees K, and form cluster ions with HCN at lower temperatures. The rate constants of the condensation reactions vary with temperature and pressure in a complex manner. Under conditions similar to those on Titan at an altitude of 100 km (T = 100--150 degrees K, NCH4 approximately 10(18) cm-3), with a methane atmosphere containing 1% H2 and traces of NH3 and H2O, ion-molecule condensation reactions followed by H+ transfer are expected to lead to the atmospheric synthesis of C2H6, C3H8, CH3OH, C2H5OH and the terminal ions NH4+, CH3NH3+ and C2H5NH3+. At higher temperatures (250 degrees K smaller than T smaller than 400 degrees K), the synthesis of i-C4H10, i-C3H7OH and t-C4H9OH and of the ions i-C3H7NH3+ and t-C4H9NH3+ is also expected. Electron recombination of the terminal ions may yield amines, imines and nitriles. Cycles of protonation and dissociative recombination of the alkanes and alcohols produced in condensation reactions will also produce unsaturated hydrocarbons, ketones and aldehydes in the ionized atmosphere.

  3. Catalytic Routes for the Conversion of Biomass Derivatives to Hydrocarbons and/or Platform Chemicals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Silks, III, Louis A.

    Unprotected carbohydrates were reacted in amine-catalyzed cascade reactions with various methyl ketones to give a direct access to C-glycosides by an operationally simple protocol. As the reaction mechanism,an aldol condensation followed by an intramolecular conjugate addition is assumed.

  4. Reactivity of Free Malondialdehyde during In Vitro Simulated Gastrointestinal Digestion.

    PubMed

    Vandemoortele, Angelique; Babat, Pinar; Yakubu, Mariam; De Meulenaer, Bruno

    2017-03-15

    An aqueous buffer, a saturated glycerol triheptanoate oil, and a Tween 20 stabilized fully hydrogenated coconut oil-in-water emulsion, all spiked with malondialdehyde, were subjected to in vitro digestion. A dynamic equilibrium between malondialdehyde, its aldol self-condensation products, and its hydrolytic cleavage products was observed. This equilibrium depended upon the kind of sample and the temperature at which these samples were preincubated during 24 h. The presence of oil during gastric digestion protected the aldol self-condensation and cleavage products from conversion to malondialdehyde, which occurred in the aqueous acidic gastric chyme. In parallel, the presence of oil enhanced the reactivity of malondialdehyde throughout the gastrointestinal digestion process. Malondialdehyde recoveries after digestion varied between 42 and 90%, depending upon the model system studied, with the aldol self-condensation as the main reaction pathway. In conclusion, this study revealed that malondialdehyde is a very reactive molecule whose reactivity does not stop at the point of ingestion.

  5. Dynamic Kinetic Resolution Enabled by Intramolecular Benzoin Reaction: Synthetic Applications and Mechanistic Insights.

    PubMed

    Zhang, Guoxiang; Yang, Shuang; Zhang, Xiaoyan; Lin, Qiqiao; Das, Deb K; Liu, Jian; Fang, Xinqiang

    2016-06-29

    The highly enantio-, diastereo-, and regioselective dynamic kinetic resolution of β-ketoesters and 1,3-diketones was achieved via a chiral N-heterocyclic carbene catalyzed intramolecular cross-benzoin reaction. A variety of tetralone derivatives bearing two contiguous stereocenters and multiple functionalities were liberated in moderate to excellent yields and with high levels of stereoselectivity (>95% ee and >20:1 dr in most cases). In addition, the excellent regioselectivity control for aryl/alkyl 1,3-diketones, and the superior electronic differentiation of 1,3-diarylketones were highlighted. Moreover, a set of new mechanistic rationale that differs with the currently widely accepted understanding of intramolecular benzoin reactions was established to demonstrate the superior preference of benzoin over aldol transformation: (1) A coexistence of competitive aldol and benzoin reactions was detected, but a retro-aldol-irreversible benzoin process performs a vital role in the generation of predominant benzoin products. (2) The most essential role of an N-electron-withdrawing substituent in triazolium catalysts was revealed to be accelerating the rate of the benzoin transformation, rather than suppressing the aldol process through reducing the inherent basicity of the catalyst.

  6. Mining chemical reactions using neighborhood behavior and condensed graphs of reactions approaches.

    PubMed

    de Luca, Aurélie; Horvath, Dragos; Marcou, Gilles; Solov'ev, Vitaly; Varnek, Alexandre

    2012-09-24

    This work addresses the problem of similarity search and classification of chemical reactions using Neighborhood Behavior (NB) and Condensed Graphs of Reaction (CGR) approaches. The CGR formalism represents chemical reactions as a classical molecular graph with dynamic bonds, enabling descriptor calculations on this graph. Different types of the ISIDA fragment descriptors generated for CGRs in combination with two metrics--Tanimoto and Euclidean--were considered as chemical spaces, to serve for reaction dissimilarity scoring. The NB method has been used to select an optimal combination of descriptors which distinguish different types of chemical reactions in a database containing 8544 reactions of 9 classes. Relevance of NB analysis has been validated in generic (multiclass) similarity search and in clustering with Self-Organizing Maps (SOM). NB-compliant sets of descriptors were shown to display enhanced mapping propensities, allowing the construction of better Self-Organizing Maps and similarity searches (NB and classical similarity search criteria--AUC ROC--correlate at a level of 0.7). The analysis of the SOM clusters proved chemically meaningful CGR substructures representing specific reaction signatures.

  7. Environmentally friendly paint and varnish additives based on isobutyrate aldehyde condensation products

    NASA Astrophysics Data System (ADS)

    Guziałowska-Tic, Joanna; Jan Tic, Wilhelm

    2017-10-01

    The demand for exploitation of new plasticizers and coalescents to be used for production of water dispersion adhesives based on poli(vinyl acetate), turned to be recently of particular significance because the use of all kind of toxic phthalates was banned and certain restrictions were made to use glycol derivatives classified as volatile organic compounds. An alternative for toxic plasticizers used for production of adhesives is hydroxyester (HE-1) obtained from isobutanal during the process of aldol condensation under subsequent Cannizaro and Tischenko reactions. The paper presents selected results of ecotoxicological tests on the environmental impact of hydroxyester HE-1. It was found that the substance is biodegradable and has no negative impact on algae growth rate, however it may inhibit algae biomass growth. The results of Daphnia immobilization test shows that the substance is safe for the aquatic environment. Whereas, at higher concentrations, hydroxyester HE-1 may exhibit acute toxicity to rainbow trout.

  8. First observation of a mass independent isotopic fractionation in a condensation reaction

    NASA Technical Reports Server (NTRS)

    Thiemens, M. H.; Nelson, R.; Dong, Q. W.; Nuth, Joseph A., III

    1994-01-01

    Thiemens and Heidenreich (1983) first demonstrated that a chemically produced mass independent isotopic fractionation process could produce an isotopic composition which is identical to that observed in Allende inclusions. This raised the possibility that the meteoritic components could be produced by chemical, rather than nuclear processes. In order to develop a mechanistic model of the early solar system, it is important that relevant reactions be studied, particularly, those which may occur in the earliest condensation reactions. The isotopic results for isotopic fractionations associated with condensation processes are reported. A large mass independent isotopic fractionation is observed in one of the experiments.

  9. Heterogeneous catalysis in complex, condensed reaction media

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cantu, David C.; Wang, Yang-Gang; Yoon, Yeohoon

    Many reactions required for the upgrading of biomass into fuels and chemicals—hydrogenation, hydrodeoxygenation, hydrocracking—are ostensibly similar to those practiced in the upgrading of petroleum into fuels. But, repurposing hydroprocessing catalysts from refinery operations to treat bio-oil has proved to be unsatisfactory. New catalysts are needed because the composition of the biogenic reactants differs from that of petroleum-derived feedstocks (e.g. the low concentration of sulfur in cellulose-derived biomass precludes use of metal sulfide catalysts unless sulfur is added to the reaction stream). New processes are needed because bio-oils oligomerize rapidly, forming intractable coke and “gunk”, at temperatures so low that themore » desired upgrading reactions are impractically slow, and so low that the bio-oil upgrading must be handled as a condensed fluid. Ideally, the new catalysts and processes would exploit the properties of the multiple phases present in condensed bio-oil, notably the polarizability and structure of the fluid near a catalyst’s surface in the cybotactic region. The results of preliminary modeling of the cybotactic region of different catalyst surfaces in the hydrogenation of phenol suggest that Pd catalysts supported on hydrophilic surfaces are more active than catalysts based on lipophilic supports because the former serve to enhance the concentration of the phenol in the vicinity of the Pd. The effect stems from thermodynamics, not the rate of mass transport. This work was supported by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies Office. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.« less

  10. Mixtures of Charged Bosons Confined in Harmonic Traps and Bose-Einstein Condensation Mechanism for Low-Energy Nuclear Reactions and Transmutation Processes in Condensed Matters

    NASA Astrophysics Data System (ADS)

    Kim, Yeong E.; Zubarev, Alexander L.

    2006-02-01

    A mixture of two different species of positively charged bosons in harmonic traps is considered in the mean-field approximation. It is shown that depending on the ratio of parameters, the two components may coexist in same regions of space, in spite of the Coulomb repulsion between the two species. Application of this result is discussed for the generalization of the Bose-Einstein condensation mechanism for low-energy nuclear reaction (LENR) and transmutation processes in condensed matters. For the case of deutron-lithium (d + Li) LENR, the result indicates that (d + 6Li) reactions may dominate over (d + d) reactions in LENR experiments.

  11. Dicarboxylic acid anhydride condensation with compounds containing active methylene groups. 4: Some 4-nitrophthalic anhydride condensation reactions

    NASA Technical Reports Server (NTRS)

    Oskaja, V.; Rotberg, J.

    1985-01-01

    By 4-nitrophthalic anhydride condensation with acetoacetate in acetic anhydride and triethylamine solution with subsequent breakdown of the intermediate condensation product, 5-nitroindanedione-1,3 was obtained. A 4-nitrophthalic anhydride with acetic anhydride, according to reaction conditions, may yield two products: in the presence of potassium acetate and at high temperatures 4-(or 5-)-nitro-2-acetylbenzoic acid is formed: in the presence of triethylamine and at room temperature 5-( or 6-)-nitrophthalic acetic acid is isolated. A 4-nitrophthalic anhydride and malonic acid in pyridine solution according to temperature yield either 5-( or 6-)-nitrophthalic acetic acid or 4-(or 5-)-nitro-2-acetylbenzoic acid.

  12. Illustrating the Utility of X-Ray Crystallography for Structure Elucidation through a Tandem Aldol Condensation/Diels-Alder Reaction Sequence

    ERIC Educational Resources Information Center

    Hoang, Giang T.; Kubo, Tomohiro; Young, Victor G., Jr.; Kautzky, Jacob A.; Wissinger, Jane E.

    2015-01-01

    Two introductory organic chemistry laboratory experiments are described based on the Diels-Alder reaction of 2,3,4,5-tetraphenylcyclopentadienone, which is synthesized prior to or in a one-pot reaction, with styrene. Students are presented with three possible products, the "endo" and "exo" diastereomers and the decarbonylated…

  13. Low-energy electron-induced reactions in condensed matter

    NASA Astrophysics Data System (ADS)

    Arumainayagam, Christopher R.; Lee, Hsiao-Lu; Nelson, Rachel B.; Haines, David R.; Gunawardane, Richard P.

    2010-01-01

    The goal of this review is to discuss post-irradiation analysis of low-energy (≤50 eV) electron-induced processes in nanoscale thin films. Because electron-induced surface reactions in monolayer adsorbates have been extensively reviewed, we will instead focus on low-energy electron-induced reactions in multilayer adsorbates. The latter studies, involving nanoscale thin films, serve to elucidate the pivotal role that the low-energy electron-induced reactions play in high-energy radiation-induced chemical reactions in condensed matter. Although electron-stimulated desorption (ESD) experiments conducted during irradiation have yielded vital information relevant to primary or initial electron-induced processes, we wish to demonstrate in this review that analyzing the products following low-energy electron irradiation can provide new insights into radiation chemistry. This review presents studies of electron-induced reactions in nanoscale films of molecular species such as oxygen, nitrogen trifluoride, water, alkanes, alcohols, aldehydes, ketones, carboxylic acids, nitriles, halocarbons, alkane and phenyl thiols, thiophenes, ferrocene, amino acids, nucleotides, and DNA using post-irradiation techniques such as temperature-programmed desorption (TPD), reflection-absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS), gel electrophoresis, and microarray fluorescence. Post-irradiation temperature-programmed desorption, in particular, has been shown to be useful in identifying labile radiolysis products as demonstrated by the first identification of methoxymethanol as a reaction product of methanol radiolysis. Results of post-irradiation studies have been used not only to identify radiolysis products, but also to determine the dynamics of electron-induced reactions. For example, studies of the radiolysis yield as a function of incident electron energy have shown that dissociative

  14. Catalytic performance of Metal-Organic-Frameworks vs. extra-large pore zeolite UTL in condensation reactions

    PubMed Central

    Shamzhy, Mariya; Opanasenko, Maksym; Shvets, Oleksiy; Čejka, Jiří

    2013-01-01

    Catalytic behavior of isomorphously substituted B-, Al-, Ga-, and Fe-containing extra-large pore UTL zeolites was investigated in Knoevenagel condensation involving aldehydes, Pechmann condensation of 1-naphthol with ethylacetoacetate, and Prins reaction of β-pinene with formaldehyde and compared with large-pore aluminosilicate zeolite beta and representative Metal-Organic-Frameworks Cu3(BTC)2 and Fe(BTC). The yield of the target product over the investigated catalysts in Knoevenagel condensation increases in the following sequence: (Al)beta < (Al)UTL < (Ga)UTL < (Fe)UTL < Fe(BTC) < (B)UTL < Cu3(BTC)2 being mainly related to the improving selectivity with decreasing strength of active sites of the individual catalysts. The catalytic performance of Fe(BTC), containing the highest concentration of Lewis acid sites of the appropriate strength is superior over large-pore zeolite (Al)beta and B-, Al-, Ga-, Fe-substituted extra-large pore zeolites UTL in Prins reaction of β-pinene with formaldehyde and Pechmann condensation of 1-naphthol with ethylacetoacetate. PMID:24790940

  15. Asymmetric Aldol Additions: A Guided-Inquiry Laboratory Activity on Catalysis

    ERIC Educational Resources Information Center

    King, Jorge H. Torres; Wang, Hong; Yezierski, Ellen J.

    2018-01-01

    Despite the importance of asymmetric catalysis in both the pharmaceutical and commodity chemicals industries, asymmetric catalysis is under-represented in undergraduate chemistry laboratory curricula. A novel guided-inquiry experiment based on the asymmetric aldol addition was developed. Students conduct lab work to compare the effectiveness of…

  16. Comparison of sugar molecule decomposition through glucose and fructose: a high-level quantum chemical study.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Assary, R. S.; Curtiss, L. A.; MSD)

    Efficient chemical conversion of biomass is essential to produce sustainable energy and industrial chemicals. Industrial level conversion of glucose to useful chemicals, such as furfural, hydroxymethylfurfural, and levulinic acid, is a major step in the biomass conversion but is difficult because of the formation of undesired products and side reactions. To understand the molecular level reaction mechanisms involved in the decomposition of glucose and fructose, we have carried out high-level quantum chemical calculations [Gaussian-4 (G4) theory]. Selective 1,2-dehydration, keto-enol tautomerization, isomerization, retro-aldol condensation, and hydride shifts of glucose and fructose molecules were investigated. Detailed kinetic and thermodynamic analyses indicate that,more » for acyclic glucose and fructose molecules, the dehydration and isomerization require larger activation barriers compared to the retro-aldol reaction at 298 K in neutral medium. The retro-aldol reaction results in the formation of C2 and C4 species from glucose and C3 species from fructose. The formation of the most stable C3 species, dihydroxyacetone from fructose, is thermodynamically downhill. The 1,3-hydride shift leads to the cleavage of the C-C bond in the acyclic species; however, the enthalpy of activation is significantly higher (50-55 kcal/mol) than that of the retro-aldol reaction (38 kcal/mol) mainly because of the sterically hindered distorted four-membered transition state compared to the hexa-membered transition state in the retro-aldol reaction. Both tautomerization and dehydration are catalyzed by a water molecule in aqueous medium; however, water has little effect on the retro-aldol reaction. Isomerization of glucose to fructose and glyceraldehyde to dihydroxyacetone proceeds through hydride shifts that require an activation enthalpy of about 40 kcal/mol at 298 K in water medium. This investigation maps out accurate energetics of the decomposition of glucose and fructose

  17. Formation of C-C and C-O bonds and oxygen removal in reactions of alkanediols, alkanols, and alkanals on copper catalysts.

    PubMed

    Sad, María E; Neurock, Matthew; Iglesia, Enrique

    2011-12-21

    This study reports evidence for catalytic deoxygenation of alkanols, alkanals, and alkanediols on dispersed Cu clusters with minimal use of external H(2) and with the concurrent formation of new C-C and C-O bonds. These catalysts selectively remove O-atoms from these oxygenates as CO or CO(2) through decarbonylation or decarboxylation routes, respectively, that use C-atoms present within reactants or as H(2)O using H(2) added or formed in situ from CO/H(2)O mixtures via water-gas shift. Cu catalysts fully convert 1,3-propanediol to equilibrated propanol-propanal intermediates that subsequently form larger oxygenates via aldol-type condensation and esterification routes without detectable involvement of the oxide supports. Propanal-propanol-H(2) equilibration is mediated by their chemisorption and interconversion at surfaces via C-H and O-H activation and propoxide intermediates. The kinetic effects of H(2), propanal, and propanol pressures on turnover rates, taken together with measured selectivities and the established chemical events for base-catalyzed condensation and esterification reactions, indicate that both reactions involve kinetically relevant bimolecular steps in which propoxide species, acting as the base, abstract the α-hydrogen in adsorbed propanal (condensation) or attack the electrophilic C-atom at its carbonyl group (esterification). These weakly held basic alkoxides render Cu surfaces able to mediate C-C and C-O formation reactions typically catalyzed by basic sites inherent in the catalyst, instead of provided by coadsorbed organic moieties. Turnover rates for condensation and esterification reactions decrease with increasing Cu dispersion, because low-coordination corner and edge atoms prevalent on small clusters stabilize adsorbed intermediates and increase the activation barriers for the bimolecular kinetically relevant steps required for both reactions. © 2011 American Chemical Society

  18. Bioinspired synthesis of pentalene-based chromophores from an oligoketone chain.

    PubMed

    Saito, Yuki; Higuchi, Masayuki; Yoshioka, Shota; Senboku, Hisanori; Inokuma, Yasuhide

    2018-04-24

    We report a bioinspired synthesis of 2,5-dihydropentalene-based chromophores from an aliphatic oligoketone bearing 1,3- and 1,4-diketone subunits. Unlike the natural polyketone sequence, fused five-membered rings were formed via an intramolecular aldol condensation. A subsequent Knoevenagel condensation reaction with malononitrile furnished a multiply cross-conjugated π-system with low-lying LUMO levels. Furthermore, pentalenes obtained from a non-conjugated aliphatic chain exhibited visible absorption and solid-state fluorescence.

  19. [Development of boomerang-type intramolecular cascade reactions and application to natural product synthesis].

    PubMed

    Takasu, K

    2001-12-01

    Intramolecular cascade reaction has received much attention as a powerful methodology to construct a polycyclic framework in organic synthesis. We have been developing "boomerang-type cascade reaction" to construct a variety of polycyclic skeletons efficiently. In the above reactions, a nucleophilic function of substrates changes the character into an electrophile after the initial reaction, and the electrophilic group acts as a nucleophile in the second reaction. That is, the reaction center stepwise moves from one functional group back to the same one via other functional groups. The stream of the electron concerning the cascade reaction is like a locus of boomerang. We show here three different boomerang-type reactions via ionic species or free radicals. 1) Diastereoselective Michael-aldol reaction based on the chiral auxiliary method and enantioselective Michael-aldol reaction by the use of external chiral sources. 2) Short and efficient total syntheses of longifolane sesquiterpenes utilizing intramolecular double Michael addition as a key step. 3) Development of boomerang-type radical cascade reaction of halopolyenes to construct terpenoid skeletons and its regioselectivity.

  20. Identification and Characterization of Visible Absorption Components in Aqueous Methylglyoxal-Ammonium Sulfate Mixtures

    NASA Astrophysics Data System (ADS)

    McGivern, W. S.; Allison, T. C.; Radney, J. G.; Zangmeister, C. D.

    2014-12-01

    The aqueous reaction of methylglyoxal (MG) with ammonium sulfate has been suggested as a source of atmospheric ``brown carbon.'' We have utilized high-performance liquid chromatography coupled to ultraviolet-visible spectroscopy and tandem mass spectrometry to study the products of this reaction at high concentrations. The overall product spectrum shows a large number of distinct components; however, the visible absorption from this mixture is derived a very small number of components. The largest contributor is an imine-substituted (C=N-H) product of aldol condensation/facile dehydration reaction between the parent MG and a hydrated product of the MG + ammonia reaction. The asymmetric nature of this compound relative to the aldol condensation of two MG results in a sufficiently large redshift of the UV absorption spectrum that absorption of visible radiation can occur in the long-wavelength tail. The simplicity of the imine products is a result of a strong bias toward ketimine products due to the extensive hydration of the aldehydic moiety in the parent in aqueous solution. In addition, a strong pH dependence of the absorption cross section was observed with significantly greater absorption under more basic conditions. We have performed time-dependent density functional theory calculations to evaluate the absorption spectra of all of the possible condensation products and their respective ions, and the results are consistent with the experimental observations. We have also observed smaller concentrations of other condensation products of the imine-substituted parent species that do not contribute significantly to the visible absorption but have not been previously discussed.

  1. Alternative Interpretation of Low-Energy Nuclear Reaction Processes with Deuterated Metals Based on the Bose-Einstein Condensation Mechanism

    NASA Astrophysics Data System (ADS)

    Kim, Yeong E.; Passell, Thomas O.

    2006-02-01

    Recently, a generalization of the Bose-Einstein condensation (BEC) mechanism has been made to a ground-state mixture of two different species of positively charged bosons in harmonic traps. The theory has been used to describe (D + Li) reactions in the low energy nuclear reaction (LENR) processes in condensed matter and predicts that the (D + Li) reaction rates can be larger than (D + D) reaction rates by as much as a factor of ~50, implying that (D + Li) reactions may be occuring in addition to the (D + D) reactions. A survey of the existing data from LENR experiments is carried out to check the validity of the theoretical prediction. We conclude that there is compelling experimental evidence which support the theoretical prediction. New experimental tests of the theoretical prediction are suggested.

  2. Enantioselective Synthesis of α-Methylene-β-hydroxy Carboxylic Acid Derivatives via a Diastereoselective Aldol-β-Elimination Sequence: Application to the C(15)–C(21) Fragment of Tedanolide C

    PubMed Central

    Barth, Roland; Roush, William R.

    2010-01-01

    An enantioselective synthesis of α-methylene-β-hydroxy carboxylic acid derivatives via a highly diastereoselective, one-pot syn-aldol and β-elimination sequence utilizing the chiral β-(phenylselenyl)propionyl imide 15 is described. This new method, which constitutes an alternative to the Baylis-Hillman reaction, has been applied to the synthesis of the C(15)-C(21) fragment of tedanolide C. PMID:20405855

  3. Study of the techniques feasible for food synthesis aboard a spacecraft

    NASA Technical Reports Server (NTRS)

    Weiss, A. H.

    1972-01-01

    Synthesis of sugars by Ca(OH)2 catalyzed formaldehyde condensation (the formose reaction) has produced branched carbohydrates that do not occur in nature. The kinetics and mechanisms of the homogeneously catalyzed autocatalytic condensation were studied and analogies between homogeneous and heterogeneous rate laws have been found. Aldol condensations proceed simultaneously with Cannizzaro and crossed-Cannizzaro reactions and Lobry de Bruyn-Van Eckenstein rearrangements. The separate steps as well as the interactions of this highly complex reaction system were elucidated. The system exhibits instabilities, competitive catalytic, mass action, and equilibrium phenomena, complexing, and parallel and consecutive reactions. Specific finding that have been made on the problem will be of interest for synthesizing sugars, both for sustained space flight and for large scale food manufacture. A contribution to methodology for studying complex catalyzed reactions and to understanding control of reaction selectivity was a broad goal of the project.

  4. QM/MM studies of the mechanism of unusual bifunctional fructose-1,6-bisphosphate aldolase/phosphatase.

    PubMed

    Hou, Qianqian; Sheng, Xiang; Liu, Yongjun

    2014-06-21

    Archaeal fructose-1,6-bisphosphate aldolase/phosphatase (FBPA/P) is a newly identified unusual bifunctional enzyme (Nature, 2010, 464, 1077), which contains one single catalytic domain but catalyzes two chemically distinct reactions of gluconeogenesis. It is different from the ordinary enzymes whose active sites are responsible for a specific reaction. To explore the catalytic characteristic of FBPA/P, the aldol condensation mechanism of bifunctional FBPA/P has been investigated using quantum mechanics/molecular mechanics (QM/MM) method. The whole reaction process can be divided into two half-reactions involving seven elementary steps. A Schiff base intermediate is theoretically confirmed, agreeing well with the recently resolved crystal structures (Nature, 2011, 478, 538). The free energy barrier of the rate-limiting step is calculated to be 22.2 kcal mol(-1), which is a concerted process of a nucleophilic attack by the enolic carbon to the ketonic carbon and a proton transfer from Tyr229 to the ketonic oxygen. Lys232 plays an important role in forming a Schiff base intermediate with the substrate (DHAP). Tyr229 functions as a proton shuttle during the catalysis. This is the first theoretical study on the aldol condensation mechanism of FBPA/P, which may provide useful information for understanding bifunctional enzymes.

  5. Oxidative condensation reactions of (diethylenetriamine)cobalt(III) complexes with substituted bis(pyridin-2-yl)methane ligands

    NASA Astrophysics Data System (ADS)

    Zhou, Xiangting; Hockless, David C. R.; Willis, Anthony C.; Jackson, W. Gregory

    2005-04-01

    The synthesis and characterisation of Co(III) complexes derived from a condensation reaction with a central or terminal nitrogen of a dien ligand and the α-carbon of a range of substituted bis(pyridin-2-yl)methane ligands are described. Aerial oxidation of bpm {bis(pyridin-2-yl)methane with Co(II)/dien or direct reaction with Co(dien)Cl 3 provided in low yield a single C-N condensation product 1 (at the primary terminal NH 2) after the pyridyl -CH 2- is formally oxidised to -CH +-. The methyl substituted ligand bpe {1,1-bis(pyridin-2-yl)ethane} behaves likewise, except both terminal (prim) and central (sec) amines condense to yield isomeric products 2 and 3. Two of these three materials have been characterised by single crystal X-ray crystallography. The corresponding reactions for the bis(pyridyl) ligand bpk {bis(pyridin-2-yl)ketone} provided C-N condensation products without the requirement for oxidation at the α-C center; two carbinolamine complexes in different geometrical configurations resulted, mer-anti-[Co(dienbpc)Cl]ZnCl 4, 5, and unsym- fac-[Co(dienbpc)Cl]ZnCl 4, 6, {dienbpc=[2-(2-aminoethylamino)-ethylamino]-di-pyridin-2-yl-methanol}. In addition, a novel complex, [Co(bpk)(bpd-OH)Cl]ZnCl 4, 4, in which one bidentate N, N-bonded bpk ligand and one tridentate N, O, N-bonded bpd (the diol from bpk+OH -) were coordinated, was obtained via the Co(II)/O 2 synthetic route. When the bpc ligand (bpc=bis(pyridin-2-yl)methanol) was employed directly as a reagent along with dien, no condensation reactions were observed, but rather a single isomeric complex [Co(dien)(bpc)]Cl.ZnCl 4, 7, in which the ligand bpc acted as a N,N,O-bonded tridentate ligand rather than as a N,N-bidentate ligand was isolated. 13C, 1D and 2D 1H NMR studies are reported for all the complexes; they establish the structures unambiguously.

  6. Ultrasound-assisted synthesis of curcumin analogs promoted by activated chicken eggshells

    NASA Astrophysics Data System (ADS)

    Mardiana, L.; Ardiansah, B.; Septiarti, A.; Bakri, R.; Kosamagi, G.

    2017-07-01

    Curcumin has been widely known as a multifunctional natural product which has many biological activities. However, the biggest limitation for the large scale application of curcumin is its poor bioavailability. This research presented a cheap, mild and efficient solvent-free synthesis of monocarbonyl analogs of curcumin via Aldol condensation using activated chicken eggshells (ACE). Dibenzalpropanone as a product of Aldol condensation was prepared by mixing benzaldehyde and acetone using a simple glass tube in the presence of ACE under ultrasound irradiation (78 % yield), while dibenzalcyclohexanone was produced from the reaction of benzaldehyde with cyclohenxanone (81 %). The products have been characterized by FTIR, UV-Vis spectrophotometer and GC-MS instruments. The FTIR spectra show a significant absorption of carbonyl group that attached to the double bond in α,β-position at 1630-1660 cm-1. The molecular cation of m/z of 234 and 274 is in agreement with the products structures.

  7. Studies of Azetidin-2-one as a Reactive Enolate Synthon of β-Alanine for Condensations with Aldehydes and Ketones.

    PubMed

    Williams, David R; Donnell, Andrew F; Kammler, David C; Ward, Sarah A; Taylor, Levin

    2016-11-04

    Studies describe formation of the lithium enolate of N-(4-methoxybenzyloxy)azetidin-2-one (1) and characterization of representative aldol reactions with aldehydes and ketones. Diastereoselectivity features the production of anti-aldol adducts from α,β-unsaturated ketones and α-branched aliphatic aldehydes. The stereoselectivity is rationalized via closed, six-membered transition-state arrangements leading to the formation of Felkin-Anh and anti-Felkin products. Examples illustrate the direct incorporation of monocyclic β-lactams into a variety of molecular architectures. The utility of 1 as an enolate synthon of homoglycine (β-alanine) is illustrated by the efficient synthesis of novel β-amino acid derivatives, including complex 4-hydroxy-2-pyridinones.

  8. Aqueous phase hydrodeoxygenation of polyols over Pd/WO3-ZrO2: Role of Pd-WO3 interaction and hydrodeoxygenation pathway

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Changjun; Sun, Junming; Brown, Heather M.

    Aqueous-phase hydrodeoxygenation of sugar and sugar-derived molecules can be used to produce a range of alkanes and oxygenates. In this paper, we have identified the reaction intermediates and reaction chemistry for the aqueous-phase hydrodeoxygenation of sorbitol over a bifunctional catalyst (Pt/SiO2–Al2O3) that contains both metal (Pt) and acid (SiO2–Al2O3) sites. A wide variety of reactions occur in this process including Csingle bondC bond cleavage, Csingle bondO bond cleavage, and hydrogenation reactions. The key Csingle bondC bond cleavage reactions include: retro-aldol condensation and decarbonylation, which both occur on metal catalytic sites. Dehydration is the key Csingle bondO bond cleavage reaction andmore » occurs on acid catalytic sites. Sorbitol initially undergoes dehydration and ring closure to produce cyclic C6 molecules or retro-aldol condensation reactions to produce primarily C3 polyols. Isosorbide is the major final product from sorbitol dehydration. Isosorbide then undergoes ring opening hydrogenation reactions and a dehydration/hydrogenation step to form 1,2,6-hexanetriol. The hexanetriol is then converted into hexanol and hexane by dehydration/hydrogenation. Smaller oxygenates are produced by Csingle bondC bond cleavage. These smaller oxygenates undergo dehydration/hydrogenation reactions to produce alkanes from C1–C5. The results from this paper suggest that hydrodeoxygenation chemistry can be tuned to make a wide variety of products from biomass-derived oxygenates.« less

  9. Highly efficient and recyclable basic mesoporous zeolite catalyzed condensation, hydroxylation, and cycloaddition reactions.

    PubMed

    Sarmah, Bhaskar; Satpati, Biswarup; Srivastava, Rajendra

    2017-05-01

    Crystalline mesoporous ZSM-5 zeolite was prepared in the presence of 1,4-diazabicyclo[2.2.2]octane derived multi-cationic structure directing agent. The calcined form of the mesoprous zeolite was treated with NH 4 OH to obtain basic mesoporous ZSM-5. Catalyst was characterized by the complementary combination of X-ray diffraction, N 2 -adsorption, electron microscopes, and temperature programme desorption techniques. Catalytic activity of the basic mesoporous ZSM-5 was systematically assessed using Knoevenagel condensation reaction for the synthesis a wide range of substituted styrene. Applications of the catalyst were investigated in the benzamide hydroxylation for the synthesis of carbinolamides and one-pot, multi-component condensation reaction for the synthesis of naphthopyrans. Finally, the catalyst was evaluated in the cycloaddition of CO 2 to epoxide for the synthesis of cyclic carbonates. Recycling study shows that no significant decrease in the catalytic activity was observed after five recycles. Copyright © 2017. Published by Elsevier Inc.

  10. Probing the Rate-Determining Step of the Claisen-Schmidt Condensation by Competition Reactions

    ERIC Educational Resources Information Center

    Mak, Kendrew K. W.; Chan, Wing-Fat; Lung, Ka-Ying; Lam, Wai-Yee; Ng, Weng-Cheong; Lee, Siu-Fung

    2007-01-01

    Competition experiments are a useful tool for preliminary study of the linear free energy relationship of organic reactions. This article describes a physical organic experiment for upper-level undergraduates to identify the rate-determining step of the Claisen-Schmidt condensation of benzaldehyde and acetophenone by studying the linear free…

  11. Free energy landscape for glucose condensation and dehydration reactions in dimethyl sulfoxide and the effects of solvent.

    PubMed

    Qian, Xianghong; Liu, Dajiang

    2014-03-31

    The mechanisms and free energy surfaces (FES) for the initial critical steps during proton-catalyzed glucose condensation and dehydration reactions were elucidated in dimethyl sulfoxide (DMSO) using Car-Parrinello molecular dynamics (CPMD) coupled with metadynamics (MTD) simulations. Glucose condensation reaction is initiated by protonation of C1--OH whereas dehydration reaction is initiated by protonation of C2--OH. The mechanisms in DMSO are similar to those in aqueous solution. The DMSO molecules closest to the C1--OH or C2--OH on glucose are directly involved in the reactions and act as proton acceptors during the process. However, the energy barriers are strongly solvent dependent. Moreover, polarization from the long-range electrostatic interaction affects the mechanisms and energetics of glucose reactions. Experimental measurements conducted in various DMSO/Water mixtures also show that energy barriers are solvent dependent in agreement with our theoretical results. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Fe3O4@MOF core-shell magnetic microspheres as excellent catalysts for the Claisen-Schmidt condensation reaction

    NASA Astrophysics Data System (ADS)

    Ke, Fei; Qiu, Ling-Guang; Zhu, Junfa

    2014-01-01

    Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this work, we present a facile fabrication and characterization of a novel type of MOF-based porous catalyst, namely, Fe3O4@MIL-100(Fe) core-shell magnetic microspheres. It has been shown that these catalysts not only exhibit high catalytic activities for the Claisen-Schmidt condensation reactions under environmentally friendly conditions, but remarkably, they can be easily separated and recycled without significant loss of catalytic efficiency after being used for many times. Therefore, compared to other reported catalysts used in the Claisen-Schmidt condensation reactions, these catalysts are green, cheap and more suitable for large scale industrial applications.Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this work, we present a facile fabrication and characterization of a novel type of MOF-based porous catalyst, namely, Fe3O4@MIL-100(Fe) core-shell magnetic microspheres. It has been shown that these catalysts not only exhibit high catalytic activities for the Claisen-Schmidt condensation reactions under environmentally friendly conditions, but remarkably, they can be easily separated and recycled without significant loss of catalytic efficiency after being used for many times. Therefore, compared to other reported catalysts used in the Claisen-Schmidt condensation reactions, these catalysts are green, cheap and more suitable for large scale industrial applications. Electronic supplementary information (ESI) available: SEM and TEM images, and GC-MS spectra for chalcones. See DOI: 10.1039/c3nr05051c

  13. Condensation Reactions and Formation of Amides, Esters, and Nitriles Under Hydrothermal Conditions

    NASA Astrophysics Data System (ADS)

    Rushdi, Ahmed I.; Simoneit, Bernd R. T.

    2004-06-01

    Hydrothermal pyrolysis experiments were performed to assess condensation (dehydration) reactions to amide, ester, and nitrile functionalities from lipid precursors. Beside product formation, organic compound alteration and stability were also evaluated. Mixtures of nonadecanoic acid, hexadecanedioic acid, or hexadecanamide with water, ammonium bicarbonate, and oxalic acid were heated at 300°C for 72 h. In addition, mixtures of ammonium bicarbonate and oxalic acid solutions were used to test the abiotic formation of organic nitrogen compounds at the same temperature. The resulting products were condensation compounds such as amides, nitriles, and minor quantities of N-methylalkyl amides, alkanols, and esters. Mixtures of alkyl amide in water or oxalic acid yielded mainly hydrolysis and dehydration products, and with ammonium bicarbonate and oxalic acid the yield of condensation products was enhanced. The synthesis experiments with oxalic acid and ammonium bicarbonate solutions yielded homologous series of alkyl amides, alkyl amines, alkanes, and alkanoic acids, all with no carbon number predominances. These organic nitrogen compounds are stable and survive under the elevated temperatures of hydrothermal fluids.

  14. Hydrolysis condensation reactions of titanium alkoxides in thin films: A study of the steric hindrance effect by X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Barlier, Vincent; Bounor-Legaré, Véronique; Boiteux, Gisèle; Davenas, Joël; Léonard, Didier

    2008-06-01

    An original approach based on X-ray photoelectron spectroscopy (XPS) is proposed to study the influence of the surrounding humidity on the hydrolysis-condensation reactions of five titanium alkoxides in thin films. More precisely, the influence of the nature of the ligands (propoxide, butoxide, isopropoxide, phenoxide, and 9H-carbazole-9-yl-ethyl-oxy) on the reaction rate was evidenced. The reaction advancement was evaluated by comparing XPS chemical compositions to theoretical compositions calculated for all the possible rates. XPS chemical environment information allowed validating the reliability of this approach through the evaluation of the condensation state. In both approaches, the influence of the steric hindrance on the reactivity of titanium alkoxides was highlighted to be similar to what has been previously observed in solution. Theses results corroborate the validity of our XPS approach to determine titanium alkoxide hydrolysis-condensation reactions in the specific application of thin films.

  15. Synthesis of jet fuel range branched cycloalkanes with mesityl oxide and 2-methylfuran from lignocellulose

    NASA Astrophysics Data System (ADS)

    Li, Shanshan; Li, Ning; Wang, Wentao; Li, Lin; Wang, Aiqin; Wang, Xiaodong; Zhang, Tao

    2016-09-01

    Jet fuel range branched cycloalkanes with high density (0.82 g mL-1) and low freezing point (217-219 K) was first prepared by the solvent-free intramolecular aldol condensation of the trione from the hydrolysis of the alkylation product of mesityl oxide and 2-methylfuran (or the one-pot reaction of mesityl oxide, 2-methylfuran and water), followed by hydrodeoxygenation (HDO).

  16. Synthesis of jet fuel range branched cycloalkanes with mesityl oxide and 2-methylfuran from lignocellulose.

    PubMed

    Li, Shanshan; Li, Ning; Wang, Wentao; Li, Lin; Wang, Aiqin; Wang, Xiaodong; Zhang, Tao

    2016-09-01

    Jet fuel range branched cycloalkanes with high density (0.82 g mL(-1)) and low freezing point (217-219 K) was first prepared by the solvent-free intramolecular aldol condensation of the trione from the hydrolysis of the alkylation product of mesityl oxide and 2-methylfuran (or the one-pot reaction of mesityl oxide, 2-methylfuran and water), followed by hydrodeoxygenation (HDO).

  17. Reaction mechanism of recombinant 3-oxoacyl-(acyl-carrier-protein) synthase III from Cuphea wrightii embryo, a fatty acid synthase type II condensing enzyme.

    PubMed

    Abbadi, A; Brummel, M; Schütt, B S; Slabaugh, M B; Schuch, R; Spener, F

    2000-01-01

    A unique feature of fatty acid synthase (FAS) type II of higher plants and bacteria is 3-oxoacyl-[acyl-carrier-protein (ACP)] synthase III (KAS III), which catalyses the committing condensing reaction. Working with KAS IIIs from Cuphea seeds we obtained kinetic evidence that KAS III catalysis follows a Ping-Pong mechanism and that these enzymes have substrate-binding sites for acetyl-CoA and malonyl-ACP. It was the aim of the present study to identify these binding sites and to elucidate the catalytic mechanism of recombinant Cuphea wrightii KAS III, which we expressed in Escherichia coli. We engineered mutants, which allowed us to dissect the condensing reaction into three stages, i.e. formation of acyl-enzyme, decarboxylation of malonyl-ACP, and final Claisen condensation. Incubation of recombinant enzyme with [1-(14)C]acetyl-CoA-labelled Cys(111), and the replacement of this residue by Ala and Ser resulted in loss of overall condensing activity. The Cys(111)Ser mutant, however, still was able to bind acetyl-CoA and to catalyse subsequent binding and decarboxylation of malonyl-ACP to acetyl-ACP. We replaced His(261) with Ala and Arg and found that the former lost activity, whereas the latter retained overall condensing activity, which indicated a general-base action of His(261). Double mutants Cys(111)Ser/His(261)Ala and Cys(111)Ser/His(261)Arg were not able to catalyse overall condensation, but the double mutant containing Arg induced decarboxylation of [2-(14)C]malonyl-ACP, a reaction indicating the role of His(261) in general-acid catalysis. Finally, alanine scanning revealed the involvement of Arg(150) and Arg(306) in KAS III catalysis. The results offer for the first time a detailed mechanism for a condensing reaction catalysed by a FAS type II condensing enzyme.

  18. Reaction mechanism of recombinant 3-oxoacyl-(acyl-carrier-protein) synthase III from Cuphea wrightii embryo, a fatty acid synthase type II condensing enzyme.

    PubMed Central

    Abbadi, A; Brummel, M; Schütt, B S; Slabaugh, M B; Schuch, R; Spener, F

    2000-01-01

    A unique feature of fatty acid synthase (FAS) type II of higher plants and bacteria is 3-oxoacyl-[acyl-carrier-protein (ACP)] synthase III (KAS III), which catalyses the committing condensing reaction. Working with KAS IIIs from Cuphea seeds we obtained kinetic evidence that KAS III catalysis follows a Ping-Pong mechanism and that these enzymes have substrate-binding sites for acetyl-CoA and malonyl-ACP. It was the aim of the present study to identify these binding sites and to elucidate the catalytic mechanism of recombinant Cuphea wrightii KAS III, which we expressed in Escherichia coli. We engineered mutants, which allowed us to dissect the condensing reaction into three stages, i.e. formation of acyl-enzyme, decarboxylation of malonyl-ACP, and final Claisen condensation. Incubation of recombinant enzyme with [1-(14)C]acetyl-CoA-labelled Cys(111), and the replacement of this residue by Ala and Ser resulted in loss of overall condensing activity. The Cys(111)Ser mutant, however, still was able to bind acetyl-CoA and to catalyse subsequent binding and decarboxylation of malonyl-ACP to acetyl-ACP. We replaced His(261) with Ala and Arg and found that the former lost activity, whereas the latter retained overall condensing activity, which indicated a general-base action of His(261). Double mutants Cys(111)Ser/His(261)Ala and Cys(111)Ser/His(261)Arg were not able to catalyse overall condensation, but the double mutant containing Arg induced decarboxylation of [2-(14)C]malonyl-ACP, a reaction indicating the role of His(261) in general-acid catalysis. Finally, alanine scanning revealed the involvement of Arg(150) and Arg(306) in KAS III catalysis. The results offer for the first time a detailed mechanism for a condensing reaction catalysed by a FAS type II condensing enzyme. PMID:10600651

  19. Assessment of tautomer distribution using the condensed reaction graph approach

    NASA Astrophysics Data System (ADS)

    Gimadiev, T. R.; Madzhidov, T. I.; Nugmanov, R. I.; Baskin, I. I.; Antipin, I. S.; Varnek, A.

    2018-03-01

    We report the first direct QSPR modeling of equilibrium constants of tautomeric transformations (logK T ) in different solvents and at different temperatures, which do not require intermediate assessment of acidity (basicity) constants for all tautomeric forms. The key step of the modeling consisted in the merging of two tautomers in one sole molecular graph ("condensed reaction graph") which enables to compute molecular descriptors characterizing entire equilibrium. The support vector regression method was used to build the models. The training set consisted of 785 transformations belonging to 11 types of tautomeric reactions with equilibrium constants measured in different solvents and at different temperatures. The models obtained perform well both in cross-validation (Q2 = 0.81 RMSE = 0.7 logK T units) and on two external test sets. Benchmarking studies demonstrate that our models outperform results obtained with DFT B3LYP/6-311 ++ G(d,p) and ChemAxon Tautomerizer applicable only in water at room temperature.

  20. Catalytic processing of lactic acid over Pt/Nb(2)O(5).

    PubMed

    Serrano-Ruiz, Juan Carlos; Dumesic, James A

    2009-01-01

    Dilute aqueous solutions of lactic acid (30 %wt.) can be catalytically processed at 573 K and 57 bar over a low-metal-content Pt(0.1 %)/Nb(2)O(5) catalyst in a spontaneously separating organic phase rich in valuable products such as C(4)-C(7) ketones. An increase in the lactic acid concentration to 60 wt % allows conversion of approximately 50 % of the carbon feed in this organic layer, while maintaining good stability of the catalyst. Experiments at low conversion showed that lactic acid reacts first over Pt(0.1 %)/Nb(2)O(5) to produce acetaldehyde and propanoic acid (along with CO and CO(2) in the gas phase). These compounds (less oxygenated than lactic acid but still reactive) are the key intermediates in the overall process, and they react differently depending on the nature of the catalyst support. In particular, reaction kinetics studies with propanoic acid as feed showed that Pt(0.1 %)/Nb(2)O(5) favored the formation of pentanones by ketonization reactions, whereas a monofunctional Pt(0.1 %)/carbon catalyst produced ethane and CO(x) by decomposition reactions. In the same manner, acetaldehyde was preferentially hydrogenated to ethanol over Pt(0.1 %)/carbon, whereas the presence of niobia allowed this intermediate to react (by successive aldol condensations) to form C(4)-C(7) condensation products stored in the organic phase. Finally, reaction pathways are proposed to explain the catalytic processing of lactic acid over bifunctional Pt(0.1 %)/Nb(2)O(5). In this scheme, metal sites catalyze hydrogenation reactions and niobia promotes C--C coupling processes (ketonization and aldol condensation), in contrast to C--C cleavage reactions which take place preferentially over Pt(0.1 %)/carbon and lead to loss of carbon in the gas effluent as CO, CO(2), and methane.

  1. Possible mechanism of structural incorporation of Al into diatomite during the deposition process I. Via a condensation reaction of hydroxyl groups.

    PubMed

    Liu, Dong; Yu, Wenbin; Deng, Liangliang; Yuan, Weiwei; Ma, Lingya; Yuan, Peng; Du, Peixin; He, Hongping

    2016-01-01

    The structural incorporation of aluminium (Al) into diatomite is investigated by preparing several Al-diatomite composites by loading an Al precursor, hydroxyl aluminum polymer (Al13), onto the surface of diatomite and heating at various temperatures. The results indicate that Al was incorporated and implanted into the structure of diatomite by the condensation reaction of the hydroxyl groups of Al13 and diatomite, and the Si-O-Al(OH) groups were formed during the condensation reaction. Al incorporation by the condensation reaction of hydroxyl groups of Al13 with single silanols of diatomite occurred more readily than that with geminal silanols. The Al incorporation increased solid acidity of diatomite after Al incorporation. The acidity improvement was various for different types of acid sites, depending on the preparation temperature of the Al-incorporated diatomite. Both Brønsted and Lewis acid sites increased greatly after heating at 250 and 350 °C, but only L acid sites significantly improved after heating at 500 °C. These results demonstrate that the structural incorporation of Al(3+) ions into diatomite can occur by the condensation reaction of the hydroxyl groups of the Al precursors and diatomite. Moreover, the rich solid acid sites of Al-incorporated diatomite show its promising application as a solid acid catalyst. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Plant polyketide synthases: a chalcone synthase-type enzyme which performs a condensation reaction with methylmalonyl-CoA in the biosynthesis of C-methylated chalcones.

    PubMed

    Schröder, J; Raiber, S; Berger, T; Schmidt, A; Schmidt, J; Soares-Sello, A M; Bardshiri, E; Strack, D; Simpson, T J; Veit, M; Schröder, G

    1998-06-09

    Heterologous screening of a cDNA library from Pinusstrobus seedlings identified clones for two chalcone synthase (CHS) related proteins (PStrCHS1 and PStrCHS2, 87.6% identity). Heterologous expression in Escherichia coli showed that PStrCHS1 performed the typical CHS reaction, that it used starter CoA-esters from the phenylpropanoid pathway, and that it performed three condensation reactions with malonyl-CoA, followed by the ring closure to the chalcone. PstrCHS2 was completely inactive with these starters and also with linear CoA-esters. Activity was detected only with a diketide derivative (N-acetylcysteamine thioester of 3-oxo-5-phenylpent-4-enoic acid) that corresponded to the CHS reaction intermediate postulated after the first condensation reaction. PstrCHS2 performed only one condensation, with 6-styryl-4-hydroxy-2-pyrone derivatives as release products. The enzyme preferred methylmalonyl-CoA against malonyl-CoA, if only methylmalonyl-CoA was available. These properties and a comparison with the CHS from Pinus sylvestris suggested for PstrCHS2 a special function in the biosynthesis of secondary products. In contrast to P. sylvestris, P. strobus contains C-methylated chalcone derivatives, and the methyl group is at the position predicted from a chain extension with methylmalonyl-CoA in the second condensation of the biosynthetic reaction sequence. We propose that PstrCHS2 specifically contributes the condensing reaction with methylmalonyl-CoA to yield a methylated triketide intermediate. We discuss a model that the biosynthesis of C-methylated chalcones represents the simplest example of a modular polyketide synthase.

  3. Synthesis of jet fuel range branched cycloalkanes with mesityl oxide and 2-methylfuran from lignocellulose

    PubMed Central

    Li, Shanshan; Li, Ning; Wang, Wentao; Li, Lin; Wang, Aiqin; Wang, Xiaodong; Zhang, Tao

    2016-01-01

    Jet fuel range branched cycloalkanes with high density (0.82 g mL−1) and low freezing point (217–219 K) was first prepared by the solvent-free intramolecular aldol condensation of the trione from the hydrolysis of the alkylation product of mesityl oxide and 2-methylfuran (or the one-pot reaction of mesityl oxide, 2-methylfuran and water), followed by hydrodeoxygenation (HDO). PMID:27582417

  4. Mesoporous TiO2 Yolk-Shell Microspheres for Dye-sensitized Solar Cells with a High Efficiency Exceeding 11%

    PubMed Central

    Li, Zhao-Qian; Chen, Wang-Chao; Guo, Fu-Ling; Mo, Li-E; Hu, Lin-Hua; Dai, Song-Yuan

    2015-01-01

    Yolk-shell TiO2 microspheres were synthesized via a one-pot template-free solvothermal method building on the aldol condensation reaction of acetylacetone. This unique structure shows superior light scattering ability resulting in power conversion efficiency as high as 11%. This work provided a new synthesis system for TiO2 microspheres from solid to hollow and a novel material platform for high performance solar cells. PMID:26384004

  5. Toward a reaction rate model of condensed-phase RDX decomposition under high temperatures

    NASA Astrophysics Data System (ADS)

    Schweigert, Igor

    2015-06-01

    Shock ignition of energetic molecular solids is driven by microstructural heterogeneities, at which even moderate stresses can result in sufficiently high temperatures to initiate material decomposition and chemical energy release. Mesoscale modeling of these ``hot spots'' requires a reaction rate model that describes the energy release with a sub-microsecond resolution and under a wide range of temperatures. No such model is available even for well-studied energetic materials such as RDX. In this presentation, I will describe an ongoing effort to develop a reaction rate model of condensed-phase RDX decomposition under high temperatures using first-principles molecular dynamics, transition-state theory, and reaction network analysis. This work was supported by the Naval Research Laboratory, by the Office of Naval Research, and by the DoD High Performance Computing Modernization Program Software Application Institute for Multiscale Reactive Modeling of Insensitive Munitions.

  6. Tunable catalytic properties of bi-functional mixed oxides in ethanol conversion to high value compounds

    DOE PAGES

    Ramasamy, Karthikeyan K.; Gray, Michel; Job, Heather; ...

    2016-02-03

    Here, a highly versatile ethanol conversion process to selectively generate high value compounds is presented here. By changing the reaction temperature, ethanol can be selectively converted to >C 2 alcohols/oxygenates or phenolic compounds over hydrotalcite derived bi-functional MgO–Al 2O 3 catalyst via complex cascade mechanism. Reaction temperature plays a role in whether aldol condensation or the acetone formation is the path taken in changing the product composition. This article contains the catalytic activity comparison between the mono-functional and physical mixture counterpart to the hydrotalcite derived mixed oxides and the detailed discussion on the reaction mechanisms.

  7. Nonenzymatic gluconeogenesis-like formation of fructose 1,6-bisphosphate in ice.

    PubMed

    Messner, Christoph B; Driscoll, Paul C; Piedrafita, Gabriel; De Volder, Michael F L; Ralser, Markus

    2017-07-11

    The evolutionary origins of metabolism, in particular the emergence of the sugar phosphates that constitute glycolysis, the pentose phosphate pathway, and the RNA and DNA backbone, are largely unknown. In cells, a major source of glucose and the large sugar phosphates is gluconeogenesis. This ancient anabolic pathway (re-)builds carbon bonds as cleaved in glycolysis in an aldol condensation of the unstable catabolites glyceraldehyde 3-phosphate and dihydroxyacetone phosphate, forming the much more stable fructose 1,6-bisphosphate. We here report the discovery of a nonenzymatic counterpart to this reaction. The in-ice nonenzymatic aldol addition leads to the continuous accumulation of fructose 1,6-bisphosphate in a permanently frozen solution as followed over months. Moreover, the in-ice reaction is accelerated by simple amino acids, in particular glycine and lysine. Revealing that gluconeogenesis may be of nonenzymatic origin, our results shed light on how glucose anabolism could have emerged in early life forms. Furthermore, the amino acid acceleration of a key cellular anabolic reaction may indicate a link between prebiotic chemistry and the nature of the first metabolic enzymes.

  8. Low-temperature Condensation of Carbon

    NASA Astrophysics Data System (ADS)

    Krasnokutski, S. A.; Goulart, M.; Gordon, E. B.; Ritsch, A.; Jäger, C.; Rastogi, M.; Salvenmoser, W.; Henning, Th.; Scheier, P.

    2017-10-01

    Two different types of experiments were performed. In the first experiment, we studied the low-temperature condensation of vaporized graphite inside bulk liquid helium, while in the second experiment, we studied the condensation of single carbon atoms together with H2, H2O, and CO molecules inside helium nanodroplets. The condensation of vaporized graphite leads to the formation of partially graphitized carbon, which indicates high temperatures, supposedly higher than 1000°C, during condensation. Possible underlying processes responsible for the instant rise in temperature during condensation are discussed. This suggests that such processes cause the presence of partially graphitized carbon dust formed by low-temperature condensation in the diffuse interstellar medium. Alternatively, in the denser regions of the ISM, the condensation of carbon atoms together with the most abundant interstellar molecules (H2, H2O, and CO), leads to the formation of complex organic molecules (COMs) and finally organic polymers. Water molecules were found not to be involved directly in the reaction network leading to the formation of COMs. It was proposed that COMs are formed via the addition of carbon atoms to H2 and CO molecules ({{C}}+{{{H}}}2\\to {HCH},{HCH}+{CO}\\to {{OCCH}}2). Due to the involvement of molecular hydrogen, the formation of COMs by carbon addition reactions should be more efficient at high extinctions compared with the previously proposed reaction scheme with atomic hydrogen.

  9. Toward a reaction rate model of condensed-phase RDX decomposition under high temperatures

    NASA Astrophysics Data System (ADS)

    Schweigert, Igor

    2014-03-01

    Shock ignition of energetic molecular solids is driven by microstructural heterogeneities, at which even moderate stresses can result in sufficiently high temperatures to initiate material decomposition and the release of the chemical energy. Mesoscale modeling of these ``hot spots'' requires a chemical reaction rate model that describes the energy release with a sub-microsecond resolution and under a wide range of temperatures. No such model is available even for well-studied energetic materials such as RDX. In this presentation, I will describe an ongoing effort to develop a reaction rate model of condensed-phase RDX decomposition under high temperatures using first-principles molecular dynamics, transition-state theory, and reaction network analysis. This work was supported by the Naval Research Laboratory, by the Office of Naval Research, and by the DOD High Performance Computing Modernization Program Software Application Institute for Multiscale Reactive Modeling of Insensitive Munitions.

  10. POLLUTION PREVENTION IN INDUSTRIAL CONDENSATION REACTIONS

    EPA Science Inventory

    The objective of this project is to develop heterogeneous acid-base catalysts to increase the economic and environmental performance of the current homogeneous catalysts used to make industrially important condensation products. Such products include methyl isobutyl ketone ...

  11. Blockage-induced condensation controlled by a local reaction

    NASA Astrophysics Data System (ADS)

    Cirillo, Emilio N. M.; Colangeli, Matteo; Muntean, Adrian

    2016-10-01

    We consider the setup of stationary zero range models and discuss the onset of condensation induced by a local blockage on the lattice. We show that the introduction of a local feedback on the hopping rates allows us to control the particle fraction in the condensed phase. This phenomenon results in a current versus blockage parameter curve characterized by two nonanalyticity points.

  12. Amine-Functionalized Sugarcane Bagasse: A Renewable Catalyst for Efficient Continuous Flow Knoevenagel Condensation Reaction at Room Temperature.

    PubMed

    Qiao, Yanhui; Teng, Junjiang; Wang, Shuangfei; Ma, Hao

    2017-12-24

    A biomass-based catalyst with amine groups (-NH₂), viz., amine-functionalized sugarcane bagasse (SCB-NH₂), was prepared through the amination of sugarcane bagasse (SCB) in a two-step process. The physicochemical properties of the catalyst were characterized through FT-IR, elemental analysis, XRD, TG, and SEM-EDX techniques, which confirmed the -NH₂ group was grafted onto SCB successfully. The catalytic performance of SCB-NH₂ in Knoevenagel condensation reaction was tested in the batch and continuous flow reactions. Significantly, it was found that the catalytic performance of SCB-NH₂ is better in flow system than that in batch system. Moreover, the SCB-NH₂ presented an excellent catalytic activity and stability at the high flow rate. When the flow rate is at the 1.5 mL/min, no obvious deactivation was observed and the product yield and selectivity are more than 97% and 99% after 80 h of continuous reaction time, respectively. After the recovery of solvent from the resulting solution, a white solid was obtained as a target product. As a result, the SCB-NH₂ is a promising catalyst for the synthesis of fine chemicals by Knoevenagel condensation reaction in large scale, and the modification of the renewable SCB with -NH₂ group is a potential avenue for the preparation of amine-functionalized catalytic materials in industry.

  13. Synthesis of high surface area nanomaterials and their application in catalysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chaudhary, Umesh

    2016-05-01

    The dissertation is organized in 4 chapters. Chapter 1 highlights the motivations behind our research along with a general introduction on ceria and carbon catalysts. Chapter 2 reports the investigations on Copper-Ceria catalysts for the selective hydrogenation of fatty acids into fatty alcohols. Chapter 3 discusses the development of nitrogen containing mesoporous carbon. The chapter also reports the catalytic investigations for aldol condensation and nitrobenzene hydrogenation reactions. Finally, Chapter 4 is a general conclusion summarizing this dissertation.

  14. Condensed phase preparation of 2,3-pentanedione

    DOEpatents

    Miller, Dennis J.; Perry, Scott M.; Fanson, Paul T.; Jackson, James E.

    1998-01-01

    A condensed phase process for the preparation of purified 2,3-pentanedione from lactic acid and an alkali metal lactate is described. The process uses elevated temperatures between about 200.degree. to 360.degree. C. for heating a reaction mixture of lactic acid and an alkali metal lactate to produce the 2,3-pentanedione in a reaction vessel. The 2,3-pentanedione produced is vaporized from the reaction vessel and condensed with water.

  15. Condensed phase preparation of 2,3-pentanedione

    DOEpatents

    Miller, D.J.; Perry, S.M.; Fanson, P.T.; Jackson, J.E.

    1998-11-03

    A condensed phase process for the preparation of purified 2,3-pentanedione from lactic acid and an alkali metal lactate is described. The process uses elevated temperatures between about 200 to 360 C for heating a reaction mixture of lactic acid and an alkali metal lactate to produce the 2,3-pentanedione in a reaction vessel. The 2,3-pentanedione produced is vaporized from the reaction vessel and condensed with water. 5 figs.

  16. π-Expanded α,β-unsaturated ketones: synthesis, optical properties, and two-photon-induced polymerization.

    PubMed

    Nazir, Rashid; Bourquard, Florent; Balčiūnas, Evaldas; Smoleń, Sabina; Gray, David; Tkachenko, Nikolai V; Farsari, Maria; Gryko, Daniel T

    2015-02-23

    A library of π-expanded α,β-unsaturated ketones was designed and synthesized. They were prepared by a combination of Wittig reaction, Sonogashira reaction, and aldol condensation. It was further demonstrated that the double aldol condensation can be performed effectively for highly polarized styrene- and diphenylacetylene-derived aldehydes. The strategic placement of two dialkylamino groups at the periphery of D-π-A-π-D molecules resulted in dyes with excellent solubility. These ketones absorb light in the region 400-550 nm. Many of them display strong solvatochromism so that the emission ranges from 530-580 nm in toluene to the near-IR region in benzonitrile. Ketones based on cyclobutanone as central moieties display very high fluorescence quantum yields in nonpolar solvents, which decrease drastically in polar media. Photophysical studies of these new functional dyes revealed that they possess an enhanced two-photon absorption cross section when compared with simpler ketone derivatives. Due to strong polarization of the resulting dyes, values of two-photon absorption cross sections on the level of 200-300 GM at 800 nm were achieved, and thanks to that as well as the presence of the keto group, these new two-photon initiators display excellent performance so that the operating region is 5-75 mW in some cases. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Amine catalyzed condensation of tetraethylorthosilicate

    NASA Technical Reports Server (NTRS)

    Jones, S.

    2001-01-01

    The catalysis of the condensation of hydrolyzed metal alkoxides by amines has been mentioned in the literature, but there has been no systematic study of their influence on the rate of the condensation reaction of the alkoxide and the microstructure of the resultant gel.

  18. Microwave: An Important and Efficient Tool for the Synthesis of Biological Potent Organic Compounds.

    PubMed

    Kumari, Kamlesh; Vishvakarma, Vijay K; Singh, Prashant; Patel, Rajan; Chandra, Ramesh

    2017-01-01

    Green Chemistry is an interdisciplinary science or it can also be explained as a branch of chemistry. It is generally described as the chemistry to aim to synthesize chemical compounds to trim down the utilization of harmful chemicals proposed by the Environmental Protection Agency (EPA). Recently, the plan of academicians, researchers, industrialists is to generate greener and more efficient methodologies to carry out various organic syntheses. In the present scenario, green chemistry utilizes the raw materials economically, minimizes the waste and prevents the uses of harmful or hazardous chemicals to make the organic reactions simple and efficient. Microwave technique is a new, simple and efficient technology which opens new prospects to the chemists to carry out various organic and inorganic reactions, which are difficult via conventional methodology. It is used to decrease the duration of time to carry various organic transformation along with maximum yield, minimum by-products, minimum energy utilization, less manpower etc. e.g. various famous organic reactions have been carried out by various research groups like Aldol condensation, Knoevenagel condensation, Beckmann rearrangement, Vilsmeier reaction, Perkin reaction, Benzil-Benzilic acid rearrangement, Fischer cyclization, Mannich reaction, Claisen-Schmidt condensation, etc. Further, reduction, oxidation, coupling, condensation reaction were also performed using microwave technology. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  19. Condensed tannins: Base-catalysed reactions of polymeric procyanidins with toluene-α-thiol, liability of the interflavanoid bond and pyran ring

    Treesearch

    Peter E. Laks; Richard W. Hemingway

    1987-01-01

    Reaction of polymeric procyanidins (condensed tannins) with toluene-α-thiol at pH 12.0 and 23°C gave predominantly one stereoisomer of 1.3-bisbenzylthio-1-(3,4-dihydroxyphenyl)-3-(2,4,6-trihydroxyphenyl) propan-2-ol (10) by stereoselective reaction at C-4 and C-2 of the Quinone methide derived from the upper 2,3-cis procyanidin units....

  20. Sub-Equimolar Hydrolysis and Condensation of Organophosphates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alam, Todd M.; Kinnan, Mark K.; Wilson, Brendan W.

    We characterized the in-situ hydrolysis and subsequent condensation reaction of the chemical agent simulant diethyl chlorophosphate (DECP) by high-resolution 31P NMR spectroscopy following the addition of water in sub-equimolar concentrations. Moreover, the identification and quantification of the multiple pyrophosphate and larger polyphosphate chemical species formed through a series of self-condensation reactions are reported. Finally, the DECP hydrolysis kinetics and distribution of breakdown species was strongly influenced by the water concentration and reaction temperature.

  1. Sub-Equimolar Hydrolysis and Condensation of Organophosphates

    DOE PAGES

    Alam, Todd M.; Kinnan, Mark K.; Wilson, Brendan W.; ...

    2016-07-16

    We characterized the in-situ hydrolysis and subsequent condensation reaction of the chemical agent simulant diethyl chlorophosphate (DECP) by high-resolution 31P NMR spectroscopy following the addition of water in sub-equimolar concentrations. Moreover, the identification and quantification of the multiple pyrophosphate and larger polyphosphate chemical species formed through a series of self-condensation reactions are reported. Finally, the DECP hydrolysis kinetics and distribution of breakdown species was strongly influenced by the water concentration and reaction temperature.

  2. Gold (III) Chloride-Catalyzed 6-endo-trig Oxa-Michael Addition Reactions for Diastereoselective Synthesis of Fused Tetrahydropyranones

    PubMed Central

    Ciesielski, Jennifer; Lebœuf, David; Stern, Harry A.

    2013-01-01

    Alkynones were treated with boron trifluoride diethyl etherate to generate β-iodoallenolates, which underwent intramolecular aldol reactions to produce cycloalkenyl alcohols. Diastereoselective oxa-Michael ring closure could then be induced by treatment with a catalytic amount of gold(III) chloride, affording highly functionalized tetrahydropyran-containing ring systems. PMID:24032002

  3. Purification and Characterization of OleA from Xanthomonas campestris and Demonstration of a Non-decarboxylative Claisen Condensation Reaction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Frias, JA; Richman, JE; Erickson, JS

    2011-03-25

    OleA catalyzes the condensation of fatty acyl groups in the first step of bacterial long-chain olefin biosynthesis, but the mechanism of the condensation reaction is controversial. In this study, OleA from Xanthomonas campestris was expressed in Escherichia coli and purified to homogeneity. The purified protein was shown to be active with fatty acyl-CoA substrates that ranged from C(8) to C(16) in length. With limiting myristoyl-CoA (C(14)), 1 mol of the free coenzyme A was released/mol of myristoyl-CoA consumed. Using [(14)C] myristoyl-CoA, the other products were identified as myristic acid, 2-myristoylmyristic acid, and 14-heptacosanone. 2-Myristoylmyristic acid was indicated to be themore » physiologically relevant product of OleA in several ways. First, 2-myristoylmyristic acid was the major condensed product in short incubations, but over time, it decreased with the concomitant increase of 14-heptacosanone. Second, synthetic 2-myristoylmyristic acid showed similar decarboxylation kinetics in the absence of OleA. Third, 2-myristoylmyristic acid was shown to be reactive with purified OleC and OleD to generate the olefin 14-heptacosene, a product seen in previous in vivo studies. The decarboxylation product, 14-heptacosanone, did not react with OleC and OleD to produce any demonstrable product. Substantial hydrolysis of fatty acyl-CoA substrates to the corresponding fatty acids was observed, but it is currently unclear if this occurs in vivo. In total, these data are consistent with OleA catalyzing a non-decarboxylative Claisen condensation reaction in the first step of the olefin biosynthetic pathway previously found to be present in at least 70 different bacterial strains.« less

  4. The crystal structure of dihydrodipicolinate synthase from Escherichia coli with bound pyruvate and succinic acid semialdehyde: unambiguous resolution of the stereochemistry of the condensation product.

    PubMed

    Boughton, Berin A; Dobson, Renwick C J; Hutton, Craig A

    2012-08-01

    The crystal structure of Escherichia coli dihydrodipicolinate synthase with pyruvate and substrate analogue succinic acid semialdehyde condensed with the active site lysine-161 was solved to a resolution of 2.3 Å. Comparative analysis to a previously reported structure both resolves the configuration at the aldol addition center, where the final addition product clearly displays the (S)-configuration, and the final conformation of the adduct within the active site. Direct comparison to two other crystal structures found in the Protein Data Bank, 1YXC, and 3DU0, demonstrates significant similarity between the active site residues of these structures. Copyright © 2012 Wiley Periodicals, Inc.

  5. Synthesis of branched iminosugars through a hypervalent iodine(III)-mediated radical-polar crossover reaction.

    PubMed

    Santana, Andrés G; Paz, Nieves R; Francisco, Cosme G; Suárez, Ernesto; González, Concepción C

    2013-08-02

    The synthesis of a novel type of branched iminosugars is described. This synthetic strategy is based on two key reactions: first, an aldol reaction with formaldehyde in order to introduce selectively the hydroxymethyl branch, and second, a tandem β-fragmentation-intramolecular cyclization reaction. The combination of both reactions afforded a battery of compounds exhibiting a great structural complexity, with the concomitant formation of a quaternary center, starting from readily available aldoses. With this approach we have demonstrated the usefulness of the fragmentation of anomeric alkoxyl radicals (ARF) promoted by the PhIO/I2 system for the preparation of new compounds with potential interest for both medicinal and synthetic chemists.

  6. Highly selective condensation of biomass-derived methyl ketones as a source of aviation fuel.

    PubMed

    Sacia, Eric R; Balakrishnan, Madhesan; Deaner, Matthew H; Goulas, Konstantinos A; Toste, F Dean; Bell, Alexis T

    2015-05-22

    Aviation fuel (i.e., jet fuel) requires a mixture of C9 -C16 hydrocarbons having both a high energy density and a low freezing point. While jet fuel is currently produced from petroleum, increasing concern with the release of CO2 into the atmosphere from the combustion of petroleum-based fuels has led to policy changes mandating the inclusion of biomass-based fuels into the fuel pool. Here we report a novel way to produce a mixture of branched cyclohexane derivatives in very high yield (>94 %) that match or exceed many required properties of jet fuel. As starting materials, we use a mixture of n-alkyl methyl ketones and their derivatives obtained from biomass. These synthons are condensed into trimers via base-catalyzed aldol condensation and Michael addition. Hydrodeoxygenation of these products yields mixtures of C12 -C21 branched, cyclic alkanes. Using models for predicting the carbon number distribution obtained from a mixture of n-alkyl methyl ketones and for predicting the boiling point distribution of the final mixture of cyclic alkanes, we show that it is possible to define the mixture of synthons that will closely reproduce the distillation curve of traditional jet fuel. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Diastereoselective synthesis of L: -threo-3,4-dihydroxyphenylserine by low-specific L: -threonine aldolase mutants.

    PubMed

    Gwon, Hui-Jeong; Baik, Sang-Ho

    2010-01-01

    Diastereoselectivity-enhanced mutants of L: -threonine aldolase (L: -TA) for L: -threo-3,4-dihydroxyphenylserine (L: -threo-DOPS) synthesis were isolated by error-prone PCR followed by a high-throughput screening. The most improved mutant was achieved from the mutant T3-3mm2, showing a 4-fold increase over the wild-type L: -TA. When aldol condensation activity was examined using whole cells of T3-3mm2, its de was constantly maintained at 55% during the batch reactions for 80 h, yielding 3.8 mg L: -threo-DOPS/ml.

  8. Temperature- and pH-dependent aqueous-phase kinetics of the reactions of glyoxal and methylglyoxal with atmospheric amines and ammonium sulfate

    NASA Astrophysics Data System (ADS)

    Sedehi, Nahzaneen; Takano, Hiromi; Blasic, Vanessa A.; Sullivan, Kristin A.; De Haan, David O.

    2013-10-01

    Reactions of glyoxal (Glx) and methylglyoxal (MG) with primary amines and ammonium salts may produce brown carbon and N-containing oligomers in aqueous aerosol. 1H NMR monitoring of reactant losses and product appearance in bulk aqueous reactions were used to derive rate constants and quantify competing reaction pathways as a function of pH and temperature. Glx + ammonium sulfate (AS) and amine reactions generate products containing C-N bonds, with rates depending directly on pH: rate = (70 ± 60) M-1 s-1fAld [Glx]totfAm [Am]tot, where fAld is the fraction of aldehyde with a dehydrated aldehyde functional group, and fAm is the fraction of amine or ammonia that is deprotonated at a given pH. MG + amine reactions generate mostly aldol condensation products and exhibit less pH dependence: rate = 10[(0.36 ± 0.06) × pH - (3.6 ± 0.3)] M-1 s-1fAld [MG]tot [Am]tot. Aldehyde + AS reactions are less temperature-dependent (Ea = 18 ± 8 kJ mol-1) than corresponding amine reactions (Ea = 50 ± 11 kJ mol-1). Using aerosol concentrations of [OH] = 10-12 M, [amine]tot = [AS] = 0.1 M, fGlx = 0.046 and fMG = 0.09, we estimate that OH radical reactions are normally the major aerosol-phase sink for both dicarbonyl compounds. However, reactions with AS and amines together can account for up to 12 and 45% of daytime aerosol-phase glyoxal and methylglyoxal reactivity, respectively, in marine aerosol at pH 5.5. Reactions with AS and amines become less important in acidic or non-marine aerosol, but may still be significant atmospheric sources of brown carbon, imidazoles, and nitrogen-containing oligomers.

  9. Rhodium-Catalyzed Asymmetric Conjugate Alkynylation/Aldol Cyclization Cascade for the Formation of α-Propargyl-β-hydroxyketones.

    PubMed

    Choo, Ken-Loon; Lautens, Mark

    2018-03-02

    A rhodium-catalyzed conjugate alkynylation/aldol cyclization cascade was developed. Densely functionalized cyclic α-propargyl-β-hydroxyketones were synthesized with simultaneous formation of a C(sp)-C(sp 3 ) bond, a C(sp 3 )-C(sp 3 ) bond, as well as three new contiguous stereocenters. The transformation was achieved with excellent enantio- and diastereoselectivities using BINAP as the ligand. The synthetic utility of the newly installed alkynyl moiety was exhibited by subjecting the products to an array of derivatizations.

  10. A new fatty aldol ester from the aerial part of Mimosa invisa (Mimosaceae).

    PubMed

    Nana, Frederic; Sandjo, Louis Pergaud; Keumedjio, Felix; Kuete, Victor; Ngadjui, Bonaventure Tchaleu

    2012-01-01

    A new aldol ester named 17-O-triacontanoylheptadecanal (1) was isolated from the aerial part of Mimosa invisa (Mimosaceae) together with eight known compounds identified as β-sitosterol (2), α-amyrine (3), lupeol (4), 4'-O-methylepinumisoflavone (5), alpinumisoflavone (6), betulinic acid (7), 3-O-β-D-glucopyranoside of sitosterol (8) and epirobinetinidol (9). The structures of compounds were determined on the basis of NMR and mass spectrometry data as well as by comparing the data reported in the literatures. The antimicrobial activities of the crude extract and compounds 1 and 9 were investigated against seven microbial species. The natural products showed moderate activities compared to that of the crude extract.

  11. Investigation of Thermochemistry Associated with the Carbon–Carbon Coupling Reactions of Furan and Furfural Using ab Initio Methods

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Cong; Assary, Rajeev S.; Curtiss, Larry A.

    2014-06-26

    Upgrading of furan and small oxygenates obtained from the decomposition of cellulosic materials via formation of carbon-carbon bonds is critical to effective conversion of biomass to liquid transportation fuels. Simulation-driven molecular level understanding of carbon-carbon bond formation is required to design efficient catalysts and processes. Accurate quantum chemical methods are utilized here to predict the reaction energetics for conversion of furan (C4H4O) to C5-C8 ethers and the transformation of furfural (C5H6O2) to C13-C26 alkanes. Furan, can be coupled with various C1 to C4 lower molecular weight carbohydrates obtained from the pyrolysis via Diels-Alder type reactions in the gas phase tomore » produce C5-C8 cyclic ethers. The computed reaction barriers for these reactions (~25 kcal/mol) are lower than the cellulose activation or decomposition reactions (~50 kcal/mol). Cycloaddition of C5-C8 cyclo-ethers with furans can also occur in the gas phase, and the computed activation energy is similar to that of the first Diels-Alder reaction. Furfural, obtained from biomass, can be coupled with aldehydes or ketones with α-hydrogen atoms to form longer chain aldol products and these aldol products can undergo vapor phase hydrocycloaddition (activation barrier of ~20 kcal/mol) to form the precursors of C26 cyclic hydrocarbons. These thermochemical studies provide the basis for further vapor phase catalytic studies required for upgrading of furans/furfurals to longer chain hydrocarbons.« less

  12. Determination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride by flow-injection analysis based on a specific condensation reaction between malonic acid and ethylenediamine.

    PubMed

    Seno, Kunihiko; Matumura, Kazuki; Oshita, Koji; Oshima, Mitsuko; Motomizu, Shoji

    2009-03-01

    A sensitive and rapid flow-injection analysis was developed for the determination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC.HCl), which was used for the formation of amide (peptide) and esters as a dehydration or condensation reagent. The EDC.HCl could be determined by the flow-injection analysis based on a specific condensation reaction between malonic acid and ethylenediamine in aquatic media. The reaction was accelerated at 60 degrees C, and the absorbance of the product was detected at 262 nm. The calibration graph of EDC.HCl showed good linearity in the range from 0 to 0.1% (0 to 0.0005 M), whose regression equation was y = 1.52 x 10(9)x (y, peak area; x, % concentration of EDC.HCl). The proposed method allowed high-throughput analysis; the sample throughput was 12 samples per hour. The limit of detection (LOD) and the relative standard deviation (RSD) were 2 x 10(-6) M and 1.0%, respectively. This reaction is proceeded in aqueous solution and specific for EDC.HCl.

  13. Formaldehyde condensation products of model phenols for conifer bark tannins

    Treesearch

    Richard W. Hemingway; Gerald W. McGraw

    1978-01-01

    Gel permeation chromatography of the condensation products of phenols and formaldehyde proved effective in understanding the reactions of condensed tannins with formaldehyde. Rates of condensation of phloroglucinols, resorcinols, catechols, (+)catechins, and (-)epicatechin were examined to determine if methylol-tannins from southern pine bark could be prepared as resin...

  14. Formaldehyde condensation products of model phenols for conifer bark tannins

    Treesearch

    R.W. Hemingway; G.W. McGraw

    1978-01-01

    Gel permeation chromatograpy of the condensation products of phenols and formaldehyde proved effective in understanding the reactions of condensed tannins with formaldehyde. Rates of condensation of phloroglucinols, resorcinols, catechols, (+)catechin, and (-)epicatechin were examined to determine if methylol-tannins from southern pine bark could be prepared as resin...

  15. Synthesis of oxazolidine-2,4-diones by a tandem phosphorus-mediated carboxylative condensation-cyclization reaction using atmospheric carbon dioxide.

    PubMed

    Zhang, Wen-Zhen; Xia, Tian; Yang, Xu-Tong; Lu, Xiao-Bing

    2015-04-11

    The oxazolidine-2,4-dione motif is found frequently in biologically important compounds. A tandem phosphorus-mediated carboxylative condensation of primary amines and α-ketoesters/base-catalyzed cyclization reaction have been developed. These processes provide a novel and convenient access to various oxazolidine-2,4-diones in a one-pot fashion using atmospheric carbon dioxide and readily available substrates under very mild and transition-metal-free conditions.

  16. Condensed Matter Nuclear Science

    NASA Astrophysics Data System (ADS)

    Biberian, Jean-Paul

    2006-02-01

    1. General. A tribute to gene Mallove - the "Genie" reactor / K. Wallace and R. Stringham. An update of LENR for ICCF-11 (short course, 10/31/04) / E. Storms. New physical effects in metal deuterides / P. L. Hagelstein ... [et al.]. Reproducibility, controllability, and optimization of LENR experiments / D. J. Nagel -- 2. Experiments. Electrochemistry. Evidence of electromagnetic radiation from Ni-H systems / S. Focardi ... [et al.]. Superwave reality / I. Dardik. Excess heat in electrolysis experiments at energetics technologies / I. Dardik ... [et al.]. "Excess heat" during electrolysis in platinum/K[symbol]CO[symbol]/nickel light water system / J. Tian ... [et al.]. Innovative procedure for the, in situ, measurement of the resistive thermal coefficient of H(D)/Pd during electrolysis; cross-comparison of new elements detected in the Th-Hg-Pd-D(H) electrolytic cells / F. Celani ... [et al.]. Emergence of a high-temperature superconductivity in hydrogen cycled Pd compounds as an evidence for superstoihiometric H/D sites / A. Lipson ... [et al.]. Plasma electrolysis. Calorimetry of energy-efficient glow discharge - apparatus design and calibration / T. B. Benson and T. O. Passell. Generation of heat and products during plasma electrolysis / T. Mizuno ... [et al.]. Glow discharge. Excess heat production in Pd/D during periodic pulse discharge current in various conditions / A. B. Karabut. Beam experiments. Accelerator experiments and theoretical models for the electron screening effect in metallic environments / A. Huke, K. Czerski, and P. Heide. Evidence for a target-material dependence of the neutron-proton branching ratio in d+d reactions for deuteron energies below 20keV / A. Huke ... [et al.]. Experiments on condensed matter nuclear events in Kobe University / T. Minari ... [et al.]. Electron screening constraints for the cold fusion / K. Czerski, P. Heide, and A. Huke. Cavitation. Low mass 1.6 MHz sonofusion reactor / R. Stringham. Particle detection. Research

  17. Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

    DOE PAGES

    Orazov, Marat; Davis, Mark E.

    2015-09-08

    Retro-aldol reactions have been implicated as the limiting steps in catalytic routes to convert biomass-derived hexoses and pentoses into valuable C2, C3, and C4 products such as glycolic acid, lactic acid, 2-hydroxy-3-butenoic acid, 2,4-dihydroxybutanoic acid, and alkyl esters thereof. Due to a lack of efficient retro-aldol catalysts, most previous investigations of catalytic pathways involving these reactions were conducted at high temperatures (≥160 °C). Here, we report moderate-temperature (around 100 °C) retro-aldol reactions of various hexoses in aqueous and alcoholic media with catalysts traditionally known for their capacity to catalyze 1,2-intramolecular carbon shift (1,2-CS) reactions of aldoses, i.e., various molybdenum oxidemore » and molybdate species, nickel(II) diamine complexes, alkali-exchanged stannosilicate molecular sieves, and amorphous TiO2–SiO2 coprecipitates. Solid Lewis acid cocatalysts that are known to catalyze 1,2-intramolecular hydride shift (1,2-HS) reactions that enable the formation of α-hydroxy carboxylic acids from tetroses, trioses, and glycolaldehyde, but cannot readily catalyze retro-aldol reactions of hexoses and pentoses at these moderate temperatures, are shown to be compatible with the aforementioned retro-aldol catalysts. The combination of a distinct retro-aldol catalyst with a 1,2-HS catalyst enables lactic acid and alkyl lactate formation from ketohexoses at moderate temperatures (around 100 °C), with yields comparable to best-reported chemocatalytic examples at high temperature conditions (≥160 °C). The use of moderate temperatures enables numerous desirable features such as lower pressure and significantly less catalyst deactivation.« less

  18. Bifunctional Organic Polymeric Catalysts with a Tunable Acid-Base Distance and Framework Flexibility

    PubMed Central

    Chen, Huanhui; Wang, Yanan; Wang, Qunlong; Li, Junhui; Yang, Shiqi; Zhu, Zhirong

    2014-01-01

    Acid-base bifunctional organic polymeric catalysts were synthesized with tunable structures. we demonstrated two synthesis approaches for structural fine-tune. In the first case, the framework flexibility was tuned by changing the ratio of rigid blocks to flexible blocks within the polymer framework. In the second case, we precisely adjusted the acid-base distance by distributing basic monomers to be adjacent to acidic monomers, and by changing the chain length of acidic monomers. In a standard test reaction for the aldol condensation of 4-nitrobenzaldehyde with acetone, the catalysts showed good reusability upon recycling and maintained relatively high conversion percentage. PMID:25267260

  19. Effect of Water on Ethanol Conversion over ZnO

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rahman, Muhammad Mahfuzur; Davidson, Stephen D.; Sun, Junming

    2015-10-01

    This work focuses on understanding the role of water on ethanol conversion over zinc oxide (ZnO). It was found that a competitive adsorption between ethanol and water occurs on ZnO, which leads to the blockage of the strong Lewis acid site by water on ZnO. As a result, both dehydration and dehydrogenation reactions are inhibited. However, the extent of inhibition for dehydration is orders of magnitude higher than that for dehydrogenation, leading to the shift of reaction pathway from ethanol dehydration to dehydrogenation. In the secondary reactions for acetaldehyde conversion, water inhibits the acetaldehyde aldol-condensation to crotonaldehyde, favoring the oxidationmore » of acetaldehyde to acetic acid, and then to acetone via ketonization at high temperature (i.e., 400 °C).« less

  20. Advances in quantum and molecular mechanical (QM/MM) simulations for organic and enzymatic reactions.

    PubMed

    Acevedo, Orlando; Jorgensen, William L

    2010-01-19

    Application of combined quantum and molecular mechanical (QM/MM) methods focuses on predicting activation barriers and the structures of stationary points for organic and enzymatic reactions. Characterization of the factors that stabilize transition structures in solution and in enzyme active sites provides a basis for design and optimization of catalysts. Continued technological advances allowed for expansion from prototypical cases to mechanistic studies featuring detailed enzyme and condensed-phase environments with full integration of the QM calculations and configurational sampling. This required improved algorithms featuring fast QM methods, advances in computing changes in free energies including free-energy perturbation (FEP) calculations, and enhanced configurational sampling. In particular, the present Account highlights development of the PDDG/PM3 semi-empirical QM method, computation of multi-dimensional potentials of mean force (PMF), incorporation of on-the-fly QM in Monte Carlo (MC) simulations, and a polynomial quadrature method for efficient modeling of proton-transfer reactions. The utility of this QM/MM/MC/FEP methodology is illustrated for a variety of organic reactions including substitution, decarboxylation, elimination, and pericyclic reactions. A comparison to experimental kinetic results on medium effects has verified the accuracy of the QM/MM approach in the full range of solvents from hydrocarbons to water to ionic liquids. Corresponding results from ab initio and density functional theory (DFT) methods with continuum-based treatments of solvation reveal deficiencies, particularly for protic solvents. Also summarized in this Account are three specific QM/MM applications to biomolecular systems: (1) a recent study that clarified the mechanism for the reaction of 2-pyrone derivatives catalyzed by macrophomate synthase as a tandem Michael-aldol sequence rather than a Diels-Alder reaction, (2) elucidation of the mechanism of action of fatty

  1. Silica functionalized Cu(II) acetylacetonate Schiff base complex: An efficient catalyst for the oxidative condensation reaction of benzyl alcohol with amines

    NASA Astrophysics Data System (ADS)

    Anbarasu, G.; Malathy, M.; Karthikeyan, P.; Rajavel, R.

    2017-09-01

    Silica functionalized Cu(II) acetylacetonate Schiff base complex via the one pot reaction of silica functionalized 3-aminopropyltriethoxysilane with acetyl acetone and copper acetate has been reported. The synthesized material was well characterized by analytical techniques such as FT-IR, UV-DRS, XRD, SEM-EDX, HR-TEM, EPR, ICP-AES and BET analysis. The characterization results confirmed the grafting of Cu(II) Schiff base complex on the silica surface. The catalytic activity of synthesized silica functionalized Cu(II) acetylacetonate Schiff base complex was evaluated through the oxidative condensation reaction of benzyl alcohol to imine.

  2. Et3B-mediated radical-polar crossover reaction for single-step coupling of O,Te-acetal, α,β-unsaturated ketones, and aldehydes/ketones.

    PubMed

    Kamimura, Daigo; Urabe, Daisuke; Nagatomo, Masanori; Inoue, Masayuki

    2013-10-04

    Et3B-mediated three-component coupling reactions between O,Te-acetal, α,β-unsaturated ketones, and aldehydes/ketones were developed. Et3B promoted the generation of the potently reactive bridgehead radical from the O,Te-acetal of the trioxaadamantane structure and converted the α-carbonyl radical of the resultant two-component adduct to the boron enolate, which then underwent a stereoselective aldol reaction with the aldehyde/ketone. This powerful, yet mild, radical-polar crossover reaction efficiently connected the hindered linkages between the three units and selectively introduced three new stereocenters.

  3. An active site–tail interaction in the structure of hexahistidine-tagged Thermoplasma acidophilum citrate synthase

    PubMed Central

    Murphy, Jesse R.; Donini, Stefano; Kappock, T. Joseph

    2015-01-01

    Citrate synthase (CS) plays a central metabolic role in aerobes and many other organisms. The CS reaction comprises two half-reactions: a Claisen aldol condensation of acetyl-CoA (AcCoA) and oxaloacetate (OAA) that forms citryl-CoA (CitCoA), and CitCoA hydrolysis. Protein conformational changes that ‘close’ the active site play an important role in the assembly of a catalytically competent condensation active site. CS from the thermoacidophile Thermoplasma acidophilum (TpCS) possesses an endogenous Trp fluorophore that can be used to monitor the condensation reaction. The 2.2 Å resolution crystal structure of TpCS fused to a C-terminal hexahistidine tag (TpCSH6) reported here is an ‘open’ structure that, when compared with several liganded TpCS structures, helps to define a complete path for active-site closure. One active site in each dimer binds a neighboring His tag, the first nonsubstrate ligand known to occupy both the AcCoA and OAA binding sites. Solution data collectively suggest that this fortuitous interaction is stabilized by the crystalline lattice. As a polar but almost neutral ligand, the active site–tail interaction provides a new starting point for the design of bisubstrate-analog inhibitors of CS. PMID:26457521

  4. An active site-tail interaction in the structure of hexahistidine-tagged Thermoplasma acidophilum citrate synthase

    DOE PAGES

    Murphy, Jesse R.; Donini, Stefano; Kappock, T. Joseph

    2015-10-01

    Citrate synthase (CS) plays a central metabolic role in aerobes and many other organisms. The CS reaction comprises two half-reactions: a Claisen aldol condensation of acetyl-CoA (AcCoA) and oxaloacetate (OAA) that forms citryl-CoA (CitCoA), and CitCoA hydrolysis. Protein conformational changes that `close' the active site play an important role in the assembly of a catalytically competent condensation active site. CS from the thermoacidophile Thermoplasma acidophilum (TpCS) possesses an endogenous Trp fluorophore that can be used to monitor the condensation reaction. The 2.2 Å resolution crystal structure of TpCS fused to a C-terminal hexahistidine tag (TpCSH6) reported here is an `open'more » structure that, when compared with several liganded TpCS structures, helps to define a complete path for active-site closure. One active site in each dimer binds a neighboring His tag, the first nonsubstrate ligand known to occupy both the AcCoA and OAA binding sites. Solution data collectively suggest that this fortuitous interaction is stabilized by the crystalline lattice. In conclusion, as a polar but almost neutral ligand, the active site-tail interaction provides a new starting point for the design of bisubstrate-analog inhibitors of CS.« less

  5. An active site-tail interaction in the structure of hexahistidine-tagged Thermoplasma acidophilum citrate synthase.

    PubMed

    Murphy, Jesse R; Donini, Stefano; Kappock, T Joseph

    2015-10-01

    Citrate synthase (CS) plays a central metabolic role in aerobes and many other organisms. The CS reaction comprises two half-reactions: a Claisen aldol condensation of acetyl-CoA (AcCoA) and oxaloacetate (OAA) that forms citryl-CoA (CitCoA), and CitCoA hydrolysis. Protein conformational changes that `close' the active site play an important role in the assembly of a catalytically competent condensation active site. CS from the thermoacidophile Thermoplasma acidophilum (TpCS) possesses an endogenous Trp fluorophore that can be used to monitor the condensation reaction. The 2.2 Å resolution crystal structure of TpCS fused to a C-terminal hexahistidine tag (TpCSH6) reported here is an `open' structure that, when compared with several liganded TpCS structures, helps to define a complete path for active-site closure. One active site in each dimer binds a neighboring His tag, the first nonsubstrate ligand known to occupy both the AcCoA and OAA binding sites. Solution data collectively suggest that this fortuitous interaction is stabilized by the crystalline lattice. As a polar but almost neutral ligand, the active site-tail interaction provides a new starting point for the design of bisubstrate-analog inhibitors of CS.

  6. Control of VOCs emissions by condenser pre-treatment in a semiconductor fab.

    PubMed

    Lin, Yu-Chih; Chang, Feng-Tang; Bai, Hsunling; Pei, Bau-Shei

    2005-04-11

    The performance of a modified design of local condensers to pre-treat a variety of volatile organic compounds (VOCs) emitted from the stripping process of a semiconductor fab was tested in this study. The reaction temperature of the condensers was controlled at around 10 degrees C, it is relatively higher than the traditional condenser reaction temperature. Both VOCs and water vapors were condensed and formed liquid films. This resulted in an enhancement of the VOCs removals, especially for VOCs of high boiling points or solubility. This can help to prevent the follow up zeolite concentrator from damage. The performance of the integrated system of condenser/zeolite concentrator could, therefore, remain highly efficient for a longer operation time. Its annualized cost would also be lower than installing the zeolite concentrator only.

  7. Influence of Catalyst Acid/Base Properties in Acrolein Production by Oxidative Coupling of Ethanol and Methanol.

    PubMed

    Lilić, Aleksandra; Bennici, Simona; Devaux, Jean-François; Dubois, Jean-Luc; Auroux, Aline

    2017-05-09

    Oxidative coupling of methanol and ethanol represents a new route to produce acrolein. In this work, the overall reaction was decoupled in two steps, the oxidation and the aldolization, by using two consecutive reactors to investigate the role of the acid/base properties of silica-supported oxide catalysts. The oxidation of a mixture of methanol and ethanol to formaldehyde and acetaldehyde was performed over a FeMoO x catalyst, and then the product mixture was transferred without intermediate separation to a second reactor, in which the aldol condensation and dehydration to acrolein were performed over the supported oxides. The impact of the acid/base properties on the selectivity towards acrolein was investigated under oxidizing conditions for the first time. The acid/base properties of the catalysts were investigated by NH 3 -, SO 2 -, and methanol-adsorption microcalorimetry. A MgO/SiO 2 catalyst was the most active in acrolein production owing to an appropriate ratio of basic to acidic sites. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Synthesis of Fe3O4@P4VP@ZIF-8 core-shell microspheres and their application in a Knoevenagel condensation reaction

    NASA Astrophysics Data System (ADS)

    Miao, Zongcheng; Yang, Fengxia; Luan, Yi; Shu, Xin; Ramella, Daniele

    2017-12-01

    In this work, a core-shell magnetic composite Fe3O4@P4VP@ZIF-8 microspheres were successfully designed and synthesized. A polymerization approach on the surface of pre-made Fe3O4 microspheres was employed for the synthesis of Fe3O4@P4VP. The zinc-derived Zeolite Imidazolate Framework (ZIF) shell was introduced through a layer-by-layer strategy. The obtained Fe3O4@P4VP@ZIF-8 core-shell structure was employed as an efficient Knoevenagel condensation catalyst for a variety of aldehydes. Furthermore, the inner P4VP layer also served as a basic additive in the condensation reaction process, while much less homogeneous basic additive was used. High catalytic reaction efficiency was achieved when the P4VP layer was utilized in combination with a Lewis acidity bearing ZIF-8 layer. The Fe3O4@P4VP@ZIF-8 catalyst was tested for recyclability and no drop in the catalytic activity was observed after more than five cycles.

  9. A cis-prenyltransferase from Methanosarcina acetivorans catalyzes both head-to-tail and nonhead-to-tail prenyl condensation.

    PubMed

    Ogawa, Takuya; Emi, Koh-Ichi; Koga, Kazushi; Yoshimura, Tohru; Hemmi, Hisashi

    2016-06-01

    Cis-prenyltransferase usually consecutively catalyzes the head-to-tail condensation reactions of isopentenyl diphosphate to allylic prenyl diphosphate in the production of (E,Z-mixed) polyprenyl diphosphate, which is the precursor of glycosyl carrier lipids. Some recently discovered homologs of the enzyme, however, catalyze the nonhead-to-tail condensation reactions between allylic prenyl diphosphates. In this study, we characterize a cis-prenyltransferase homolog from a methanogenic archaeon, Methanosarcina acetivorans, to obtain information on the biosynthesis of the glycosyl carrier lipids within it. This enzyme catalyzes both head-to-tail and nonhead-to-tail condensation reactions. The kinetic analysis shows that the main reaction of the enzyme is consecutive head-to-tail prenyl condensation reactions yielding polyprenyl diphosphates, while the chain lengths of the major products seem shorter than expected for the precursor of glycosyl carrier lipids. On the other hand, a subsidiary reaction of the enzyme, i.e., nonhead-to-tail condensation between dimethylallyl diphosphate and farnesyl diphosphate, gives a novel diterpenoid compound, geranyllavandulyl diphosphate. © 2016 Federation of European Biochemical Societies.

  10. Direct Conversion of Cellulose into Ethyl Lactate in Supercritical Ethanol-Water Solutions.

    PubMed

    Yang, Lisha; Yang, Xiaokun; Tian, Elli; Lin, Hongfei

    2016-01-08

    Biomass-derived ethyl lactate is a green solvent with a growing market as the replacement for petroleum-derived toxic organic solvents. Here we report, for the first time, the production of ethyl lactate directly from cellulose with the mesoporous Zr-SBA-15 silicate catalyst in a supercritical mixture of ethanol and water. The relatively strong Lewis and weak Brønsted acid sites on the catalyst, as well as the surface hydrophobicity, were beneficial to the reaction and led to synergy during consecutive reactions, such as depolymerization, retro-aldol condensation, and esterification. Under the optimum reaction conditions, ∼33 % yield of ethyl lactate was produced from cellulose with the Zr-SBA-15 catalyst at 260 °C in supercritical 95:5 (w/w) ethanol/water. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. NHC-Catalyzed Asymmetric Benzoin Reaction in Water.

    PubMed

    Yan, Jun; Sun, Rong; Shi, Kuangxi; Li, Kai; Yang, Limin; Zhong, Guofu

    2018-06-11

    A chiral NHC-catalyzed benzoin condensation reaction in water was developed, thereby affording α-hydroxy ketones in good to high yields and high enantioselectivities. Water was proposed as a proton shuttle in the aqueous asymmetric condensation reaction.

  12. COBRA: A Computational Brewing Application for Predicting the Molecular Composition of Organic Aerosols

    PubMed Central

    Fooshee, David R.; Nguyen, Tran B.; Nizkorodov, Sergey A.; Laskin, Julia; Laskin, Alexander; Baldi, Pierre

    2012-01-01

    Atmospheric organic aerosols (OA) represent a significant fraction of airborne particulate matter and can impact climate, visibility, and human health. These mixtures are difficult to characterize experimentally due to their complex and dynamic chemical composition. We introduce a novel Computational Brewing Application (COBRA) and apply it to modeling oligomerization chemistry stemming from condensation and addition reactions in OA formed by photooxidation of isoprene. COBRA uses two lists as input: a list of chemical structures comprising the molecular starting pool, and a list of rules defining potential reactions between molecules. Reactions are performed iteratively, with products of all previous iterations serving as reactants for the next. The simulation generated thousands of structures in the mass range of 120–500 Da, and correctly predicted ~70% of the individual OA constituents observed by high-resolution mass spectrometry. Select predicted structures were confirmed with tandem mass spectrometry. Esterification was shown to play the most significant role in oligomer formation, with hemiacetal formation less important, and aldol condensation insignificant. COBRA is not limited to atmospheric aerosol chemistry; it should be applicable to the prediction of reaction products in other complex mixtures for which reasonable reaction mechanisms and seed molecules can be supplied by experimental or theoretical methods. PMID:22568707

  13. Iron Oxide-Supported Copper Oxide Nanoparticles (Nanocat-Fe-CuO): Magnetically Recyclable Catalysts for the Synthesis of Pyrazole Derivatives, 4-Methoxyaniline, and Ullmann-type Condensation Reactions

    EPA Science Inventory

    An efficient and benign protocol is reported for the synthesis of 4-methoxyaniline, medicinally important pyrazole derivatives, and Ullmann-type condensation reaction using magnetically separable and reusable magnetite-supported copper (nanocat-Fe-CuO) nanoparticles under mild co...

  14. Towards the development of continuous, organocatalytic, and stereoselective reactions in deep eutectic solvents

    PubMed Central

    Brenna, Davide; Massolo, Elisabetta; Puglisi, Alessandra; Rossi, Sergio; Celentano, Giuseppe; Capriati, Vito

    2016-01-01

    Different deep eutectic solvent (DES) mixtures were studied as reaction media for the continuous synthesis of enantiomerically enriched products by testing different experimental set-ups. L-Proline-catalysed cross-aldol reactions were efficiently performed in continuo, with high yield (99%), anti-stereoselectivity, and enantioselectivity (up to 97% ee). Moreover, using two different DES mixtures, the diastereoselectivity of the process could be tuned, thereby leading to the formation, under different experimental conditions, to both the syn- and the anti-isomer with very high enantioselectivity. The excess of cyclohexanone was recovered and reused, and the reaction could be run and the product isolated without the use of any organic solvent by a proper choice of DES components. The dramatic influence of the reaction media on the reaction rate and stereoselectivity of the process suggests that the intimate architecture of DESs deeply influences the reactivity of different species involved in the catalytic cycle. PMID:28144332

  15. Direct conversion of bio-ethanol to isobutene on nanosized Zn(x)Zr(y)O(z) mixed oxides with balanced acid-base sites.

    PubMed

    Sun, Junming; Zhu, Kake; Gao, Feng; Wang, Chongmin; Liu, Jun; Peden, Charles H F; Wang, Yong

    2011-07-27

    We report the design and synthesis of nanosized Zn(x)Zr(y)O(z) mixed oxides for direct and high-yield conversion of bio-ethanol to isobutene (~83%). ZnO is addded to ZrO(2) to selectively passivate zirconia's strong Lewis acidic sites and weaken Brönsted acidic sites, while simultaneously introducing basicity. As a result, the undesired reactions of bio-ethanol dehydration and acetone polymerization/coking are suppressed. Instead, a surface basic site-catalyzed ethanol dehydrogenation to acetaldehyde, acetaldehyde to acetone conversion via a complex pathway including aldol-condensation/dehydrogenation, and a Brönsted acidic site-catalyzed acetone-to-isobutene reaction pathway dominates on the nanosized Zn(x)Zr(y)O(z) mixed oxide catalyst, leading to a highly selective process for direct conversion of bio-ethanol to isobutene.

  16. Divergent Synthesis of Multisubstituted Tetrahydrofurans and Pyrrolidines via Intramolecular Aldol-type Trapping of Onium Ylide Intermediates.

    PubMed

    Jing, Changcheng; Xing, Dong; Gao, Lixin; Li, Jia; Hu, Wenhao

    2015-12-21

    This paper reports a divergent strategy for the synthesis of multisubstituted tetrahydrofurans and pyrrolidines, starting from easily accessible β-hydroxyketones or β-aminoketones to react with diazo compounds. Under Rh(II) catalysis, this transformation is proposed to proceed through a metal-carbene-induced oxonium ylide or ammonium ylide formation followed by an intramolecular aldol-type trapping of these active intermediates. A series of highly substituted tetrahydrofurans and pyrrolidines are synthesized in high yields with good to excellent diastereoselectivities. Preliminary biological evaluations revealed that both types of heterocycles show good PTP1B inhibitory activities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Ultrasonic evidence of hydrophobic interactions. Effect of ultrasound on benzoin condensation and some other reactions in aqueous ethanol.

    PubMed

    Tuulmets, Ants; Hagu, Hannes; Salmar, Siim; Cravotto, Giancarlo; Järv, Jaak

    2007-03-29

    The kinetics of KCN-catalyzed benzoin condensation of benzaldehyde in water and ethanol-water binary mixtures was investigated both under ultrasound at 22 kHz and without sonication. Thermodynamic activation parameters were calculated from kinetic data obtained at 35, 50, and 65 degrees C. Evidence that ultrasound can retard reactions is reported and hence a direct proof that sonochemical processes occur in the bulk solution. Former results and literature data for ester hydrolyses and tert-butyl chloride solvolysis are involved in the discussion. A quantitative relationship between sonication effects and the hydrophobicity of reagents is presented for the first time. Ultrasound affects hydrophobic interactions with the solvent, which are not manifested in conventional kinetics. When it suppresses the stabilization of the encounter complexes between reagents, sonication hinders the reaction but accelerates it when it perturbs the hydrophobic stabilization of the ground state of a reagent.

  18. Microwave-Assisted Condensation Reactions of Acetophenone Derivatives and Activated Methylene Compounds with Aldehydes Catalyzed by Boric Acid under Solvent-Free Conditions.

    PubMed

    Brun, Elodie; Safer, Abdelmounaim; Carreaux, François; Bourahla, Khadidja; L'helgoua'ch, Jean-Martial; Bazureau, Jean-Pierre; Villalgordo, Jose Manuel

    2015-06-23

    We here disclosed a new protocol for the condensation of acetophenone derivatives and active methylene compounds with aldehydes in the presence of boric acid under microwave conditions. Implementation of the reaction is simple, healthy and environmentally friendly owing to the use of a non-toxic catalyst coupled to a solvent-free procedure. A large variety of known or novel compounds have thus been prepared, including with substrates bearing acid or base-sensitive functional groups.

  19. Gold catalyzed double condensation reaction: Synthesis, antimicrobial and cytotoxicity of spirooxindole derivatives.

    PubMed

    Parthasarathy, K; Praveen, Chandrasekar; Jeyaveeran, J C; Prince, A A M

    2016-09-01

    Microwave assisted synthesis of spirooxindoles via tandem double condensation between isatins and 4-hydroxycoumarin under gold catalysis is reported. The reaction is practical to perform, since the products can be isolated by simple filtration without requiring tedious column chromatography. The scope of this chemistry is exemplified by preparing structurally diverse spirooxindoles (22 examples) in excellent yields. Antimicrobial evaluation of the synthesized compounds revealed that three compounds (3a, 3f and 3s) exhibited significant MIC values in comparison to the standard drugs. Molecular docking studies of these compounds with AmpC-β-lactamase receptor revealed that 3a exhibited minimum binding energy (-117.819kcal/mol) indicating its strong affinity towards amino acid residues via strong hydrogen bond interaction. All compounds were also evaluated for their in vitro cytotoxicity against COLO320 cancer cells. Biological assay and molecular docking studies demonstrated that 3g is the most active compound in terms of its low IC50 value (50.0μM) and least free energy of binding (-8.99kcal/mol) towards CHK1 receptor, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Detonation Reaction Zones in Condensed Explosives

    NASA Astrophysics Data System (ADS)

    Tarver, Craig M.

    2006-07-01

    Experimental measurements using nanosecond time resolved embedded gauges and laser interferometric techniques, combined with Non-Equilibrium Zeldovich - von Neumann - Doling (NEZND) theory and Ignition and Growth reactive flow hydrodynamic modeling, have revealed the average pressure/particle velocity states attained in reaction zones of self-sustaining detonation waves in several solid and liquid explosives. The time durations of these reaction zone processes are discussed for explosives based on pentaerythritol tetranitrate (PETN), nitromethane, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), triaminitrinitrobenzene(TATB) and trinitrotoluene (TNT).

  1. Compressible Heating in the Condense Phase due to Pore Collapse in HMX

    NASA Astrophysics Data System (ADS)

    Zhang, Ju; Jackson, Thomas

    Axisymmetric pore collapse in HMX is studied numerically by solving multi-phase reactive Euler equations. The generation of hot spots in the condense phase due to compressible heating is examined. The motivation is to improve the understanding of the role of embedded cavities in the initiation of reaction in explosives, and to investigate the effect of hot spots in the condense phase due to compressible heating alone, complementing previous study on hot spots due to the reaction in the gas phase and at the interface. It is found that the shock-cavity interaction results in pressures and thus temperatures that are substantially higher than the post-shock values in the condense phase. However, these hot spots in the condense phase due to compressible heating alone do not seem to be sufficiently hot to lead to ignition at shock pressures of 1-3 GPa. Thus, compressible heating in the condense phase may be excluded as a mechanism for initiation of explosives. It should be pointed out that the ignition threshold for the temperature, the so-called ``switch-on'' temperature, of hot spots depend on chemistry kinetics parameters. Switch-on temperature is lower for faster reaction rate. The current chemistry kinetics parameters are based on previous experimental work. This work was supported in part by the Defense Threat Reduction Agency and by the U.S. Department of Energy.

  2. Condensation model for the ESBWR passive condensers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Revankar, S. T.; Zhou, W.; Wolf, B.

    2012-07-01

    In the General Electric's Economic simplified boiling water reactor (GE-ESBWR) the passive containment cooling system (PCCS) plays a major role in containment pressure control in case of an loss of coolant accident. The PCCS condenser must be able to remove sufficient energy from the reactor containment to prevent containment from exceeding its design pressure following a design basis accident. There are three PCCS condensation modes depending on the containment pressurization due to coolant discharge; complete condensation, cyclic venting and flow through mode. The present work reviews the models and presents model predictive capability along with comparison with existing data frommore » separate effects test. The condensation models in thermal hydraulics code RELAP5 are also assessed to examine its application to various flow modes of condensation. The default model in the code predicts complete condensation well, and basically is Nusselt solution. The UCB model predicts through flow well. None of condensation model in RELAP5 predict complete condensation, cyclic venting, and through flow condensation consistently. New condensation correlations are given that accurately predict all three modes of PCCS condensation. (authors)« less

  3. Inorganic Polymers and the Elimination-Condensation Reaction.

    DTIC Science & Technology

    1987-04-29

    studies of the elimination reaction will involve the reaction of an organoindium compound with a phosphine . The system, InMe 3-PMePhH, would be ideal. We...deprotonating reagents and potential amphoteric ligands. The compound C5H5GaMe2 reacts readily with FeCI2 to form ferrocene and with Fe2(CO)9 to...organogallium derivatives of ferrocene Fe(C5H4GaR2 )2 are being investigated by studying the reactions of Li2 (C5H4 )2Fe with two moles of GaMe2 CI or Ga(CH2SiMe3

  4. Lewis base activation of Lewis acids: catalytic, enantioselective addition of silyl ketene acetals to aldehydes.

    PubMed

    Denmark, Scott E; Beutner, Gregory L; Wynn, Thomas; Eastgate, Martin D

    2005-03-23

    The concept of Lewis base activation of Lewis acids has been reduced to practice for catalysis of the aldol reaction of silyl ketene acetals and silyl dienol ethers with aldehydes. The weakly acidic species, silicon tetrachloride (SiCl4), can be activated by binding of a strongly Lewis basic chiral phosphoramide, leading to in situ formation of a chiral Lewis acid. This species has proven to be a competent catalyst for the aldol addition of acetate-, propanoate-, and isobutyrate-derived silyl ketene acetals to conjugated and nonconjugated aldehydes. Furthermore, vinylogous aldol reactions of silyl dienol ethers are also demonstrated. The high levels of regio-, anti diastereo-, and enantioselectivity observed in these reactions can be rationalized through consideration of an open transition structure where steric interactions between the silyl cation complex and the approaching nucleophile are dominant.

  5. Schreibersite: an effective catalyst in the formose reaction network

    NASA Astrophysics Data System (ADS)

    Pallmann, S.; Šteflová (neé Svobodová, J.; Haas, M.; Lamour, S.; Henß, A.; Trapp, O.

    2018-05-01

    We report on the ability of the meteoritic material schreibersite to catalyze the generation of higher sugars from simple carbohydrates in the formose reaction network. Since the analysis of carbonaceous meteorites like the Murchison meteorite it has become generally accepted that a substantial amount of organic material has been delivered to the early earth and, therefore, ought to be considered in scenarios for the origin(s) of life. Also for the open question of accessible phosphorus sources, an extraterrestrial material called schreibersite has been identified that is capable of releasing soluble and reactive phosphorus oxyanions that would react with organics to form for instance nucleotides and membrane associated molecules. We have reinvestigated this material using capillary electrophoresis to monitor its corrosion process in water and probed its ability to phosphorylate a wide range of organics. Although showing a poor reactivity of schreibersite, we have found that the material catalyzes the aldol reaction of small carbohydrates forming larger sugar molecules. This reaction in the formose reaction network is a prebiotically likely route to biologically relevant sugars. The results of our study present one of the first instances of connecting extraterrestrial material to prebiotic chemistry on the early earth.

  6. Does increasing pressure always accelerate the condensed material decay initiated through bimolecular reactions? A case of the thermal decomposition of TKX-50 at high pressures.

    PubMed

    Lu, Zhipeng; Zeng, Qun; Xue, Xianggui; Zhang, Zengming; Nie, Fude; Zhang, Chaoyang

    2017-08-30

    Performances and behaviors under high temperature-high pressure conditions are fundamentals for many materials. We study in the present work the pressure effect on the thermal decomposition of a new energetic ionic salt (EIS), TKX-50, by confining samples in a diamond anvil cell, using Raman spectroscopy measurements and ab initio simulations. As a result, we find a quadratic increase in decomposition temperature (T d ) of TKX-50 with increasing pressure (P) (T d = 6.28P 2 + 12.94P + 493.33, T d and P in K and GPa, respectively, and R 2 = 0.995) and the decomposition under various pressures initiated by an intermolecular H-transfer reaction (a bimolecular reaction). Surprisingly, this finding is contrary to a general observation about the pressure effect on the decomposition of common energetic materials (EMs) composed of neutral molecules: increasing pressure will impede the decomposition if it starts from a bimolecular reaction. Our results also demonstrate that increasing pressure impedes the H-transfer via the enhanced long-range electrostatic repulsion of H +δ H +δ of neighboring NH 3 OH + , with blue shifts of the intermolecular H-bonds. And the subsequent decomposition of the H-transferred intermediates is also suppressed, because the decomposition proceeds from a bimolecular reaction to a unimolecular one, which is generally prevented by compression. These two factors are the basic root for which the decomposition retarded with increasing pressure of TKX-50. Therefore, our finding breaks through the previously proposed concept that, for the condensed materials, increasing pressure will accelerate the thermal decomposition initiated by bimolecular reactions, and reveals a distinct mechanism of the pressure effect on thermal decomposition. That is to say, increasing pressure does not always promote the condensed material decay initiated through bimolecular reactions. Moreover, such a mechanism may be feasible to other EISs due to the similar intermolecular

  7. Integrated Rig for the Production of Boron Nitride Nanotubes via the Pressurized Vapor-Condenser Method

    NASA Technical Reports Server (NTRS)

    Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor)

    2014-01-01

    An integrated production apparatus for production of boron nitride nanotubes via the pressure vapor-condenser method. The apparatus comprises: a pressurized reaction chamber containing a continuously fed boron containing target having a boron target tip, a source of pressurized nitrogen and a moving belt condenser apparatus; a hutch chamber proximate the pressurized reaction chamber containing a target feed system and a laser beam and optics.

  8. Integrated rig for the production of boron nitride nanotubes via the pressurized vapor-condenser method

    DOEpatents

    Smith, Michael W; Jordan, Kevin C

    2014-03-25

    An integrated production apparatus for production of boron nitride nanotubes via the pressure vapor-condenser method. The apparatus comprises: a pressurized reaction chamber containing a continuously fed boron containing target having a boron target tip, a source of pressurized nitrogen and a moving belt condenser apparatus; a hutch chamber proximate the pressurized reaction chamber containing a target feed system and a laser beam and optics.

  9. Aerosol-Phase Production of Nitrogen-Containing Oligomers After Uptake of Methylglyoxal and Cloud Processing

    NASA Astrophysics Data System (ADS)

    De Haan, D. O.; Riva, M.; Surratt, J. D.; Cazaunau, M.; Doussin, J. F.

    2016-12-01

    Minimal organic aerosol forms when aerosol particles are exposed to gas-phase methylglyoxal, but condensed phase laboratory studies of aerosol chemistry have suggested that methylglyoxal is a significant source of oligomerized aerosol material. In this study, various types of seed particles were exposed to gaseous methylglyoxal and then cloud-processed in the CESAM chamber. The gas phase was continuously probed by high-resolution PTR-MS during the experiments, and the particle phase WSOC was chemically characterized by high-resolution UPLC/ESI-DAD-QTOFMS. Uptake of methylglyoxal to dry particles caused optical rather than size changes, along with the release of imine products to the gas phase. High RH and cloud processing released some particle-bound methylglyoxal back to the gas phase but triggered an uptake of imine products. Analysis of the particle phase identified N-containing aldol condensation products derived from methylglyoxal, imine (produced from methylglyoxal and amine reactions), acetaldehyde (produced by methylglyoxal photolysis) and hydroxyacetone (produced by methylglyoxal disproportionation) monomers.

  10. A Comparative Study of Basic, Amphoteric, and Acidic Catalysts in the Oxidative Coupling of Methanol and Ethanol for Acrolein Production.

    PubMed

    Lilić, Aleksandra; Wei, Tiantian; Bennici, Simona; Devaux, Jean-François; Dubois, Jean-Luc; Auroux, Aline

    2017-09-11

    The impact of acid/base properties (determined by adsorption microcalorimetry) of various catalysts on the cross-aldolization of acetaldehyde and formaldehyde leading to acrolein was methodically studied in oxidizing conditions starting from a mixture of methanol and ethanol. The aldol condensation and further dehydration to acrolein were carried out on catalysts presenting various acid/base properties (MgO, Mg-Al oxides, Mg/SiO 2 , NbP, and heteropolyanions on silica, HPA/SiO 2 ). Thermodynamic calculations revealed that cross-aldolization is always favored compared with self-aldolization of acetaldehyde, which leads to crotonaldehyde formation. The presence of strong basic sites is shown to be necessary, but a too high amount drastically increases CO x production. On strong acid sites, production of acrolein and carbon oxides (CO x ) does not increase with temperature. The optimal catalyst for this process should be amphoteric with a balanced acid/base cooperation of medium strength sites and a small amount (<100 μmol g -1 ) of very strong basic sites (Q diff >150 kJ mol -1 ). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Synthesis and biological evaluation of chalcone derivatives (mini review).

    PubMed

    Bukhari, Syed Nasir Abbas; Jasamai, Malina; Jantan, Ibrahim

    2012-11-01

    Chalcones are the principal precursors for the biosynthesis of flavonoids and isoflavonoids. A three carbon α, β-unsaturated carbonyl system constitutes chalcones. Chalcones are the condensation products of aromatic aldehyde with acetophenones in attendance of catalyst. They go through an assortment of chemical reactions and are found advantageous in synthesis of pyrazoline, isoxazole and a variety of heterocyclic compounds. In synthesizing a range of therapeutic compounds, chalcones impart key role. They have showed worth mentioning therapeutic efficacy for the treatment of various diseases. Chalcone based derivatives have gained heed since they own simple structures, and diverse pharmacological actions. A lot of methods and schemes have been reported for the synthesis of these compounds. Amongst all, Aldol condensation and Claisen-Schmidt condensation still grasp high up position. Other distinguished techniques include Suzuki reaction, Witting reaction, Friedel-Crafts acylation with cinnamoyl chloride, Photo-Fries rearrangement of phenyl cinnamates etc. These inventive techniques utilize various catalysts and reagents including SOCl(2) natural phosphate, lithium nitrate, amino grafted zeolites, zinc oxide, water, Na(2)CO(3), PEG400, silicasulfuric acid, ZrCl(4) and ionic liquid etc. The development of better techniques for the synthesis of α, β- unsaturated carbonyl compounds is still in high demand. In brief, we have explained the methods and catalysts used in the synthesis of chalcones along with their biological activities in a review form to provide information for the development of new-fangled processes targeting better yield, less reaction time and least side effects with utmost pharmacological properties.

  12. Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

    PubMed Central

    Engelen, Bernward; Panthöfer, Martin; Deiseroth, Hans-Jörg; Schlirf, Jens

    2016-01-01

    Summary A one-pot transformation, which involves the reaction of ketones with aldehydes in the presence of metal halides to furnish tetrahydro-2H-pyran-2,4-diols in a highly diastereoselective manner, is investigated thoroughly by experiments and computations. The reaction was also successfully implemented on a flow micro reactor system. PMID:27340472

  13. A Rapid, One-Pot Synthesis of β-Siloxy-α-Haloaldehydes

    PubMed Central

    Saadi, Jakub; Akakura, Matsujiro

    2011-01-01

    The Mukaiyama cross aldol reaction of α-fluoro-, α-chloro-, and α-bromoacetaldehyde-derived (Z)-tris(trimethylsilyl)- silyl enol ethers furnishing anti-β-siloxy-α-haloaldehydes is described. A highly diastereoselective, one-pot, sequential double aldol process, affording novel β,δ-bissiloxy-α,γ-bishaloaldehydes is developed. Reactions are catalyzed by C6F5CHTf2 and C6F5CTf2AlMe2 (0.5–1.5 mol%) and provide access to halogenated polyketide fragments. PMID:21815682

  14. A Multistep Synthesis Featuring Classic Carbonyl Chemistry for the Advanced Organic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Duff, David B.; Abbe, Tyler G.; Goess, Brian C.

    2012-01-01

    A multistep synthesis of 5-isopropyl-1,3-cyclohexanedione is carried out from three commodity chemicals. The sequence involves an aldol condensation, Dieckmann-type annulation, ester hydrolysis, and decarboxylation. No purification is required until after the final step, at which point gravity column chromatography provides the desired product in…

  15. Evaporation and condensation at a liquid surface. I. Argon

    NASA Astrophysics Data System (ADS)

    Yasuoka, Kenji; Matsumoto, Mitsuhiro; Kataoka, Yosuke

    1994-11-01

    Molecular dynamics computer simulations were carried out to investigate the dynamics of evaporation and condensation for argon at the temperature of 80 and 100 K. From the decrease of the survival probability of vapor molecules, the ratio of self reflection to collision is estimated to be 12%-15%, only weakly dependent on the temperature. This suggests that argon vapor molecules are in the condition of almost complete capture, and the condensation is considered to be a barrierless process. The total ratio of reflection which is evaluated with the flux correlation of condensation and evaporation is 20% at both temperature. The difference between these two ratios of reflection is ascribed to a phenomenon that vapor molecules colliding with the surface drive out other liquid molecules. This molecule exchange at the surface is as important as the self-reflection, and the conventional picture of condensation as a unimolecular chemical reaction is not appropriate.

  16. Asymmetric Total Synthesis of (-)-(3 R)-Inthomycin C.

    PubMed

    Balcells, Sandra; Haughey, Maxwell B; Walker, Johannes C L; Josa-Culleré, Laia; Towers, Christopher; Donohoe, Timothy J

    2018-06-04

    A short (10 step) and efficient (15% overall yield) synthesis of the natural product (-)-(3 R)-inthomycin C is reported. The key steps comprise three C-C bond-forming reactions: (i) a vinylogous Mukaiyama aldol, (ii) an olefin cross-metathesis reaction, and (iii) an asymmetric Mukaiyama-Kiyooka aldol. This route is notable for its brevity and has the advantage of lacking stoichiometric tin-promoted cross-coupling reactions present in previous approaches. Initial investigations on the biological activity of (-)-(3 R)-inthomycin C and structural analogues on human cancer cell lines are also described for the first time.

  17. Regioselectivity switch in chiral amine-catalysed asymmetric addition of aldehydes to reactive enals.

    PubMed

    Kano, Taichi; Maruyama, Hiroki; Sakamoto, Ryu; Maruoka, Keiji

    2015-06-21

    In this communication, we present a regioselectivity switch for the chiral amine-catalysed asymmetric addition of aldehydes to reactive enals to afford either aldol adducts or conjugate adducts in a stereoselective fashion. The unprecedented asymmetric aldol reaction of aldehydes with enals was realized by the use of a diarylprolinol catalyst, giving synthetically useful and important chiral allylic alcohols.

  18. Process for gasifying carbonaceous material from a recycled condensate slurry

    DOEpatents

    Forney, Albert J.; Haynes, William P.

    1981-01-01

    Coal or other carbonaceous material is gasified by reaction with steam and oxygen in a manner to minimize the problems of effluent water stream disposal. The condensate water from the product gas is recycled to slurry the coal feed and the amount of additional water or steam added for cooling or heating is minimized and preferably kept to a level of about that required to react with the carbonaceous material in the gasification reaction. The gasification is performed in a pressurized fluidized bed with the coal fed in a water slurry and preheated or vaporized by indirect heat exchange contact with product gas and recycled steam. The carbonaceous material is conveyed in a gas-solid mixture from bottom to top of the pressurized fluidized bed gasifier with the solids removed from the product gas and recycled steam in a supported moving bed filter of the resulting carbonaceous char. Steam is condensed from the product gas and the condensate recycled to form a slurry with the feed coal carbonaceous particles.

  19. Sensitive inexpensive spectrophotometric and spectrofluorimetric analysis of ezogabine, levetiracetam and topiramate in tablet formulations using Hantzsch condensation reaction

    NASA Astrophysics Data System (ADS)

    Ibrahim, F. A.; El-Yazbi, A. F.; Wagih, M. M.; Barary, M. A.

    2017-09-01

    Two highly sensitive, simple and selective spectrophotometric and spectrofluorimetric assays have been investigated for the analysis of ezogabine, levetiracetam and topiramate in their pure and in pharmaceutical dosage forms. The suggested methods depend on the condensation of the primary amino-groups in the three drugs with acetylacetone and formaldehyde according to Hantzsch reaction yielding highly fluorescent yellow colored dihydropyridine derivatives. The reaction products of ezogabine, levetiracetam and topiramate were measured spectrophotometrically at 418, 390 and 380 nm or spectrofluorimetrically at λem/ex of 495/425 nm, 490/415 nm and 488/410 nm, respectively. Various experimental conditions have been carefully studied to maximize the reaction yield. At the optimum reaction conditions, the calibration curves were rectilinear over the concentration ranges of 8-25, 60-180 and 80-200 μg/mL spectrophotometrically and 0.02-0.2, 0.2-1.2 and 0.2-1.5 μg/mL spectrofluorimetrically for ezogabine, levetiracetam and topiramate, respectively with good correlation coefficients. The suggested methods were applied successfully for the analysis of ezogabine, levetiracetam and topiramate in their commercial tablets with high percentage recoveries and negligible interference from various excipients in pharmaceutical dosage forms. The results were statistically analyzed and showed the absence of any significant difference between both developed and published methods. The procedures were validated and evaluated by the ICH guidelines revealing good reproducibility and accuracy. Therefore, the two proposed methods may be considered of high interest for practical and reliable analysis of ezogabine, levetiracetam and topiramate in pharmaceutical dosage forms.

  20. Chemically Amplified Bilevel Resist Based on Condensation of Siloxanes

    NASA Astrophysics Data System (ADS)

    Sakata, Miwa; Ito, Toshio; Yamashita, Yoshio

    1991-11-01

    This paper deals with a negative bilevel resist which is based on the acid-catalyzed condensation reaction of poly(siloxane)s. The resist systems consist of photoacid generators and poly(siloxane). Ph3S+OTf- reveals an efficient activity for silanol condensation and the system has a high sensitivity of 0.31 mJ/cm2. Tetrafunctional silane plays the role of crosslinker in this system. Sensitivity improvement of low-sensitivity systems such as benzoin p-toluenesulfonate/poly(siloxane) can be achieved by this method.

  1. Hydrodeoxygenation processes: advances on catalytic transformations of biomass-derived platform chemicals into hydrocarbon fuels.

    PubMed

    De, Sudipta; Saha, Basudeb; Luque, Rafael

    2015-02-01

    Lignocellulosic biomass provides an attractive source of renewable carbon that can be sustainably converted into chemicals and fuels. Hydrodeoxygenation (HDO) processes have recently received considerable attention to upgrade biomass-derived feedstocks into liquid transportation fuels. The selection and design of HDO catalysts plays an important role to determine the success of the process. This review has been aimed to emphasize recent developments on HDO catalysts in effective transformations of biomass-derived platform molecules into hydrocarbon fuels with reduced oxygen content and improved H/C ratios. Liquid hydrocarbon fuels can be obtained by combining oxygen removal processes (e.g. dehydration, hydrogenation, hydrogenolysis, decarbonylation etc.) as well as by increasing the molecular weight via C-C coupling reactions (e.g. aldol condensation, ketonization, oligomerization, hydroxyalkylation etc.). Fundamentals and mechanistic aspects of the use of HDO catalysts in deoxygenation reactions will also be discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Linking the historical and chemical definitions of diabatic states for charge and excitation energy transfer reactions in condensed phase.

    PubMed

    Pavanello, Michele; Neugebauer, Johannes

    2011-10-07

    Marcus theory of electron transfer (ET) and Förster theory of excitation energy transfer (EET) rely on the Condon approximation and the theoretical availability of initial and final states of ET and EET reactions, often called diabatic states. Recently [Subotnik et al., J. Chem. Phys. 130, 234102 (2009)], diabatic states for practical calculations of ET and EET reactions were defined in terms of their interactions with the surrounding environment. However, from a purely theoretical standpoint, the definition of diabatic states must arise from the minimization of the dynamic couplings between the trial diabatic states. In this work, we show that if the Condon approximation is valid, then a minimization of the derived dynamic couplings leads to corresponding diabatic states for ET reactions taking place in solution by diagonalization of the dipole moment matrix, which is equivalent to a Boys localization algorithm; while for EET reactions in solution, diabatic states are found through the Edmiston-Ruedenberg localization algorithm. In the derivation, we find interesting expressions for the environmental contribution to the dynamic coupling of the adiabatic states in condensed-phase processes. In one of the cases considered, we find that such a contribution is trivially evaluable as a scalar product of the transition dipole moment with a quantity directly derivable from the geometry arrangement of the nuclei in the molecular environment. Possibly, this has applications in the evaluation of dynamic couplings for large scale simulations. © 2011 American Institute of Physics

  3. Production of alpha-hydroxy carboxylic acids and esters from higher sugars using tandem catalyst systems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Orazov, Marat; Davis, Mark E.

    The present disclosure is directed to methods and composition used in the preparation of alpha-hydroxy carboxylic acids and esters from higher sugars using a tandem catalyst system comprising retro-aldol catalysts and Lewis acid catalysts. In some embodiments, these alpha-hydroxy carboxylic acids may be prepared from pentoses and hexoses. The retro-aldol and Lewis catalysts may be characterized by their respective ability to catalyze a 1,2-carbon shift reaction and a 1,2-hydride shift reaction on an aldose or ketose substrate.

  4. Low Energy Nuclear Reactions: 2007 Update

    NASA Astrophysics Data System (ADS)

    Krivit, Steven B.

    2007-03-01

    This paper presents an overview of low energy nuclear reactions, a subset of the field of condensed matter nuclear science. Condensed matter nuclear science studies nuclear effects in and/or on condensed matter, including low energy nuclear reactions, an entirely new branch of science that gained widespread attention and notoriety beginning in 1989 with the announcement of a previously unrecognized source of energy by Martin Fleischmann and Stanley Pons that came to be known as cold fusion. Two branches of LENR are recognized. The first includes a set of reactions like those observed by Fleischmann and Pons that use palladium and deuterium and yield excess heat and helium-4. Numerous mechanisms have been proposed to explain these reactions, however there is no consensus for, or general acceptance of, any of the theories. The claim of fusion is still considered speculative and, as such, is not an ideal term for this work. The other branch is a wide assortment of nuclear reactions that may occur with either hydrogen or deuterium. Anomalous nuclear transmutations are reported that involve light as well as heavy elements. The significant questions that face this field of research are: 1) Are LENRs a genuine nuclear reaction? 2) If so, is there a release of excess energy? 3) If there is, is the energy release cost-effective?

  5. Catalytic Upgrading of 5-Hydroxymethylfurfural to Drop-in Biofuels by Solid Base and Bifunctional Metal-Acid Catalysts.

    PubMed

    Bohre, Ashish; Saha, Basudeb; Abu-Omar, Mahdi M

    2015-12-07

    Design and synthesis of effective heterogeneous catalysts for the conversion of biomass intermediates into long chain hydrocarbon precursors and their subsequent deoxygenation to hydrocarbons is a viable strategy for upgrading lignocellulose into distillate range drop-in biofuels. Herein, we report a two-step process for upgrading 5-hydroxymethylfurfural (HMF) to C9 and C11 fuels with high yield and selectivity. The first step involves aldol condensation of HMF and acetone with a water tolerant solid base catalyst, zirconium carbonate (Zr(CO3 )x ), which gave 92 % C9 -aldol product with high selectivity at nearly 100 % HMF conversion. The as-synthesised Zr(CO3 )x was analysed by several analytical methods for elucidating its structural properties. Recyclability studies of Zr(CO3 )x revealed a negligible loss of its activity after five consecutive cycles over 120 h of operation. Isolated aldol product from the first step was hydrodeoxygenated with a bifunctional Pd/Zeolite-β catalyst in ethanol, which showed quantitative conversion of the aldol product to n-nonane and 1-ethoxynonane with 40 and 56 % selectivity, respectively. 1-Ethoxynonane, a low oxygenate diesel range fuel, which we report for the first time in this paper, is believed to form through etherification of the hydroxymethyl group of the aldol product with ethanol followed by opening of the furan ring and hydrodeoxygenation of the ether intermediate. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS AND CARBONACEOUS SOLIDS IN GAS-PHASE CONDENSATION EXPERIMENTS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jaeger, C.; Huisken, F.; Henning, Th.

    2009-05-01

    Carbonaceous grains represent a major component of cosmic dust. In order to understand their formation pathways, they have been prepared in the laboratory by gas-phase condensation reactions such as laser pyrolysis and laser ablation. Our studies demonstrate that the temperature in the condensation zone determines the formation pathway of carbonaceous particles. At temperatures lower than 1700 K, the condensation by-products are mainly polycyclic aromatic hydrocarbons (PAHs) that are also the precursors or building blocks for the condensing soot grains. The low-temperature condensates contain PAH mixtures that are mainly composed of volatile three to five ring systems. At condensation temperatures highermore » than 3500 K, fullerene-like carbon grains and fullerene compounds are formed. Fullerene fragments or complete fullerenes equip the nucleating particles. Fullerenes can be identified as soluble components. Consequently, condensation products in cool and hot astrophysical environments such as cool and hot asymptotic giant branch stars or Wolf-Rayet stars should be different and should have distinct spectral properties.« less

  7. Wettability modified nanoporous ceramic membrane for simultaneous residual heat and condensate recovery.

    PubMed

    Hu, H W; Tang, G H; Niu, D

    2016-06-07

    Recovery of both latent heat and condensate from boiler flue gas is significant for improving boiler efficiency and water conservation. The condensation experiments are carried out to investigate the simultaneous heat and mass transfer across the nanoporous ceramic membranes (NPCMs) which are treated to be hydrophilic and hydrophobic surfaces using the semicontinuous supercritical reactions. The effects of typical parameters including coolant flow rate, vapor/nitrogen gas mixture temperature, water vapor volume fraction and transmembrane pressure on heat and mass transfer performance are studied. The experimental results show that the hydrophilic NPCM exhibits higher performances of condensation heat transfer and condensate recovery. However, the hydrophobic modification results in remarkable degradation of heat and condensate recovery from the mixture. Molecular dynamics simulations are conducted to establish a hydrophilic/hydrophobic nanopore/water liquid system, and the infiltration characteristics of the single hydrophilic/hydrophobic nanopore is revealed.

  8. Wettability modified nanoporous ceramic membrane for simultaneous residual heat and condensate recovery

    NASA Astrophysics Data System (ADS)

    Hu, H. W.; Tang, G. H.; Niu, D.

    2016-06-01

    Recovery of both latent heat and condensate from boiler flue gas is significant for improving boiler efficiency and water conservation. The condensation experiments are carried out to investigate the simultaneous heat and mass transfer across the nanoporous ceramic membranes (NPCMs) which are treated to be hydrophilic and hydrophobic surfaces using the semicontinuous supercritical reactions. The effects of typical parameters including coolant flow rate, vapor/nitrogen gas mixture temperature, water vapor volume fraction and transmembrane pressure on heat and mass transfer performance are studied. The experimental results show that the hydrophilic NPCM exhibits higher performances of condensation heat transfer and condensate recovery. However, the hydrophobic modification results in remarkable degradation of heat and condensate recovery from the mixture. Molecular dynamics simulations are conducted to establish a hydrophilic/hydrophobic nanopore/water liquid system, and the infiltration characteristics of the single hydrophilic/hydrophobic nanopore is revealed.

  9. Recovery of condensate water quality in power generator's surface condenser

    NASA Astrophysics Data System (ADS)

    Kurniawan, Lilik Adib

    2017-03-01

    In PT Badak NGL Plant, steam turbines are used to drive major power generators, compressors, and pumps. Steam exiting the turbines is condensed in surface condensers to be returned to boilers. Therefore, surface condenser performance and quality of condensate water are very important. One of the recent problem was caused by the leak of a surface condenser of Steam Turbine Power Generator. Thesteam turbine was overhauled, leaving the surface condenser idle and exposed to air for more than 1.5 years. Sea water ingress due to tube leaks worsens the corrosionof the condenser shell. The combination of mineral scale and corrosion product resulting high conductivity condensate at outlet condenser when we restarted up, beyond the acceptable limit. After assessing several options, chemical cleaning was the best way to overcome the problem according to condenser configuration. An 8 hour circulation of 5%wt citric acid had succeed reducing water conductivity from 50 μmhos/cm to below 5 μmhos/cm. The condensate water, then meets the required quality, i.e. pH 8.3 - 9.0; conductivity ≤ 5 μmhos/cm, therefore the power generator can be operated normally without any concern until now.

  10. Compounds and methods for the production of long chain hydrocarbons from biological sources

    DOEpatents

    Gordon, John Cameron; Silks, Louis A; Sutton, Andrew D; Wu, Ruilian; Schlaf, Marcel; Waldie, Fraser; West, Ryan; Collias, Dimitris Ioannis

    2016-08-23

    The present invention is directed to the preparation of oxygenated, unsaturated hydrocarbon compounds, such as derivatives of furfural or hydroxymethyl furfural produced by aldol condensation with a ketone or a ketoester, as well as methods of deoxidatively reducing those compounds with hydrogen under acidic conditions to provide saturated hydrocarbons useful as fuels.

  11. Anomalous nuclear reactions in condensed matter: Recent results and open questions

    NASA Astrophysics Data System (ADS)

    Jones, S. E.; Palmer, E. P.; Czirr, J. B.; Decker, D. L.; Jensen, G. L.; Thorne, J. M.; Taylor, S. F.; Rafelski, J.

    1990-06-01

    We have observed clear signatures for neutron emission during deuteron infusion into metals, implying the occurrence of nuclear fusion in condensed matter near room temperature. The low-level nuclear phenomenon has been demonstrated in collaborative experiments at Brigham Young University, at the Gran Sasso laboratory in Italy, and at the Los Alamos National Laboratory. We have shown that neutron emission can be induced in metals using both electrochemical and variational temperature/pressure means to generate non-equilibrium conditions. Observed average neutron emission rates are approximately 0.04-0.4 no/ s. Current efforts focus on trying to understand and control the phenomenon. In particular, we wish to understand the correlation of neutron yields with parameters such as hydrogen/metal ion ratio, pressure (induced, for example, by electrical field or gas pressure or mechanical pressure), temperature variation, hydride phase changes, and surface conditions, e.g., a palladium coating on titanium. We want to know if fusion arises due to the close proximity of the deuterons in the lattice (piezonuclear fusion), or possibly from “microscopic hot fusion”, accompanying strong electric fields at propagating cracks in the hydride. The latter interpretation would imply neutron emission in bursts. Our experiments show clear evidence for emission of ˜102 neutrons in bursts lasting <128 μs, although random neutron-singles emissions were also observed. Experiments now underway to compare the d-d, and p-d, and d-t reaction rates will be important to a consistent description of the new phenomenon. Careful scrutiny of this effect could increase our understanding of heat, helium-3, and tritium production in the earth, other planets, and even the stars.

  12. Formation of polychlorinated diphenyl ethers from condensation of chlorophenols with chlorobenzenes.

    PubMed

    Liu, Wenxia; Zheng, Minghui; Liu, Wenbin; Ma, Xiaodong; Qian, Yong; Zhang, Bing

    2008-01-01

    Polychlorinated diphenyl ethers (PCDEs), which are among the members of persistent organic pollutants, and PCDEs have been determined in a number of environmental samples. The main possible sources are the technical production of chlorinated phenols and all processes of incomplete combustion. PCDEs were observed in the fly ash from a municipal waste incinerator (MWI). It was speculated that the condensation of chlorophenols with chlorobenzenes occurred via PCDEs to form polychlorinated dibenzofurans (PCDFs). Nevertheless, PCDEs formation from condensation of chlorophenols with chlorobenzenes has not been confirmed by experimental observation. The objective of this paper is to investigate the formation mechanism of PCDEs from the condensation of chlorophenols with chlorobenzenes. The results are expected to be helpful in understanding the formation of PCDEs and in controlling and abating PCDEs emissions from MWI. The pyrolysis of pentachlorophenol (PCP) and/or polychlorobenzenes (PCBz) was carried out in a sealed glass tube. The reaction products were extracted and purified with K2CO3 solution. The samples were concentrated and then cleaned up on an alumina column. GC/MS was used for identification and quantification of reaction products. The results showed that the pyrolysis of hexachlorobenzene (HCB) at 340 degrees C for 6 h led to the formation of decachlorodiphenyl ether (DCDE) (2.41 microg/mg) and octachlorodibenzo-p-dioxins (OCDD) (0.24 micropg/mg), while the pyrolysis of PCP yielded DCDE (13.08 microg/mg) and OCDD (180.13 microg/mg). In addition, the amount of DCDE formation from the pyrolysis of the mixture of PCP and HCB was 4.65 times higher than the total amount of DCDE formation from the pyrolysis of HCB and PCP, respectively. This indicated that PCP and HCB were prone to condensation and formation of DCDE. DCDE was the main congener of PCDEs from condensation of PCP with HCB at 340, 400 and 450 degrees C. A small amount of nonachlorodiphenyl ether (NCDE

  13. An active site–tail interaction in the structure of hexahistidine-tagged Thermoplasma acidophilum citrate synthase

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Murphy, Jesse R.; Donini, Stefano; Kappock, T. Joseph, E-mail: kappock@purdue.edu

    2015-09-23

    Citrate synthase from the thermophilic euryarchaeon T. acidophilum fused to a hexahistidine tag was purified and biochemically characterized. The structure of the unliganded enzyme at 2.2 Å resolution contains tail–active site contacts in half of the active sites. Citrate synthase (CS) plays a central metabolic role in aerobes and many other organisms. The CS reaction comprises two half-reactions: a Claisen aldol condensation of acetyl-CoA (AcCoA) and oxaloacetate (OAA) that forms citryl-CoA (CitCoA), and CitCoA hydrolysis. Protein conformational changes that ‘close’ the active site play an important role in the assembly of a catalytically competent condensation active site. CS from themore » thermoacidophile Thermoplasma acidophilum (TpCS) possesses an endogenous Trp fluorophore that can be used to monitor the condensation reaction. The 2.2 Å resolution crystal structure of TpCS fused to a C-terminal hexahistidine tag (TpCSH6) reported here is an ‘open’ structure that, when compared with several liganded TpCS structures, helps to define a complete path for active-site closure. One active site in each dimer binds a neighboring His tag, the first nonsubstrate ligand known to occupy both the AcCoA and OAA binding sites. Solution data collectively suggest that this fortuitous interaction is stabilized by the crystalline lattice. As a polar but almost neutral ligand, the active site–tail interaction provides a new starting point for the design of bisubstrate-analog inhibitors of CS.« less

  14. Wettability modified nanoporous ceramic membrane for simultaneous residual heat and condensate recovery

    PubMed Central

    Hu, H. W.; Tang, G. H.; Niu, D.

    2016-01-01

    Recovery of both latent heat and condensate from boiler flue gas is significant for improving boiler efficiency and water conservation. The condensation experiments are carried out to investigate the simultaneous heat and mass transfer across the nanoporous ceramic membranes (NPCMs) which are treated to be hydrophilic and hydrophobic surfaces using the semicontinuous supercritical reactions. The effects of typical parameters including coolant flow rate, vapor/nitrogen gas mixture temperature, water vapor volume fraction and transmembrane pressure on heat and mass transfer performance are studied. The experimental results show that the hydrophilic NPCM exhibits higher performances of condensation heat transfer and condensate recovery. However, the hydrophobic modification results in remarkable degradation of heat and condensate recovery from the mixture. Molecular dynamics simulations are conducted to establish a hydrophilic/hydrophobic nanopore/water liquid system, and the infiltration characteristics of the single hydrophilic/hydrophobic nanopore is revealed. PMID:27270997

  15. Structural basis for cyclization specificity of two Azotobacter type III polyketide synthases: a single amino acid substitution reverses their cyclization specificity.

    PubMed

    Satou, Ryutaro; Miyanaga, Akimasa; Ozawa, Hiroki; Funa, Nobutaka; Katsuyama, Yohei; Miyazono, Ken-ichi; Tanokura, Masaru; Ohnishi, Yasuo; Horinouchi, Sueharu

    2013-11-22

    Type III polyketide synthases (PKSs) show diverse cyclization specificity. We previously characterized two Azotobacter type III PKSs (ArsB and ArsC) with different cyclization specificity. ArsB and ArsC, which share a high sequence identity (71%), produce alkylresorcinols and alkylpyrones through aldol condensation and lactonization of the same polyketomethylene intermediate, respectively. Here we identified a key amino acid residue for the cyclization specificity of each enzyme by site-directed mutagenesis. Trp-281 of ArsB corresponded to Gly-284 of ArsC in the amino acid sequence alignment. The ArsB W281G mutant synthesized alkylpyrone but not alkylresorcinol. In contrast, the ArsC G284W mutant synthesized alkylresorcinol with a small amount of alkylpyrone. These results indicate that this amino acid residue (Trp-281 of ArsB or Gly-284 of ArsC) should occupy a critical position for the cyclization specificity of each enzyme. We then determined crystal structures of the wild-type and G284W ArsC proteins at resolutions of 1.76 and 1.99 Å, respectively. Comparison of these two ArsC structures indicates that the G284W substitution brings a steric wall to the active site cavity, resulting in a significant reduction of the cavity volume. We postulate that the polyketomethylene intermediate can be folded to a suitable form for aldol condensation only in such a relatively narrow cavity of ArsC G284W (and presumably ArsB). This is the first report on the alteration of cyclization specificity from lactonization to aldol condensation for a type III PKS. The ArsC G284W structure is significant as it is the first reported structure of a microbial resorcinol synthase.

  16. Condensed tannin-resorcinol adducts in laminating adhesives

    Treesearch

    Richard W. Hemingway; Roland E. Kreibich

    1985-01-01

    A condensed tannin-resorcinol adduct made by co-reaction of an extract from southern pine bark with resorcinol at a 2 to 1 weight ratio was used to prepare a laminating resin in which the entire amount of resorcinol normally used was replaced by this adduct. The resin was formulated into a room temperature setting adhesive that meets the basic criteria of product...

  17. Synthesis of Renewable Lubricant Alkanes from Biomass-Derived Platform Chemicals.

    PubMed

    Gu, Mengyuan; Xia, Qineng; Liu, Xiaohui; Guo, Yong; Wang, Yanqin

    2017-10-23

    The catalytic synthesis of liquid alkanes from renewable biomass has received tremendous attention in recent years. However, bio-based platform chemicals have not to date been exploited for the synthesis of highly branched lubricant alkanes, which are currently produced by hydrocracking and hydroisomerization of long-chain n-paraffins. A selective catalytic synthetic route has been developed for the production of highly branched C 23 alkanes as lubricant base oil components from biomass-derived furfural and acetone through a sequential four-step process, including aldol condensation of furfural with acetone to produce a C 13 double adduct, selective hydrogenation of the adduct to a C 13 ketone, followed by a second condensation of the C 13 ketone with furfural to generate a C 23 aldol adduct, and finally hydrodeoxygenation to give highly branched C 23 alkanes in 50.6 % overall yield from furfural. This work opens a general strategy for the synthesis of high-quality lubricant alkanes from renewable biomass. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Synthesis of Renewable Triketones, Diketones, and Jet-Fuel Range Cycloalkanes with 5-Hydroxymethylfurfural and Ketones.

    PubMed

    Li, Shanshan; Chen, Fang; Li, Ning; Wang, Wentao; Sheng, Xueru; Wang, Aiqin; Cong, Yu; Wang, Xiaodong; Zhang, Tao

    2017-02-22

    A series of renewable C 9 -C 12 triketones with repeating [COCH 2 CH 2 ] units were synthesized in high carbon yields (ca. 90 %) by the aqueous-phase hydrogenation of the aldol-condensation products of 5-hydroxylmethylfurfural (HMF) and ketones over an Au/TiO 2 catalyst. Compared with the reported routes, this new route has many advantages such as being environmentally friendly, having fewer steps, using a cheaper and reusable catalyst, etc. The triketones as obtained can be used as feedstocks in the production of conducting or semi-conducting polymers. Through a solvent-free intramolecular aldol condensation over solid-base catalysts, the triketones were selectively converted to diketones, which can be used as intermediates in the synthesis of useful chemicals or polymers. As another application, the tri- and diketones can also be utilized as precursors for the synthesis of jet-fuel range branched cycloalkanes with low freezing points (224-248 K) and high densities (ca. 0.81 g mL -1 ). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Controlling condensation and frost growth with chemical micropatterns.

    PubMed

    Boreyko, Jonathan B; Hansen, Ryan R; Murphy, Kevin R; Nath, Saurabh; Retterer, Scott T; Collier, C Patrick

    2016-01-22

    In-plane frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from neighboring supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of ice bridges across the population of supercooled condensate. Here, we demonstrate that when the separation between adjacent nucleation sites for supercooled condensate is properly controlled with chemical micropatterns prior to freezing, inter-droplet ice bridging can be slowed and even halted entirely. Since the edge-to-edge separation between adjacent supercooled droplets decreases with growth time, deliberately triggering an early freezing event to minimize the size of nascent condensation was also necessary. These findings reveal that inter-droplet frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and by temporally controlling the onset of freezing events.

  20. Controlling condensation and frost growth with chemical micropatterns

    DOE PAGES

    Boreyko, Jonathan B.; Hansen, Ryan R.; Murphy, Kevin R.; ...

    2016-01-22

    Frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of frost across the population of supercooled condensate. Here, we demonstrate that when the nucleation sites for supercooled condensate are properly controlled with chemical micropatterns, the speed of frost growth can be slowed and even halted entirely. This stoppage of frost growth is attributed to the large interdroplet separation between condensate upon the onset ofmore » freezing, which was controlled by the pitch of the chemical patterns and by deliberately triggering an early freezing event. Lastly, these findings reveal that frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and/or temporally control the onset of freezing events.« less

  1. Controlling condensation and frost growth with chemical micropatterns

    PubMed Central

    Boreyko, Jonathan B.; Hansen, Ryan R.; Murphy, Kevin R.; Nath, Saurabh; Retterer, Scott T.; Collier, C. Patrick

    2016-01-01

    In-plane frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from neighboring supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of ice bridges across the population of supercooled condensate. Here, we demonstrate that when the separation between adjacent nucleation sites for supercooled condensate is properly controlled with chemical micropatterns prior to freezing, inter-droplet ice bridging can be slowed and even halted entirely. Since the edge-to-edge separation between adjacent supercooled droplets decreases with growth time, deliberately triggering an early freezing event to minimize the size of nascent condensation was also necessary. These findings reveal that inter-droplet frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and by temporally controlling the onset of freezing events. PMID:26796663

  2. The synthesis of 2-(5-(3-methoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl)phenol using sodium impregnated on activated chicken eggshells catalyst

    NASA Astrophysics Data System (ADS)

    Mardiana, L.; Bakri, R.; Septiarti, A.; Ardiansah, B.

    2017-04-01

    The novel compound of 2-(5-(3-methoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl)phenol as a pyrazoline derivative has been synthesized by two-steps reaction using sodium impregnated on activated chicken eggshells (Na-ACE) catalyst. Na-ACE was primarily prepared by a simple wet impregnation of NaOH solution on activated chicken eggshells solid support. The Na-ACE catalyst produced was characterized using FTIR spectrophotometer, XRD and SEM then applied in pyrazoline synthesis. First, chalcone was prepared from the reaction of 2-hydroxyacetophenone and 3-methoxybenzaldehyde by base-catalyzed aldol condensation. This product was subsequently reacted with hydrazine hydrate to give corresponding pyrazoline. The structure elucidation of the compound using FTIR, UV-Vis, LC-ESI-MS and 1H-NMR indicated the desired product has been successfully synthesized. Furthermore, the potential antioxidant activities of chalcone and pyrazoline have also been studied in-vitro using DPPH radical scavenging method. The results revealed that pyrazoline has a greater antioxidant activity than chalcone.

  3. Fused electron deficient semiconducting polymers for air stable electron transport.

    PubMed

    Onwubiko, Ada; Yue, Wan; Jellett, Cameron; Xiao, Mingfei; Chen, Hung-Yang; Ravva, Mahesh Kumar; Hanifi, David A; Knall, Astrid-Caroline; Purushothaman, Balaji; Nikolka, Mark; Flores, Jean-Charles; Salleo, Alberto; Bredas, Jean-Luc; Sirringhaus, Henning; Hayoz, Pascal; McCulloch, Iain

    2018-01-29

    Conventional semiconducting polymer synthesis typically involves transition metal-mediated coupling reactions that link aromatic units with single bonds along the backbone. Rotation around these bonds contributes to conformational and energetic disorder and therefore potentially limits charge delocalisation, whereas the use of transition metals presents difficulties for sustainability and application in biological environments. Here we show that a simple aldol condensation reaction can prepare polymers where double bonds lock-in a rigid backbone conformation, thus eliminating free rotation along the conjugated backbone. This polymerisation route requires neither organometallic monomers nor transition metal catalysts and offers a reliable design strategy to facilitate delocalisation of frontier molecular orbitals, elimination of energetic disorder arising from rotational torsion and allowing closer interchain electronic coupling. These characteristics are desirable for high charge carrier mobilities. Our polymers with a high electron affinity display long wavelength NIR absorption with air stable electron transport in solution processed organic thin film transistors.

  4. Preparation of Fe3O4/SiO2-guanidine organobase catalyst for 1,5-diphenylpenta-2,4-dien-1-one synthesis

    NASA Astrophysics Data System (ADS)

    Cahyana, A. H.; Fitria, D.; Ardiansah, B.; Rahayu, D. U. C.

    2017-04-01

    A novel heterogeneous organobase catalyst of Fe3O4/SiO2-guanidine was prepared in three stages. First, Fe3O4 nanoparticle was obtained by co-precipitation method using seaweed Sargassum Sp. as natural reductant. Fe3O4 was then coated by SiO2 using TEOS as silica source, resulting Fe3O4/SiO2. Finally, Fe3O4/SiO2-Guanidine was obtained by modifying Fe3O4/SiO2 with guanidine in the suitable reaction condition. This organobase catalyst was characterized by Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Particle Size Analyzer (PSA). The material was then used as a highly active catalyst in aldol condensation reaction between acetophenone and cinnamaldehyde to produce 1,5-diphenylpenta-2,4-dien-1-one. The structure elucidation of the organic product was confirmed by UV-Vis, FTIR, and LC-MS.

  5. N-silyl oxyketene imines are underused yet highly versatile reagents for catalytic asymmetric synthesis

    NASA Astrophysics Data System (ADS)

    Denmark, Scott E.; Wilson, Tyler W.

    2010-11-01

    The reactions of acyl anion equivalents (d1 synthons) with carbonyl electrophiles allow for the construction of a wide range of molecules useful for the synthesis of biologically active compounds, natural products and chiral ligands. Despite their utility, significant challenges still exist for developing catalytic, enantioselective variants of these reactions. For example, the asymmetric benzoin process, arguably the most characteristic reaction of d synthetic equivalents, finds no general solution for reactions involving aliphatic acyl anions. In this Article, we introduce a new class of stable, isolable silyl ketene imines derived from protected cyanohydrins. These nucleophiles serve as acyl anion equivalents in Lewis base catalysed aldol addition reactions and allow for the preparation of cross-benzoin and glycolate-aldol products in high yield and with exceptional diastereo- and enantioselectivities.

  6. Transport-induced shifts in condensate dew-point and composition in multicomponent systems with chemical reaction

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.; Nagarajan, R.

    1985-01-01

    Partial heterogeneous condensation phenomena in multicomponent reacting systems are analyzed taking into consideration the chemical element transport phenomena. It is demonstrated that the dew-point surface temperature in chemically reactive systems is not a purely thermodynamic quantity, but is influenced by the multicomponent diffusion and Soret-mass diffusion phenomena. Several distinct dew-points are shown to exist in such systems and, as a result of transport constraints, the 'sharp' locus between two chemically distinct condensates is systematically moved to a difference mainstream composition.

  7. One-pot conversion of biomass-derived xylose and furfural into levulinate esters via acid catalysis.

    PubMed

    Hu, Xun; Jiang, Shengjuan; Wu, Liping; Wang, Shuai; Li, Chun-Zhu

    2017-03-07

    Direct conversion of biomass-derived xylose and furfural into levulinic acid, a platform molecule, via acid-catalysis has been accomplished for the first time in dimethoxymethane/methanol. Dimethoxymethane acted as an electrophile to transform furfural into 5-hydroxymethylfurfural (HMF). Methanol suppressed both the polymerisation of the sugars/furans and the Aldol condensation of levulinic acid/ester.

  8. Collecting exhaled breath condensate (EBC) with two condensers in series: a promising technique for studying the mechanisms of EBC formation, and the volatility of selected biomarkers.

    PubMed

    Corradi, Massimo; Goldoni, Matteo; Caglieri, Andrea; Folesani, Giuseppina; Poli, Diana; Corti, Marina; Mutti, Antonio

    2008-03-01

    Exhaled breath condensate (EBC) consists mainly of water, but also contains semivolatile and nonvolatile compounds. The aim of this study was to develop a system in which two condensers are simultaneously used in series to clarify the mechanisms of EBC condensation. Two aliquots of EBC (EBC1 and EBC2) were collected from 20 asymptomatic smokers and 20 healthy young nonsmokers using a specifically designed device having two condensers in series in which total volume, hydrogen peroxide (H(2)O(2)), ammonium (NH(4)(+)), and conductivity before and after lyophilization were measured. Water, NH(4)(+) levels and conductivity before lyophilization were significantly lower in the EBC2 than in the EBC1 of smokers and nonsmokers; the contrary was true for H(2)O(2) levels. Almost all nonvolatile salts were collected in the first condenser, because more than 50% of postlyophilization conductivity was below the detection limit in EBC2. The recovery of volatile molecules and their derivatives (water and NH(4)(+)) was partial in the first condenser, but appreciable amounts of both were measured in the second; however, the condenser immediately in contact with exhaled air was more efficient in terms of water, NH(4)(+) and conductivity before lyophilization. On the contrary, nonvolatile ions (conductivity after lyophilization) were mainly collected in the first condenser. Finally, the behavior of H(2)O(2) cannot be explained on the basis of its chemical and physical properties, and the most probable explanation is that some was byproduced by a radical reaction in the gas phase or during the condensation process in water.

  9. CFD simulation of water vapour condensation in the presence of non-condensable gas in vertical cylindrical condensers.

    PubMed

    Li, Jun-De

    2013-02-01

    This paper presents the simulation of the condensation of water vapour in the presence of non-condensable gas using computational fluid dynamics (CFD) for turbulent flows in a vertical cylindrical condenser tube. The simulation accounts for the turbulent flow of the gas mixture, the condenser wall and the turbulent flow of the coolant in the annular channel with no assumptions of constant wall temperature or heat flux. The condensate film is assumed to occupy a negligible volume and its effect on the condensation of the water vapour has been taken into account by imposing a set of boundary conditions. A new strategy is used to overcome the limitation of the currently available commercial CFD package to solve the simultaneous simulation of flows involving multispecies and fluids of gas and liquid in separate channels. The results from the CFD simulations are compared with the experimental results from the literature for the condensation of water vapour with air as the non-condensable gas and for inlet mass fraction of the water vapour from 0.66 to 0.98. The CFD simulation results in general agree well with the directly measured quantities and it is found that the variation of heat flux in the condenser tube is more complex than a simple polynomial curve fit. The CFD results also show that, at least for flows involving high water vapour content, the axial velocity of the gas mixture at the interface between the gas mixture and the condensate film is in general not small and cannot be neglected.

  10. CFD simulation of water vapour condensation in the presence of non-condensable gas in vertical cylindrical condensers

    PubMed Central

    Li, Jun-De

    2013-01-01

    This paper presents the simulation of the condensation of water vapour in the presence of non-condensable gas using computational fluid dynamics (CFD) for turbulent flows in a vertical cylindrical condenser tube. The simulation accounts for the turbulent flow of the gas mixture, the condenser wall and the turbulent flow of the coolant in the annular channel with no assumptions of constant wall temperature or heat flux. The condensate film is assumed to occupy a negligible volume and its effect on the condensation of the water vapour has been taken into account by imposing a set of boundary conditions. A new strategy is used to overcome the limitation of the currently available commercial CFD package to solve the simultaneous simulation of flows involving multispecies and fluids of gas and liquid in separate channels. The results from the CFD simulations are compared with the experimental results from the literature for the condensation of water vapour with air as the non-condensable gas and for inlet mass fraction of the water vapour from 0.66 to 0.98. The CFD simulation results in general agree well with the directly measured quantities and it is found that the variation of heat flux in the condenser tube is more complex than a simple polynomial curve fit. The CFD results also show that, at least for flows involving high water vapour content, the axial velocity of the gas mixture at the interface between the gas mixture and the condensate film is in general not small and cannot be neglected. PMID:24850953

  11. On the onset of surface condensation: formation and transition mechanisms of condensation mode

    PubMed Central

    Sheng, Qiang; Sun, Jie; Wang, Qian; Wang, Wen; Wang, Hua Sheng

    2016-01-01

    Molecular dynamics simulations have been carried out to investigate the onset of surface condensation. On surfaces with different wettability, we snapshot different condensation modes (no-condensation, dropwise condensation and filmwise condensation) and quantitatively analyze their characteristics by temporal profiles of surface clusters. Two different types of formation of nanoscale droplets are identified, i.e. the formations with and without film-like condensate. We exhibit the effect of surface tensions on the formations of nanoscale droplets and film. We reveal the formation mechanisms of different condensation modes at nanoscale based on our simulation results and classical nucleation theory, which supplements the ‘classical hypotheses’ of the onset of dropwise condensation. We also reveal the transition mechanism between different condensation modes based on the competition between surface tensions and reveal that dropwise condensation represents the transition states from no-condensation to filmwise condensation. PMID:27481071

  12. On the onset of surface condensation: formation and transition mechanisms of condensation mode.

    PubMed

    Sheng, Qiang; Sun, Jie; Wang, Qian; Wang, Wen; Wang, Hua Sheng

    2016-08-02

    Molecular dynamics simulations have been carried out to investigate the onset of surface condensation. On surfaces with different wettability, we snapshot different condensation modes (no-condensation, dropwise condensation and filmwise condensation) and quantitatively analyze their characteristics by temporal profiles of surface clusters. Two different types of formation of nanoscale droplets are identified, i.e. the formations with and without film-like condensate. We exhibit the effect of surface tensions on the formations of nanoscale droplets and film. We reveal the formation mechanisms of different condensation modes at nanoscale based on our simulation results and classical nucleation theory, which supplements the 'classical hypotheses' of the onset of dropwise condensation. We also reveal the transition mechanism between different condensation modes based on the competition between surface tensions and reveal that dropwise condensation represents the transition states from no-condensation to filmwise condensation.

  13. Mechanistic Investigation of Catalyst-Transfer Suzuki-Miyaura Condensation Polymerization of Thiophene-Pyridine Biaryl Monomers with the Aid of Model Reactions.

    PubMed

    Tokita, Yu; Katoh, Masaru; Ohta, Yoshihiro; Yokozawa, Tsutomu

    2016-11-21

    We have investigated the requirements for efficient Pd-catalyzed Suzuki-Miyaura catalyst-transfer condensation polymerization (Pd-CTCP) reactions of 2-alkoxypropyl-6-(5-bromothiophen-2-yl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (12) as a donor-acceptor (D-A) biaryl monomer. As model reactions, we first carried out the Suzuki-Miyaura coupling reaction of X-Py-Th-X' (Th=thiophene, Py=pyridine, X, X'=Br or I) 1 with phenylboronic acid ester 2 by using tBu 3 PPd 0 as the catalyst. Monosubstitution with a phenyl group at Th-I mainly took place in the reaction of Br-Py-Th-I (1 b) with 2, whereas disubstitution selectively occurred in the reaction of I-Py-Th-Br (1 c) with 2, indicating that the Pd catalyst is intramolecularly transferred from acceptor Py to donor Th. Therefore, we synthesized monomer 12 by introduction of a boronate moiety and bromine into Py and Th, respectively. However, examination of the relationship between monomer conversion and the M n of the obtained polymer, as well as the matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra, indicated that Suzuki-Miyaura coupling polymerization of 12 with (o-tolyl)tBu 3 PPdBr initiator 13 proceeded in a step-growth polymerization manner through intermolecular transfer of the Pd catalyst. To understand the discrepancy between the model reactions and polymerization reaction, Suzuki-Miyaura coupling reactions of 1 c with thiopheneboronic acid ester instead of 2 were carried out. This resulted in a decrease of the disubstitution product. Therefore, step-growth polymerization appears to be due to intermolecular transfer of the Pd catalyst from Th after reductive elimination of the Th-Pd-Py complex formed by transmetalation of polymer Th-Br with (Pin)B-Py-Th-Br monomer 12 (Pin=pinacol). Catalysts with similar stabilization energies of metal-arene η 2 -coordination for D and A monomers may be needed for CTCP reactions of biaryl D-A monomers. © 2016 Wiley

  14. Influence of iodine on the treatment of spacecraft humidity condensate to produce potable water

    NASA Technical Reports Server (NTRS)

    Symons, James M.; Muckle, Susan V.

    1990-01-01

    Several compounds in the ersatz humidity condensate do react with iodine to form iodine-substituted organic compounds (TOI), most notably phenol, acetaldehyde, ethanol, and sodium formate. Iodination of the ersatz humidity condensate produced 3.0 to 3.5 mg/L of TOI within 24 hours. The TOI that was produced by the passage of the ersatz humidity condensate through the first iodinated resin (IR) in the adsorption system was removed by the granular activated carbon that followed. TOI detected in the final effluent was formed by the reaction of the non-adsorbable condensate compounds with the final IR in the treatment series. The activated carbon bed series in the adsorption system performed poorly in its removal of TOC. The rapid breakthrough of TOC was not surprising, as the ersatz humidity condensate contained several highly soluble organic compounds, alcohols and organic acids.

  15. ProPhenol-Catalyzed Asymmetric Additions by Spontaneously Assembled Dinuclear Main Group Metal Complexes

    PubMed Central

    2016-01-01

    Conspectus The development of catalytic enantioselective transformations has been the focus of many research groups over the past half century and is of paramount importance to the pharmaceutical and agrochemical industries. Since the award of the Nobel Prize in 2001, the field of enantioselective transition metal catalysis has soared to new heights, with the development of more efficient catalysts and new catalytic transformations at increasing frequency. Furthermore, catalytic reactions that allow higher levels of redox- and step-economy are being developed. Thus, alternatives to asymmetric alkene dihydroxylation and the enantioselective reduction of α,β-unsaturated ketones can invoke more strategic C–C bond forming reactions, such as asymmetric aldol reactions of an aldehyde with α-hydroxyketone donors or enantioselective alkynylation of an aldehyde, respectively. To facilitate catalytic enantioselective addition reactions, including the aforementioned aldol and alkynylation reactions, our lab has developed the ProPhenol ligand. In this Account, we describe the development and application of the ProPhenol ligand for asymmetric additions of both carbon- and heteroatom-based nucleophiles to various electrophiles. The ProPhenol ligand spontaneously forms chiral dinuclear metal complexes when treated with an alkyl metal reagent, such as Et2Zn or Bu2Mg. The resulting complex contains both a Lewis acidic site to activate an electrophile and a Brønsted basic site to deprotonate a pronucleophile. Initially, our research focused on the use of Zn-ProPhenol complexes to facilitate the direct aldol reaction. Fine tuning of the reaction through ligand modification and the use of additives enabled the direct aldol reaction to proceed in high yields and stereoselectivities with a broad range of donor substrates, including acetophenones, methyl ynones, methyl vinyl ketone, acetone, α-hydroxy carbonyl compounds, and glycine Schiff bases. Additionally, an analogous

  16. Breath condenser coatings affect measurement of biomarkers in exhaled breath condensate.

    PubMed

    Rosias, P P; Robroeks, C M; Niemarkt, H J; Kester, A D; Vernooy, J H; Suykerbuyk, J; Teunissen, J; Heynens, J; Hendriks, H J; Jöbsis, Q; Dompeling, E

    2006-11-01

    Exhaled breath condensate collection is not yet standardised and biomarker measurements are often close to lower detection limits. In the current study, it was hypothesised that adhesive properties of different condenser coatings interfere with measurements of eicosanoids and proteins in breath condensate. In vitro, condensate was derived from a collection model using two test solutions (8-isoprostane and albumin) and five condenser coatings (silicone, glass, aluminium, polypropylene and Teflon). In vivo, condensate was collected using these five coatings and the EcoScreen condenser to measure 8-isoprostane, and three coatings (silicone, glass, EcoScreen) to measure albumin. In vitro, silicone and glass coatings had significantly higher albumin recovery compared with the other coatings. A similar trend was observed for 8-isoprostane recovery. In vivo, median (interquartile range) 8-isoprostane concentrations were significantly higher using silicone (9.2 (18.8) pg.mL(-1)) or glass (3.0 (4.5) pg.mL(-1)) coating, compared with aluminium (0.5 (2.4) pg.mL(-1)), polypropylene (0.5 (0.5) pg.mL(-1)), Teflon (0.5 (0.0) pg.mL(-1)), and EcoScreen (0.5 (2.0) pg.mL(-1)). Albumin in vivo was mainly detectable using glass coating. In conclusion, a condenser with silicone or glass coating is more efficient for measurement of 8-isoprostane or albumin in exhaled breath condensate, than EcoScreen, aluminium, polypropylene or Teflon. Guidelines for exhaled breath condensate standardisation should include the most valid condenser coating to measure a specific biomarker.

  17. CONDENSATION CAN

    DOEpatents

    Booth, E.T. Jr.; Pontius, R.B.; Jacobsohn, B.A.; Slade, C.B.

    1962-03-01

    An apparatus is designed for condensing a vapor to a solid at relatively low back pressures. The apparatus comprises a closed condensing chamber, a vapor inlet tube extending to the central region of the chamber, a co-axial tubular shield surrounding the inlet tube, means for heating the inlet tube at a point outside the condensing chamber, and means for refrigeratirg the said chamber. (AEC)

  18. High-surface-area mesoporous TiO2 microspheres via one-step nanoparticle self-assembly for enhanced lithium-ion storage

    NASA Astrophysics Data System (ADS)

    Wang, Hsin-Yi; Chen, Jiazang; Hy, Sunny; Yu, Linghui; Xu, Zhichuan; Liu, Bin

    2014-11-01

    Mesoporous TiO2 microspheres assembled from TiO2 nanoparticles with specific surface areas as high as 150 m2 g-1 were synthesized via a facile one-step solvothermal reaction of titanium isopropoxide and anhydrous acetone. Aldol condensation of acetone gradually releases structural H2O, which hydrolyzes and condenses titanium isopropoxide, forming TiO2 nanocrystals. Simultaneous growth and aggregation of TiO2 nanocrystals leads to the formation of high-surface-area TiO2 microspheres under solvothermal conditions. After a low-temperature post-synthesis calcination, carbonate could be incorporated into TiO2 as a dopant with the carbon source coming from the organic byproducts during the synthesis. Carbonate doping modifies the electronic structure of TiO2 (e.g., Fermi level, Ef), and thus influences its electrochemical properties. Solid electrolyte interface (SEI) formation, which is not common for titania, could be initiated in carbonate-doped TiO2 due to elevated Ef. After removing carbonate dopants by high-temperature calcination, the mesoporous TiO2 microspheres showed much improved performance in lithium insertion and stability at various current rates, attributed to a synergistic effect of high surface area, large pore size and good anatase crystallinity.Mesoporous TiO2 microspheres assembled from TiO2 nanoparticles with specific surface areas as high as 150 m2 g-1 were synthesized via a facile one-step solvothermal reaction of titanium isopropoxide and anhydrous acetone. Aldol condensation of acetone gradually releases structural H2O, which hydrolyzes and condenses titanium isopropoxide, forming TiO2 nanocrystals. Simultaneous growth and aggregation of TiO2 nanocrystals leads to the formation of high-surface-area TiO2 microspheres under solvothermal conditions. After a low-temperature post-synthesis calcination, carbonate could be incorporated into TiO2 as a dopant with the carbon source coming from the organic byproducts during the synthesis. Carbonate doping

  19. MICROWAVE-ACCELERATED MULTICOMPONENT REACTIONS UNDER SOLVENT-FREE CONDITIONS

    EPA Science Inventory

    The application of microwave-accelerated solventless synthetic protocols in multicomponent (MCC) reactions will be exemplified by several condensation and cyclization reactions including the rapid one-pot assembly of valuable heterocyclic compounds from in situ generated intermed...

  20. Condensation polyimides

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M.

    1989-01-01

    Polyimides belong to a class of polymers known as polyheterocyclics. Unlike most other high temperature polymers, polyimides can be prepared from a variety of inexpensive monomers by several synthetic routes. The glass transition and crystalline melt temperature, thermooxidative stability, toughness, dielectric constant, coefficient of thermal expansion, chemical stability, mechanical performance, etc. of polyimides can be controlled within certain boundaries. This versatility has permitted the development of various forms of polyimides. These include adhesives, composite matrices, coatings, films, moldings, fibers, foams and membranes. Polyimides are synthesized through both condensation (step-polymerization) and addition (chain growth polymerization) routes. The precursor materials used in addition polyimides or imide oligomers are prepared by condensation method. High molecular weight polyimide made via polycondensation or step-growth polymerization is studied. The various synthetic routes to condensation polyimides, structure/property relationships of condensation polyimides and composite properties of condensation polyimides are all studied. The focus is on the synthesis and chemical structure/property relationships of polyimides with particular emphasis on materials for composite application.

  1. Radiochemical study of reactions of alkyl cations with amines. I. Reactions of methyl and sec-butyl cations with diethylamine

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ignat`ev, I.S.; Kochina, T.A.; Nefedov, V.D.

    1995-08-10

    Ion-molecular gas-phase reactions of free methyl and sec-butyl cations with diethylamine were studied. These reactions proceed via two competing pathways involving formation of a condensation complex or a proton-transfer complex, the latter process predominating. 32 refs., 1 tab.

  2. Freeze-Tolerant Condensers

    NASA Technical Reports Server (NTRS)

    Crowley, Christopher J.; Elkouhk, Nabil

    2004-01-01

    Two condensers designed for use in dissipating heat carried by working fluids feature two-phase, self-adjusting configurations such that their working lengths automatically vary to suit their input power levels and/or heat-sink temperatures. A key advantage of these condensers is that they can function even if the temperatures of their heat sinks fall below the freezing temperatures of their working fluids and the fluids freeze. The condensers can even be restarted from the frozen condition. The top part of the figure depicts the layout of the first condenser. A two-phase (liquid and vapor) condenser/vapor tube is thermally connected to a heat sink typically, a radiatively or convectively cooled metal panel. A single-phase (liquid) condensate-return tube (return artery) is also thermally connected to the heat sink. At intervals along their lengths, the condenser/vapor tube and the return artery are interconnected through porous plugs. This condenser configuration affords tolerance of freezing, variable effective thermal conductance (such that the return temperature remains nearly constant, independently of the ultimate sink temperature), and overall pressure drop smaller than it would be without the porous interconnections. An additional benefit of this configuration is that the condenser can be made to recover from the completely frozen condition either without using heaters, or else with the help of heaters much smaller than would otherwise be needed. The second condenser affords the same advantages and is based on a similar principle, but it has a different configuration that affords improved flow of working fluid, simplified construction, reduced weight, and faster recovery from a frozen condition.

  3. MICROWAVE-FACILITATED MULTICOMPONENT REACTIONS UNDER SOLVENT-FREE CONDITIONS

    EPA Science Inventory

    The application of microwave-expedited solvent-free synthetic protocols in multi-component (MCC) reactions will be exemplified by several condensation and cyclization reactions including the rapid one-pot assembly of heterocyclic compounds from in situ generated intermediates. R...

  4. Golden rule kinetics of transfer reactions in condensed phase: The microscopic model of electron transfer reactions in disordered solid matrices

    NASA Astrophysics Data System (ADS)

    Basilevsky, M. V.; Odinokov, A. V.; Titov, S. V.; Mitina, E. A.

    2013-12-01

    postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode/medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.

  5. Golden rule kinetics of transfer reactions in condensed phase: The microscopic model of electron transfer reactions in disordered solid matrices

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Basilevsky, M. V.; Mitina, E. A.; Odinokov, A. V.

    beyond the kinetic regimes, which are usually postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode/medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.« less

  6. Golden rule kinetics of transfer reactions in condensed phase: the microscopic model of electron transfer reactions in disordered solid matrices.

    PubMed

    Basilevsky, M V; Odinokov, A V; Titov, S V; Mitina, E A

    2013-12-21

    postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode∕medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.

  7. Zwitterion radicals and anion radicals from electron transfer and solvent condensation with the fingerprint developing agent ninhydrin.

    PubMed

    Schertz, T D; Reiter, R C; Stevenson, C D

    2001-11-16

    Ninhydrin (the fingerprint developing agent) spontaneously dehydrates in liquid ammonia and in hexamethylphosphoramide (HMPA) to form indantrione, which has a sufficiently large solution electron affinity to extract an electron from the solvent (HMPA) to produce the indantrione anion radical. In liquid NH(3), the presence of trace amounts of amide ion causes the spontaneous formation of an anion radical condensation product, wherein the no. 2 carbon (originally a carbonyl carbon) becomes substituted with -NH(2) and -OH groups. In HMPA, the indantrione anion radical spontaneously forms condensation products with the HMPA to produce a variety of zwitterionic radicals, wherein the no. 2 carbon becomes directly attached to a nitrogen of the HMPA. The mechanisms for the formation of the zwitterionic paramagnetic condensation products are analogous to that observed in the reaction of ninhydrin with amino acids to yield Ruhemann's Purple, the contrast product in fingerprint development. The formation of anion and zwitterionic radical condensation products from ninhydrin and nitrogen-containing solvents may represent an example of a host of analogous polyketone-solvent reactions.

  8. Pd/NbOPO₄ multifunctional catalyst for the direct production of liquid alkanes from aldol adducts of furans.

    PubMed

    Xia, Qi-Neng; Cuan, Qian; Liu, Xiao-Hui; Gong, Xue-Qing; Lu, Guan-Zhong; Wang, Yan-Qin

    2014-09-08

    Great efforts have been made to convert renewable biomass into transportation fuels. Herein, we report the novel properties of NbO(x)-based catalysts in the hydrodeoxygenation of furan-derived adducts to liquid alkanes. Excellent activity and stability were observed with almost no decrease in octane yield (>90% throughout) in a 256 h time-on-stream test. Experimental and theoretical studies showed that NbO(x) species play the key role in C-O bond cleavage. As a multifunctional catalyst, Pd/NbOPO4 plays three roles in the conversion of aldol adducts into alkanes: 1) The noble metal (in this case Pd) is the active center for hydrogenation; 2) NbO(x) species help to cleave the C-O bond, especially of the tetrahydrofuran ring; and 3) a niobium-based solid acid catalyzes the dehydration, thus enabling the quantitative conversion of furan-derived adducts into alkanes under mild conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Divergent Total Syntheses of (-)-Huperzine Q, (+)-Lycopladine B, (+)-Lycopladine C, and (-)-4-epi-Lycopladine D.

    PubMed

    Hong, Benke; Hu, Dachao; Wu, Jinbao; Zhang, Jing; Li, Houhua; Pan, Yingming; Lei, Xiaoguang

    2017-07-04

    We report herein our synthetic efforts towards the divergent syntheses of (-)-huperzine Q (1), (+)-lycopladine B (2), (+)-lycopladine C (3), and (-)-lycopladine D (4). The 10-step total synthesis of (-)-huperzine Q (1) and the first total syntheses of (+)-lycopladines B (2) and C (3) were accomplished through a series of cascade reactions. Our approach involved a Michael addition/aldol/intramolecular C-alkylation sequence to forge the 6/9 spirocycle ring, and this was followed by an ethylene-accelerated carbonyl-olefin metathesis to construct the common 6/5/9 ring system. Finally, late-stage enamine bromofunctionalization enabled us to access (-)-huperzine Q (1), (+)-lycopladine B (2), and (+)-lycopladine C (3), and a tandem C4-epimerization/retro-Claisen condensation furnished (-)-4-epi-lycopladine D (63). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Enhanced Condensation Heat Transfer

    NASA Astrophysics Data System (ADS)

    Rose, John Winston

    The paper gives some personal observations on various aspects of enhanced condensation heat transfer. The topics discussed are external condensation (horizontal low-finned tubes and wire-wrapped tubes), internal condensation (microfin tubes and microchannels) and Marangoni condensation of binary mixtures.

  11. Novel multicomponent reaction for the combinatorial synthesis of 2-imidazolines.

    PubMed

    Bon, Robin S; Hong, Chongen; Bouma, Marinus J; Schmitz, Rob F; de Kanter, Frans J J; Lutz, Martin; Spek, Anthony L; Orru, Romano V A

    2003-10-02

    [reaction: see text] The three-component condensation between an amine, an aldehyde, and an alpha-acidic isocyanide efficiently provides substituted 2-imidazolines in a one-pot reaction under mild conditions.

  12. Potentially Prebiotic Syntheses of Condensed Phosphates

    NASA Technical Reports Server (NTRS)

    Keefe, Anthony D.; Miller, Stanley L.

    1996-01-01

    In view of the importance of a prebiotic source of high energy phosphates, we have investigated a number of potentially prebiotic processes to produce condensed phosphates from orthophosphate and cyclic trimetaphosphate from tripolyphosphate. The reagents investigated include polymerizing nitriles, acid anhydrides, lactones, hexamethylene tetramine and carbon suboxide. A number of these processes give substantial yields of pyrophosphate from orthophosphate and trimetaphosphate from tripolyphosphate. Although these reactions may have been applicable in local areas, they are not sufficiently robust to have been of importance in the prebiotic open ocean.

  13. Condensation Temperature in Non-Equilibrium Condensation.

    NASA Astrophysics Data System (ADS)

    Tanaka, K. K.; Tanaka, H.; Nakazawa, K.

    1999-09-01

    In investigation of the origins of the presolar grains, it is important to clear the formation process of grains in ejecta of AGB stars or supernovae, where most presolar grains are suggested to be formed. The grain formation has been investigated based on the classical nucleation theory in many previous studies. On the other hand it has been pointed out that the classical nucleation rate is significantly different from that obtained by experiments, and should not be applied to grain formation in astrophysical environments (Donn and Nuth, 1985, ApJ 288, 187-190). Recently Dillmann and Meier (1991, J. Chem. Phys. 94, 3872-3884) proposed new semi-phenomological nucleation model, which achieved excellent agreements with experiments. In this study we applied the nucleation rate in the semi-phenomological model to the grain formation in astrophysical environment in order to make it clear how the grain formation changes due to the new nucleation rate. For various parameters determined by surface energy of grain and cooling time of vapor, we solved equations describing the grain formation. From the comparison between the results obtained by new nucleation rate and that by classical one we found that there is no significant difference in grain number density and grain size, but the condensation temperature is considerably different from the previous one. For example in carbon rich AGB star the condensation temperature of graphite is lower than that obtained by classical one by a few hundreds Kelvin: this means the condensation temperature is lower than the equilibrium condensation temperature by about 500 Kelvin. Furthermore we investigated the condensation of vapor in which grain impurities are already present. We obtained the condition for formation of core-mantle type grains. Our obtained condition would give constraint on the formation of core-mantle type presolar grains.

  14. An Experimental Study of Filmwise Condensation on Horizontal Enhanced Condenser Tubing.

    DTIC Science & Technology

    1979-12-01

    with a 51 mm thick sheet of Johns - Manville Aerotube insulation. 22 D. CONDENSATE AND FEEDWATER SYSTEMS The condensate and feedwater systems are shown...desuperheater. The condensate and feedwater lines are insulated with 25.4 mm thick Johns - Manville Aerotube insulation. E. COOLING WATER SYSTEM The cooling

  15. Semi-classical statistical description of Fröhlich condensation.

    PubMed

    Preto, Jordane

    2017-06-01

    Fröhlich's model equations describing phonon condensation in open systems of biological relevance are reinvestigated within a semi-classical statistical framework. The main assumptions needed to deduce Fröhlich's rate equations are identified and it is shown how they lead us to write an appropriate form for the corresponding master equation. It is shown how solutions of the master equation can be numerically computed and can highlight typical features of the condensation effect. Our approach provides much more information compared to the existing ones as it allows to investigate the time evolution of the probability density function instead of following single averaged quantities. The current work is also motivated, on the one hand, by recent experimental evidences of long-lived excited modes in the protein structure of hen-egg white lysozyme, which were reported as a consequence of the condensation effect, and, on the other hand, by a growing interest in investigating long-range effects of electromagnetic origin and their influence on the dynamics of biochemical reactions.

  16. Solvent-free synthesis of C10 and C11 branched alkanes from furfural and methyl isobutyl ketone.

    PubMed

    Yang, Jinfan; Li, Ning; Li, Guangyi; Wang, Wentao; Wang, Aiqin; Wang, Xiaodong; Cong, Yu; Zhang, Tao

    2013-07-01

    Our best results jet: C10 and C11 branched alkanes, with low freezing points, are synthesized through the aldol condensation of furfural and methyl isobutyl ketone from lignocellulose, which is then followed by hydrodeoxygenation. These jet-fuel-range alkanes are obtained in high overall yields (≈90%) under solvent-free conditions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Cyclopentanone Derivatives from 5-Hydroxymethylfurfural via 1-Hydroxyhexane-2,5-dione as Intermediate.

    PubMed

    Wozniak, Bartosz; Spannenberg, Anke; Li, Yuehui; Hinze, Sandra; de Vries, Johannes G

    2018-01-23

    An efficient strategy for the conversion of biomass derived 5-hydroxymethylfurfural (HMF) into 2-hydroxy-3-methylcyclopent-2-enone (MCP) by an intramolecular aldol condensation of 1-hydroxyhexane-2,5-dione (HHD) has been developed. Further transformations of MCP towards the diol, enol acetate, levulinic acid and N-heterocyclic compounds are also reported. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Preparing Students for Research: Synthesis of Substituted Chalcones as a Comprehensive Guided-Inquiry Experience

    NASA Astrophysics Data System (ADS)

    Vyvyan, James R.; Pavia, Donald L.; Lampman, Gary M.; Kriz, George S., Jr.

    2002-09-01

    A guided inquiry experiment involving the synthesis and characterization of substituted benzalacetophenones (chalcones) is described. The chalcones are produced in the aldol condensation of substituted benzaldehydes with substituted acetophenones. Each student is assigned a different target chalcone and conducts online and printed literature searches on the target. After completing the synthesis and purification of their product, the students compare their data with those found in the literature.

  19. Condensed tannins: Reactions of model compounds with furfuryl alcohol and furfuraldehyde

    Treesearch

    L. Foo; Richard W. Hemingway

    1985-01-01

    Reaction products of phloroglucinol or catechin with furfuryl alcohol and furfuraldehyde were studied. In reactions of furfuryl alcohol with phloroglucinol, only 2-furyl-(11, 31, 51-trihydroxyphenyl) methane was obtained as product, and 53% of the phloroglucinol was recovered. Reactions of furfuryl...

  20. Furan production from glycoaldehyde over HZSM-5

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, Seonah; Evans, Tabitha J.; Mukarakate, Calvin

    Catalytic fast pyrolysis of biomass over zeolite catalysts results primarily in aromatic (e.g. benzene, toluene, xylene) and olefin products. However, furans are a higher value intermediate for their ability to be readily transformed into gasoline, diesel, and chemicals. Here we investigate possible mechanisms for the coupling of glycoaldehyde, a common product of cellulose pyrolysis, over HZSM-5 for the formation of furans. Experimental measurements of neat glycoaldehyde over a fixed bed of HZSM-5 confirm furans (e.g. furanone) are products of this reaction at temperatures below 300 degrees C with several aldol condensation products as co-products (e.g. benzoquinone). However, under typical catalyticmore » fast pyrolysis conditions (>400 degrees C), further reactions occur that lead to the usual aromatic product slate. ONIOM calculations were utilized to identify the pathway for glycoaldehyde coupling toward furanone and hydroxyfuranone products with dehydration reactions serving as the rate determining steps with typical intrinsic reaction barriers of 40 kcal mol-1. The reaction mechanisms for glycoaldehyde will likely be similar to that of other small oxygenates such as acetaldehyde, lactaldehyde, and hydroxyacetone and this study provides a generalizable mechanism of oxygenate coupling and furan formation over zeolite catalysts.« less

  1. Furan production from glycoaldehyde over HZSM-5

    DOE PAGES

    Kim, Seonah; Evans, Tabitha J.; Mukarakate, Calvin; ...

    2016-04-03

    Catalytic fast pyrolysis of biomass over zeolite catalysts results primarily in aromatic (e.g. benzene, toluene, xylene) and olefin products. However, furans are a higher value intermediate for their ability to be readily transformed into gasoline, diesel, and chemicals. Here we investigate possible mechanisms for the coupling of glycoaldehyde, a common product of cellulose pyrolysis, over HZSM-5 for the formation of furans. Experimental measurements of neat glycoaldehyde over a fixed bed of HZSM-5 confirm furans (e.g. furanone) are products of this reaction at temperatures below 300 degrees C with several aldol condensation products as co-products (e.g. benzoquinone). However, under typical catalyticmore » fast pyrolysis conditions (>400 degrees C), further reactions occur that lead to the usual aromatic product slate. ONIOM calculations were utilized to identify the pathway for glycoaldehyde coupling toward furanone and hydroxyfuranone products with dehydration reactions serving as the rate determining steps with typical intrinsic reaction barriers of 40 kcal mol-1. The reaction mechanisms for glycoaldehyde will likely be similar to that of other small oxygenates such as acetaldehyde, lactaldehyde, and hydroxyacetone and this study provides a generalizable mechanism of oxygenate coupling and furan formation over zeolite catalysts.« less

  2. Study on the syhthesis process of tetracaine hydrochloride

    NASA Astrophysics Data System (ADS)

    Li, Wenli; Zhao, Jie; Cui, Yujie

    2017-05-01

    Tetrachloride hydrochloride is a local anesthetic with long-acting ester, and it is usually present in the form of a hydrochloride salt. Firsleb first synthesized the tetracaine by experiment in 1928, which is one of the recognized clinical potent anesthetics. This medicine has the advantages of stable physical and chemical properties, the rapid role and long maintenance. Tetracaine is also used for ophthalmic surface anesthesia as one of the main local anesthetic just like conduction block anesthesia, mucosal surface anesthesia and epidural anesthesia. So far, the research mainly engaged in its clinical application research, and the research strength is relatively small in the field of synthetic technology. The general cost of the existing production process is high, and the yield is low. In addition, the reaction time is long and the reaction conditions are harsh. In this paper, a new synthetic method was proposed for the synthesis of tetracaine hydrochloride. The reaction route has the advantages of few steps, high yield, short reaction time and mild reaction conditions. The cheap p-nitrobenzoic acid was selected as raw material. By esterification with ethanol and reaction with n-butyraldehyde (the reaction process includes nitro reduction, aldol condensation and hydrogenation reduction), the intermediate was transesterified with dimethylaminoethanol under basic conditions. Finally, the PH value was adjusted in the ethanol solvent. After experiencing 4 steps reaction, the crude tetracaine hydrochloride was obtained.

  3. Formation of a Ge-rich Si1-x Ge x (x > 0.9) fin epitaxial layer condensed by dry oxidation

    NASA Astrophysics Data System (ADS)

    Jang, Hyunchul; Kim, Byongju; Koo, Sangmo; Ko, Dae-Hong

    2017-11-01

    We have selectively grown an epitaxial Si0.35Ge0.65 fin layer in a 65 nm oxide trench pattern array and formed a Ge-rich Si1-x Ge x (x > 0.9) fin layer with condensed Ge using dry oxidation. During oxidation of the SiGe fin structure, we found that the compressive strain of the condensed SiGe layer was increased by about 1.3% while Ge was efficiently condensed due to a two-dimensional oxidation reaction. In this paper, we discussed in detail the diffusion during the two-dimensional condensation reaction as well as the asymmetric biaxial strain of the SiGe fin before and after oxidation using a reciprocal space mapping measurement. The application of dry oxidation on selectively grown SiGe fin layer can be an effective method for increasing hole mobility of SiGe fin with increased Ge content and self-induced compressive strain.

  4. Numerical Simulation of the Detonation of Condensed Explosives

    NASA Astrophysics Data System (ADS)

    Wang, Cheng; Ye, Ting; Ning, Jianguo

    Detonation process of a condensed explosive was simulated using a finite difference method. Euler equations were applied to describe the detonation flow field, an ignition and growth model for the chemical reaction and Jones-Wilkins-Lee (JWL) equations of state for the state of explosives and detonation products. Based on the simple mixture rule that assumes the reacting explosives to be a mixture of the reactant and product components, 1D and 2D codes were developed to simulate the detonation process of high explosive PBX9404. The numerical results are in good agreement with the experimental results, which demonstrates that the finite difference method, mixture rule and chemical reaction proposed in this paper are adequate and feasible.

  5. One-Step Condensation and Hydrogenation of Furfural-Acetone Using Mixed and Single Catalyst Based on Ni/M-Oxide [M=Al; Mg

    NASA Astrophysics Data System (ADS)

    Ulfa, S. M.; Pramesti, I. N.; Mustafidah, H.

    2018-01-01

    Modification of furfural by condensation and hydrogenation reaction is a promising approach to produce higher alkane derivatives (C8-C13) as diesel fraction. This research investigated the catalytic activity of Ni/MgO as bifunctional catalyst compared with MgO-Ni/Al2O3 mixed catalyst for condensation-hydrogenation reaction. The Ni/MgO and Ni/Al2O3 with 20% Ni loading were prepared by wet impregnation methods using Ni(NO3)2.6H2O salt, calcined and reduced at 500°C. The catalyst performance was tested for one-step condensation-hydrogenation reaction using autoclave oil batch reactor. The reaction was conducted by reacting furfural and acetone in 1:1 ratio using water as solvent. Condensation reaction was performed at 100°C for 8 hours, followed by hydrogenation at 120°C during 7 hours. Analysis by gas chromatography showed that C=C double bond of furfurylidene acetone were successfully hydrogenated. Using Ni/MgO catalyst at 120°C, the products were identified as 1,5-bis-(2-furanyl)-1,4-penta-1-ene-3-one (2.68%) and 1,5-bis-(2-furanyl)-1,4-pentan-3-one (trace amount). On the other hand, reaction using mixed catalyst, MgO-Ni/Al2O3 showed better activity over bifunctional Ni/MgO at the same reaction temperature. The products were identified as 4-(2-furanyl)-3-butan-2-one (27.30%); 1,5-bis-(2-furanyl)-1,4-penta-1-ene-3-one (3.82%) and 1,5-bis-(2-furanyl)-1,4-pentan-3-one (1.11%). The impregnation of Ni on MgO decrease the physical properties of catalyst, confirmed by surface area analysis (SAA).

  6. NHC-catalysed benzoin condensation - is it all down to the Breslow intermediate?

    PubMed

    Rehbein, Julia; Ruser, Stephanie-M; Phan, Jenny

    2015-10-01

    The Breslow catalytic cycle describing the benzoin condensation promoted by N-heterocyclic carbenes (NHC) as proposed in the late 1950s has since then been tried by generations of physical organic chemists. Emphasis has been laid on proofing the existence of an enaminol like structure (Breslow intermediate) that explains the observed umpolung of an otherwise electrophilic aldehyde. The present study is not focusing on spectroscopic elucidation of a thiazolydene based Breslow intermediate but rather tries to clarify if this key-intermediate is indeed directly linked with the product side of the overall reaction. The here presented EPR-spectroscopic and computational data provide a fundamentally different view on how the benzoin condensation may proceed: a radical pair could be identified as a second key-intermediate that is derived from the Breslow-intermediate via an SET process. These results highlight the close relationship to the Cannizarro reaction and oxidative transformations of aldehydes under NHC catalysis.

  7. Antibody-catalyzed benzoin oxidation as a mechanistic probe for nucleophilic catalysis by an active site lysine.

    PubMed

    Sklute, Genia; Oizerowich, Rachel; Shulman, Hagit; Keinan, Ehud

    2004-05-03

    Aldolase antibody 24H6, which was obtained by reactive immunization against a 1,3-diketone hapten, is shown to catalyze additional reactions, including H/D exchange and oxidation reactions. Comparison of the H/D exchange reaction at the alpha-position of a wide range of aldehydes and ketones by 24H6 and by other aldolase antibodies, such as 38C2, pointed at the significantly larger size of the 24H6 active site. This property allowed for the catalysis of the oxidation of substituted benzoins to benzils by potassium ferricyanide. This reaction was used as a mechanistic probe to learn about the initial steps of the 24H6-catalyzed aldol condensation reaction. The Hammett correlation (rho=4.7) of log(k(cat)) versus the substituent constant, sigma, revealed that the reaction involves rapid formation of a Schiff base intermediate from the ketone and an active site lysine residue. The rate-limiting step in this oxidation reaction is the conversion of the Schiff base to an enamine intermediate. In addition, linear correlation (rho=3.13) was found between log(K(M)) and sigma, indicating that electronic rather than steric factors are dominant in the antibody-substrate binding phenomenon and confirming that the reversible formation of a Schiff base intermediate comprises part of the substrate-binding mechanism.

  8. A review on wetting and water condensation - Perspectives for CO2 condensation.

    PubMed

    Snustad, Ingrid; Røe, Ingeborg T; Brunsvold, Amy; Ervik, Åsmund; He, Jianying; Zhang, Zhiliang

    2018-06-01

    Liquefaction of vapor is a necessary, but energy intensive step in several important process industries. This review identifies possible materials and surface structures for promoting dropwise condensation, known to increase efficiency of condensation heat transfer. Research on superhydrophobic and superomniphobic surfaces promoting dropwise condensation constitutes the basis of the review. In extension of this, knowledge is extrapolated to condensation of CO 2 . Global emissions of CO 2 need to be minimized in order to reduce global warming, and liquefaction of CO 2 is a necessary step in some carbon capture, transport and storage (CCS) technologies. The review is divided into three main parts: 1) An overview of recent research on superhydrophobicity and promotion of dropwise condensation of water, 2) An overview of recent research on superomniphobicity and dropwise condensation of low surface tension substances, and 3) Suggested materials and surface structures for dropwise CO 2 condensation based on the two first parts. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Selective condensation of aminoacyl adenylates by nucleoproteinoid microparticles.

    NASA Technical Reports Server (NTRS)

    Nakashima, T.; Fox, S. W.

    1972-01-01

    Microparticles composed of each of four enzymically synthesized homopolynucleotides and the same lysine-rich proteinoid have been found to influence the condensation of the AMP-anhydrides of each of four amino acids. The conditions of preparation of the particles and other variables of the experiments control the types of reaction. When a period set of conditions was identified empirically, the incorporation favored the amino acids whose present-day codons are related to the homopolynucleotide in the particle.

  10. Numerical Simulation of Detonation in Condensed Phase Explosives

    DTIC Science & Technology

    1998-08-01

    34Numerical modelling of shocks in solids with elastic-plastic conditions", Shock Waves, 3: 55-66. 22. Jones, D.A., Oran, E.S. and Guirguis , R. (1990). "A...China Lake, CA 93555-6001, preprint. 55. P.J. Miller , P.J. and G.T. Sutherland, G.T. (1996) Reaction Rate Modelling of PBXN- 110, Shock Compression...report describes the development of a two-dimensional multi-material Eulerian hydrocode to model the effects of detonating condensed phase explosives on

  11. Detail of Bright Angel stone vault, containing condenser, Hoffman condensation ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of Bright Angel stone vault, containing condenser, Hoffman condensation pump, Jennings vacuum heating pump, and misc. pipes and valves. - Grand Canyon Village Utilities, Grand Canyon National Park, Grand Canyon Village, Coconino County, AZ

  12. A Multistep Organocatalysis Experiment for the Undergraduate Organic Laboratory: An Enantioselective Aldol Reaction Catalyzed by Methyl Prolinamide

    ERIC Educational Resources Information Center

    Wade, Edmir O.; Walsh, Kenneth E.

    2011-01-01

    In recent years, there has been an explosion of research concerning the area of organocatalysis. A multistep capstone laboratory project that combines traditional reactions frequently found in organic laboratory curriculums with this new field of research is described. In this experiment, the students synthesize a prolinamide-based organocatalyst…

  13. Abiotic Condensation Synthesis of Glyceride Lipids and Wax Esters Under Simulated Hydrothermal Conditions

    NASA Astrophysics Data System (ADS)

    Rushdi, Ahmed I.; Simoneit, Bernd R. T.

    2006-04-01

    Precursor compounds for abiotic proto cellular membranes are necessary for the origin of life. Amphipathic compounds such as fatty acids and acyl glycerols are important candidates for micelle/bilayer/vesicle formation. Two sets of experiments were conducted to study dehydration reactions of model lipid precursors in aqueous media to form acyl polyols and wax esters, and to evaluate the stability and reactions of the products at elevated temperatures. In the first set, mixtures of n-nonadecanoic acid and ethylene glycol in water, with and without oxalic acid, were heated at discrete temperatures from 150 ∘C to 300 ∘C for 72 h. The products were typically alkyl alkanoates, ethylene glycolyl alkanoates, ethylene glycolyl bis-alkanoates and alkanols. The condensation products had maximum yields between 150 ∘C and 250 ∘C, and were detectable and thus stable under hydrothermal conditions to temperatures < 300 ∘C. In the second set of experiments, mixtures of n-heptanoic acid and glycerol were heated using the same experimental conditions, with and without oxalic acid, between 100 ∘C and 250 ∘C. The main condensation products were two isomers each of monoacylglycerols and diacylglycerols at all temperatures, as well as minor amounts of the fatty acid anhydride and methyl ester. The yield of glyceryl monoheptanoates generally increased with increasing temperature and glyceryl diheptanoates decreased noticeably with increasing temperature. The results indicate that condensation reactions and abiotic synthesis of organic lipid compounds under hydrothermal conditions occur easily, provided precursor concentrations are sufficiently high.

  14. Abiotic condensation synthesis of glyceride lipids and wax esters under simulated hydrothermal conditions.

    PubMed

    Rushdi, Ahmed I; Simoneit, Bernd R T

    2006-04-01

    Precursor compounds for abiotic proto cellular membranes are necessary for the origin of life. Amphipathic compounds such as fatty acids and acyl glycerols are important candidates for micelle/bilayer/vesicle formation. Two sets of experiments were conducted to study dehydration reactions of model lipid precursors in aqueous media to form acyl polyols and wax esters, and to evaluate the stability and reactions of the products at elevated temperatures. In the first set, mixtures of n-nonadecanoic acid and ethylene glycol in water, with and without oxalic acid, were heated at discrete temperatures from 150 ( composite function)C to 300 ( composite function)C for 72 h. The products were typically alkyl alkanoates, ethylene glycolyl alkanoates, ethylene glycolyl bis-alkanoates and alkanols. The condensation products had maximum yields between 150 ( composite function)C and 250 ( composite function)C, and were detectable and thus stable under hydrothermal conditions to temperatures < 300 ( composite function)C. In the second set of experiments, mixtures of n-heptanoic acid and glycerol were heated using the same experimental conditions, with and without oxalic acid, between 100 ( composite function)C and 250 ( composite function)C. The main condensation products were two isomers each of monoacylglycerols and diacylglycerols at all temperatures, as well as minor amounts of the fatty acid anhydride and methyl ester. The yield of glyceryl monoheptanoates generally increased with increasing temperature and glyceryl diheptanoates decreased noticeably with increasing temperature. The results indicate that condensation reactions and abiotic synthesis of organic lipid compounds under hydrothermal conditions occur easily, provided precursor concentrations are sufficiently high.

  15. Dropwise condensation

    PubMed Central

    Leach, R. N.; Stevens, F.; Langford, S. C.; Dickinson, J. T.

    2008-01-01

    Dropwise condensation of water vapor from a naturally cooling, hot water reservoir onto a hydrophobic polymer film and a silanized glass slide was studied by direct observation and simulations. The observed drop growth kinetics suggest that smallest drops grow principally by the diffusion of water adsorbed on the substrate to the drop perimeter, while drops larger than 50 μm in diameter grow principally by direct deposition from the vapor onto the drop surface. Drop coalescence plays a critical role in determining the drop size distribution, and stimulates the nucleation of new, small drops on the substrates. Simulations of drop growth incorporating these growth mechanisms provide a good description of the observed drop size distribution. Because of the large role played by coalescence, details of individual drop growth make little difference to the final drop size distribution. The rate of condensation per unit substrate area is especially high for the smallest drops, and may help account for the high heat transfer rates associated with dropwise condensation relative to filmwise condensation in heat exchange applications. PMID:17014129

  16. Ultrasound accelerated Claisen Schmidt condensation: A green route to chalcones

    NASA Astrophysics Data System (ADS)

    Calvino, V.; Picallo, M.; López-Peinado, A. J.; Martín-Aranda, R. M.; Durán-Valle, C. J.

    2006-06-01

    Chalcones have been synthesized under sonochemical irradiation by Claisen-Schmidt condensation between benzaldehyde and acetophenone. Two basic activated carbons (Na and Cs-Norit) have been used as catalysts. The effect of the ultrasound activation has been studied. A substantial enhancing effect in the yield was observed when the carbon catalyst was activated under ultrasonic waves. This "green" method (combination of alkaline-doped carbon catalyst and ultrasound waves) has been applied to the synthesis of several chalcones with antibacterial properties achieving, in all cases, excellent activities and selectivities. A comparative study under non-sonic activation has showed that the yields are lower in silent conditions, indicating that the sonication exerts a positive effect on the activity of the catalyst. Cs-doped carbon is presented as the optimum catalyst, giving excellent activity for this type of condensation. Cs-Norit carbon catalyst can compete with the traditional NaOH/EtOH when the reaction is carried out under ultrasounds. The role of solvent in this reaction was studied with ethanol. High conversion was obtained in absence of solvent. The carbons were characterized by thermal analysis, nitrogen adsorption and X-ray photoelectron spectroscopy.

  17. Formation of Amino Acid Thioesters for Prebiotic Peptide Synthesis: Catalysis By Amino Acid Products

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.; DeVincenzi, Donald L. (Technical Monitor)

    1999-01-01

    The origin of life can be described as a series of events in which a prebiotic chemical process came increasingly under the control of its catalytic products. In our search for this prebiotic process that yielded catalytic takeover products (such as polypeptides), we have been investigating a reaction system that generates peptide-forming amino acid thioesters from formaldehyde, glycolaldehyde, and ammonia in the presence of thiols. As shown below, this model process begins by aldol condensation of formaldehyde and glycolaldehyde to give trioses and releases. These sugars then undergo beta-dehydration yielding their respective alpha-ketoaldehydes. Addition of ammonia to the alpha-ketoaldehydes yields imines which can either: (a) rearrange in the presence of thesis to give amino acid thioesters or (be react with another molecule of aldehyde to give imidazoles. This 'one-pot' reaction system operates under mild aqueous conditions, and like modem amino acid biosynthesis, uses sugar intermediates which are converted to products by energy-yielding redox reactions. Recently, we discovered that amino acids, such as the alanine reaction product, catalyze the first and second steps of the process. In the presence of ammonia the process also generates other synthetically useful products, like the important biochemical -- pyruvic acid.

  18. Experimental study on steam condensation with non-condensable gas in horizontal microchannels

    NASA Astrophysics Data System (ADS)

    Ma, Xuehu; Fan, Xiaoguang; Lan, Zhong; Jiang, Rui; Tao, Bai

    2013-07-01

    This paper experimentally studied steam condensation with non-condensable gas in trapezoidal microchannels. The effect of noncondensable gas on condensation two-phase flow patterns and the characteristics of heat transfer and frictional pressure drop were investigated. The visualization study results showed that the special intermittent annular flow was found in the microchannel under the condition of larger mole fraction of noncondensable gas and lower steam mass flux; the apical area of injection was much larger and the neck of injection was longer for mixture gas with lower mole fraction of noncondensable gas in comparison with pure steam condensation; meanwhile, the noncondensable gas resulted in the decrease of flow patterns transitional steam mass flux and quality. The experimental results also indicated that the frictional pressure drop increased with the increasing mole fraction of noncondensable gas when the steam mass flux was fixed. Unlike nature convective condensation heat transfer, the mole fraction of noncondensable gas had little effect on Nusselt number. Based on experimental data, the predictive correlation of Nusselt number for mixture gas condensation in microchannels was established showed good agreement with experimental data.

  19. Geothermal steam condensate reinjection

    NASA Technical Reports Server (NTRS)

    Chasteen, A. J.

    1974-01-01

    Geothermal electric generating plants which use condensing turbines and generate and excess of condensed steam which must be disposed of are discussed. At the Geysers, California, the largest geothermal development in the world, this steam condensate has been reinjected into the steam reservoir since 1968. A total of 3,150,000,000 gallons of steam condensate has been reinjected since that time with no noticeable effect on the adjacent producing wells. Currently, 3,700,000 gallons/day from 412 MW of installed capacity are being injected into 5 wells. Reinjection has also proven to be a satisfactory method of disposing of geothermal condensate a Imperial Valley, California, and at the Valles Caldera, New Mexico.

  20. Condenser assembly system for an appliance

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Litch, Andrew David

    2017-10-17

    An appliance includes a compact condenser assembly formed with at least two separately and independently produced wire on tube condensers. Each of the at least two wire on tube condensers has a condenser inlet and a condenser outlet. The at least two wire on tube condensers are at least substantially locked and positioned in a matingly engaged configuration forming a compact condenser assembly. The at least two wire on tube condensers are configured to be operationally connected in at least one of a parallel configuration, a series configuration, a selectable configuration, and a bypass configuration.

  1. Influence of condensing equipment and temperature on exhaled breath condensate pH, total protein and leukotriene concentrations.

    PubMed

    Czebe, Krisztina; Barta, Imre; Antus, Balázs; Valyon, Márta; Horváth, Ildikó; Kullmann, Tamás

    2008-05-01

    Exhaled breath condensate analysis is an attractive but still not fully standardised method for investigating airway pathology. Adherence of biomarkers to various condensing surfaces and changes in condensing temperature has been considered to be responsible for the variability of the results. Our aims were to compare the efficacy of different types of condensers and to test the influence of condensing temperature on condensate composition. Breath condensates from 12 healthy persons were collected in two settings: (1) by using three condensers of different type (EcoScreen, R-Tube, Anacon) and (2) by using R-Tube condenser either cooled to -20 or -70 degrees C. Condensate pH at standardised CO(2) level was determined; protein content was measured by the Bradford method and leukotrienes by EIA. Breath condensates collected using EcoScreen were more alkaline (6.45+/-0.20 vs. 6.19+/-0.23, p<0.05 and 6.10+/-0.26, p<0.001) and contained more protein (3.89+/-2.03 vs. 2.65+/-1.98, n.s. and 1.88+/-1.99 microg/ml, p<0.004) as compared to the other devices. Only parameters obtained with R-Tube and Anacon correlated. Condensing temperature affected condensate pH (5.99+/-0.20 at -20 degrees C and 5.82+/-0.07 at -70 degrees C, p<0.05) but not protein content. Leukotriene B(4) was not found in any sample and cysteinyl-leukotriene was not found in condensates collected with R-Tube or Anacon. Condenser type influences sample pH, total protein content and cysteinyl-leukotriene concentration. Condensing temperature influences condensate pH but not total protein content. These results suggest that adherence of the biomarkers to condenser surface and condensing temperature may play a role but does not fully explain the variability of EBC biomarker levels.

  2. Conversion of raw lignocellulosic biomass into branched long-chain alkanes through three tandem steps.

    PubMed

    Li, Chunrui; Ding, Daqian; Xia, Qineng; Liu, Xiaohui; Wang, Yanqin

    2016-07-07

    Synthesis of branched long-chain alkanes from renewable biomass has attracted intensive interest in recent years, but the feedstock for this synthesis is restricted to platform chemicals. Here, we develop an effective and energy-efficient process to convert raw lignocellulosic biomass (e.g., corncob) into branched diesel-range alkanes through three tandem steps for the first time. Furfural and isopropyl levulinate (LA ester) were prepared from hemicellulose and cellulose fractions of corncob in toluene/water biphasic system with added isopropanol, which was followed by double aldol condensation of furfural with LA ester into C15 oxygenates and the final hydrodeoxygenation of C15 oxygenates into branched long-chain alkanes. The core point of this tandem process is the addition of isopropanol in the first step, which enables the spontaneous transfer of levulinic acid (LA) into the toluene phase in the form of LA ester through esterification, resulting in LA ester co-existing with furfural in the same phase, which is the basis for double aldol condensation in the toluene phase. Moreover, the acidic aqueous phase and toluene can be reused and the residues, including lignin and humins in aqueous phase, can be separated and carbonized to porous carbon materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Electrolyte vapor condenser

    DOEpatents

    Sederquist, Richard A.; Szydlowski, Donald F.; Sawyer, Richard D.

    1983-01-01

    A system is disclosed for removing electrolyte from a fuel cell gas stream. The gas stream containing electrolyte vapor is supercooled utilizing conventional heat exchangers and the thus supercooled gas stream is passed over high surface area passive condensers. The condensed electrolyte is then drained from the condenser and the remainder of the gas stream passed on. The system is particularly useful for electrolytes such as phosphoric acid and molten carbonate, but can be used for other electrolyte cells and simple vapor separation as well.

  4. Electrolyte vapor condenser

    DOEpatents

    Sederquist, R.A.; Szydlowski, D.F.; Sawyer, R.D.

    1983-02-08

    A system is disclosed for removing electrolyte from a fuel cell gas stream. The gas stream containing electrolyte vapor is supercooled utilizing conventional heat exchangers and the thus supercooled gas stream is passed over high surface area passive condensers. The condensed electrolyte is then drained from the condenser and the remainder of the gas stream passed on. The system is particularly useful for electrolytes such as phosphoric acid and molten carbonate, but can be used for other electrolyte cells and simple vapor separation as well. 3 figs.

  5. Sedimentary condensation and authigenesis

    NASA Astrophysics Data System (ADS)

    Föllmi, Karl

    2016-04-01

    Most marine authigenic minerals form in sediments, which are subjected to condensation. Condensation processes lead to the formation of well individualized, extremely thin (< 1m) beds, which were accumulated during extremely long time periods (> 100ky), and which experienced authigenesis and the precipitation of glaucony, verdine, phosphate, iron and manganese oxyhydroxides, iron sulfide, carbonate and/or silica. They usually show complex internal stratigraphies, which result from an interplay of sediment accumulation, halts in sedimentation, sediment winnowing, erosion, reworking and bypass. They may include amalgamated faunas of different origin and age. Hardgrounds may be part of condensed beds and may embody strongly condensed beds by themselves. Sedimentary condensation is the result of a hydrodynamically active depositional regime, in which sediment accumulation, winnowing, erosion, reworking and bypass are processes, which alternate as a function of changes in the location and intensity of currents, and/or as the result of episodic high-energy events engendered by storms and gravity flow. Sedimentary condensation has been and still is a widespread phenomenon in past and present-day oceans. The present-day distribution of glaucony and verdine-rich sediments on shelves and upper slopes, phosphate-rich sediments and phosphorite on outer shelves and upper slopes, ferromanganese crusts on slopes, seamounts and submarine plateaus, and ferromanganese nodules on abyssal seafloors is a good indication of the importance of condensation processes today. In the past, we may add the occurrence of oolitic ironstone, carbonate hardgrounds, and eventually also silica layers in banded iron formations as indicators of the importance of condensation processes. Besides their economic value, condensed sediments are useful both as a carrier of geochemical proxies of paleoceanographic and paleoenvironmental change, as well as the product of episodes of paleoceanographic and

  6. Universal Themes of Bose-Einstein Condensation

    NASA Astrophysics Data System (ADS)

    Proukakis, Nick P.; Snoke, David W.; Littlewood, Peter B.

    2017-04-01

    Foreword; List of contributors; Preface; Part I. Introduction: 1. Universality and Bose-Einstein condensation: perspectives on recent work D. W. Snoke, N. P. Proukakis, T. Giamarchi and P. B. Littlewood; 2. A history of Bose-Einstein condensation of atomic hydrogen T. Greytak and D. Kleppner; 3. Twenty years of atomic quantum gases: 1995-2015 W. Ketterle; 4. Introduction to polariton condensation P. B. Littlewood and A. Edelman; Part II. General Topics: Editorial notes; 5. The question of spontaneous symmetry breaking in condensates D. W. Snoke and A. J. Daley; 6. Effects of interactions on Bose-Einstein condensation R. P. Smith; 7. Formation of Bose-Einstein condensates M. J. Davis, T. M. Wright, T. Gasenzer, S. A. Gardiner and N. P. Proukakis; 8. Quenches, relaxation and pre-thermalization in an isolated quantum system T. Langen and J. Schmiedmayer; 9. Ultracold gases with intrinsic scale invariance C. Chin; 10. Berezinskii-Kosterlitz-Thouless phase of a driven-dissipative condensate N. Y. Kim, W. H. Nitsche and Y. Yamamoto; 11. Superfluidity and phase correlations of driven dissipative condensates J. Keeling, L. M. Sieberer, E. Altman, L. Chen, S. Diehl and J. Toner; 12. BEC to BCS crossover from superconductors to polaritons A. Edelman and P. B. Littlewood; Part III. Condensates in Atomic Physics: Editorial notes; 13. Probing and controlling strongly correlated quantum many-body systems using ultracold quantum gases I. Bloch; 14. Preparing and probing chern bands with cold atoms N. Goldman, N. R. Cooper and J. Dalibard; 15. Bose-Einstein condensates in artificial gauge fields L. J. LeBlanc and I. B. Spielman; 16. Second sound in ultracold atomic gases L. Pitaevskii and S. Stringari; 17. Quantum turbulence in atomic Bose-Einstein condensates N. G. Parker, A. J. Allen, C. F. Barenghi and N. P. Proukakis; 18. Spinor-dipolar aspects of Bose-Einstein condensation M. Ueda; Part IV. Condensates in Condensed Matter Physics: Editorial notes; 19. Bose

  7. Chemistry and kinetics of I2 loss in urine distillate and humidity condensate

    NASA Technical Reports Server (NTRS)

    Atwater, James E.; Wheeler, Richard R., Jr.; Olivadoti, J. T.; Sauer, Richard L.

    1992-01-01

    Time-resolved molecular absorption spectrophotometry of iodinated ersatz humidity condensates and iodinated ersatz urine distillates across the UV and visible spectral regions are used to investigate the chemistry and kinetics of I2 loss in urine distillate and humidity condensate. Single contaminant systems at equivalent concentrations are also employed to study rates of iodine. Pseudo-first order rate constants are identified for ersatz contaminant model mixtures and for individual reactive constituents. The second order bimolecular reaction of elemental iodine with formic acid, producing carbon dioxide and iodine anion, is identified as the primary mechanism underlying the decay of residual I2 in ersatz humidity concentrate.

  8. Cascade Cyclizations of Acyclic and Macrocyclic Alkynones: Studies toward the Synthesis of Phomactin A

    PubMed Central

    Ciesielski, Jennifer; Gandon, Vincent; Frontier, Alison J.

    2013-01-01

    A study of the reactivity and diastereoselectivity of the Lewis acid-promoted cascade cyclizations of both acyclic and macrocyclic alkynones is described. In these reactions, a β-iodoallenolate intermediate is generated via conjugate addition of iodide to an alkynone, followed by an intramolecular aldol reaction with a tethered aldehyde to afford a cyclohexenyl alcohol. The Lewis acid magnesium iodide (MgI2) was found to promote irreversible ring closure, while cyclizations using BF3·OEt2 as promoter occurred reversibly. For both acyclic and macrocyclic ynones, high diastereoselectivity was observed in the intramolecular aldol reaction. The MgI2 protocol for cyclization was applied to the synthesis of advanced intermediates relevant to the synthesis of phomactin natural products, during which a novel transannular cation-olefin cyclization was observed. DFT calculations were conducted to analyze the mechanism of this unusual MgI2-promoted process. PMID:23724905

  9. Effect of flow velocity on the process of air-steam condensation in a vertical tube condenser

    NASA Astrophysics Data System (ADS)

    Havlík, Jan; Dlouhý, Tomáš

    2018-06-01

    This article describes the influence of flow velocity on the condensation process in a vertical tube. For the case of condensation in a vertical tube condenser, both the pure steam condensation process and the air-steam mixture condensation process were theoretically and experimentally analyzed. The influence of steam flow velocity on the value of the heat transfer coefficient during the condensation process was evaluated. For the condensation of pure steam, the influence of flow velocity on the value of the heat transfer coefficient begins to be seen at higher speeds, conversely, this effect is negligible at low values of steam velocity. On the other hand, for the air-steam mixture condensation, the influence of flow velocity must always be taken into account. The flow velocity affects the water vapor diffusion process through non-condensing air. The presence of air significantly reduces the value of the heat transfer coefficient. This drop in the heat transfer coefficient is significant at low velocities; on the contrary, the decrease is relatively small at high values of the velocity.

  10. The Effect of Condensate Inundation on Steam Condensation Heat Transfer in a Tube Bundle.

    DTIC Science & Technology

    1985-06-01

    predicted by Nusselt [Ref. 10] were measured. This increase was attributed to the effect of surface tension drawing the condensate to the wire and acting...analysis of film condensation on a horizontal tube was set forth by Nusselt in 1916. His analy- sis was, however, for laminar film condensation on a single...temperature. Jakob [Ref. 17] extended the Nusselt analysis to film condensation on a vertical in-line column of horizontal tubes by assuming that all

  11. N-cyanoimidazole and diimidazole imine: water-soluble condensing agents for the formation of the phosphodiester bond

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Huang, C. H.; Hagan, W. J. Jr

    1989-01-01

    The reaction of BrCN with imidazole results in the formation of N-cyanoimidazole and diimidazole imine. These compounds were shown to be useful condensing agents for the formation of the phosphodiester bound in aqueous solution.

  12. DNA condensation and size effects of DNA condensation agent

    NASA Astrophysics Data System (ADS)

    Liu, Yan-Hui; Jiang, Chong-Ming; Guo, Xin-Miao; Tang, Yan-Lin; Hu, Lin

    2013-08-01

    Based on the model of the strong correlation of counterions condensed on DNA molecule, by tailoring interaction potential, interduplex spacing and correlation spacing between condensed counterions on DNA molecule and interduplex spacing fluctuation strength, toroidal configuration, rod-like configuration and two-hole configurations are possible. The size effects of counterion structure on the toroidal structure can be detected by this model. The autocorrelation function of the tangent vectors is found as an effective way to detect the structure of toroidal conformations and the generic pathway of the process of DNA condensation. The generic pathway of all of the configurations involves an initial nucleation loop, and the next part of the DNA chain is folded on the top of the initial nucleation loop with different manners, in agreement with the recent experimental results.

  13. Low-energy electron-induced chemistry of condensed methanol: implications for the interstellar synthesis of prebiotic molecules.

    PubMed

    Boamah, Mavis D; Sullivan, Kristal K; Shulenberger, Katie E; Soe, ChanMyae M; Jacob, Lisa M; Yhee, Farrah C; Atkinson, Karen E; Boyer, Michael C; Haines, David R; Arumainayagam, Christopher R

    2014-01-01

    In the interstellar medium, UV photolysis of condensed methanol (CH3OH), contained in ice mantles surrounding dust grains, is thought to be the mechanism that drives the formation of "complex" molecules, such as methyl formate (HCOOCH3), dimethyl ether (CH3OCH3), acetic acid (CH3COOH), and glycolaldehyde (HOCH2CHO). The source of this reaction-initiating UV light is assumed to be local because externally sourced UV radiation cannot penetrate the ice-containing dark, dense molecular clouds. Specifically, exceedingly penetrative high-energy cosmic rays generate secondary electrons within the clouds through molecular ionizations. Hydrogen molecules, present within these dense molecular clouds, are excited in collisions with these secondary electrons. It is the UV light, emitted by these electronically excited hydrogen molecules, that is generally thought to photoprocess interstellar icy grain mantles to generate "complex" molecules. In addition to producing UV light, the large numbers of low-energy (< 20 eV) secondary electrons, produced by cosmic rays, can also directly initiate radiolysis reactions in the condensed phase. The goal of our studies is to understand the low-energy, electron-induced processes that occur when high-energy cosmic rays interact with interstellar ices, in which methanol, a precursor of several prebiotic species, is the most abundant organic species. Using post-irradiation temperature-programmed desorption, we have investigated the radiolysis initiated by low-energy (7 eV and 20 eV) electrons in condensed methanol at - 85 K under ultrahigh vacuum (5 x 10(-10) Torr) conditions. We have identified eleven electron-induced methanol radiolysis products, which include many that have been previously identified as being formed by methanol UV photolysis in the interstellar medium. These experimental results suggest that low-energy, electron-induced condensed phase reactions may contribute to the interstellar synthesis of "complex" molecules previously

  14. Implementation of non-condensable gases condensation suppression model into the WCOBRA/TRAC-TF2 LOCA safety evaluation code

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liao, J.; Cao, L.; Ohkawa, K.

    2012-07-01

    The non-condensable gases condensation suppression model is important for a realistic LOCA safety analysis code. A condensation suppression model for direct contact condensation was previously developed by Westinghouse using first principles. The model is believed to be an accurate description of the direct contact condensation process in the presence of non-condensable gases. The Westinghouse condensation suppression model is further revised by applying a more physical model. The revised condensation suppression model is thus implemented into the WCOBRA/TRAC-TF2 LOCA safety evaluation code for both 3-D module (COBRA-TF) and 1-D module (TRAC-PF1). Parametric study using the revised Westinghouse condensation suppression model ismore » conducted. Additionally, the performance of non-condensable gases condensation suppression model is examined in the ACHILLES (ISP-25) separate effects test and LOFT L2-5 (ISP-13) integral effects test. (authors)« less

  15. Iron(II) supramolecular helicates condense plasmid DNA and inhibit vital DNA-related enzymatic activities.

    PubMed

    Malina, Jaroslav; Hannon, Michael J; Brabec, Viktor

    2015-07-27

    The dinuclear iron(II) supramolecular helicates [Fe2 L3 ]Cl4 (L=C25 H20 N4 ) bind to DNA through noncovalent (i.e., hydrogen-bonding, electrostatic) interactions and exhibit antimicrobial and anticancer effects. In this study, we show that the helicates condense plasmid DNA with a much higher potency than conventional DNA-condensing agents. Notably, molecules of DNA in the presence of the M enantiomer of [Fe2 L3 ]Cl4 do not form intermolecular aggregates typically formed by other condensing agents, such as spermidine or spermine. The helicates inhibit the activity of several DNA-processing enzymes, such as RNA polymerase, DNA topoisomerase I, deoxyribonuclease I, and site-specific restriction endonucleases. However, the results also indicate that the DNA condensation induced by the helicates does not play a crucial role in these inhibition reactions. The mechanisms for the inhibitory effects of [Fe2 L3 ]Cl4 helicates on DNA-related enzymatic activities have been proposed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Synthesis of sterically hindered enamides via a Ti-mediated condensation of amides with aldehydes and ketones.

    PubMed

    Genovino, Julien; Lagu, Bharat; Wang, Yaping; Touré, B Barry

    2012-07-07

    The first TiCl(4)-mediated condensation of secondary amides with aldehydes and ketones has been achieved. The reaction proceeds at room temperature and is complete within 5 h in most cases. The optimized procedure used 5 equiv of an amine base hinting that the in situ activation of both the amide and the Lewis acid is required. The reaction affords polysubstituted (E)-enamides.

  17. Water condensation: a multiscale phenomenon.

    PubMed

    Jensen, Kasper Risgaard; Fojan, Peter; Jensen, Rasmus Lund; Gurevich, Leonid

    2014-02-01

    The condensation of water is a phenomenon occurring in multiple situations in everyday life, e.g., when fog is formed or when dew forms on the grass or on windows. This means that this phenomenon plays an important role within the different fields of science including meteorology, building physics, and chemistry. In this review we address condensation models and simulations with the main focus on heterogeneous condensation of water. The condensation process is, at first, described from a thermodynamic viewpoint where the nucleation step is described by the classical nucleation theory. Further, we address the shortcomings of the thermodynamic theory in describing the nucleation and emphasize the importance of nanoscale effects. This leads to the description of condensation from a molecular viewpoint. Also presented is how the nucleation can be simulated by use of molecular models, and how the condensation process is simulated on the macroscale using computational fluid dynamics. Finally, examples of hybrid models combining molecular and macroscale models for the simulation of condensation on a surface are presented.

  18. Condensation in Nanoporous Packed Beds.

    PubMed

    Ally, Javed; Molla, Shahnawaz; Mostowfi, Farshid

    2016-05-10

    In materials with tiny, nanometer-scale pores, liquid condensation is shifted from the bulk saturation pressure observed at larger scales. This effect is called capillary condensation and can block pores, which has major consequences in hydrocarbon production, as well as in fuel cells, catalysis, and powder adhesion. In this study, high pressure nanofluidic condensation studies are performed using propane and carbon dioxide in a colloidal crystal packed bed. Direct visualization allows the extent of condensation to be observed, as well as inference of the pore geometry from Bragg diffraction. We show experimentally that capillary condensation depends on pore geometry and wettability because these factors determine the shape of the menisci that coalesce when pore filling occurs, contrary to the typical assumption that all pore structures can be modeled as cylindrical and perfectly wetting. We also observe capillary condensation at higher pressures than has been done previously, which is important because many applications involving this phenomenon occur well above atmospheric pressure, and there is little, if any, experimental validation of capillary condensation at such pressures, particularly with direct visualization.

  19. Gravity Effects in Condensing and Evaporating Films

    NASA Technical Reports Server (NTRS)

    Hermanson, J. C.; Som, S. M.; Allen, J. S.; Pedersen, P. C.

    2004-01-01

    A general overview of gravity effects in condensing and evaporating films is presented. The topics include: 1) Research Overview; 2) NASA Recognizes Critical Need for Condensation & Evaporation Research to Enable Human Exploration of Space; 3) Condensation and Evaporation Research in Reduced Gravity is Enabling for AHST Technology Needs; 4) Differing Role of Surface Tension on Condensing/Evaporating Film Stability; 5) Fluid Mechanisms in Condensing and Evaporating Films in Reduced Gravity; 6) Research Plan; 7) Experimental Configurations for Condensing Films; 8) Laboratory Condensation Test Cell; 9) Aircraft Experiment; 10) Condensation Study Current Test Conditions; 11) Diagnostics; 12) Shadowgraph Images of Condensing n- pentane Film in Unstable (-1g) Configuration; 13) Condensing n-Pentane Film in Normal Gravity (-1g) at Constant Pressure; 14) Condensing n-Pentane Film in Normal Gravity (-1g) with Cyclic Pressure; 15) Non-condensing Pumped Film in Normal Gravity (-1g); 16) Heat Transfer Coefficient in Developing, Unstable Condensing Film in Normal Gravity; 17) Heat Transfer for Unsteady Condensing Film (-1g); 18) Ultrasound Measurement of Film Thickness N-pentane Film, Stable (+1g) Configuration; and 19) Ultrasound Measurement of Film Thickness N-pentane Film, Unstable (-1g) Configuration.

  20. Proposal for New Experimental Tests of the Bose-Einstein Condensation Mechanism for Low-Energy Nuclear Reaction and Transmutation Processes in Deuterium Loaded - and Nano-Scale Cavities

    NASA Astrophysics Data System (ADS)

    Kim, Yeong E.; Koltick, David S.; Reifenberger, Ronald G.; Zubarev, Alexander L.

    2006-02-01

    Most of experimental results of low-energy nuclear reaction (LENR) reported so far cannot be reproduced on demand. There have been persistent experimental results indicating that the LENR and transmutation processes in condensed matters (LENRTPCM) are surface phenomena rather than bulk phenomena. Recently proposed Bose-Einstein condensation (BEC) mechanism may provide a suitable theoretical description of the surface phenomena. New experiments are proposed and described for testing the BEC mechanism for LENR and transmutation processes in micro- and nano-scale traps. (1) We propose the use of micro- or nano-porous conducting materials as a cathode in electrolysis experiments with heavy water with or without Li in order to stabilize the active surface spots and to enhance the effect for the purpose of improving the reproducibility of excess heat generation and nuclear emission. (2) We propose new experimental tests of the BEC mechanism by measuring the pressure and temperature dependence of LENR events using deuterium gas and these deuterated metals with or without Li. If the LENRTPCM are surface phenomena, the proposed use of micro-/nano-scale porous materials is expected to enhance and scale up the LENRTPCM effects by many order of magnitude, and thus may lead to better reproductivity and theoretical understanding of the phenomena.

  1. Bio-oil fractionation and condensation

    DOEpatents

    Brown, Robert C; Jones, Samuel T; Pollard, Anthony

    2013-07-02

    A method of fractionating bio-oil vapors which involves providing bio-oil vapors comprising bio-oil constituents is described. The bio-oil vapors are cooled in a first stage which comprises a condenser having passages for the bio-oil separated by a heat conducting wall from passages for a coolant. The coolant in the condenser of the first stage is maintained at a substantially constant temperature, set at a temperature in the range of 75 to 100.degree. C., to condense a first liquid fraction of liquefied bio-oil constituents in the condenser of the first stage. The first liquid fraction of liquified bio-oil constituents from the condenser in the first stage is collected. Also described are steps for subsequently recovering further liquid fractions of liquefied bio-oil constituents. Particular compositions of bio-oil condensation products are also described.

  2. Rapid, conformal gas-phase formation of silica (SiO2) nanotubes from water condensates

    NASA Astrophysics Data System (ADS)

    Bae, Changdeuck; Kim, Hyunchul; Yang, Yunjeong; Yoo, Hyunjun; Montero Moreno, Josep M.; Bachmann, Julien; Nielsch, Kornelius; Shin, Hyunjung

    2013-06-01

    An innovative atomic layer deposition (ALD) concept, with which nanostructures of water condensates with high aspect ratio at equilibrium in cylindrical nanopores can be transformed uniformly into silica (SiO2) at near room temperature and ambient pressure, has been demonstrated for the first time. As a challenging model system, we first prove the conversion of cylindrical water condensates in porous alumina membranes to silica nanotubes (NTs) by introducing SiCl4 as a metal reactant without involving any catalytic reaction. Surprisingly, the water NTs reproducibly transformed into silica NTs, where the wall thickness of the silica NTs deposited per cycle was found to be limited by the amount of condensed water, and it was on the orders of ten nanometers per cycle (i.e., over 50 times faster than that of conventional ALD). More remarkably, the reactions only took place for 10-20 minutes or less without vacuum-related equipment. The thickness of initially adsorbed water layers in cylindrical nanopores was indirectly estimated from the thickness of formed SiO2 layers. With systematic experimental designs, we tackle the classical Kelvin equation in the nanosized pores, and the role of van der Waals forces in the nanoscale wetting phenomena, which is a long-standing issue lacking experimental insight. Moreover, we show that the present strategy is likely generalized to other oxide systems such as TiO2. Our approach opens up a new avenue for ultra-simple preparation of porous oxides and allows for the room temperature formation of dielectric layers toward organic electronic and photovoltaic applications.An innovative atomic layer deposition (ALD) concept, with which nanostructures of water condensates with high aspect ratio at equilibrium in cylindrical nanopores can be transformed uniformly into silica (SiO2) at near room temperature and ambient pressure, has been demonstrated for the first time. As a challenging model system, we first prove the conversion of

  3. Upgrading Lignocellulosic Products to Drop-In Biofuels via Dehydrogenative Cross-Coupling and Hydrodeoxygenation Sequence.

    PubMed

    Sreekumar, Sanil; Balakrishnan, Madhesan; Goulas, Konstantinos; Gunbas, Gorkem; Gokhale, Amit A; Louie, Lin; Grippo, Adam; Scown, Corinne D; Bell, Alexis T; Toste, F Dean

    2015-08-24

    Life-cycle analysis (LCA) allows the scientific community to identify the sources of greenhouse gas (GHG) emissions of novel routes to produce renewable fuels. Herein, we integrate LCA into our investigations of a new route to produce drop-in diesel/jet fuel by combining furfural, obtained from the catalytic dehydration of lignocellulosic pentose sugars, with alcohols that can be derived from a variety of bio- or petroleum-based feedstocks. As a key innovation, we developed recyclable transition-metal-free hydrotalcite catalysts to promote the dehydrogenative cross-coupling reaction of furfural and alcohols to give high molecular weight adducts via a transfer hydrogenation-aldol condensation pathway. Subsequent hydrodeoxygenation of adducts over Pt/NbOPO4 yields alkanes. Implemented in a Brazilian sugarcane biorefinery such a process could result in a 53-79% reduction in life-cycle GHG emissions relative to conventional petroleum fuels and provide a sustainable source of low carbon diesel/jet fuel. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Bio-oil fractionation and condensation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brown, Robert C.; Jones, Samuel T.; Pollard, Anthony

    The present invention relates to a method of fractionating bio-oil vapors which involves providing bio-oil vapors comprising bio-oil constituents. The bio-oil vapors are cooled in a first stage which comprises a condenser having passages for the bio-oil separated by a heat conducting wall from passages for a coolant. The coolant in the condenser of the first stage is maintained at a substantially constant temperature, set at a temperature in the range of 75 to 100.degree. C., to condense a first liquid fraction of liquefied bio-oil constituents in the condenser of the first stage. The first liquid fraction of liquified bio-oilmore » constituents from the condenser in the first stage is collected. Also disclosed are steps for subsequently recovering further liquid fractions of liquefied bio-oil constituents. Particular compositions of bio-oil condensation products are also described.« less

  5. Acid-catalyzed condensed-phase reactions of limonene and terpineol and their impacts on gas-to-particle partitioning in the formation of organic aerosols.

    PubMed

    Li, Yong Jie; Cheong, Gema Y L; Lau, Arthur P S; Chan, Chak K

    2010-07-15

    We investigated the condensed-phase reactions of biogenic VOCs with C double bond C bonds (limonene, C(10)H(16), and terpineol, C(10)H(18)O) catalyzed by sulfuric acid by both bulk solution (BS) experiments and gas-particle (GP) experiments using a flow cell reactor. Product analysis by gas chromatography-mass spectrometry (GC-MS) showed that cationic polymerization led to dimeric and trimeric product formation under conditions of relative humidity (RH) <20% (in the GP experiments) and a sulfuric acid concentration of 57.8 wt % (in the BS experiments), while hydration occurred under conditions of RH > 20% (in the GP experiments) and sulfuric acid concentrations of 46.3 wt % or lower (in the BS experiments). Apparent partitioning coefficients (K(p,rxn)) were estimated from the GP experiments by including the reaction products. Only under extremely low RH conditions (RH < 5%) did the values of K(p,rxn) ( approximately 5 x 10(-6) m(3)/microg for limonene and approximately 2 x 10(-5) m(3)/microg for terpineol) substantially exceed the physical partitioning coefficients (K(p) = 6.5 x 10(-8) m(3)/microg for limonene and =2.3 x 10(-6) m(3)/microg for terpineol) derived from the absorptive partitioning theory. At RH higher than 5%, the apparent partitioning coefficients (K(p,rxn)) of both limonene and terpineol were in the same order of magnitude as the K(p) values derived from the absorptive partitioning theory. Compared with other conditions including VOC concentration and degree of neutralization (by ammonium) of acidic particles, RH is a critical parameter that influences both the reaction mechanisms and the uptake ability (K(p,rxn) values) of these processes. The finding suggests that RH needs to be considered when taking the effects of acid-catalyzed reactions into account in estimating organic aerosol formation from C double bond C containing VOCs.

  6. Elaboration of 2-(trifluoromethyl)indoles via a cascade coupling/condensation/deacylation process.

    PubMed

    Chen, Yu; Wang, Yuji; Sun, Zheming; Ma, Dawei

    2008-02-21

    CuI/l-proline-catalyzed coupling of 2-halotrifluoroacetanilides with beta-keto esters in anhydrous DMSO under the action of Cs2CO3 at 40-80 degrees C produces polysubstituted 2-(trifluoromethyl)indoles in good to excellent yields. This reaction is suggested to occur via a novel coupling/condensation/deacylation mechanism, and many functional groups are tolerated under these conditions.

  7. On the early and developed stages of surface condensation: competition mechanism between interfacial and condensate bulk thermal resistances.

    PubMed

    Sun, Jie; Wang, Hua Sheng

    2016-10-10

    We use molecular dynamics simulation to investigate the early and developed stages of surface condensation. We find that the liquid-vapor and solid-liquid interfacial thermal resistances depend on the properties of solid and fluid, which are time-independent, while the condensate bulk thermal resistance depends on the condensate thickness, which is time-dependent. There exists intrinsic competition between the interfacial and condensate bulk thermal resistances in timeline and the resultant total thermal resistance determines the condensation intensity for a given vapor-solid temperature difference. We reveal the competition mechanism that the interfacial thermal resistance dominates at the onset of condensation and holds afterwards while the condensate bulk thermal resistance gradually takes over with condensate thickness growing. The weaker the solid-liquid bonding, the later the takeover occurs. This competition mechanism suggests that only when the condensate bulk thermal resistance is reduced after it takes over the domination can the condensation be effectively intensified. We propose a unified theoretical model for the thermal resistance analysis by making dropwise condensation equivalent to filmwise condensation. We further find that near a critical point (contact angle being ca. 153°) the bulk thermal resistance has the least opportunity to take over the domination while away from it the probability increases.

  8. On the early and developed stages of surface condensation: competition mechanism between interfacial and condensate bulk thermal resistances

    PubMed Central

    Sun, Jie; Wang, Hua Sheng

    2016-01-01

    We use molecular dynamics simulation to investigate the early and developed stages of surface condensation. We find that the liquid-vapor and solid-liquid interfacial thermal resistances depend on the properties of solid and fluid, which are time-independent, while the condensate bulk thermal resistance depends on the condensate thickness, which is time-dependent. There exists intrinsic competition between the interfacial and condensate bulk thermal resistances in timeline and the resultant total thermal resistance determines the condensation intensity for a given vapor-solid temperature difference. We reveal the competition mechanism that the interfacial thermal resistance dominates at the onset of condensation and holds afterwards while the condensate bulk thermal resistance gradually takes over with condensate thickness growing. The weaker the solid-liquid bonding, the later the takeover occurs. This competition mechanism suggests that only when the condensate bulk thermal resistance is reduced after it takes over the domination can the condensation be effectively intensified. We propose a unified theoretical model for the thermal resistance analysis by making dropwise condensation equivalent to filmwise condensation. We further find that near a critical point (contact angle being ca. 153°) the bulk thermal resistance has the least opportunity to take over the domination while away from it the probability increases. PMID:27721397

  9. Mass Spectrometry of Intact Proteins Reveals +98 u Chemical Artifacts Following Precipitation in Acetone.

    PubMed

    Güray, Melda Z; Zheng, Shi; Doucette, Alan A

    2017-02-03

    Protein precipitation in acetone is frequently employed ahead of mass spectrometry for sample preconcentration and purification. Unfortunately, acetone is not chemically inert; mass artifacts have previously been observed on glycine-containing peptides when exposed to acetone under acidic conditions. We herein report a distinct chemical modification occurring at the level of intact proteins when incubated in acetone. This artifact manifests as one or more satellite peaks in the MS spectrum of intact protein, spaced 98 u above the mass of the unmodified protein. Other artifacts (+84, +112 u) also appear upon incubation of proteins or peptides in acetone. The reaction is pH-sensitive, being suppressed when proteins are exposed to acetone under acidic conditions. The +98 u artifact is speculated to originate through an intermediate product of aldol condensation of acetone to form diacetone alcohol and mesityl oxide. A +98 u product could originate from nucleophilic attack on mesityl oxide or through condensation with diacetone alcohol. Given the extent of modification possible upon exposure of proteins to acetone, particularly following overnight solvent exposure or incubation at room temperature, an awareness of the variables influencing this novel modification is valued by proteomics researchers who employ acetone precipitation for protein purification.

  10. APPARATUS FOR CONDENSATION AND SUBLIMATION

    DOEpatents

    Schmidt, R.J.; Fuis, F. Jr.

    1958-10-01

    An apparatus is presented for the sublimation and condensation of uranium compounds in order to obtain an improved crystalline structure of this material. The apparatus comprises a vaporizing chamber and condensing structure connected thereto. There condenser is fitted with a removable liner having a demountable baffle attached to the liner by means of brackets and a removable pin. The baffle is of spiral cross-section and is provided with cooling coils disposed between the surfaces of the baffle for circulation of a temperature controlling liquid within the baffle. The cooling coll provides for controlllng the temperature of the baffle to insure formatlon of a satisfactory condensate, and the removable liner facilitates the removal of condensate formed during tbe sublimation process.

  11. Investigations on the promoting effect of ammonium hydrogencarbonate on the formation of acrylamide in model systems.

    PubMed

    Amrein, Thomas M; Andres, Luca; Manzardo, Giuseppe G G; Amado, Renato

    2006-12-27

    NH4HCO3 is known to promote acrylamide formation in sweet bakery products. This effect was investigated with respect to sugar fragmentation and formation of acrylamide from asparagine and sugar fragments in model systems under mild conditions. The presence of NH4HCO3 led to increases in acrylamide and alpha-dicarbonyls from glucose and fructose, respectively. As compared to glucose or fructose, sugar fragments such as glyoxal, hydroxyethanal, and glyceraldehyde formed much higher amounts of acrylamide in reaction with asparagine. The enhancing effect of NH4HCO3 is explained by (1) the action of NH3 as base in the retro-aldol reactions leading to sugar fragments, (2) facilitated retro-aldol-type reactions of imines in their protonated forms leading to sugar fragments, and (3) oxidation of the enaminols whereby glyoxal and other reactive sugar fragments are formed. These alpha-dicarbonyl and alpha-hydroxy carbonyl compounds may play a key role in acrylamide formation, especially under mild conditions.

  12. Impact of ultrasound on hydrophobic interactions in solutions: ultrasonic retardation of benzoin condensation.

    PubMed

    Hagu, Hannes; Salmar, Siim; Tuulmets, Ants

    2007-04-01

    Kinetics of the benzoin condensation of benzaldehyde in presence of KCN as the catalyst in water and in ethanol-water binary solutions were investigated without sonication and under ultrasound at 22 kHz. A statistically significant 20% decrease of the rate was observed in water. The retardation effect of ultrasound gradually decreases up to 45 wt% ethanol content. We report an evidence of ultrasonic retardation of reactions and thereby a direct evidence for sonochemical processes in the bulk solution. Ultrasound can disturb solvation of the species in the solution. If breaking down the stabilization of the encounter complexes between the reagents, sonication hinders the reaction while perturbation of the solvent-stabilization of the reagents accelerates the reaction.

  13. Propagation of a Chemical Reaction through Heterogeneous Lithium- Polytetrafluoroethylene Mixtures

    DTIC Science & Technology

    1975-12-11

    Condensed Phases ........... ............... 9 1.2.1 Lithium-Gas Surface Reactions. .......... 10 1.2.2 Composite Solid Propellant Combustion. . .. 13...f:- the o:cu:=ence _A a surface reaction was developed, but no analyti7al reaction zate model was presented- 1.2.2 Composite S’-lid Propellant...Combustion Composite solid propellants are plastic-like materials consisting of small oxidizer particles embedded in a fuel matrix. Ammonium perchlorate is

  14. Kinetics and mechanism of the condensation of pyridoxal hydrochloride with L-tryptophan and D-tryptophan, and the chemical transformation of their products

    NASA Astrophysics Data System (ADS)

    Pishchugin, F. V.; Tuleberdiev, I. T.

    2017-10-01

    The kinetics and mechanism of interaction between pyridoxal and L-tryptophan, D-tryptophan, and their derivatives are studied. It is found that condensation reactions proceed via three kinetically distinguishable stages: (1) the rapid intraplanar addition of the NH2 groups of the amino acids to pyridoxal with the formation of amino alcohols; (2) the rotational isomerism of amino alcohol fragments with their subsequent dehydration and the formation of a Schiff base with a specific configuration; (3) the abstraction of α-hydrogen in the product of condensation of pyridoxal with L-tryptophan, or the abstraction of CO2 in the product of condensation of pyridoxal with D-tryptophan with the formation of quinoid structures, hydrolysis of which results in the preparation of pyridoxamine and keto acid or pyridoxal and tryptamine, respectively. Schiff bases resistant to further chemical transformations are formed in the reaction with tryptophan methyl ester.

  15. Photoinduced catalytic synthesis of biologically important metabolites from formaldehyde and ammonia under plausible "prebiotic" conditions

    NASA Astrophysics Data System (ADS)

    Delidovich, I. V.; Taran, O. P.; Simonov, A. N.; Matvienko, L. G.; Parmon, V. N.

    2011-08-01

    The article analyzes new and previously reported data on several catalytic and photochemical processes yielding biologically important molecules. UV-irradiation of formaldehyde aqueous solution yields acetaldehyde, glyoxal, glycolaldehyde and glyceraldehyde, which can serve as precursors of more complex biochemically relevant compounds. Photolysis of aqueous solution of acetaldehyde and ammonium nitrate results in formation of alanine and pyruvic acid. Dehydration of glyceraldehyde catalyzed by zeolite HZSM-5-17 yields pyruvaldehyde. Monosaccharides are formed in the course of the phosphate-catalyzed aldol condensation reactions of glycolaldehyde, glyceraldehyde and formaldehyde. The possibility of the direct synthesis of tetroses, keto- and aldo-pentoses from pure formaldehyde due to the combination of the photochemical production of glycolahyde and phosphate-catalyzed carbohydrate chain growth is demonstrated. Erythrulose and 3-pentulose are the main products of such combined synthesis with selectivity up to 10%. Biologically relevant aldotetroses, aldo- and ketopentoses are more resistant to the photochemical destruction owing to the stabilization in hemiacetal cyclic forms. They are formed as products of isomerization of erythrulose and 3-pentulose. The conjugation of the concerned reactions results in a plausible route to the formation of sugars, amino and organic acids from formaldehyde and ammonia under presumed 'prebiotic' conditions.

  16. Drinking influences exhaled breath condensate acidity.

    PubMed

    Kullmann, Tamás; Barta, Imre; Antus, Balázs; Horváth, Ildikó

    2008-01-01

    Exhaled breath condensate analysis is a developing method for investigating airway pathology. Impact of food and drink on breath condensate composition has not been systematically addressed. The aim of the study was to follow exhaled breath condensate pH after drinking an acidic and a neutral beverage. Breath condensate, capillary blood, and urine of 12 healthy volunteers were collected before and after drinking either 1 l of coke or 1 l of mineral water. The pH of each sample was determined with a blood gas analyzer. The mean difference between the pH of two breath condensate samples collected within 15 min before drinking was 0.13+/-0.03. Condensate pH decreased significantly from 6.29+/-0.02 to 6.24+/-0.02 (p<0.03) after drinking coke and from 6.37+/-0.03 to 6.22+/-0.04 (p<0.003) after drinking water. Drinking coke induced significant changes in blood and urine pH as well. Drinking influences exhaled breath condensate composition and may contribute to the variability of exhaled breath condensate pH.

  17. Silanol-assisted carbinolamine formation in an amine-functionalized mesoporous silica surface: Theoretical investigation by fragmentation methods

    DOE PAGES

    de Lima Batista, Ana P.; Zahariev, Federico; Slowing, Igor I.; ...

    2015-12-15

    The aldol reaction catalyzed by an amine-substituted mesoporous silica nanoparticle (amine-MSN) surface was investigated using a large molecular cluster model (Si 392O 958C 6NH 361) combined with the surface integrated molecular orbital/molecular mechanics (SIMOMM) and fragment molecular orbital (FMO) methods. Three distinct pathways for the carbinolamine formation, the first step of the amine-catalyzed aldol reaction, are proposed and investigated in order to elucidate the role of the silanol environment on the catalytic capability of the amine-MSN material. Here the computational study reveals that the most likely mechanism involves the silanol groups actively participating in the reaction, forming and breaking covalentmore » bonds in the carbinolamine step. Furthermore, the active participation of MSN silanol groups in the reaction mechanism leads to a significant reduction in the overall energy barrier for the carbinolamine formation. In addition, a comparison between the findings using a minimal cluster model and the Si 392O 958C 6NH 361 cluster suggests that the use of larger models is important when heterogeneous catalysis problems are the target.« less

  18. Condensation of Refrigerants on Small Tube Bundles

    DTIC Science & Technology

    1988-12-01

    first comprehensive condensation model was developed by Nusselt in 1916 [Ref. 4] based on the assumption that a quiescent vapor at saturation...vapor is condensed by an auxiliary condenser . The auxiliary condenser is composed of five helically wound copper tubes of 9.53 mm diameter suspended...copper tubing located in the top center of the condenser chamber. The vapor is condensed in the storage cylinder by means of a helical copper coil

  19. Dissociative Electron Attachment in the condensed phase: sample morphology and bio-molecules

    NASA Astrophysics Data System (ADS)

    Bass, A. D.

    2001-10-01

    Recent electron impact experiments on condensed plasmid DNA have shown low energy electrons to be remarkably effective in causing damage and reveal that electron-scattering phenomena, such as transient anion formation and their decay via dissociative electron attachment, play a central role in this process. Such experiments may prompt a revision of our understanding of the mutagenic effects of radiation and have significant implications for both radiotherapy and radio-protection. These results can be better understood by investigating electron scattering with the various functional constituents of DNA in condensed environments. Recent work, to be presented here, has focused on electron attachment processes in condensed DNA bases and sugar-like analogues of the DNA backbone, as evidenced by the desorption of fragment anions. Despite this progress, a complete understanding of these processes requires parallel study of simpler `model' systems, which allow the characteristic condensed-phase phenomena modulating electron-scattering to be identified. Factors affecting anion formation and DEA can been classed as either intrinsic (affecting the properties of the resonance) or extrinsic (modifying the energy of electrons before attachment and/or the reactions of fragments, post-dissociation). In this talk we will present new results in which the extrinsic factors of porosity and phase of a sample are probed via the desorption of anionic fragments from either the pure film or from probe molecules condensed upon its surface. We show that anion desorption and hence our ability to observe DEA process, is highly sensitive to sample morphology and phase, a property which can be exploited to study the morphology of the film itself.

  20. Multichannel quench-flow microreactor chip for parallel reaction monitoring.

    PubMed

    Bula, Wojciech P; Verboom, Willem; Reinhoudt, David N; Gardeniers, Han J G E

    2007-12-01

    This paper describes a multichannel silicon-glass microreactor which has been utilized to investigate the kinetics of a Knoevenagel condensation reaction under different reaction conditions. The reaction is performed on the chip in four parallel channels under identical conditions but with different residence times. A special topology of the reaction coils overcomes the common problem arising from the difference in pressure drop of parallel channels having different length. The parallelization of reaction coils combined with chemical quenching at specific locations results in a considerable reduction in experimental effort and cost. The system was tested and showed good reproducibility in flow properties and reaction kinetic data generation.

  1. Formation of pyrophosphate on hydroxyapatite with thioesters as condensing agents

    NASA Technical Reports Server (NTRS)

    Weber, A. L.

    1982-01-01

    'Energy-rich' thioesters are shown to act as condensing agents in the formation of pyrophosphate on hydroxyapatite in the presence of water at ambient temperature. The yield of pyrophosphate based on thioester ranges from 2.5% to 11.4% and depends upon the pH and concentration of reactants. Reaction of 0.130 M hydroxyapatite suspended in a solution of 0.08 M sodium phosphate and 0.20 M imidazole hydrochloride (pH 7.0) with 0.10 M N,S-diacetylcysteamine for 6 days gives the highest yield of pyrophosphate (11.4%). Pyrophosphate formation requires the presence of hydroxyapatite, sodium phosphate and the thioester, N,S-diacetylcysteamine. The related thioester, N,S-diacetylcysteine, also yields pyrophosphate in reactions on hydroxyapatite.

  2. Chromatin condensation during terminal erythropoiesis.

    PubMed

    Zhao, Baobing; Yang, Jing; Ji, Peng

    2016-09-02

    Mammalian terminal erythropoiesis involves gradual but dramatic chromatin condensation steps that are essential for cell differentiation. Chromatin and nuclear condensation is followed by a unique enucleation process, which is believed to liberate more spaces for hemoglobin enrichment and enable the generation of a physically flexible mature red blood cell. Although these processes have been known for decades, the mechanisms are still unclear. Our recent study reveals an unexpected nuclear opening formation during mouse terminal erythropoiesis that requires caspase-3 activity. Major histones, except H2AZ, are partially released from the opening, which is important for chromatin condensation. Block of the nuclear opening through caspase inhibitor or knockdown of caspase-3 inhibits chromatin condensation and enucleation. We also demonstrate that nuclear opening and histone release are cell cycle regulated. These studies reveal a novel mechanism for chromatin condensation in mammalia terminal erythropoiesis.

  3. Dropwise condensation dynamics in humid air

    NASA Astrophysics Data System (ADS)

    Castillo Chacon, Julian Eduardo

    Dropwise condensation of atmospheric water vapor is important in multiple practical engineering applications. The roles of environmental factors and surface morphology/chemistry on the condensation dynamics need to be better understood to enable efficient water-harvesting, dehumidication, and other psychrometric processes. Systems and surfaces that promote faster condensation rates and self-shedding of condensate droplets could lead to improved mass transfer rates and higher water yields in harvesting applications. The thesis presents the design and construction of an experimental facility that allows visualization of the condensation process as a function of relative humidity. Dropwise condensation experiments are performed on a vertically oriented, hydrophobic surface at a controlled relative humidity and surface subcooling temperature. The distribution and growth of water droplets are monitored across the surface at different relative humidities (45%, 50%, 55%, and 70%) at a constant surface subcooling temperature of 15 °C below the ambient temperature. The droplet growth dynamics exhibits a strong dependency on relative humidity in the early stages during which there is a large population of small droplets on the surface and single droplet growth dominates over coalescence effects. At later stages, the dynamics of droplet growth is insensitive to relative humidity due to the dominance of coalescence effects. The overall volumetric rate of condensation on the surface is also assessed as a function of time and ambient relative humidity. Low relative humidity conditions not only slow the absolute rate of condensation, but also prolong an initial transient regime over which the condensation rate remains significantly below the steady-state value. The current state-of-the-art in dropwise condensation research indicates the need for systematic experimental investigations as a function of relative humidity. The improved understanding of the relative humidity

  4. Research Status of Evaporative Condenser

    NASA Astrophysics Data System (ADS)

    Wang, Feifei; Yang, Yongan

    2018-02-01

    Reducing energy consumption, saving water resources, recycling cool water are main directions of China’s development. Evaporative condenser using latent heat reduces water resources waste, with energy-saving advantages. This paper reviews the research status of evaporative condenser at home and abroad, and introduces the principle, classification, various influencing factors of evaporative condenser, and puts forward the future research direction.

  5. Film condensation in a horizontal rectangular duct

    NASA Technical Reports Server (NTRS)

    Lu, Qing; Suryanarayana, N. V.

    1992-01-01

    Condensation heat transfer in an annular flow regime with and without interfacial waves was experimentally investigated. The study included measurements of heat transfer rate with condensation of vapor flowing inside a horizontal rectangular duct and experiments on the initiation of interfacial waves in condensation, and adiabatic air-liquid flow. An analytical model for the condensation was developed to predict condensate film thickness and heat transfer coefficients. Some conclusions drawn from the study are that the condensate film thickness was very thin (less than 0.6 mm). The average heat transfer coefficient increased with increasing the inlet vapor velocity. The local heat transfer coefficient decreased with the axial distance of the condensing surface, with the largest change at the leading edge of the test section. The interfacial shear stress, which consisted of the momentum shear stress and the adiabatic shear stress, appeared to have a significant effect on the heat transfer coefficients. In the experiment, the condensate flow along the condensing surface experienced a smooth flow, a two-dimensional wavy flow, and a three-dimensional wavy flow. In the condensation experiment, the local wave length decreased with the axial distance of the condensing surface and the average wave length decreased with increasing inlet vapor velocity, while the wave speed increased with increasing vapor velocity. The heat transfer measurements are reliable. And, the ultrasonic technique was effective for measuring the condensate film thickness when the surface was smooth or had waves of small amplitude.

  6. The Effect of Condensate Inundation on Steam Condensation Heat Transfer to Wire-Wrapped Tubing.

    DTIC Science & Technology

    1983-06-01

    wrapped in a helical manner. The measured condensing coefficient was approximately three times that predicted by the Nusselt equation for a smooth tube...Du. Em0At Block 20 (continued) --"- condensing coefficient measured for 30 smooth tubes was 0.59 times the Nusselt coefficient calculated for the...of 0.029 was found, while it was 0.061 for the roped tubes. The average condensing coefficient measured for 30 smooth tubes was 0.59 times the Nusselt

  7. Enhanced condensation heat transfer with wettability patterning

    NASA Astrophysics Data System (ADS)

    Sinha Mahapatra, Pallab; Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine

    2015-11-01

    Condensation of water vapor on metal surfaces is useful for many engineering applications. A facile and scalable method is proposed for removing condensate from a vertical plate during dropwise condensation (DWC) in the presence of non-condensable gases (NCG). We use wettability-patterned superhydrophilic tracks (filmwise condensing domains) on a mirror-finish (hydrophilic) aluminum surface that promotes DWC. Tapered, horizontal ``collection'' tracks are laid to create a Laplace pressure driven flow, which collects condensate from the mirror-finish domains and sends it to vertical ``drainage tracks'' for gravity-induced shedding. An optimal design is achieved by changing the fractional area of superhydrophilic tracks with respect to the overall plate surface, and augmenting capillary-driven condensate-drainage by adjusting the track spatial layout. The design facilitates pump-less condensate drainage and enhances DWC heat transfer on the mirror-finish regions. The study highlights the relative influences of the promoting and retarding effects of dropwise and filmwise condensation zones on the overall heat transfer improvement on the substrate. The study demonstrated ~ 34% heat transfer improvement on Aluminum surface for the optimized design.

  8. Shock Interaction of Metal Particles in Condensed Explosive Detonation

    NASA Astrophysics Data System (ADS)

    Ripley, Robert; Zhang, Fan; Lien, Fue-Sang

    2005-07-01

    For detonation propagation in a condensed explosive with metal particles, a macro-scale physical model describing the momentum transfer between the explosive and particles has yet to be completely established. Previous 1D and 2D meso-scale modeling studies indicated that significant momentum transfer from the explosive to the particles occurs as the leading shock front crosses the particles, thus influencing the initiation and detonation structure. In this work, 3D meso-scale modeling is conducted to further study the two-phase momentum transfer during the shock diffraction and subsequent detonation in liquid nitromethane containing packed metal particles. Detonation of the condensed explosive is computed using an Arrhenius reaction model and a hybrid EOS model that combines the Mie-Gruneisen equation for reactants and the JWL equation for products. The compressible particles are modeled using the Tait EOS, where the material strength is negligible. The effect of particle packing configuration and inter-particle spacing is shown by parametric studies. Finally, a physical description of the momentum transfer is discussed.

  9. Electric field enhanced dropwise condensation on hydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Baratian, Davood; Hoek, Harmen; van den Ende, Dirk; Mugele, Frieder; Physics of Complex Fluids Team

    2016-11-01

    Dropwise condensation occurs when vapor condenses on a low surface energy surface, and the substrate is just partially wetted by the condensate. Dropwise condensation has attracted significant attention due to its reported superior heat transfer performance compared to filmwise condensation. Extensive research efforts are focused on how to promote, and enhance dropwise condensation by considering both physical and chemical factors. We have studied electrowetting-actuated condensation on hydrophobic surfaces, aiming for enhancement of heat transfer in dropwise condensation. The idea is to use suitably structured patterns of micro-electrodes that generate a heterogeneous electric field at the interface and thereby promote both the condensation itself and the shedding of condensed drops. Comforting the shedding of droplets on electrowetting-functionalized surfaces allows more condensing surface area for re-nucleation of small droplets, leading to higher condensation rates. Possible applications of this innovative concept include heat pipes for (micro) coolers in electronics as well as in more efficient heat exchangers. We acknowledge financial support by the Dutch Technology Foundation STW, which is part of the Netherlands Organization for Scientific Research (NWO), within the VICI program.

  10. Condensation of the isoprenoid and amino precursors in the biosynthesis of domoic acid.

    PubMed

    Savage, Thomas J; Smith, G Jason; Clark, Amy T; Saucedo, Portia N

    2012-01-01

    Understanding how environmental signals regulate production of domoic acid in blooms of Pseudo-nitzschia spp. at a molecular level requires description of the biochemical pathway to this kainoid neurotoxin. Precursor feeding studies have suggested domoic acid arises from the condensation of the C(10) isoprenoid geranyl diphosphate with glutamate, but the specific reactions leading to domoic acid from these precursors remain undescribed. Here, we develop a method to derivatize domoic acid with propyl chloroformate that enables gas chromatography-mass spectrometry (GC-MS) analysis to measure incorporation of stable isotopes into domoic acid generated in cultures incubated with isotopically-labeled substrates. We apply this method to demonstrate that both (2)H from [1-(2)H(2)]geraniol are incorporated into domoic acid, suggesting that the condensation of geranyl diphosphate with an amino group occurs by nucleophilic substitution of the diphosphate rather than by oxidation of geraniol to the aldehyde before reaction with an amino group to form an imine. Ultimately, these and similar studies will facilitate the identification of DA biosynthetic enzymes and genes which will enable the study of how environmental factors regulate DA biosynthesis at the molecular level. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Grain formation in astronomical systems: A critical review of condensation processes

    NASA Technical Reports Server (NTRS)

    Donn, B.

    1978-01-01

    An analysis is presented of the assumption and the applicability of the three theoretical methods for calculating condensations in cosmic clouds where no pre-existing nuclei exist. The three procedures are: thermodynamic equilibrium calculations, nucleation theory, and a kinetic treatment which would take into account the characteristics of each individual collision. Thermodynamics provide detailed results on the composition temperature and composition of the condensate provided the system attains equilibrium. Because of the cosmic abundance mixture of elements, large supersaturations in some cases and low pressures, equilibrium is not expected in astronomical clouds. Nucleation theory, a combination of thermodynamics and kinetics, has the limitations of each scheme. Kinetics, not requiring equilibrium, avoids nearly all the thermodynamics difficulties but requires detailed knowledge of many reactions which thermodynamics avoids. It appears to be the only valid way to treat grain formation in space. A review of experimental studies is given.

  12. Decay of ultralight axion condensates

    DOE PAGES

    Eby, Joshua; Ma, Michael; Suranyi, Peter; ...

    2018-01-15

    Axion particles can form macroscopic condensates, whose size can be galactic in scale for models with very small axion massesmore » $$m\\sim10^{-22}$$ eV, and which are sometimes referred to under the name of Fuzzy Dark Matter. Many analyses of these condensates are done in the non-interacting limit, due to the weakness of the self-interaction coupling of axions. We investigate here how certain results change upon inclusion of these interactions, finding a decreased maximum mass and a modified mass-radius relationship. Further, these condensates are, in general, unstable to decay through number-changing interactions. We analyze the stability of galaxy-sized condensates of axion-like particles, and sketch the parameter space of stable configurations as a function of a binding energy parameter. As a result, we find a strong lower bound on the size of Fuzzy Dark Matter condensates which are stable to decay, with lifetimes longer than the age of the universe.« less

  13. Decay of ultralight axion condensates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Eby, Joshua; Ma, Michael; Suranyi, Peter

    Axion particles can form macroscopic condensates, whose size can be galactic in scale for models with very small axion massesmore » $$m\\sim10^{-22}$$ eV, and which are sometimes referred to under the name of Fuzzy Dark Matter. Many analyses of these condensates are done in the non-interacting limit, due to the weakness of the self-interaction coupling of axions. We investigate here how certain results change upon inclusion of these interactions, finding a decreased maximum mass and a modified mass-radius relationship. Further, these condensates are, in general, unstable to decay through number-changing interactions. We analyze the stability of galaxy-sized condensates of axion-like particles, and sketch the parameter space of stable configurations as a function of a binding energy parameter. As a result, we find a strong lower bound on the size of Fuzzy Dark Matter condensates which are stable to decay, with lifetimes longer than the age of the universe.« less

  14. Aerosol-chamber study of the α-pinene/O 3 reaction: influence of particle acidity on aerosol yields and products

    NASA Astrophysics Data System (ADS)

    Iinuma, Yoshiteru; Böge, Olaf; Gnauk, Thomas; Herrmann, Hartmut

    α-Pinene ozonolysis was carried out in the presence of ammonium sulfate or sulfuric acid seed particles in a 9 m 3 Teflon chamber at the mixing ratios of 100 ppbv for α-pinene and about 70 ppbv for ozone. The evolution of size distribution was measured by means of a differential mobility particle sizer (DMPS). The resulting secondary organic aerosol (SOA) was sampled by a denuder/quartz fiber filter combination for the determination of the total organic carbon concentration (TOC) in the particle phase, using a thermographic method and by a denuder/PTFE filter combination for the analysis of individual chemical species in the particle phase using capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS). cis-Pinic acid ( m/ z 185) and another species tentatively identified at m/ z 171 and 199 were the major particle phase species for both seed particles although the product yields were different, indicating the influence of seed particle acidity. A thermographic method for the determination of TOC showed an increase of particle phase organics by 40% for the experiments with higher acidity. CE-ESI-MS analysis showed a large increase in the concentration of compounds with Mw>300 from the experiments with sulfuric acid seed particles. These results suggest that the seed particle acidity enhances the yield of SOA and plays an important role in the formation of larger molecules in the particle phase. Our results from direct particle phase chemical analysis suggest for the first time that condensation of smaller organics takes place by polymerization or aldol condensation following the formation of aldehydes, such as pinonaldehyde from the terpene ozonolysis.

  15. Nuclear Reactions in Micro/Nano-Scale Metal Particles

    NASA Astrophysics Data System (ADS)

    Kim, Y. E.

    2013-03-01

    Low-energy nuclear reactions in micro/nano-scale metal particles are described based on the theory of Bose-Einstein condensation nuclear fusion (BECNF). The BECNF theory is based on a single basic assumption capable of explaining the observed LENR phenomena; deuterons in metals undergo Bose-Einstein condensation. The BECNF theory is also a quantitative predictive physical theory. Experimental tests of the basic assumption and theoretical predictions are proposed. Potential application to energy generation by ignition at low temperatures is described. Generalized theory of BECNF is used to carry out theoretical analyses of recently reported experimental results for hydrogen-nickel system.

  16. Characterization of spacecraft humidity condensate

    NASA Technical Reports Server (NTRS)

    Muckle, Susan; Schultz, John R.; Sauer, Richard L.

    1994-01-01

    When construction of Space Station Freedom reaches the Permanent Manned Capability (PMC) stage, the Water Recovery and Management Subsystem will be fully operational such that (distilled) urine, spent hygiene water, and humidity condensate will be reclaimed to provide water of potable quality. The reclamation technologies currently baselined to process these waste waters include adsorption, ion exchange, catalytic oxidation, and disinfection. To ensure that the baseline technologies will be able to effectively remove those compounds presenting a health risk to the crew, the National Research Council has recommended that additional information be gathered on specific contaminants in waste waters representative of those to be encountered on the Space Station. With the application of new analytical methods and the analysis of waste water samples more representative of the Space Station environment, advances in the identification of the specific contaminants continue to be made. Efforts by the Water and Food Analytical Laboratory at JSC were successful in enlarging the database of contaminants in humidity condensate. These efforts have not only included the chemical characterization of condensate generated during ground-based studies, but most significantly the characterization of cabin and Spacelab condensate generated during Shuttle missions. The analytical results presented in this paper will be used to show how the composition of condensate varies amongst enclosed environments and thus the importance of collecting condensate from an environment close to that of the proposed Space Station. Although advances were made in the characterization of space condensate, complete characterization, particularly of the organics, requires further development of analytical methods.

  17. 46 CFR 56.50-35 - Condensate pumps.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... APPURTENANCES Design Requirements Pertaining to Specific Systems § 56.50-35 Condensate pumps. Two means shall be provided for discharging the condensate from the main condenser, one of which shall be mechanically... suction from the condenser and a discharge to the feed tank, it may be accepted as an independent...

  18. EFFECT OF PH ON THE REACTION OF 2,4-DINITROPHENYLHYDRAZINE WITH FORMALDEHYDE AND ACETALDEHYDE

    EPA Science Inventory

    The acid-catalyzed condensation reaction of a molecule of 2,4-dinitrophenyl-hydrazine (DNPH) with a carbonyl compound is a well known reaction for characterizing aldehydes and ketones. The DNPH derivatives are used to identify qualitatively the parent carbonyl compound by melting...

  19. Electrochemical Coupling of Biomass-Derived Acids: New C8 Platforms for Renewable Polymers and Fuels.

    PubMed

    Wu, Linglin; Mascal, Mark; Farmer, Thomas J; Arnaud, Sacha Pérocheau; Wong Chang, Maria-Angelica

    2017-01-10

    Electrolysis of biomass-derived carbonyl compounds is an alternative to condensation chemistry for supplying products with chain length >C 6 for biofuels and renewable materials production. Kolbe coupling of biomass-derived levulinic acid is used to obtain 2,7-octanedione, a new platform molecule only two low process-intensity steps removed from raw biomass. Hydrogenation to 2,7-octanediol provides a chiral secondary diol largely unknown to polymer chemistry, whereas intramolecular aldol condensation followed by hydrogenation yields branched cycloalkanes suitable for use as high-octane, cellulosic gasoline. Analogous electrolysis of an itaconic acid-derived methylsuccinic monoester yields a chiral 2,5-dimethyladipic acid diester, another underutilized monomer owing to lack of availability. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Intranuclear DNA density affects chromosome condensation in metazoans

    PubMed Central

    Hara, Yuki; Iwabuchi, Mari; Ohsumi, Keita; Kimura, Akatsuki

    2013-01-01

    Chromosome condensation is critical for accurate inheritance of genetic information. The degree of condensation, which is reflected in the size of the condensed chromosomes during mitosis, is not constant. It is differentially regulated in embryonic and somatic cells. In addition to the developmentally programmed regulation of chromosome condensation, there may be adaptive regulation based on spatial parameters such as genomic length or cell size. We propose that chromosome condensation is affected by a spatial parameter called the chromosome amount per nuclear space, or “intranuclear DNA density.” Using Caenorhabditis elegans embryos, we show that condensed chromosome sizes vary during early embryogenesis. Of importance, changing DNA content to haploid or polyploid changes the condensed chromosome size, even at the same developmental stage. Condensed chromosome size correlates with interphase nuclear size. Finally, a reduction in nuclear size in a cell-free system from Xenopus laevis eggs resulted in reduced condensed chromosome sizes. These data support the hypothesis that intranuclear DNA density regulates chromosome condensation. This suggests an adaptive mode of chromosome condensation regulation in metazoans. PMID:23783035

  1. Compression set in gas-blown condensation-cured polysiloxane elastomers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Patel, Mogon; Chinn, Sarah; Maxwell, Robert S.

    2010-12-01

    Accelerated thermal ageing studies on foamed condensation cured polysiloxane materials have been performed in support of life assessment and material replacement programmes. Two different types of filled hydrogen-blown and condensation cured polysiloxane foams were tested; commercial (RTV S5370), and an in-house formulated polysiloxane elastomer (Silfoam). Compression set properties were investigated using Thermomechanical (TMA) studies and compared against two separate longer term ageing trials carried out in air and in dry inert gas atmospheres using compression jigs. Isotherms measured from these studies were assessed using time-temperature (T/t) superposition. Acceleration factors were determined and fitted to Arrhenius kinetics. For both materials, themore » thermo-mechanical results were found to closely follow the longer term accelerated ageing trials. Comparison of the accelerated ageing data in dry nitrogen atmospheres against field trial results showed the accelerated ageing trends over predict, however the comparison is difficult as the field data suffer from significant component to component variability. Of the long term ageing trials reported here, those carried out in air deviate more significantly from field trials data compared to those carried out in dry nitrogen atmospheres. For field return samples, there is evidence for residual post-curing reactions influencing mechanical performance, which would accelerate compression set. Multiple quantum-NMR studies suggest that compression set is not associated with significant changes in net crosslink density, but that some degree of network rearrangement has occurred due to viscoelastic relaxation as well as bond breaking and forming processes, with possible post-curing reactions at early times.« less

  2. A unified diabatic description for electron transfer reactions, isomerization reactions, proton transfer reactions, and aromaticity.

    PubMed

    Reimers, Jeffrey R; McKemmish, Laura K; McKenzie, Ross H; Hush, Noel S

    2015-10-14

    While diabatic approaches are ubiquitous for the understanding of electron-transfer reactions and have been mooted as being of general relevance, alternate applications have not been able to unify the same wide range of observed spectroscopic and kinetic properties. The cause of this is identified as the fundamentally different orbital configurations involved: charge-transfer phenomena involve typically either 1 or 3 electrons in two orbitals whereas most reactions are typically closed shell. As a result, two vibrationally coupled electronic states depict charge-transfer scenarios whereas three coupled states arise for closed-shell reactions of non-degenerate molecules and seven states for the reactions implicated in the aromaticity of benzene. Previous diabatic treatments of closed-shell processes have considered only two arbitrarily chosen states as being critical, mapping these states to those for electron transfer. We show that such effective two-state diabatic models are feasible but involve renormalized electronic coupling and vibrational coupling parameters, with this renormalization being property dependent. With this caveat, diabatic models are shown to provide excellent descriptions of the spectroscopy and kinetics of the ammonia inversion reaction, proton transfer in N2H7(+), and aromaticity in benzene. This allows for the development of a single simple theory that can semi-quantitatively describe all of these chemical phenomena, as well as of course electron-transfer reactions. It forms a basis for understanding many technologically relevant aspects of chemical reactions, condensed-matter physics, chemical quantum entanglement, nanotechnology, and natural or artificial solar energy capture and conversion.

  3. The application of condensate water as an additional cooling media intermittently in condenser of a split air conditioning

    NASA Astrophysics Data System (ADS)

    Ardita, I. N.; Subagia, I. W. A.

    2018-01-01

    The condensate water produced by indoor a split air conditioning is usually not utilized and thrown away into the environment. The result of measurement shows that the temperature of condensate water produced by split air conditioning is quite low, that is 19-22 °C at the rate of 16-20 mL / min and it has PH balance. Under such conditions, Air Condensate produced by split air conditioning should still be recovered as an additional cooling medium on the condenser. This research will re-investigate the use of condensate water as an intermittent additional cooling of the condenser to increase the cooling capacity and performance of the air conditioning system. This research is done by experimental method whose implementation includes; designing and manufacturing of experimental equipment, mounting measuring tools, experimental data retrieval, data processing and yield analysis. The experimental results show that the use of condensate water as an intermittent additional cooling medium on split air conditioning condenser can increase the refrigeration effect about 2%, cooling capacity about 4% and 7% of COP system. Experimental results also show a decrease in power consumption in the system compressor about 3%

  4. Einstein–Bose condensation of Onsager vortices

    NASA Astrophysics Data System (ADS)

    Valani, Rahil N.; Groszek, Andrew J.; Simula, Tapio P.

    2018-05-01

    We have studied statistical mechanics of a gas of vortices in two dimensions. We introduce a new observable—a condensate fraction of Onsager vortices—to quantify the emergence of the vortex condensate. The condensation of Onsager vortices is most transparently observed in a single vortex species system and occurs due to a competition between solid body rotation (see vortex lattice) and potential flow (see multiple quantum vortex state). We propose an experiment to observe the condensation transition of the vortices in such a single vortex species system.

  5. A Local Condensation Analysis Representing Two-phase Annular Flow in Condenser/radiator Capillary Tubes

    NASA Technical Reports Server (NTRS)

    Karimi, Amir

    1991-01-01

    NASA's effort for the thermal environmental control of the Space Station Freedom is directed towards the design, analysis, and development of an Active Thermal Control System (ATCS). A two phase, flow through condenser/radiator concept was baselined, as a part of the ATCS, for the radiation of space station thermal load into space. The proposed condenser rejects heat through direct condensation of ATCS working fluid (ammonia) in the small diameter radiator tubes. Analysis of the condensation process and design of condenser tubes are based on the available two phase flow models for the prediction of flow regimes, heat transfer, and pressure drops. The prediction formulas use the existing empirical relationships of friction factor at gas-liquid interface. An attempt is made to study the stability of interfacial waves in two phase annular flow. The formulation is presented of a stability problem in cylindrical coordinates. The contribution of fluid viscosity, surface tension, and transverse radius of curvature to the interfacial surface is included. A solution is obtained for Kelvin-Helmholtz instability problem which can be used to determine the critical and most dangerous wavelengths for interfacial waves.

  6. Non-equilibrium effects on the chemistry of nebular condensates - Implications for the planets and asteroids

    NASA Technical Reports Server (NTRS)

    Blander, M.

    1979-01-01

    Kinetic effects, for example nucleation constraints and slow reactions, should have been important in nebular condensation. Consideration of these effects leads to the prediction of pressure-dependent compositions and physical properties of nebular condensates which is consistent with (1) the differences between different classes of chondritic meteorites, (2) some of the differences between planets, and (3) the presence of oxidized iron on the moon and in the eucrite parent body (presumably an asteroid) despite the low abundance of volatiles. Diffusion effects appear to be important for understanding oxygen isotope anomalies in refractory inclusions in Allende. The consideration of kinetic effects leads to more information concerning nebular processes than if equilibrium is assumed.

  7. Textbook Forum: Equilibrium Constants of Chemical Reactions Involving Condensed Phases: Pressure Dependence and Choice of Standard State.

    ERIC Educational Resources Information Center

    Perlmutter-Hayman, Berta

    1984-01-01

    Problems of equilibria in condensed phases (particularly those involving solutes in dilute solutions) are encountered by students in their laboratory work; the thermodynamics of these equilibria is neglected in many textbooks. Therefore, several aspects of this topic are explored, focusing on pressure dependence and choice of standard state. (JN)

  8. Gravitationally Driven Wicking for Enhanced Condensation Heat Transfer.

    PubMed

    Preston, Daniel J; Wilke, Kyle L; Lu, Zhengmao; Cruz, Samuel S; Zhao, Yajing; Becerra, Laura L; Wang, Evelyn N

    2018-04-17

    Vapor condensation is routinely used as an effective means of transferring heat or separating fluids. Filmwise condensation is prevalent in typical industrial-scale systems, where the condensed fluid forms a thin liquid film due to the high surface energy associated with many industrial materials. Conversely, dropwise condensation, where the condensate forms discrete liquid droplets which grow, coalesce, and shed, results in an improvement in heat transfer performance of an order of magnitude compared to filmwise condensation. However, current state-of-the-art dropwise technology relies on functional hydrophobic coatings, for example, long chain fatty acids or polymers, which are often not robust and therefore undesirable in industrial conditions. In addition, low surface tension fluid condensates, such as hydrocarbons, pose a unique challenge because common hydrophobic condenser coatings used to shed water (with a surface tension of 73 mN/m) often do not repel fluids with lower surface tensions (<25 mN/m). We demonstrate a method to enhance condensation heat transfer using gravitationally driven flow through a porous metal wick, which takes advantage of the condensate's affinity to wet the surface and also eliminates the need for condensate-phobic coatings. The condensate-filled wick has a lower thermal resistance than the fluid film observed during filmwise condensation, resulting in an improved heat transfer coefficient of up to an order of magnitude and comparable to that observed during dropwise condensation. The improved heat transfer realized by this design presents the opportunity for significant energy savings in natural gas processing, thermal management, heating and cooling, and power generation.

  9. Design analysis of a Helium re-condenser

    NASA Astrophysics Data System (ADS)

    Muley, P. K.; Bapat, S. L.; Atrey, M. D.

    2017-02-01

    Modern helium cryostats deploy a cryocooler with a re-condenser at its II stage for in-situ re-condensation of boil-off vapor. The present work is a vital step in the ongoing research work of design of cryocooler based 100 litre helium cryostat with in-situ re-condensation. The cryostat incorporates a two stage Gifford McMahon cryocooler having specified refrigerating capacity of 40 W at 43 K for I stage and 1 W at 4.2 K for II stage. Although design of cryostat ensures thermal load for cryocooler below its specified refrigerating capacity at the second stage, successful in-situ re-condensation depends on proper design of re-condenser which forms the objective of this work. The present work proposes design of helium re-condenser with straight rectangular fins. Fins are analyzed for optimization of thermal performance parameters such as condensation heat transfer coefficient, surface area for heat transfer, re-condensing capacity, efficiency and effectiveness. The present work provides design of re-condenser with 19 integral fins each of 10 mm height and 1.5 mm thickness with a gap of 1.5 mm between two fins, keeping in mind the manufacturing feasibility, having efficiency of 80.96 % and effectiveness of 10.34.

  10. Reflection Patterns Generated by Condensed-Phase Oblique Detonation Interaction with a Rigid Wall

    NASA Astrophysics Data System (ADS)

    Short, Mark; Chiquete, Carlos; Bdzil, John; Meyer, Chad

    2017-11-01

    We examine numerically the wave reflection patterns generated by a detonation in a condensed phase explosive inclined obliquely but traveling parallel to a rigid wall as a function of incident angle. The problem is motivated by the characterization of detonation-material confiner interactions. We compare the reflection patterns for two detonation models, one where the reaction zone is spatially distributed, and the other where the reaction is instantaneous (a Chapman-Jouguet detonation). For the Chapman-Jouguet model, we compare the results of the computations with an asymptotic study recently conducted by Bdzil and Short for small detonation incident angles. We show that the ability of a spatially distributed reaction energy release to turn flow streamlines has a significant impact on the nature of the observed reflection patterns. The computational approach uses a shock-fit methodology.

  11. Capillary-Condenser-Pumped Heat-Transfer Loop

    NASA Technical Reports Server (NTRS)

    Silverstein, Calvin C.

    1989-01-01

    Heat being transferred supplies operating power. Capillary-condenser-pumped heat-transfer loop similar to heat pipe and to capillary-evaporator-pumped heat-transfer loop in that heat-transfer fluid pumped by evaporation and condensation of fluid at heat source and sink, respectively. Capillary condenser pump combined with capillary evaporator pump to form heat exchanger circulating heat-transfer fluids in both loops. Transport of heat more nearly isothermal. Thermal stress in loop reduced, and less external surface area needed in condenser section for rejection of heat to heat sink.

  12. Biological evaluation of indolizine-chalcone hybrids as new anticancer agents.

    PubMed

    Park, Sujin; Kim, Eun Hye; Kim, Jinwoo; Kim, Seong Hwan; Kim, Ikyon

    2018-01-20

    A new chemical space was explored based on an indolizine-chalcone hybrid, which was readily accessible by base-mediated aldol condensation of indolizine bearing a 7-acetyl group with various (hetero)aromatic aldehydes. Their anticancer effect was evaluated, revealing that indolizine-chalcone hybrids with 3,5-dimethoxyphenyl group (4h) or the halogen at the meta position (4j and 4l) could have the potential to induce the caspase-dependent apoptosis of human lymphoma cells. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  13. Tachyon condensation due to domain-wall annihilation in Bose-Einstein condensates.

    PubMed

    Takeuchi, Hiromitsu; Kasamatsu, Kenichi; Tsubota, Makoto; Nitta, Muneto

    2012-12-14

    We show theoretically that a domain-wall annihilation in two-component Bose-Einstein condensates causes tachyon condensation accompanied by spontaneous symmetry breaking in a two-dimensional subspace. Three-dimensional vortex formation from domain-wall annihilations is considered a kink formation in subspace. Numerical experiments reveal that the subspatial dynamics obey the dynamic scaling law of phase-ordering kinetics. This model is experimentally feasible and provides insights into how the extra dimensions influence subspatial phase transition in higher-dimensional space.

  14. Ultra-low threshold polariton condensation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Steger, Mark; Fluegel, Brian; Alberi, Kirstin

    Here, we demonstrate the condensation of microcavity polaritons with a very sharp threshold occurring at a two orders of magnitude pump intensity lower than previous demonstrations of condensation. The long cavity lifetime and trapping and pumping geometries are crucial to the realization of this low threshold. Polariton condensation, or 'polariton lasing' has long been proposed as a promising source of coherent light at a lower threshold than traditional lasing, and these results indicate some considerations for optimizing designs for lower thresholds.

  15. Ultra-low threshold polariton condensation

    DOE PAGES

    Steger, Mark; Fluegel, Brian; Alberi, Kirstin; ...

    2017-03-13

    Here, we demonstrate the condensation of microcavity polaritons with a very sharp threshold occurring at a two orders of magnitude pump intensity lower than previous demonstrations of condensation. The long cavity lifetime and trapping and pumping geometries are crucial to the realization of this low threshold. Polariton condensation, or 'polariton lasing' has long been proposed as a promising source of coherent light at a lower threshold than traditional lasing, and these results indicate some considerations for optimizing designs for lower thresholds.

  16. Rapid, conformal gas-phase formation of silica (SiO2) nanotubes from water condensates.

    PubMed

    Bae, Changdeuck; Kim, Hyunchul; Yang, Yunjeong; Yoo, Hyunjun; Montero Moreno, Josep M; Bachmann, Julien; Nielsch, Kornelius; Shin, Hyunjung

    2013-07-07

    An innovative atomic layer deposition (ALD) concept, with which nanostructures of water condensates with high aspect ratio at equilibrium in cylindrical nanopores can be transformed uniformly into silica (SiO2) at near room temperature and ambient pressure, has been demonstrated for the first time. As a challenging model system, we first prove the conversion of cylindrical water condensates in porous alumina membranes to silica nanotubes (NTs) by introducing SiCl4 as a metal reactant without involving any catalytic reaction. Surprisingly, the water NTs reproducibly transformed into silica NTs, where the wall thickness of the silica NTs deposited per cycle was found to be limited by the amount of condensed water, and it was on the orders of ten nanometers per cycle (i.e., over 50 times faster than that of conventional ALD). More remarkably, the reactions only took place for 10-20 minutes or less without vacuum-related equipment. The thickness of initially adsorbed water layers in cylindrical nanopores was indirectly estimated from the thickness of formed SiO2 layers. With systematic experimental designs, we tackle the classical Kelvin equation in the nanosized pores, and the role of van der Waals forces in the nanoscale wetting phenomena, which is a long-standing issue lacking experimental insight. Moreover, we show that the present strategy is likely generalized to other oxide systems such as TiO2. Our approach opens up a new avenue for ultra-simple preparation of porous oxides and allows for the room temperature formation of dielectric layers toward organic electronic and photovoltaic applications.

  17. NUMERICAL TECHNIQUES TO SOLVE CONDENSATIONAL AND DISSOLUTIONAL GROWTH EQUATIONS WHEN GROWTH IS COUPLED TO REVERSIBLE REACTIONS (R823186)

    EPA Science Inventory

    Noniterative, unconditionally stable numerical techniques for solving condensational and
    dissolutional growth equations are given. Growth solutions are compared to Gear-code solutions for
    three cases when growth is coupled to reversible equilibrium chemistry. In all cases, ...

  18. Direct condensation refrigerant recovery and restoration system

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grant, D.C.H.

    1992-03-10

    This patent describes a refrigerant recovery and purification system for removing gaseous refrigerant from a disabled refrigeration unit, cleaning the refrigerant of contaminants, and converting the gaseous refrigerant to a liquid state for storage. It comprises a low pressure inlet section; a high pressure storage section; the low pressure inlet section comprising: an oil and refrigerant gas separator, including a separated oil removal means, first conduit means for connecting an inlet of the separator to the disabled refrigerant unit, a slack-sided accumulator, second conduit means connecting the separator to the slack-sided accumulator, a reclaim condenser, third conduit means connecting themore » separator and the reclaim condenser in series, an evaporator coil in the reclaim condenser connectable to a conventional operating refrigeration system for receiving a liquid refrigerant under pressure for expansion therein, the evaporator coil forming a condensing surface for condensing the refrigerant gas at near atmospheric pressure in the condenser, a liquid receiver, a reclaimed refrigerant storage tank, fourth conduit means further connecting the liquid receiver in series with the reclaim condenser, downstream thereof, means between the reclaim condenser and the liquid receiver.« less

  19. Catalytic solid substrate room temperature phosphorimetry for the determination of trace rhamnose based on its condensation reaction with calcein

    NASA Astrophysics Data System (ADS)

    Liu, Jia-Ming; Lin, Li-Ping; Wang, Hong-Xin; Lin, Shao-Qin; Zhang, Li-Hong; Cai, Wen-Lian; Lin, Xuan; Pan, You-Zhu; Wang, Xin-Xing; Li, Zhi-Ming; Jiao, Li; Cui, Ma-Lin

    2011-12-01

    Calcein (R) could not only emit strong and stable room temperature phosphorescence (RTP) on filter paper using I - as perturber, but also could be oxidized by H 2O 2 to form a non-phosphorescence compound (R'), resulting in the quenching of RTP signal of R. Moreover, the ortho-hydrogen of phenolic hydroxyl in R took condensation reaction with rhamnose (Rha) to produce non-phosphorescence compound (R-Rha) causing the RTP signal of R to further quench, and R-Rha was oxidized by H 2O 2 to form R' and Rha, bringing about the sharp RTP signal quenching of R. Thus, a new solid substrate room temperature phosphorimetry (SSRTP) for the determination of trace Rha based on its strong catalytic effect on H 2O 2 oxidizing R has been established, with the detection limit (LD) of 7.8 zg spot -1 (corresponding concentration: 2.0 × 10 -17 g ml -1, sample volume: 0.40 μl spot -1). This method has been applied to determine trace Rha in cigarettes and jujubes, with the results coinciding well with those determined by a high performance liquid chromatography (HPLC). The component of R-Rha also was analyzed by means of HPLC, mass spectrometer and nuclear magnetic resonance (NMR) measurements. The mechanism of catalytic SSRTP for the determination of trace Rha was discussed.

  20. 46 CFR 56.50-35 - Condensate pumps.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... provided for discharging the condensate from the main condenser, one of which shall be mechanically... suction from the condenser and a discharge to the feed tank, it may be accepted as an independent...

  1. Treatment of evaporator condensates by pervaporation

    DOEpatents

    Blume, Ingo; Baker, Richard W.

    1990-01-01

    A pervaporation process for separating organic contaminants from evaporator condensate streams is disclosed. The process employs a permselective membrane that is selectively permeable to an organic component of the condensate. The process involves contacting the feed side of the membrane with a liquid condensate stream, and withdrawing from the permeate side a vapor enriched in the organic component. The driving force for the process is the in vapor pressure across the membrane. This difference may be provided for instance by maintaining a vacuum on the permeate side, or by condensing the permeate. The process offers a simple, economic alternative to other separation techniques.

  2. Analytic Approximation of Carbon Condensation Issues in Type ii Supernovae

    NASA Astrophysics Data System (ADS)

    Clayton, Donald D.

    2013-01-01

    I present analytic approximations for some issues related to condensation of graphite, TiC, and silicon carbide in oxygen-rich cores of supernovae of Type II. Increased understanding, which mathematical analysis can support, renders researchers more receptive to condensation in O-rich supernova gases. Taking SN 1987A as typical, my first analysis shows why the abundance of CO molecules reaches an early maximum in which free carbon remains more abundant than CO. This analysis clarifies why O-rich gas cannot oxidize C if 56Co radioactivity is as strong as in SN 1987A. My next analysis shows that the CO abundance could be regarded as being in chemical equilibrium if the CO molecule is given an effective binding energy rather than its laboratory dissociation energy. The effective binding energy makes the thermal dissociation rate of CO equal to its radioactive dissociation rate. This preserves possible relevance for the concept of chemical equilibrium. My next analysis shows that the observed abundances of CO and SiO molecules in SN 1987A rule out frequent suggestions that equilibrium condensation of SUNOCONs has occurred following atomic mixing of the He-burning shell with more central zones in such a way as to reproduce roughly the observed spectrum of isotopes in SUNOCONs while preserving C/O > 1. He atoms admixed along with the excess carbon would destroy CO and SiO molecules, leaving their observed abundances unexplained. The final analysis argues that a chemical quasiequilibrium among grains (but not gas) may exist approximately during condensation, so that its computational use is partially justified as a guide to which mineral phases would be stable against reactions with gas. I illustrate this point with quasiequilibrium calculations by Ebel & Grossman that have shown that graphite is stable even when O/C >1 if prominent molecules are justifiably excluded from the calculation of chemical equilibrium.

  3. Annual Letter Report on ONR (Office of Naval Research) Contract Number N00014-85-K-0228.

    DTIC Science & Technology

    1985-12-02

    olefination, ".. and thioketalization, are currently under way. Stabilization of these polyketones _ with respect to aldolization is particularly important for...11 NaH High Dilution 67 ..- expected that a knotted polyketone will be especially prone to intramolecular trans-annular reactions. The four-rung THYME

  4. Fly-ash:H2SO4 catalyzed solvent free efficient synthesis of some aryl chalcones under microwave irradiation

    NASA Astrophysics Data System (ADS)

    Thirunarayanan, G.; Mayavel, P.; Thirumurthy, K.

    2012-06-01

    Some 2E aryl chalcones have been synthesized using greener catalyst Fly-ash:H2SO4 assisted solvent free environmentally benign Crossed-Aldol reaction. The yields of chalcones are more than 90%. The synthesized chalcones are characterized by their physical constants and spectral data.

  5. Synthesis of (±)-Tetrapetalone A-Me Aglycon**

    PubMed Central

    Carlsen, Peter N.; Mann, Tyler J.; Hoveyda, Amir H.

    2014-01-01

    The first synthesis of (±)-tetrapetalone A-Me aglycon is described. Key bond-forming reactions include Nazarov cyclization, a ring-closing metathesis (RCM) promoted with complete diastereoselectivity by a chiral Mo-based complex, tandem conjugate reduction-intramolecular aldol cyclization, and oxidative dearomatization. PMID:25045072

  6. Condensed Matter Nuclear Science

    NASA Astrophysics Data System (ADS)

    Takahashi, Akito; Ota, Ken-Ichiro; Iwamura, Yashuhiro

    Preface -- 1. General. Progress in condensed matter nuclear science / A. Takahashi. Summary of ICCF-12 / X. Z. Li. Overview of light water/hydrogen-based low-energy nuclear reactions / G. H. Miley and P. J. Shrestha -- 2. Excess heat and He detection. Development of "DS-reactor" as the practical reactor of "cold fusion" based on the "DS-cell" with "DS-cathode" / Y. Arata and Y.-C. Zhang. Progress in excess of power experiments with electrochemical loading of deuterium in palladium / V. Violante ... [et al.]. Anomalous energy generation during conventional electrolysis / T. Mizuno and Y. Toriyabe. "Excess heat" induced by deuterium flux in palladium film / B. Liu ... [et al.]. Abnormal excess heat observed during Mizuno-type experiments / J.-F. Fauvarque, P. P. Clauzon and G. J.-M. Lallevé. Seebeck envelope calorimetry with a Pd|D[symbol]O + H[symbol]SO[symbol] electrolytic cell / W.-S. Zhang, J. Dash and Q. Wang. Observation and investigation of nuclear fusion and self-induced electric discharges in liquids / A. I. Koldamasov ... [et al.]. Description of a sensitive seebeck calorimeter used for cold fusion studies / E. Storms. Some recent results at ENEA / M. Apicella ... [et al.]. Heat measurement during plasma electrolysis / K. Iizumi ... [et al.]. Effect of an additive on thermal output during electrolysis of heavy water with a palladium cathode / Q. Wang and J. Dash. Thermal analysis of calorimetric systems / L. D'Aulerio ... [et al.]. Surface plasmons and low-energy nuclear reactions triggering / E. Castagna ... [et al.]. Production method for violent TCB jet plasma from cavity / F. Amini. New results and an ongoing excess heat controversy / L. Kowalski ... [et al.] -- 3. Transmutation. Observation of surface distribution of products by X-ray fluorescence spectrometry during D[symbol] gas permeation through Pd Complexes / Y. Iwamura ... [et al.]. Discharge experiment using Pd/CaO/Pd multi-layered cathode / S. Narita ... [et al.]. Producing transmutation

  7. Bose-Einstein condensates form in heuristics learned by ciliates deciding to signal 'social' commitments.

    PubMed

    Clark, Kevin B

    2010-03-01

    Fringe quantum biology theories often adopt the concept of Bose-Einstein condensation when explaining how consciousness, emotion, perception, learning, and reasoning emerge from operations of intact animal nervous systems and other computational media. However, controversial empirical evidence and mathematical formalism concerning decoherence rates of bioprocesses keep these frameworks from satisfactorily accounting for the physical nature of cognitive-like events. This study, inspired by the discovery that preferential attachment rules computed by complex technological networks obey Bose-Einstein statistics, is the first rigorous attempt to examine whether analogues of Bose-Einstein condensation precipitate learned decision making in live biological systems as bioenergetics optimization predicts. By exploiting the ciliate Spirostomum ambiguum's capacity to learn and store behavioral strategies advertising mating availability into heuristics of topologically invariant computational networks, three distinct phases of strategy use were found to map onto statistical distributions described by Bose-Einstein, Fermi-Dirac, and classical Maxwell-Boltzmann behavior. Ciliates that sensitized or habituated signaling patterns to emit brief periods of either deceptive 'harder-to-get' or altruistic 'easier-to-get' serial escape reactions began testing condensed on initially perceived fittest 'courting' solutions. When these ciliates switched from their first strategy choices, Bose-Einstein condensation of strategy use abruptly dissipated into a Maxwell-Boltzmann computational phase no longer dominated by a single fittest strategy. Recursive trial-and-error strategy searches annealed strategy use back into a condensed phase consistent with performance optimization. 'Social' decisions performed by ciliates showing no nonassociative learning were largely governed by Fermi-Dirac statistics, resulting in degenerate distributions of strategy choices. These findings corroborate

  8. Reactivity landscape of pyruvate under simulated hydrothermal vent conditions

    PubMed Central

    Novikov, Yehor; Copley, Shelley D.

    2013-01-01

    Pyruvate is an important “hub” metabolite that is a precursor for amino acids, sugars, cofactors, and lipids in extant metabolic networks. Pyruvate has been produced under simulated hydrothermal vent conditions from alkyl thiols and carbon monoxide in the presence of transition metal sulfides at 250 °C [Cody GD et al. (2000) Science 289(5483):1337–1340], so it is plausible that pyruvate was formed in hydrothermal systems on the early earth. We report here that pyruvate reacts readily in the presence of transition metal sulfide minerals under simulated hydrothermal vent fluids at more moderate temperatures (25–110 °C) that are more conducive to survival of biogenic molecules. We found that pyruvate partitions among five reaction pathways at rates that depend upon the nature of the mineral present; the concentrations of H2S, H2, and NH4Cl; and the temperature. In most cases, high yields of one or two primary products are found due to preferential acceleration of certain pathways. Reactions observed include reduction of ketones to alcohols and aldol condensation, both reactions that are common in extant metabolic networks. We also observed reductive amination to form alanine and reduction to form propionic acid. Amino acids and fatty acids formed by analogous processes may have been important components of a protometabolic network that allowed the emergence of life. PMID:23872841

  9. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT: NEW CONDENSATOR, INC.--THE CONDENSATOR DIESEL ENGINE RETROFIT CRANKCASE VENTILATION SYSTEM

    EPA Science Inventory

    EPA's Environmental Technology Verification Program has tested New Condensator Inc.'s Condensator Diesel Engine Retrofit Crankcase Ventilation System. Brake specific fuel consumption (BSFC), the ratio of engine fuel consumption to the engine power output, was evaluated for engine...

  10. Continuous condensation in nanogrooves

    NASA Astrophysics Data System (ADS)

    Malijevský, Alexandr

    2018-05-01

    We consider condensation in a capillary groove of width L and depth D , formed by walls that are completely wet (contact angle θ =0 ), which is in a contact with a gas reservoir of the chemical potential μ . On a mesoscopic level, the condensation process can be described in terms of the midpoint height ℓ of a meniscus formed at the liquid-gas interface. For macroscopically deep grooves (D →∞ ), and in the presence of long-range (dispersion) forces, the condensation corresponds to a second-order phase transition, such that ℓ ˜(μcc-μ ) -1 /4 as μ →μcc - where μc c is the chemical potential pertinent to capillary condensation in a slit pore of width L . For finite values of D , the transition becomes rounded and the groove becomes filled with liquid at a chemical potential higher than μc c with a difference of the order of D-3. For sufficiently deep grooves, the meniscus growth initially follows the power law ℓ ˜(μcc-μ ) -1 /4 , but this behavior eventually crosses over to ℓ ˜D -(μ-μc c) -1 /3 above μc c, with a gap between the two regimes shown to be δ ¯μ ˜D-3 . Right at μ =μc c , when the groove is only partially filled with liquid, the height of the meniscus scales as ℓ*˜(D3L) 1 /4 . Moreover, the chemical potential (or pressure) at which the groove is half-filled with liquid exhibits a nonmonotonic dependence on D with a maximum at D ≈3 L /2 and coincides with μc c when L ≈D . Finally, we show that condensation in finite grooves can be mapped on the condensation in capillary slits formed by two asymmetric (competing) walls a distance D apart with potential strengths depending on L . All these predictions, based on mesoscopic arguments, are confirmed by fully microscopic Rosenfeld's density functional theory with a reasonable agreement down to surprisingly small values of both L and D .

  11. Organic condensation: a vital link connecting aerosol formation to cloud condensation nuclei (CCN) concentrations

    NASA Astrophysics Data System (ADS)

    Riipinen, I.; Pierce, J. R.; Yli-Juuti, T.; Nieminen, T.; Häkkinen, S.; Ehn, M.; Junninen, H.; Lehtipalo, K.; Petäjä, T.; Slowik, J.; Chang, R.; Shantz, N. C.; Abbatt, J.; Leaitch, W. R.; Kerminen, V.-M.; Worsnop, D. R.; Pandis, S. N.; Donahue, N. M.; Kulmala, M.

    2011-04-01

    Atmospheric aerosol particles influence global climate as well as impair air quality through their effects on atmospheric visibility and human health. Ultrafine (<100 nm) particles often dominate aerosol numbers, and nucleation of atmospheric vapors is an important source of these particles. To have climatic relevance, however, the freshly nucleated particles need to grow in size. We combine observations from two continental sites (Egbert, Canada and Hyytiälä, Finland) to show that condensation of organic vapors is a crucial factor governing the lifetimes and climatic importance of the smallest atmospheric particles. We model the observed ultrafine aerosol growth with a simplified scheme approximating the condensing species as a mixture of effectively non-volatile and semi-volatile species, demonstrate that state-of-the-art organic gas-particle partitioning models fail to reproduce the observations, and propose a modeling approach that is consistent with the measurements. We find that roughly half of the mass of the condensing mass needs to be distributed proportional to the aerosol surface area (thus implying that the condensation is governed by gas-phase concentration rather than the equilibrium vapour pressure) to explain the observed aerosol growth. We demonstrate the large sensitivity of predicted number concentrations of cloud condensation nuclei (CCN) to these interactions between organic vapors and the smallest atmospheric nanoparticles - highlighting the need for representing this process in global climate models.

  12. Demonstration of Nautilus Centripetal Capillary Condenser Technology

    NASA Technical Reports Server (NTRS)

    Wheeler, RIchard; Tang, Linh; Wambolt, Spencer; Golliher, Eric; Agui, Juan

    2016-01-01

    This paper describes the results of a proof of concept effort for development of a Nautilus Centripetal Capillary Condenser (NCCC or NC3) used for microgravity compatible water recovery from moist air with integral passive phase separation. Removal of liquid condensate from the air stream exiting a condenser is readily performed here on Earth. In order to perform this function in space however, without gravity or mechanical action, other tactics including utilization of inertial, drag and capillary forces are required. Within the NC3, liquid water forms via condensation on cold condenser surfaces as humid air passes along multiple spiral channels, each in its own plane, all together forming a stacked plate assembly. Non-mechanical inertial forces are employed to transfer condensate, as it forms, via centripetal action to the outer perimeter of each channel. A V-shaped groove, constructed on this outer edge of the spiral channel, increases local capillary forces thereby retaining the liquid. Air drag then pulls the liquid along to a collection region near the center of the device. Dry air produced by each parallel spiral channel is combined in a common orthogonal, out-of-plane conduit passing down the axial center of the stacked device. Similarly, the parallel condensate streams are combined and removed from the condenser/separator through yet another out-of-plane axial conduit. NC3 is an integration of conventional finned condenser operation, combined with static phase separation and capillary transport phenomena. A Mars' transit mission would be a logical application for this technology where gravity is absent and the use of vibrating, energy-intensive, motor-driven centrifugal separators is undesired. Here a vapor stream from either the Heat Melt Compactor or the Carbon dioxide Reduction Assembly, for example, would be dried to a dew point of 10 deg using a passive NC3 condenser/separator with the precious water condensate recycled to the water bus.

  13. Condensation heat transfer and flow friction in silicon microchannels

    NASA Astrophysics Data System (ADS)

    Wu, Huiying; Wu, Xinyu; Qu, Jian; Yu, Mengmeng

    2008-11-01

    An experimental investigation was performed on heat transfer and flow friction characteristics during steam condensation flow in silicon microchannels. Three sets of trapezoidal silicon microchannels, with hydraulic diameters of 77.5 µm, 93.0 µm and 128.5 µm respectively, were tested under different flow and cooling conditions. It was found that both the condensation heat transfer Nusselt number (Nu) and the condensation two-phase frictional multiplier (phi2Lo) were dependent on the steam Reynolds number (Rev), condensation number (Co) and dimensionless hydraulic diameter (Dh/L). With the increase in the steam Reynolds number, condensation number and dimensionless hydraulic diameter, the condensation Nusselt number increased. However, different variations were observed for the condensation two-phase frictional multiplier. With the increase in the steam Reynolds number and dimensionless hydraulic diameter, the condensation two-phase frictional multiplier decreased, while with the increase in the condensation number, the condensation two-phase frictional multiplier increased. Based on the experimental results, dimensionless correlations for condensation heat transfer and flow friction in silicon microchannels were proposed for the first time. These correlations can be used to determine the condensation heat transfer coefficient and pressure drop in silicon microchannels if the steam mass flow rate, cooling rate and geometric parameters are fixed. It was also found that the condensation heat transfer and flow friction have relations to the injection flow (a transition flow pattern from the annular flow to the slug/bubbly flow), and with injection flow moving toward the outlet, both the condensation heat transfer coefficient and the condensation two-phase frictional multiplier increased.

  14. Synthesis and evaluation of a dimer of 2-(4-pyridylmethyl)-1-indanone as a novel nonsteroidal aromatase inhibitor.

    PubMed

    Gupta, Ranju; Jindal, Dharam Paul; Jit, Birinder; Narang, Gaurav; Palusczak, Anja; Hartmann, Rolf W

    2004-07-01

    A novel dimer of 2-(4-pyridylmethyl)-1-indanone (2) was obtained while carrying out aldol condensation of 1-indanone with pyridine-4-carboxaldehyde in potassium hydroxide. The structure of dimer 3 has been established using various spectral techniques and was screened for its ability to inhibit the cytochrome P(450) enzyme aromatase. The dimer showed strong inhibition of human placental aromatase and was found 3 times more potent (RP = 3, IC(50) = 10.2 microM) as compared to aminoglutethimide (RP = 1, IC(50) = 18.5 microM.

  15. Bose-Einstein condensation of light: general theory.

    PubMed

    Sob'yanin, Denis Nikolaevich

    2013-08-01

    A theory of Bose-Einstein condensation of light in a dye-filled optical microcavity is presented. The theory is based on the hierarchical maximum entropy principle and allows one to investigate the fluctuating behavior of the photon gas in the microcavity for all numbers of photons, dye molecules, and excitations at all temperatures, including the whole critical region. The master equation describing the interaction between photons and dye molecules in the microcavity is derived and the equivalence between the hierarchical maximum entropy principle and the master equation approach is shown. The cases of a fixed mean total photon number and a fixed total excitation number are considered, and a much sharper, nonparabolic onset of a macroscopic Bose-Einstein condensation of light in the latter case is demonstrated. The theory does not use the grand canonical approximation, takes into account the photon polarization degeneracy, and exactly describes the microscopic, mesoscopic, and macroscopic Bose-Einstein condensation of light. Under certain conditions, it predicts sub-Poissonian statistics of the photon condensate and the polarized photon condensate, and a universal relation takes place between the degrees of second-order coherence for these condensates. In the macroscopic case, there appear a sharp jump in the degrees of second-order coherence, a sharp jump and kink in the reduced standard deviations of the fluctuating numbers of photons in the polarized and whole condensates, and a sharp peak, a cusp, of the Mandel parameter for the whole condensate in the critical region. The possibility of nonclassical light generation in the microcavity with the photon Bose-Einstein condensate is predicted.

  16. Condensation Enhancement by Surface Porosity: Three-Stage Mechanism.

    PubMed

    Yarom, Michal; Marmur, Abraham

    2015-08-18

    Surface defects, such as pores, cracks, and scratches, are naturally occurring and commonly found on solid surfaces. However, the mechanism by which such imperfections promote condensation has not been fully explored. In the current paper we thermodynamically analyze the ability of surface porosity to enhance condensation on a hydrophilic solid. We show that the presence of a surface-embedded pore brings about three distinct stages of condensation. The first is capillary condensation inside the pore until it is full. This provides an ideal hydrophilic surface for continuing the condensation. As a result, spontaneous condensation and wetting can be achieved at lower vapor pressure than on a smooth surface.

  17. Advances in modelling of condensation phenomena

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, W.S.; Zaltsgendler, E.; Hanna, B.

    1997-07-01

    The physical parameters in the modelling of condensation phenomena in the CANDU reactor system codes are discussed. The experimental programs used for thermal-hydraulic code validation in the Canadian nuclear industry are briefly described. The modelling of vapour generation and in particular condensation plays a key role in modelling of postulated reactor transients. The condensation models adopted in the current state-of-the-art two-fluid CANDU reactor thermal-hydraulic system codes (CATHENA and TUF) are described. As examples of the modelling challenges faced, the simulation of a cold water injection experiment by CATHENA and the simulation of a condensation induced water hammer experiment by TUFmore » are described.« less

  18. Competition between Bose-Einstein Condensation and Spin Dynamics.

    PubMed

    Naylor, B; Brewczyk, M; Gajda, M; Gorceix, O; Maréchal, E; Vernac, L; Laburthe-Tolra, B

    2016-10-28

    We study the impact of spin-exchange collisions on the dynamics of Bose-Einstein condensation by rapidly cooling a chromium multicomponent Bose gas. Despite relatively strong spin-dependent interactions, the critical temperature for Bose-Einstein condensation is reached before the spin degrees of freedom fully thermalize. The increase in density due to Bose-Einstein condensation then triggers spin dynamics, hampering the formation of condensates in spin-excited states. Small metastable spinor condensates are, nevertheless, produced, and they manifest in strong spin fluctuations.

  19. Magnetofermionic condensate in two dimensions

    PubMed Central

    Kulik, L. V.; Zhuravlev, A. S.; Dickmann, S.; Gorbunov, A. V.; Timofeev, V. B.; Kukushkin, I. V.; Schmult, S.

    2016-01-01

    Coherent condensate states of particles obeying either Bose or Fermi statistics are in the focus of interest in modern physics. Here we report on condensation of collective excitations with Bose statistics, cyclotron magnetoexcitons, in a high-mobility two-dimensional electron system in a magnetic field. At low temperatures, the dense non-equilibrium ensemble of long-lived triplet magnetoexcitons exhibits both a drastic reduction in the viscosity and a steep enhancement in the response to the external electromagnetic field. The observed effects are related to formation of a super-absorbing state interacting coherently with the electromagnetic field. Simultaneously, the electrons below the Fermi level form a super-emitting state. The effects are explicable from the viewpoint of a coherent condensate phase in a non-equilibrium system of two-dimensional fermions with a fully quantized energy spectrum. The condensation occurs in the space of vectors of magnetic translations, a property providing a completely new landscape for future physical investigations. PMID:27848969

  20. 21 CFR 886.1380 - Diagnostic condensing lens.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Diagnostic condensing lens. 886.1380 Section 886...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1380 Diagnostic condensing lens. (a) Identification. A diagnostic condensing lens is a device used in binocular indirect ophthalmoscopy (a procedure...

  1. Study of the antibacterial and antifungal activities of synthetic benzyl bromides, ketones, and corresponding chalcone derivatives.

    PubMed

    Shakhatreh, Muhamad Ali K; Al-Smadi, Mousa L; Khabour, Omar F; Shuaibu, Fatima A; Hussein, Emad I; Alzoubi, Karem H

    2016-01-01

    Several applications of chalcones and their derivatives encouraged researchers to increase their synthesis as an alternative for the treatment of pathogenic bacterial and fungal infections. In the present study, chalcone derivatives were synthesized through cross aldol condensation reaction between 4-( N , N -dimethylamino)benzaldehyde and multiarm aromatic ketones. The multiarm aromatic ketones were synthesized through nucleophilic substitution reaction between 4-hydroxy acetophenone and benzyl bromides. The benzyl bromides, multiarm aromatic ketones, and corresponding chalcone derivatives were evaluated for their activities against eleven clinical pathogenic Gram-positive, Gram-negative bacteria, and three pathogenic fungi by the disk diffusion method. The minimum inhibitory concentration was determined by the microbroth dilution technique. The results of the present study demonstrated that benzyl bromide derivatives have strong antibacterial and antifungal properties as compared to synthetic chalcone derivatives and ketones. Benzyl bromides (1a and 1c) showed high ester activity against Gram-positive bacteria and fungi but moderate activity against Gram-negative bacteria. Therefore, these compounds may be considered as good antibacterial and antifungal drug discovery. However, substituted ketones (2a-b) as well as chalcone derivatives (3a-c) showed no activity against all the tested strains except for ketone (2c), which showed moderate activity against Candida albicans .

  2. Study of the antibacterial and antifungal activities of synthetic benzyl bromides, ketones, and corresponding chalcone derivatives

    PubMed Central

    Shakhatreh, Muhamad Ali K; Al-Smadi, Mousa L; Khabour, Omar F; Shuaibu, Fatima A; Hussein, Emad I; Alzoubi, Karem H

    2016-01-01

    Several applications of chalcones and their derivatives encouraged researchers to increase their synthesis as an alternative for the treatment of pathogenic bacterial and fungal infections. In the present study, chalcone derivatives were synthesized through cross aldol condensation reaction between 4-(N,N-dimethylamino)benzaldehyde and multiarm aromatic ketones. The multiarm aromatic ketones were synthesized through nucleophilic substitution reaction between 4-hydroxy acetophenone and benzyl bromides. The benzyl bromides, multiarm aromatic ketones, and corresponding chalcone derivatives were evaluated for their activities against eleven clinical pathogenic Gram-positive, Gram-negative bacteria, and three pathogenic fungi by the disk diffusion method. The minimum inhibitory concentration was determined by the microbroth dilution technique. The results of the present study demonstrated that benzyl bromide derivatives have strong antibacterial and antifungal properties as compared to synthetic chalcone derivatives and ketones. Benzyl bromides (1a and 1c) showed high ester activity against Gram-positive bacteria and fungi but moderate activity against Gram-negative bacteria. Therefore, these compounds may be considered as good antibacterial and antifungal drug discovery. However, substituted ketones (2a–b) as well as chalcone derivatives (3a–c) showed no activity against all the tested strains except for ketone (2c), which showed moderate activity against Candida albicans. PMID:27877017

  3. Modeling the Kinetics of Deactivation of Catalysts during the Upgrading of Bio-Oil

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Weber, Robert S.; Olarte, Mariefel V.; Wang, Huamin

    The fouling of catalysts for the upgrading of bio-oils appears to be very different from the fouling of catalysts for the hydroprocessing of petroleum-derived streams. There are two reasons for the differences: a) bio-oil contains polarizable components and phases that can stabilize reaction intermediates exhibiting charge separation and b) bio-oil components contain functional groups that contain O, notably carbonyls (>C=O). Aldol condensation of carbonyls affords very different pathways for the production of oligomeric, refractory deposits than does dehydrogenation/polymerization of petroleum-derived hydrocarbons. Colloquially, we refer to the bio-oil derived deposits as “gunk” to discriminate them from coke, the carbonaceous deposits encounteredmore » in petroleum refining. Classical gelation, appears to be a suitable model for the “gunking” reaction. Our work has helped explain the temperature range at which bio-oil should be pre-processed (“stabilized”) to confer longer lifetimes on the catalysts used for more severe processing. Stochastic modeling (kinetic Monte Carlo simulations) appears suitable to capture the rates of oligomerization of bio-oil. This work was supported by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies Office. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.« less

  4. Quantitative analysis of chromosome condensation in fission yeast.

    PubMed

    Petrova, Boryana; Dehler, Sascha; Kruitwagen, Tom; Hériché, Jean-Karim; Miura, Kota; Haering, Christian H

    2013-03-01

    Chromosomes undergo extensive conformational rearrangements in preparation for their segregation during cell divisions. Insights into the molecular mechanisms behind this still poorly understood condensation process require the development of new approaches to quantitatively assess chromosome formation in vivo. In this study, we present a live-cell microscopy-based chromosome condensation assay in the fission yeast Schizosaccharomyces pombe. By automatically tracking the three-dimensional distance changes between fluorescently marked chromosome loci at high temporal and spatial resolution, we analyze chromosome condensation during mitosis and meiosis and deduct defined parameters to describe condensation dynamics. We demonstrate that this method can determine the contributions of condensin, topoisomerase II, and Aurora kinase to mitotic chromosome condensation. We furthermore show that the assay can identify proteins required for mitotic chromosome formation de novo by isolating mutants in condensin, DNA polymerase ε, and F-box DNA helicase I that are specifically defective in pro-/metaphase condensation. Thus, the chromosome condensation assay provides a direct and sensitive system for the discovery and characterization of components of the chromosome condensation machinery in a genetically tractable eukaryote.

  5. Quantitative Analysis of Chromosome Condensation in Fission Yeast

    PubMed Central

    Petrova, Boryana; Dehler, Sascha; Kruitwagen, Tom; Hériché, Jean-Karim; Miura, Kota

    2013-01-01

    Chromosomes undergo extensive conformational rearrangements in preparation for their segregation during cell divisions. Insights into the molecular mechanisms behind this still poorly understood condensation process require the development of new approaches to quantitatively assess chromosome formation in vivo. In this study, we present a live-cell microscopy-based chromosome condensation assay in the fission yeast Schizosaccharomyces pombe. By automatically tracking the three-dimensional distance changes between fluorescently marked chromosome loci at high temporal and spatial resolution, we analyze chromosome condensation during mitosis and meiosis and deduct defined parameters to describe condensation dynamics. We demonstrate that this method can determine the contributions of condensin, topoisomerase II, and Aurora kinase to mitotic chromosome condensation. We furthermore show that the assay can identify proteins required for mitotic chromosome formation de novo by isolating mutants in condensin, DNA polymerase ε, and F-box DNA helicase I that are specifically defective in pro-/metaphase condensation. Thus, the chromosome condensation assay provides a direct and sensitive system for the discovery and characterization of components of the chromosome condensation machinery in a genetically tractable eukaryote. PMID:23263988

  6. Formaldehyde-aminoguanidine condensation and aminoguanidine self-condensation products: syntheses, crystal structures and characterization.

    PubMed

    Buvaylo, Elena A; Kokozay, Vladimir N; Strutynska, Nataliia Yu; Vassilyeva, Olga Yu; Skelton, Brian W

    2018-02-01

    Guanidine is the functional group on the side chain of arginine, one of the fundamental building blocks of life. In recent years, a number of compounds based on the aminoguanidine (AG) moiety have been described as presenting high anticancer activities. The product of condensation between two molecules of AG and one molecule of formaldehyde was isolated in the protonated form as the dinitrate salt (systematic name: 2,8-diamino-1,3,4,6,7,9-hexaazanona-1,8-diene-1,9-diium dinitrate), C 3 H 14 N 8 2+ ·2NO 3 - , (I). The cation lacks crystallographically imposed symmetry and comprises two terminal planar guanidinium groups, which share an N-C-N unit. Each cation in (I) builds 14 N-H...O hydrogen bonds and is separated from adjacent cations by seven nitrate anions. The AG self-condensation reaction in the presence of copper(II) chloride and chloride anions led to the formation of the organic-inorganic hybrid 1,2-bis(diaminomethylidene)hydrazine-1,2-diium tetrachloridocuprate(II), (C 2 H 10 N 6 )[CuCl 4 ], (II). Its asymmetric unit is composed of half a diprotonated 1,2-bis(diaminomethylidene)hydrazine-1,2-diium dication and half a tetrachloridocuprate(II) dianion, with the Cu II atom situated on a twofold rotation axis. The planar guanidinium fragments in (II) have their planes twisted by approximately 77.64 (5)° with respect to each other. The tetrahedral [CuCl 4 ] 2- anion is severely distorted and its pronounced `planarity' must originate from its involvement in multiple N-H...Cl hydrogen bonds. It was reported that [CuCl 4 ] 2- anions, with a trans-Cl-Cu-Cl angle (Θ) of ∼140°, are yellow-green at room temperature, with the colour shifting to a deeper green as Θ increases and toward orange as Θ decreases. Brown salt (II), with a Θ value of 142.059 (8)°, does not fit the trend, which emphasizes the need to take other structural factors into consideration. In the crystal of salt (II), layers of cations and anions alternate along the b axis, with the

  7. Multiple Condensation Reactions Involving Pt(II) /Pd(II) -OH2 , Pt-NH3 , and Cytosine-NH2 Groups: New Twists in Cisplatin-Nucleobase Chemistry.

    PubMed

    Yin-Bandur, Lu; Sanz Miguel, Pablo J; Rodríguez-Santiago, Luis; Sodupe, Mariona; Berghaus, Melanie; Lippert, Bernhard

    2016-09-12

    The coordination chemistry of the antitumor agent cisplatin and related complexes with DNA and its constituents, that is, the nucleobases, appears to be dominated by 1:1 and 1:2 adducts of the types cis-[Pta2 (nucleobase)X] and cis-[Pta2 (nucleobase)2 ] (a=NH3 or amine; a2 =diamine or diimine; X=Cl, OH or OH2 ). Here, we have studied the interactions of the putative 1:1 adducts cis-[Pta2 (1-MeC-N3)(OH2 )](2+) (with a=NH3 , a2 =2,2'-bpy (2,2'-bipyridine), 1-MeC=model nucleobase 1-methylcytosine) with additional cis-[Pt(NH3 )2 (OH2 )2 ](2+) or its kinetically superior analogues [Pd(en)(OH2 )2 ](2+) (en=ethylenediamine) and [Pd(2,2'-bpy)(OH2 )2 ](2+) . Depending upon the conditions applied different compounds of different nuclearity are formed. Without exception they represent condensation products of the components, containing μ-1-MeC-H , μ-OH(-) , as well as μ-NH2 (-) bridges. In the presence of Ag(+) ions, the isolated products in several cases display additionally Pt→Ag dative bonds. On the basis of the cytosine-containing structures established by X-ray crystallography, it is proposed that any of the feasible initial 1:1 nucleobase adducts of cisplatin could form dinuclear Pt complexes upon reaction with additional hydrolyzed cisplatin, thereby generating nucleobase adducts other than the presently established ones. Two findings appear to be of particular significance: First, hydrolyzed cisplatin can have a moderately accelerating effect on the formation of a secondary nucleobase product. Second, NH3 ligands of the cisplatin moiety can be converted into bridging amido ligands following condensation with the diaqua species of cisplatin. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. 40 CFR 721.639 - Amine aldehyde condensate.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Amine aldehyde condensate. 721.639... Substances § 721.639 Amine aldehyde condensate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an amine aldehyde condensate (PMN P-94-1810...

  9. 40 CFR 721.639 - Amine aldehyde condensate.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Amine aldehyde condensate. 721.639... Substances § 721.639 Amine aldehyde condensate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an amine aldehyde condensate (PMN P-94-1810...

  10. 40 CFR 721.639 - Amine aldehyde condensate.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amine aldehyde condensate. 721.639... Substances § 721.639 Amine aldehyde condensate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an amine aldehyde condensate (PMN P-94-1810...

  11. 40 CFR 721.639 - Amine aldehyde condensate.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Amine aldehyde condensate. 721.639... Substances § 721.639 Amine aldehyde condensate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an amine aldehyde condensate (PMN P-94-1810...

  12. 40 CFR 721.639 - Amine aldehyde condensate.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Amine aldehyde condensate. 721.639... Substances § 721.639 Amine aldehyde condensate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an amine aldehyde condensate (PMN P-94-1810...

  13. Condensation phenomenon detection through surface plasmon resonance.

    PubMed

    Ibrahim, Joyce; Al Masri, Mostafa; Veillas, Colette; Celle, Frédéric; Cioulachtjian, Serge; Verrier, Isabelle; Lefèvre, Frédéric; Parriaux, Olivier; Jourlin, Yves

    2017-10-02

    The aim of this work is to optically detect the condensation of acetone vapor on an aluminum plate cooled down in a two-phase environment (liquid/vapor). Sub-micron period aluminum based diffraction gratings with appropriate properties, exhibiting a highly sensitive plasmonic response, were successfully used for condensation experiments. A shift in the plasmonic wavelength resonance has been measured when acetone condensation on the aluminum surface takes place due to a change of the surrounding medium close to the surface, demonstrating that the surface modification occurs at the very beginning of the condensation phenomenon. This paper presents important steps in comprehending the incipience of condensate droplet and frost nucleation (since both mechanisms are similar) and thus to control the phenomenon by using an optimized engineered surface.

  14. Film condensation in a horizontal rectangular duct

    NASA Technical Reports Server (NTRS)

    Lu, Qing; Suryanarayana, N. V.

    1993-01-01

    Condensation heat transfer in a horizontal rectangular duct was experimentally and analytically investigated. To prevent the dripping of condensate on the film, the experiment was conducted inside a horizontal rectangular duct with vapor condensing only on the bottom cooled plate of the duct. R-113 and FC-72 (Fluorinert Electronic Fluid developed by the 3M Company) were used as the condensing fluids. The experimental program included measurements of film thickness, local and average heat transfer coefficients, wave length, wave speed, and a study of wave initiation. The measured film thickness was used to obtain the local heat transfer coefficient. The wave initiation was studied both with condensation and with an adiabatic air-liquid flow. The test sections used in both experiments were identical.

  15. Flow condensation on copper-based nanotextured superhydrophobic surfaces.

    PubMed

    Torresin, Daniele; Tiwari, Manish K; Del Col, Davide; Poulikakos, Dimos

    2013-01-15

    Superhydrophobic surfaces have shown excellent ability to promote dropwise condensation with high droplet mobility, leading to enhanced surface thermal transport. To date, however, it is unclear how superhydrophobic surfaces would perform under the stringent flow condensation conditions of saturated vapor at high temperature, which can affect superhydrophobicity. Here, we investigate this issue employing "all-copper" superhydrophobic surfaces with controlled nanostructuring for minimal thermal resistance. Flow condensation tests performed with saturated vapor at a high temperature (110 °C) showed the condensing drops penetrate the surface texture (i.e., attain the Wenzel state with lower droplet mobility). At the same time, the vapor shear helped ameliorate the mobility and enhanced the thermal transport. At the high end of the examined vapor velocity range, a heat flux of ~600 kW m(-2) was measured at 10 K subcooling and 18 m s(-1) vapor velocity. This clearly highlights the excellent potential of a nanostructured superhydrophobic surface in flow condensation applications. The surfaces sustained dropwise condensation and vapor shear for five days, following which mechanical degradation caused a transition to filmwise condensation. Overall, our results underscore the need to investigate superhydrophobic surfaces under stringent and realistic flow condensation conditions before drawing conclusions regarding their performance in practically relevant condensation applications.

  16. Quantification of chromatin condensation level by image processing.

    PubMed

    Irianto, Jerome; Lee, David A; Knight, Martin M

    2014-03-01

    The level of chromatin condensation is related to the silencing/activation of chromosomal territories and therefore impacts on gene expression. Chromatin condensation changes during cell cycle, progression and differentiation, and is influenced by various physicochemical and epigenetic factors. This study describes a validated experimental technique to quantify chromatin condensation. A novel image processing procedure is developed using Sobel edge detection to quantify the level of chromatin condensation from nuclei images taken by confocal microscopy. The algorithm was developed in MATLAB and used to quantify different levels of chromatin condensation in chondrocyte nuclei achieved through alteration in osmotic pressure. The resulting chromatin condensation parameter (CCP) is in good agreement with independent multi-observer qualitative visual assessment. This image processing technique thereby provides a validated unbiased parameter for rapid and highly reproducible quantification of the level of chromatin condensation. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

  17. Molecular simulation of steady-state evaporation and condensation in the presence of a non-condensable gas

    NASA Astrophysics Data System (ADS)

    Liang, Zhi; Keblinski, Pawel

    2018-02-01

    Using molecular dynamics simulations, we study evaporation and condensation of fluid Ar in the presence of a non-condensable Ne gas in a nanochannel. The evaporation and condensation are driven by the temperature difference, ΔTL, between the evaporating and condensing liquid surfaces. The steady-state evaporation and condensation fluxes (JMD) are also affected by the Ne concentration, ρNe, and the nanochannel length. We find that across a wide range of ΔTL and ρNe, JMD is in good agreement with the prediction from Stefan's law and from Schrage relationships. Furthermore, for ΔTL less than ˜20% of the absolute average temperature, we find that both steady-state heat and mass fluxes are proportional to ΔTL. This allows us to determine the interfacial resistance to the heat and mass transfer and compare it with the corresponding resistances in the gas phase. In this context, we derive an analytical expression for the effective thermal conductivity of the gas region in the nanochannel and the mass transport interfacial resistance equivalent length, i.e., the length of the nanochannel for which the resistance to the mass flow is the same as the interfacial resistance to the mass flow.

  18. GENOTOXICITY OF TEN CIGARETTE SMOKE CONDENSATES IN FOUR TEST SYSTEMS: COMPARISONS BETWEEN ASSAYS AND CONDENSATES

    EPA Science Inventory

    What is the study?
    This the first assessment of a set of cigarette smoke condensates from a range of cigarette types in a variety (4) of short-term genotoxicity assays.
    Why was it done?
    No such comparative study of cigarette smoke condensates has been reported. H...

  19. Evolutionary games of condensates in coupled birth–death processes

    PubMed Central

    Knebel, Johannes; Weber, Markus F.; Krüger, Torben; Frey, Erwin

    2015-01-01

    Condensation phenomena arise through a collective behaviour of particles. They are observed in both classical and quantum systems, ranging from the formation of traffic jams in mass transport models to the macroscopic occupation of the energetic ground state in ultra-cold bosonic gases (Bose–Einstein condensation). Recently, it has been shown that a driven and dissipative system of bosons may form multiple condensates. Which states become the condensates has, however, remained elusive thus far. The dynamics of this condensation are described by coupled birth–death processes, which also occur in evolutionary game theory. Here we apply concepts from evolutionary game theory to explain the formation of multiple condensates in such driven-dissipative bosonic systems. We show that the vanishing of relative entropy production determines their selection. The condensation proceeds exponentially fast, but the system never comes to rest. Instead, the occupation numbers of condensates may oscillate, as we demonstrate for a rock–paper–scissors game of condensates. PMID:25908384

  20. Wettability Patterning for Enhanced Dropwise Condensation

    NASA Astrophysics Data System (ADS)

    Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine

    2014-11-01

    Dropwise condensation (DwC), in order to be sustainable, requires removal of the condensate droplets. This removal is frequently facilitated by gravity. The rate of DwC heat transfer depends strongly on the maximum departing droplet diameter. Based on wettability patterning, we present a facile technique designed to control the maximum droplet size in DwC within vapor/air atmospheres, and demonstrate how this approach can be used to enhance the corresponding heat transfer rate. We examine various hydrophilic-superhydrophilic patterns, which, respectively sustain DwC and filmwise (FwC) condensation on the substrate. The fabrication method does notemploy any hydrophobizing agent. By juxtaposing parallel lines of hydrophilic (CA ~ 78°) and superhydrophilic (CA ~ 0°) regions on the condensing surface, we create alternating domains of DwC and FwC. The average droplet size on the DwC domain is reduced by ~ 60% compared to the theoretical maximum, which corresponds to the line width. We compare heat transfer rate between unpatternend DwC surfaces and patterned DwC surfaces. Even after sacrificing 40% of condensing area, we achieve up to 20% improvement in condensate collection rate using an interdigitated superhydrophilic pattern, inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern, particularly under higher vapor loadings in an air/vapor ambient atmosphere. NSF STTR Grant 1331817 via NBD Nano.

  1. Scalable graphene coatings for enhanced condensation heat transfer.

    PubMed

    Preston, Daniel J; Mafra, Daniela L; Miljkovic, Nenad; Kong, Jing; Wang, Evelyn N

    2015-05-13

    Water vapor condensation is commonly observed in nature and routinely used as an effective means of transferring heat with dropwise condensation on nonwetting surfaces exhibiting heat transfer improvement compared to filmwise condensation on wetting surfaces. However, state-of-the-art techniques to promote dropwise condensation rely on functional hydrophobic coatings that either have challenges with chemical stability or are so thick that any potential heat transfer improvement is negated due to the added thermal resistance of the coating. In this work, we show the effectiveness of ultrathin scalable chemical vapor deposited (CVD) graphene coatings to promote dropwise condensation while offering robust chemical stability and maintaining low thermal resistance. Heat transfer enhancements of 4× were demonstrated compared to filmwise condensation, and the robustness of these CVD coatings was superior to typical hydrophobic monolayer coatings. Our results indicate that graphene is a promising surface coating to promote dropwise condensation of water in industrial conditions with the potential for scalable application via CVD.

  2. Highly condensed fluorinated methacrylate hybrid material for transparent low-kappa passivation layer in LCD-TFT.

    PubMed

    Oh, Ji-Hoon; Kwak, Seung-Yeon; Yang, Seung-Cheol; Bae, Byeong-Soo

    2010-03-01

    Photocurable and highly condensed fluorinated methacrylate oligosiloxane, with a low dielectric constant (kappa = 2.54), was prepared by a nonhydrolytic sol-gel condensation reaction. The oligosiloxane resin was then spin-coated, photocured, and thermally baked in order to fabricate a fluorinated methacrylate hybrid material (FM hybrimer) thin film. This study investigated the application of this FM hybrimer film as a low-kappa passivation layer in LCD-based thin film transistors (TFT). It was found that a dielectric constant as low as kappa = 2.54 could be obtained, without introducing pores in the dense FM hybrimer films. This study compares FM hybrimer film characteristics with those required for passivation layers in LCD-TFTs, including thermal stability, optical transmittance, hydrophobicity, gap fill, and planarization effects as well as electrical insulation.

  3. Reactive simulation of the chemistry behind the condensed-phase ignition of RDX from hot spots.

    PubMed

    Joshi, Kaushik L; Chaudhuri, Santanu

    2015-07-28

    Chemical events that lead to thermal initiation and spontaneous ignition of the high-pressure phase of RDX are presented using reactive molecular dynamics simulations. In order to initiate the chemistry behind thermal ignition, approximately 5% of RDX crystal is subjected to a constant temperature thermal pulse for various time durations to create a hot spot. After application of the thermal pulse, the ensuing chemical evolution of the system is monitored using reactive molecular dynamics under adiabatic conditions. Thermal pulses lasting longer than certain time durations lead to the spontaneous ignition of RDX after an incubation period. For cases where the ignition is observed, the incubation period is dominated by intermolecular and intramolecular hydrogen transfer reactions. Contrary to the widely accepted unimolecular models of initiation chemistry, N-N bond dissociations that produce NO2 species are suppressed in the condensed phase. The gradual temperature and pressure increase in the incubation period is accompanied by the accumulation of short-lived, heavier polyradicals. The polyradicals contain intact triazine rings from the RDX molecules. At certain temperatures and pressures, the polyradicals undergo ring-opening reactions, which fuel a series of rapid exothermic chemical reactions leading to a thermal runaway regime with stable gas-products such as N2, H2O and CO2. The evolution of the RDX crystal throughout the thermal initiation, incubation and thermal runaway phases observed in the reactive simulations contains a rich diversity of condensed-phase chemistry of nitramines under high-temperature/pressure conditions.

  4. 7 CFR 58.238 - Condensed storage tanks.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Condensed storage tanks. 58.238 Section 58.238... Procedures § 58.238 Condensed storage tanks. (a) Excess production of condensed product over that which the dryer will take continuously from the pans should be bypassed through a cooler into a storage tank at 50...

  5. 7 CFR 58.238 - Condensed storage tanks.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Condensed storage tanks. 58.238 Section 58.238... Procedures § 58.238 Condensed storage tanks. (a) Excess production of condensed product over that which the dryer will take continuously from the pans should be bypassed through a cooler into a storage tank at 50...

  6. 7 CFR 58.238 - Condensed storage tanks.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Condensed storage tanks. 58.238 Section 58.238... Procedures § 58.238 Condensed storage tanks. (a) Excess production of condensed product over that which the dryer will take continuously from the pans should be bypassed through a cooler into a storage tank at 50...

  7. 7 CFR 58.238 - Condensed storage tanks.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Condensed storage tanks. 58.238 Section 58.238... Procedures § 58.238 Condensed storage tanks. (a) Excess production of condensed product over that which the dryer will take continuously from the pans should be bypassed through a cooler into a storage tank at 50...

  8. Deepak Condenser Model (DeCoM)

    NASA Technical Reports Server (NTRS)

    Patel, Deepak

    2013-01-01

    Development of the DeCoM comes from the requirement of analyzing the performance of a condenser. A component of a loop heat pipe (LHP), the condenser, is interfaced with the radiator in order to reject heat. DeCoM simulates the condenser, with certain input parameters. Systems Improved Numerical Differencing Analyzer (SINDA), a thermal analysis software, calculates the adjoining component temperatures, based on the DeCoM parameters and interface temperatures to the radiator. Application of DeCoM is (at the time of this reporting) restricted to small-scale analysis, without the need for in-depth LHP component integrations. To efficiently develop a model to simulate the LHP condenser, DeCoM was developed to meet this purpose with least complexity. DeCoM is a single-condenser, single-pass simulator for analyzing its behavior. The analysis is done based on the interactions between condenser fluid, the wall, and the interface between the wall and the radiator. DeCoM is based on conservation of energy, two-phase equations, and flow equations. For two-phase, the Lockhart- Martinelli correlation has been used in order to calculate the convection value between fluid and wall. Software such as SINDA (for thermal analysis analysis) and Thermal Desktop (for modeling) are required. DeCoM also includes the ability to implement a condenser into a thermal model with the capability of understanding the code process and being edited to user-specific needs. DeCoM requires no license, and is an open-source code. Advantages to DeCoM include time dependency, reliability, and the ability for the user to view the code process and edit to their needs.

  9. Spatial Control of Condensation using Chemical Micropatterns

    NASA Astrophysics Data System (ADS)

    Murphy, Kevin; Hansen, Ryan; Nath, Saurabh; Retterer, Scott; Collier, Patrick; Boreyko, Jonathan; Nature-Inspired Fluids; Interfaces Team; CenterNanophase Materials Sciences Team

    2015-11-01

    Surfaces exhibiting wettability patterns can spatially control the nucleation of condensation to enable enhanced fog harvesting and phase-change heat transfer. To date, studies of patterned condensation have utilized a combination of chemical and topographical features, making it difficult to isolate the effects of intrinsic wettability versus surface roughness on spatially controlling the condensate. Here, we fabricate chemical micropatterns consisting of hydrophilic silicon oxide and a smooth hydrophobic silane monolayer to isolate the effects of changes in intrinsic wettability on the spatial control of condensation. Complete spatial control, defined as every nucleation and growth event occurring exclusively on the hydrophilic features, was observed even for supercooled droplets at high water vapor supersaturation. However, this complete spatial control was found to break down beyond a critical spacing that depended upon the extent of supersaturation. The average diameter of condensate was found to be smaller for the chemically micropatterned surfaces compared to a uniformly hydrophobic surface. Control of inter-droplet spacing between supercooled condensate through chemical patterning can be employed to minimize the growth of inter-droplet frost on cold surfaces.

  10. Systematic text condensation: a strategy for qualitative analysis.

    PubMed

    Malterud, Kirsti

    2012-12-01

    To present background, principles, and procedures for a strategy for qualitative analysis called systematic text condensation and discuss this approach compared with related strategies. Giorgi's psychological phenomenological analysis is the point of departure and inspiration for systematic text condensation. The basic elements of Giorgi's method and the elaboration of these in systematic text condensation are presented, followed by a detailed description of procedures for analysis according to systematic text condensation. Finally, similarities and differences compared with other frequently applied methods for qualitative analysis are identified, as the foundation of a discussion of strengths and limitations of systematic text condensation. Systematic text condensation is a descriptive and explorative method for thematic cross-case analysis of different types of qualitative data, such as interview studies, observational studies, and analysis of written texts. The method represents a pragmatic approach, although inspired by phenomenological ideas, and various theoretical frameworks can be applied. The procedure consists of the following steps: 1) total impression - from chaos to themes; 2) identifying and sorting meaning units - from themes to codes; 3) condensation - from code to meaning; 4) synthesizing - from condensation to descriptions and concepts. Similarities and differences comparing systematic text condensation with other frequently applied qualitative methods regarding thematic analysis, theoretical methodological framework, analysis procedures, and taxonomy are discussed. Systematic text condensation is a strategy for analysis developed from traditions shared by most of the methods for analysis of qualitative data. The method offers the novice researcher a process of intersubjectivity, reflexivity, and feasibility, while maintaining a responsible level of methodological rigour.

  11. Thermal Decomposition of Condensed-Phase Nitromethane from Molecular Dynamics from ReaxFF Reactive Dynamics

    DTIC Science & Technology

    2011-05-04

    pubs.acs.org/JPCB Thermal Decomposition of Condensed-Phase Nitromethane from Molecular Dynamics from ReaxFF Reactive Dynamics Si-ping Han,†,‡ Adri C. T. van...ABSTRACT: We studied the thermal decomposition and subsequent reaction of the energetic material nitromethane (CH3NO2) using molec- ular dynamics...with ReaxFF, a first principles-based reactive force field. We characterize the chemistry of liquid and solid nitromethane at high temperatures (2000

  12. Radiochemical Reactions Between Tritium Molecule and Carbon Dioxide

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shu, W.M.; O'Hira, S.; Suzuki, T.

    To have better understanding of radiochemical reactions among oxygen baking products in a fusion reactor, reactions in equimolar tritium molecule (T{sub 2}) and carbon dioxide (CO{sub 2}) were examined by laser Raman spectroscopy and mass spectrometry. After mixing them at room temperature, T{sub 2} and CO{sub 2} decreased rapidly in the first 30 minutes and then the reactions between them became much slower. As the predominant products of the reactions, carbon monoxide (CO) and tritiated water (T{sub 2}O) were found in gaseous phase and condensed phase, respectively. However, there likely existed also some solid products that were thermally decomposed intomore » CO, CO{sub 2}, T{sub 2}, T{sub 2}O, etc. during baking up to 523 K.« less

  13. Thermodynamic entanglement of magnonic condensates

    NASA Astrophysics Data System (ADS)

    Yuan, H. Y.; Yung, Man-Hong

    2018-02-01

    Over the past decade, significant progress has been achieved to create Bose-Einstein condensates (BECs) of magnetic excitations, i.e., magnons, at room temperature, which is a novel quantum many-body system with a strong spin-spin correlation, and contains potential applications in magnonic spintronics. For quantum information science, the magnonic condensates can become an attractive source of quantum entanglement, which plays a central role in most of the quantum information processing tasks. Here we theoretically study the entanglement properties of a magnon gas above and below the condensation temperature. We show that the thermodynamic entanglement of the spins is a manifestation of the off-diagonal long-range order; the entanglement of the condensate does not vanish, even if the spins are separated by an infinitely long distance, which is fundamentally distinct from the normal magnetic ordering below the Curie temperature. In addition, the phase-transition point occurs when the derivative of the entanglement changes abruptly. These results provide a theoretical foundation for a future investigation of the magnon BEC in terms of quantum entanglement.

  14. Dynamics of inhomogeneous chiral condensates

    NASA Astrophysics Data System (ADS)

    Carlomagno, Juan Pablo; Krein, Gastão; Kroff, Daniel; Peixoto, Thiago

    2018-01-01

    We study the dynamics of the formation of inhomogeneous chirally broken phases in the final stages of a heavy-ion collision, with particular interest on the time scales involved in the formation process. The study is conducted within the framework of a Ginzburg-Landau time evolution, driven by a free energy functional motivated by the Nambu-Jona-Lasinio model. Expansion of the medium is modeled by one-dimensional Bjorken flow and its effect on the formation of inhomogeneous condensates is investigated. We also use a free energy functional from a nonlocal Nambu-Jona-Lasinio model which predicts metastable phases that lead to long-lived inhomogeneous condensates before reaching an equilibrium phase with homogeneous condensates.

  15. Random matrices and condensation into multiple states

    NASA Astrophysics Data System (ADS)

    Sadeghi, Sina; Engel, Andreas

    2018-03-01

    In the present work, we employ methods from statistical mechanics of disordered systems to investigate static properties of condensation into multiple states in a general framework. We aim at showing how typical properties of random interaction matrices play a vital role in manifesting the statistics of condensate states. In particular, an analytical expression for the fraction of condensate states in the thermodynamic limit is provided that confirms the result of the mean number of coexisting species in a random tournament game. We also study the interplay between the condensation problem and zero-sum games with correlated random payoff matrices.

  16. HPLC, NMR and MALDI-TOF MS analysis of condensed tannins from Lithocarpus glaber leaves with potent free radical scavenging activity.

    PubMed

    Zhang, Liang Liang; Lin, Yi Ming

    2008-12-04

    Using acid-catalyzed degradation in the presence of cysteamine, the condensed tannins from Lithocarpus glaber leaves were characterized, following thiolysis, by means of reversed-phase HPLC, 13C-NMR and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analyses. The thiolysis reaction products showed the presence of the procyanidin (PC) and prodelphinidin (PD) structures. The 13C-NMR spectrum revealed that the condensed tannins were comprised of PD (72.4%) and PC (27.6%), and with a greater content of cis configuration rather than the trans configuration of C2-C3. The MALDI-TOF MS analysis proved the presence of PD units, and the maximum degree of polymerization (DP) was an undecamer. The antioxidant activity of condensed tannins from L. glaber leaves was evaluated by using a free radical scavenging activity assay.

  17. Time symmetry breaking in Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Mendonça, J. T.; Gammal, A.

    2017-09-01

    We consider different processes leading to time symmetry breaking in a Bose-Einstein condensate. Our approach provides a global description of time symmetry breaking, based on the equations of a thermal condensate. This includes quenching and expansion of the condensate, the Kibble-Zurek mechanism associated with the creation of vorticity, the dynamical Casimir effect and the formation of time crystals.

  18. Selective and eco-friendly procedures for the synthesis of benzimidazole derivatives. The role of the Er(OTf)3 catalyst in the reaction selectivity

    PubMed Central

    Herrera Cano, Natividad; Uranga, Jorge G; Nardi, Mónica; Procopio, Antonio; Wunderlin, Daniel A

    2016-01-01

    An improved and greener protocol for the synthesis of benzimidazole derivatives, starting from o-phenylenediamine, with different aldehydes is reported. Double-condensation products were selectively obtained when Er(OTf)3 was used as the catalyst in the presence of electron-rich aldehydes. Conversely, the formation of mono-condensation products was the preferred path in absence of this catalyst. One of the major advantages of these reactions was the formation of a single product, avoiding extensive isolation and purification of products, which is frequently associated with these reactions. Theoretical calculations helped to understand the different reactivity established for these reactions. Thus, we found that the charge density on the oxygen of the carbonyl group has a significant impact on the reaction pathway. For instance, electron-rich aldehydes better coordinate to the catalyst, which favours the addition of the amine group to the carbonyl group, therefore facilitating the formation of double-condensation products. Reactions with aliphatic or aromatic aldehydes were possible, without using organic solvents and in a one-pot procedure with short reaction time (2–5 min), affording single products in excellent yields (75–99%). This convenient and eco-friendly methodology offers numerous benefits with respect to other protocols reported for similar compounds. PMID:28144309

  19. Selective and eco-friendly procedures for the synthesis of benzimidazole derivatives. The role of the Er(OTf)3 catalyst in the reaction selectivity.

    PubMed

    Herrera Cano, Natividad; Uranga, Jorge G; Nardi, Mónica; Procopio, Antonio; Wunderlin, Daniel A; Santiago, Ana N

    2016-01-01

    An improved and greener protocol for the synthesis of benzimidazole derivatives, starting from o -phenylenediamine, with different aldehydes is reported. Double-condensation products were selectively obtained when Er(OTf) 3 was used as the catalyst in the presence of electron-rich aldehydes. Conversely, the formation of mono-condensation products was the preferred path in absence of this catalyst. One of the major advantages of these reactions was the formation of a single product, avoiding extensive isolation and purification of products, which is frequently associated with these reactions. Theoretical calculations helped to understand the different reactivity established for these reactions. Thus, we found that the charge density on the oxygen of the carbonyl group has a significant impact on the reaction pathway. For instance, electron-rich aldehydes better coordinate to the catalyst, which favours the addition of the amine group to the carbonyl group, therefore facilitating the formation of double-condensation products. Reactions with aliphatic or aromatic aldehydes were possible, without using organic solvents and in a one-pot procedure with short reaction time (2-5 min), affording single products in excellent yields (75-99%). This convenient and eco-friendly methodology offers numerous benefits with respect to other protocols reported for similar compounds.

  20. Extreme-UV lithography condenser

    DOEpatents

    Sweatt, William C.; Sweeney, Donald W.; Shafer, David; McGuire, James

    2001-01-01

    Condenser system for use with a ringfield camera in projection lithography where the condenser includes a series of segments of a parent aspheric mirror having one foci at a quasi-point source of radiation and the other foci at the radius of a ringfield have all but one or all of their beams translated and rotated by sets of mirrors such that all of the beams pass through the real entrance pupil of a ringfield camera about one of the beams and fall onto the ringfield radius as a coincident image as an arc of the ringfield. The condenser has a set of correcting mirrors with one of the correcting mirrors of each set, or a mirror that is common to said sets of mirrors, from which the radiation emanates, is a concave mirror that is positioned to shape a beam segment having a chord angle of about 25 to 85 degrees into a second beam segment having a chord angle of about 0 to 60 degrees.

  1. Why double-stranded RNA resists condensation

    PubMed Central

    Tolokh, Igor S.; Pabit, Suzette A.; Katz, Andrea M.; Chen, Yujie; Drozdetski, Aleksander; Baker, Nathan; Pollack, Lois; Onufriev, Alexey V.

    2014-01-01

    The addition of small amounts of multivalent cations to solutions containing double-stranded DNA leads to inter-DNA attraction and eventual condensation. Surprisingly, the condensation is suppressed in double-stranded RNA, which carries the same negative charge as DNA, but assumes a different double helical form. Here, we combine experiment and atomistic simulations to propose a mechanism that explains the variations in condensation of short (25 base-pairs) nucleic acid (NA) duplexes, from B-like form of homopolymeric DNA, to mixed sequence DNA, to DNA:RNA hybrid, to A-like RNA. Circular dichroism measurements suggest that duplex helical geometry is not the fundamental property that ultimately determines the observed differences in condensation. Instead, these differences are governed by the spatial variation of cobalt hexammine (CoHex) binding to NA. There are two major NA-CoHex binding modes—internal and external—distinguished by the proximity of bound CoHex to the helical axis. We find a significant difference, up to 5-fold, in the fraction of ions bound to the external surfaces of the different NA constructs studied. NA condensation propensity is determined by the fraction of CoHex ions in the external binding mode. PMID:25123663

  2. gem-Difluoroolefination of diaryl ketones and enolizable aldehydes with difluoromethyl 2-pyridyl sulfone: new insights into the Julia-Kocienski reaction.

    PubMed

    Gao, Bing; Zhao, Yanchuan; Hu, Mingyou; Ni, Chuanfa; Hu, Jinbo

    2014-06-16

    The direct conversion of diaryl ketones and enolizable aliphatic aldehydes into gem-difluoroalkenes has been a long-standing challenge in organofluorine chemistry. Herein, we report efficient strategies to tackle this problem by using difluoromethyl 2-pyridyl sulfone as a general gem-difluoroolefination reagent. The gem-difluoroolefination of diaryl ketones proceeds by acid-promoted Smiles rearrangement of the carbinol intermediate; the gem-difluoroolefination is otherwise difficult to achieve through a conventional Julia-Kocienski olefination protocol under basic conditions due to the retro-aldol type decomposition of the key intermediate. Efficient gem-difluoroolefination of aliphatic aldehydes was achieved by the use of an amide base generated in situ (from CsF and tris(trimethylsilyl)amine), which diminishes the undesired enolization of aliphatic aldehydes and provides a powerful synthetic method for chemoselective gem-difluoroolefination of multi-carbonyl compounds. Our results provide new insights into the mechanistic understanding of the classical Julia-Kocienski reaction. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Moist Adiabats with Multiple Condensing Species: A New Theory with Application to Giant-Planet Atmospheres

    NASA Astrophysics Data System (ADS)

    Li, Cheng; Ingersoll, Andrew P.; Oyafuso, Fabiano

    2018-04-01

    We derived a new formula for calculating the moist adiabatic temperature profile of an atmosphere consisting of ideal gases with multiple condensing species. This expression unifies various formulas published in the literature and can be generalized to account for chemical reactions. Unlike previous methods, it converges to machine precision independent of mesh size. It accounts for any ratio of condensable vapors to dry gas, from zero to infinity, and for variable heat capacities as a function of temperature. Because the derivation is generic, the new formula is not only applicable to planetary atmosphere in the solar system, but also to hot Jupiters and brown dwarfs in which a variety of alkali metals, silicates and exotic materials condense. We demonstrate that even though the vapors are ideal gases, they interact in their effects on the moist adiabatic lapse rate. Finally, we apply the new thermodynamic model to study the effects of downdrafts on the distribution of minor constituents and thermal profile in the Galileo probe hotspot. We find that the Galileo Probe measurements can be interpreted as a strong downdraft that displaces an air parcel from 1 bar to the 4 bar level.

  4. Bose-Einstein condensation and indirect excitons: a review.

    PubMed

    Combescot, Monique; Combescot, Roland; Dubin, François

    2017-06-01

    We review recent progress on Bose-Einstein condensation (BEC) of semiconductor excitons. The first part deals with theory, the second part with experiments. This Review is written at a time where the problem of exciton Bose-Einstein condensation has just been revived by the understanding that the exciton condensate must be dark because the exciton ground state is not coupled to light. Here, we theoretically discuss this missed understanding before providing its experimental support through experiments that scrutinize indirect excitons made of spatially separated electrons and holes. The theoretical part first discusses condensation of elementary bosons. In particular, the necessary inhibition of condensate fragmentation by exchange interaction is stressed, before extending the discussion to interacting bosons with spin degrees of freedom. The theoretical part then considers composite bosons made of two fermions like semiconductor excitons. The spin structure of the excitons is detailed, with emphasis on the crucial fact that ground-state excitons are dark: indeed, this imposes the exciton Bose-Einstein condensate to be not coupled to light in the dilute regime. Condensate fragmentations are then reconsidered. In particular, it is shown that while at low density, the exciton condensate is fully dark, it acquires a bright component, coherent with the dark one, beyond a density threshold: in this regime, the exciton condensate is 'gray'. The experimental part first discusses optical creation of indirect excitons in quantum wells, and the detection of their photoluminescence. Exciton thermalisation is also addressed, as well as available approaches to estimate the exciton density. We then switch to specific experiments where indirect excitons form a macroscopic fragmented ring. We show that such ring provides efficient electrostatic trapping in the region of the fragments where an essentially-dark exciton Bose-Einstein condensate is formed at sub-Kelvin bath

  5. Enhancing dropwise condensation through bioinspired wettability patterning.

    PubMed

    Ghosh, Aritra; Beaini, Sara; Zhang, Bong June; Ganguly, Ranjan; Megaridis, Constantine M

    2014-11-04

    Dropwise condensation (DWC) heat transfer depends strongly on the maximum diameter (Dmax) of condensate droplets departing from the condenser surface. This study presents a facile technique implemented to gain control of Dmax in DWC within vapor/air atmospheres. We demonstrate how this approach can enhance the corresponding heat transfer rate by harnessing the capillary forces in the removal of the condensate from the surface. We examine various hydrophilic-superhydrophilic patterns, which, respectively, sustain and combine DWC and filmwise condensation on the substrate. The material system uses laser-patterned masking and chemical etching to achieve the desired wettability contrast and does not employ any hydrophobizing agent. By applying alternating straight parallel strips of hydrophilic (contact angle ∼78°) mirror-finish aluminum and superhydrophilic regions (etched aluminum) on the condensing surface, we show that the average maximum droplet size on the less-wettable domains is nearly 42% of the width of the corresponding strips. An overall improvement in the condensate collection rate, up to 19% (as compared to the control case of DWC on mirror-finish aluminum) was achieved by using an interdigitated superhydrophilic track pattern (on the mirror-finish hydrophilic surface) inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern design, particularly under higher humidity conditions in the presence of noncondensable gases (NCG), a condition that is more challenging for maintaining sustained DWC.

  6. Cold Bose-Einstein condensates for surface reflection

    NASA Astrophysics Data System (ADS)

    Saba, M.; Leanhardt, A. E.; Pasquini, T. A.; Sanner, C.; Schirotzek, A.; Shin, Y.; Pritchard, D. E.; Ketterle, W.

    2004-05-01

    Atoms can be reflected from a solid surface in spite of the attraction provided by the Casimir-Polder potential if their de Broglie wavelength exceeds the range of the attractive potential, an effect known as quantum reflection and demonstrated for atomic beams hitting a surface at grazing angle [1]. Quantum reflection of atomic Bose-Einstein condensates would have important consequences for experiments and applications requiring manipulation of condensates close to surfaces. However, no matter how cold a condensate is when approaching a surface, the atoms will hit the surface with a kinetic energy appropriate to the healing length, an energy roughly equal to the chemical potential and determined by atom-atom interactions. We circumvented this limitation by building a loose trap for the condensate, so that the atomic cloud can be kept very dilute, reaching the large healing length required to observe quantum reflection [2]. The trap consisted of a small single coil with electric current running in it that pushes the atoms upward, balancing gravity downward. The gravito-magnetic trap had a mean trap frequency of 1 Hz, so that condensates could sit in the trap for several minutes and reach temperatures as low as 500 pK, the lowest temperature ever recorded. We will then discuss how these condensates, whose healing length equals the condensate size, behave when approached to a silicon surface. [1] F. Shimizu, Phys. Rev. Lett. 86, 987 (2001); [2] A. E. Leanhardt et al., Science 301, 1513 (2003)

  7. Mechanism of the Intramolecular Claisen Condensation Reaction Catalyzed by MenB, a Crotonase Superfamily Member†

    PubMed Central

    Li, Huei-Jiun; Li, Xiaokai; Liu, Nina; Zhang, Huaning; Truglio, James J.; Mishra, Shambhavi; Kisker, Caroline; Garcia-Diaz, Miguel; Tonge, Peter J.

    2014-01-01

    MenB, the 1,4-dihydroxy-2-naphthoyl-CoA synthase from the bacterial menaquinone biosynthesis pathway, catalyzes an intramolecular Claisen condensation (Dieckmann reaction) in which the electrophile is an unactivated carboxylic acid. Mechanistic studies on this crotonase family member have been hindered by partial active site disorder in existing MenB X-ray structures. In the current work the 2.0 Å structure of O-succinylbenzoyl-aminoCoA (OSB-NCoA) bound to the MenB from Escherichia coli provides important insight into the catalytic mechanism by revealing the position of all active site residues. This has been accomplished by the use of a stable analogue of the O-succinylbenzoyl-CoA (OSB-CoA) substrate in which the CoA thiol has been replaced by an amine. The resulting OSB-NCoA is stable and the X-ray structure of this molecule bound to MenB reveals the structure of the enzyme-substrate complex poised for carbon-carbon bond formation. The structural data support a mechanism in which two conserved active site Tyr residues, Y97 and Y258, participate directly in the intramolecular transfer of the substrate α-proton to the benzylic carboxylate of the substrate, leading to protonation of the electrophile and formation of the required carbanion. Y97 and Y258 are also ideally positioned to function as the second oxyanion hole required for stabilization of the tetrahedral intermediate formed during carbon-carbon bond formation. In contrast, D163, which is structurally homologous to the acid-base catalyst E144 in crotonase, is not directly involved in carbanion formation and may instead play a structural role by stabilizing the loop that carries Y97. When similar studies were performed on the MenB from Mycobacterium tuberculosis, a twisted hexamer was unexpectedly observed, demonstrating the flexibility of the interfacial loops that are involved in the generation of the novel tertiary and quaternary structures found in the crotonase superfamily. This work reinforces the

  8. Mechanism of the intramolecular Claisen condensation reaction catalyzed by MenB, a crotonase superfamily member.

    PubMed

    Li, Huei-Jiun; Li, Xiaokai; Liu, Nina; Zhang, Huaning; Truglio, James J; Mishra, Shambhavi; Kisker, Caroline; Garcia-Diaz, Miguel; Tonge, Peter J

    2011-11-08

    MenB, the 1,4-dihydroxy-2-naphthoyl-CoA synthase from the bacterial menaquinone biosynthesis pathway, catalyzes an intramolecular Claisen condensation (Dieckmann reaction) in which the electrophile is an unactivated carboxylic acid. Mechanistic studies on this crotonase family member have been hindered by partial active site disorder in existing MenB X-ray structures. In the current work the 2.0 Å structure of O-succinylbenzoyl-aminoCoA (OSB-NCoA) bound to the MenB from Escherichia coli provides important insight into the catalytic mechanism by revealing the position of all active site residues. This has been accomplished by the use of a stable analogue of the O-succinylbenzoyl-CoA (OSB-CoA) substrate in which the CoA thiol has been replaced by an amine. The resulting OSB-NCoA is stable, and the X-ray structure of this molecule bound to MenB reveals the structure of the enzyme-substrate complex poised for carbon-carbon bond formation. The structural data support a mechanism in which two conserved active site Tyr residues, Y97 and Y258, participate directly in the intramolecular transfer of the substrate α-proton to the benzylic carboxylate of the substrate, leading to protonation of the electrophile and formation of the required carbanion. Y97 and Y258 are also ideally positioned to function as the second oxyanion hole required for stabilization of the tetrahedral intermediate formed during carbon-carbon bond formation. In contrast, D163, which is structurally homologous to the acid-base catalyst E144 in crotonase (enoyl-CoA hydratase), is not directly involved in carbanion formation and may instead play a structural role by stabilizing the loop that carries Y97. When similar studies were performed on the MenB from Mycobacterium tuberculosis, a twisted hexamer was unexpectedly observed, demonstrating the flexibility of the interfacial loops that are involved in the generation of the novel tertiary and quaternary structures found in the crotonase superfamily. This

  9. Template properties of oligocytidylates formed in the montmorillonite catalyzed condensation of ImpC. [Abstract only

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Ertem, Goezen

    1994-01-01

    In an attempt to investigate the prebiotic formation of phosphodiester bond in RNA, we have studied the self condensation of 5'-phosphorimidazolide of adenosine (ImpA), in aqueous solutions containing 0.2 M sodium chloride and 0.075 M magnesium chloride at pH 8 using clay minerals as catalyst. In the presence of certain montmorillonites, oligomers containing up to ten monomer units in their chain were formed, while in control experiments, where no catalyst was added, the major product was 5',5'-diadenosine diphosphate, A(sup 5')ppA. In reactions carried out with ImpA: A(sup 5')ppA mixtures at 9:1 mole ratio, oligomers of the type A(sup 5')p(pA)(sub n) and (A(sup 5')p)(sub n)A(sup 5')ppA(pA)(sub n) formed at the expense of (pA)(sub n) type oligomers. Addition of A(sup 5')ppA to the reaction mixture increased the regiospecifity of 3',5'-link formation from 67% to 79%. The condensation of the 5'-phosphorimidazolide of cytidine, ImpC, was also carried out in the presence and absence of A(sup 5')ppA under the same conditions and oligomers containing up to twelve monomer units were obtained.

  10. Spectral Properties of Gas-phase Condensed Fullerene-like Carbon Nanoparticles from Far-ultraviolet to Infrared Wavelengths

    NASA Astrophysics Data System (ADS)

    Jäger, C.; Mutschke, H.; Henning, Th.; Huisken, F.

    2008-12-01

    Carbon solids are ubiquitous material in interstellar space. However, the formation pathway of carbonaceous matter in astrophysical environments, as well as in terrestrial gas-phase condensation reactions, is not yet understood. Laser ablation of graphite in different quenching gas atmospheres, such as pure He, He/H2, and He/H2O at varying pressures, is used to synthesize very small, fullerene-like carbon nanoparticles. The particles are characterized by very small diameters between 1 and 4 nm and a disturbed onion-like structure. The soot particles extracted from the condensation zone obviously represent a very early stage of particle condensation. The spectral properties have been measured from the far-ultraviolet (FUV; λ = 120 nm) to the mid-infrared (MIR; λ = 15 μm). The seedlike soot particles show strong absorption bands in the 3.4 μm range. The profile and the intensity pattern of the 3.4 μm band of the diffuse interstellar medium can be well reproduced by the measured 3.4 μm profile of the condensed particles; however, all the carbon which is left to form solids is needed to fit the intensity of the interstellar bands. In contrast to the assumption that onion-like soot particles could be the carriers of the interstellar ultraviolet (UV) bump, our very small onion-like carbon nanoparticles do not show distinct UV bands due to (π-π*) transitions.

  11. Condenser design for AMTEC power conversion

    NASA Technical Reports Server (NTRS)

    Crowley, Christopher J.

    1991-01-01

    The condenser and the electrodes are the two elements of an alkali metal thermal-to-electric conversion (AMTEC) cell which most greatly affect the energy conversion performance. A condenser is described which accomplishes two critical functions in an AMTEC cell: management of the fluid under microgravity conditions and optimization of conversion efficiency. The first function is achieved via the use of a controlled surface shape, along with drainage grooves and arteries to collect the fluid. Capillary forces manage the fluid in microgravity and dominate hydrostatic effects on the ground so the device is ground-testable. The second function is achieved via a smooth film of highly reflective liquid sodium on the condensing surface, resulting in minimization of parasitic heat losses due to radiation heat transfer. Power conversion efficiencies of 25 percent to 30 percent are estimated with this condenser using present technology for the electrodes.

  12. Capillary Condensation in 8 nm Deep Channels.

    PubMed

    Zhong, Junjie; Riordon, Jason; Zandavi, Seyed Hadi; Xu, Yi; Persad, Aaron H; Mostowfi, Farshid; Sinton, David

    2018-02-01

    Condensation on the nanoscale is essential to understand many natural and synthetic systems relevant to water, air, and energy. Despite its importance, the underlying physics of condensation initiation and propagation remain largely unknown at sub-10 nm, mainly due to the challenges of controlling and probing such small systems. Here we study the condensation of n-propane down to 8 nm confinement in a nanofluidic system, distinct from previous studies at ∼100 nm. The condensation initiates significantly earlier in the 8 nm channels, and it initiates from the entrance, in contrast to channels just 10 times larger. The condensate propagation is observed to be governed by two liquid-vapor interfaces with an interplay between film and bridging effects. We model the experimental results using classical theories and find good agreement, demonstrating that this 8 nm nonpolar fluid system can be treated as a continuum from a thermodynamic perspective, despite having only 10-20 molecular layers.

  13. The Development of Enhanced Heat Transfer Condenser Tubing

    DTIC Science & Technology

    1973-07-01

    side coeffic ient. The profiled tube condensing coefficient h’ is derived by analogy with the Nusselt ( 8 ) equation for the average condensing ... condensing coefficient value s = 0.925 was derived by Nusselt for laminar flow cnditions. It is well known that under turbulent film flow with waves...DTICSEL ECTE SEPA 0O1981ŕ jjH E DEVELOPME NTI OF ENHANCED HEAT TRANSFER CONDENSER TUBING! I H .EWSON T. D. AODGSON ! 0L L U I-.L V.i 1-- Chemical

  14. Why double-stranded RNA resists condensation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tolokh, Igor S.; Pabit, Suzette; Katz, Andrea M.

    2014-09-15

    The addition of small amounts of multivalent cations to solutions containing double-stranded DNA leads to attraction between the negatively charged helices and eventually to condensation. Surprisingly, this effect is suppressed in double-stranded RNA, which carries the same charge as the DNA, but assumes a different double helical form. However, additional characterization of short (25 base-pairs) nucleic acid (NA) duplex structures by circular dichroism shows that measured differences in condensation are not solely determined by duplex helical geometry. Here we combine experiment, theory, and atomistic simulations to propose a mechanism that connects the observed variations in condensation of short NA duplexesmore » with the spatial variation of cobalt hexammine (CoHex) binding at the NA duplex surface. The atomistic picture that emerged showed that CoHex distributions around the NA reveals two major NA-CoHex binding modes -- internal and external -- distinguished by the proximity of bound CoHex to the helical axis. Decreasing trends in experimentally observed condensation propensity of the four studied NA duplexes (from B-like form of homopolymeric DNA, to mixed sequence DNA, to DNA:RNA hybrid, to A-like RNA) are explained by the progressive decrease of a single quantity: the fraction of CoHex ions in the external binding mode. Thus, while NA condensation depends on a complex interplay between various structural and sequence features, our coupled experimental and theoretical results suggest a new model in which a single parameter connects the NA condensation propensity with geometry and sequence dependence of CoHex binding.« less

  15. Modeling of Kerena Emergency Condenser

    NASA Astrophysics Data System (ADS)

    Bryk, Rafał; Schmidt, Holger; Mull, Thomas; Wagner, Thomas; Ganzmann, Ingo; Herbst, Oliver

    2017-12-01

    KERENA is an innovative boiling water reactor concept equipped with several passive safety systems. For the experimental verification of performance of the systems and for codes validation, the Integral Test Stand Karlstein (INKA) was built in Karlstein, Germany. The emergency condenser (EC) system transfers heat from the reactor pressure vessel (RPV) to the core flooding pool in case of water level decrease in the RPV. EC is composed of a large number of slightly inclined tubes. During accident conditions, steam enters into the tubes and condenses due to the contact of the tubes with cold water at the secondary side. The condensed water flows then back to the RPV due to gravity. In this paper two approaches for modeling of condensation in slightly inclined tubes are compared and verified against experiments. The first approach is based on the flow regime map. Depending on the regime, heat transfer coefficient is calculated according to specific semi-empirical correlation. The second approach uses a general, fully-empirical correlation. The models are developed with utilization of the object-oriented Modelica language and the open-source OpenModelica environment. The results are compared with data obtained during a large scale integral test, simulating loss of coolant accident performed at Integral Test Stand Karlstein (INKA). The comparison shows a good agreement.Due to the modularity of models, both of them may be used in the future in systems incorporating condensation in horizontal or slightly inclined tubes. Depending on his preferences, the modeller may choose one-equation based approach or more sophisticated model composed of several exchangeable semi-empirical correlations.

  16. Self-Consistency of the Theory of Elementary Stage Rates of Reversible Processes and the Equilibrium Distribution of Reaction Mixture Components

    NASA Astrophysics Data System (ADS)

    Tovbin, Yu. K.

    2018-06-01

    An analysis is presented of one of the key concepts of physical chemistry of condensed phases: the theory self-consistency in describing the rates of elementary stages of reversible processes and the equilibrium distribution of components in a reaction mixture. It posits that by equating the rates of forward and backward reactions, we must obtain the same equation for the equilibrium distribution of reaction mixture components, which follows directly from deducing the equation in equilibrium theory. Ideal reaction systems always have this property, since the theory is of a one-particle character. Problems arise in considering interparticle interactions responsible for the nonideal behavior of real systems. The Eyring and Temkin approaches to describing nonideal reaction systems are compared. Conditions for the self-consistency of the theory for mono- and bimolecular processes in different types of interparticle potentials, the degree of deviation from the equilibrium state, allowing for the internal motions of molecules in condensed phases, and the electronic polarization of the reagent environment are considered within the lattice gas model. The inapplicability of the concept of an activated complex coefficient for reaching self-consistency is demonstrated. It is also shown that one-particle approximations for considering intermolecular interactions do not provide a theory of self-consistency for condensed phases. We must at a minimum consider short-range order correlations.

  17. Local condensate depletion at trap center under strong interactions

    NASA Astrophysics Data System (ADS)

    Yukalov, V. I.; Yukalova, E. P.

    2018-04-01

    Cold trapped Bose-condensed atoms, interacting via hard-sphere repulsive potentials are considered. Simple mean-field approximations show that the condensate distribution inside a harmonic trap always has the shape of a hump with the maximum condensate density occurring at the trap center. However, Monte Carlo simulations at high density and strong interactions display the condensate depletion at the trap center. The explanation of this effect of local condensate depletion at trap center is suggested in the frame of self-consistent theory of Bose-condensed systems. The depletion is shown to be due to the existence of the anomalous average that takes into account pair correlations and appears in systems with broken gauge symmetry.

  18. Enhanced Evaporation and Condensation in Tubes

    NASA Astrophysics Data System (ADS)

    Honda, Hiroshi

    A state-of-the-art review of enhanced evaporation and condensation in horizontal microfin tubes and micro-channels that are used for air-conditioning and refrigeration applications is presented. The review covers the effects of flow pattern and geometrical parameters of the tubes on the heat transfer performance. Attention is paid to the effect of surface tension which leads to enhanced evaporation and condensation in the microfin tubes and micro-channels. A review of prior efforts to develop empirical correlations of the heat transfer coefficient and theoretical models for evaporation and condensation in the horizontal microfin tubes and micro-channels is also presented.

  19. Synthesis and Hydrogenation of Disubstituted Chalcones: A Guided-Inquiry Organic Chemistry Project

    ERIC Educational Resources Information Center

    Mohrig, Jerry R.; Hammond, Christina Noring; Schatz, Paul F.; Davidson, Tammy A.

    2009-01-01

    Guided-inquiry experiments offer the same opportunities to participate in the process of science as classical organic qualitative analysis used to do. This three-week guided-inquiry project involves an aldol-dehydration synthesis of a chalcone chosen from a set of nine, followed by a catalytic transfer hydrogenation reaction using ammonium formate…

  20. Simulation of Inviscid Compressible Multi-Phase Flow with Condensation

    NASA Technical Reports Server (NTRS)

    Kelleners, Philip

    2003-01-01

    Condensation of vapours in rapid expansions of compressible gases is investigated. In the case of high temperature gradients the condensation will start at conditions well away from thermodynamic equilibrium of the fluid. In those cases homogeneous condensation is dominant over heterogeneous condensation. The present work is concerned with development of a simulation tool for computation of high speed compressible flows with homogeneous condensation. The resulting ow solver should preferably be accurate and robust to be used for simulation of industrial flows in general geometries.

  1. Numerical simulation of condensation on structured surfaces.

    PubMed

    Fu, Xiaowu; Yao, Zhaohui; Hao, Pengfei

    2014-11-25

    Condensation of liquid droplets on solid surfaces happens widely in nature and industrial processes. This phase-change phenomenon has great effect on the performance of some microfluidic devices. On the basis of micro- and nanotechnology, superhydrophobic structured surfaces can be well-fabricated. In this work, the nucleating and growth of droplets on different structured surfaces are investigated numerically. The dynamic behavior of droplets during the condensation is simulated by the multiphase lattice Boltzmann method (LBM), which has the ability to incorporate the microscopic interactions, including fluid-fluid interaction and fluid-surface interaction. The results by the LBM show that, besides the chemical properties of surfaces, the topography of structures on solid surfaces influences the condensation process. For superhydrophobic surfaces, the spacing and height of microridges have significant influence on the nucleation sites. This mechanism provides an effective way for prevention of wetting on surfaces in engineering applications. Moreover, it suggests a way to prevent ice formation on surfaces caused by the condensation of subcooled water. For hydrophilic surfaces, however, microstructures may be submerged by the liquid films adhering to the surfaces. In this case, microstructures will fail to control the condensation process. Our research provides an optimized way for designing surfaces for condensation in engineering systems.

  2. 21 CFR 573.200 - Condensed animal protein hydrolysate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Condensed animal protein hydrolysate. 573.200... (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive Listing § 573.200 Condensed animal protein hydrolysate. (a) Identity. The condensed...

  3. Liquid-Infused Smooth Surface for Improved Condensation Heat Transfer.

    PubMed

    Tsuchiya, Hirotaka; Tenjimbayashi, Mizuki; Moriya, Takeo; Yoshikawa, Ryohei; Sasaki, Kaichi; Togasawa, Ryo; Yamazaki, Taku; Manabe, Kengo; Shiratori, Seimei

    2017-09-12

    Control of vapor condensation properties is a promising approach to manage a crucial part of energy infrastructure conditions. Heat transfer by vapor condensation on superhydrophobic coatings has garnered attention, because dropwise condensation on superhydrophobic surfaces with rough structures leads to favorable heat-transfer performance. However, pinned condensed water droplets within the rough structure and a high thermodynamic energy barrier for nucleation of superhydrophobic surfaces limit their heat-transfer increase. Recently, slippery liquid-infused surfaces (SLIPS) have been investigated, because of their high water sliding ability and surface smoothness originating from the liquid layer. However, even on SLIPS, condensed water droplets are eventually pinned to degrade their heat-transfer properties after extended use, because the rough base layer is exposed as infused liquid is lost. Herein, we report a liquid-infused smooth surface named "SPLASH" (surface with π electron interaction liquid adsorption, smoothness, and hydrophobicity) to overcome the problems derived from the rough structures in previous approaches to obtain stable, high heat-transfer performance. The SPLASH displayed a maximum condensation heat-transfer coefficient that was 175% higher than that of an uncoated substrate. The SPLASH also showed higher heat-transfer performance and more stable dropwise condensation than superhydrophobic surfaces and SLIPS from the viewpoints of condensed water droplet mobility and the thermodynamic energy barrier for nucleation. The effects of liquid-infused surface roughness and liquid viscosity on condensation heat transfer were investigated to compare heat-transfer performance. This research will aid industrial applications using vapor condensation.

  4. Rh(II)-catalyzed Reactions of Diazoesters with Organozinc Reagents

    PubMed Central

    Panish, Robert; Selvaraj, Ramajeyam; Fox, Joseph M.

    2015-01-01

    Rh(II)-catalyzed reactions of diazoesters with organozinc reagents are described. Diorganozinc reagents participate in reactions with diazo compounds by two distinct, catalyst-dependent mechanisms. With bulky diisopropylethylacetate ligands, the reaction mechanism is proposed to involve initial formation of a Rh-carbene and subsequent carbozincation to give a zinc enolate. With Rh2(OAc)4, it is proposed that initial formation of an azine precedes 1,2-addition by an organozinc reagent. This straightforward route to the hydrazone products provides a useful method for preparing chiral quaternary α-aminoesters or pyrazoles via the Paul-Knorr condensation with 1,3-diketones. Crossover and deuterium labeling experiments provide evidence for the mechanisms proposed. PMID:26241081

  5. Rh(II)-Catalyzed Reactions of Diazoesters with Organozinc Reagents.

    PubMed

    Panish, Robert; Selvaraj, Ramajeyam; Fox, Joseph M

    2015-08-21

    Rh(II)-catalyzed reactions of diazoesters with organozinc reagents are described. Diorganozinc reagents participate in reactions with diazo compounds by two distinct, catalyst-dependent mechanisms. With bulky diisopropylethyl acetate ligands, the reaction mechanism is proposed to involve initial formation of a Rh-carbene and subsequent carbozincation to give a zinc enolate. With Rh2(OAc)4, it is proposed that initial formation of an azine precedes 1,2-addition by an organozinc reagent. This straightforward route to the hydrazone products provides a useful method for preparing chiral quaternary α-aminoesters or pyrazoles via the Paul-Knorr condensation with 1,3-diketones. Crossover and deuterium labeling experiments provide evidence for the mechanisms proposed.

  6. Rapid Covalent Modification of Silicon Oxide Surfaces through Microwave-Assisted Reactions with Alcohols.

    PubMed

    Lee, Austin W H; Gates, Byron D

    2016-07-26

    We demonstrate the method of a rapid covalent modification of silicon oxide surfaces with alcohol-containing compounds with assistance by microwave reactions. Alcohol-containing compounds are prevalent reagents in the laboratory, which are also relatively easy to handle because of their stability against exposure to atmospheric moisture. The condensation of these alcohols with the surfaces of silicon oxides is often hindered by slow reaction kinetics. Microwave radiation effectively accelerates this condensation reaction by heating the substrates and/or solvents. A variety of substrates were modified in this demonstration, such as silicon oxide films of various thicknesses, glass substrates such as microscope slides (soda lime), and quartz. The monolayers prepared through this strategy demonstrated the successful formation of covalent surface modifications of silicon oxides with water contact angles of up to 110° and typical hysteresis values of 2° or less. An evaluation of the hydrolytic stability of these monolayers demonstrated their excellent stability under acidic conditions. The techniques introduced in this article were successfully applied to tune the surface chemistry of silicon oxides to achieve hydrophobic, oleophobic, and/or charged surfaces.

  7. Loss of superhydrophobicity of hydrophobic micro/nano structures during condensation.

    PubMed

    Jo, HangJin; Hwang, Kyung Won; Kim, DongHyun; Kiyofumi, Moriyama; Park, Hyun Sun; Kim, Moo Hwan; Ahn, Ho Seon

    2015-04-23

    Condensed liquid behavior on hydrophobic micro/nano-structured surfaces is a subject with multiple practical applications, but remains poorly understood. In particular, the loss of superhydrophobicity of hydrophobic micro/nanostructures during condensation, even when the same surface shows water-repellant characteristics when exposed to air, requires intensive investigation to improve and apply our understanding of the fundamental physics of condensation. Here, we postulate the criterion required for condensation to form from inside the surface structures by examining the grand potentials of a condensation system, including the properties of the condensed liquid and the conditions required for condensation. The results imply that the same hydrophobic micro/nano-structured surface could exhibit different liquid droplet behavior depending on the conditions. Our findings are supported by the observed phenomena: the initiation of a condensed droplet from inside a hydrophobic cavity, the apparent wetted state changes, and the presence of sticky condensed droplets on the hydrophobic micro/nano-structured surface.

  8. Synthesis of cyclopentadiene-fused chromanones via one-pot multicomponent reactions.

    PubMed

    Ghandi, Mehdi; Ghomi, Ali-Tabatabaei; Kubicki, Maciej

    2013-03-15

    We have developed one-pot method for the synthesis of functionalized novel cyclopentadiene-fused chromanone scaffolds. A variety of 4-oxo-2,4-dihydrocyclopenta[c]chromene-1,2-dicarboxylates were obtained in moderate to good yields via condensation of 2-hydroxybenzaldehydes and ethyl acetoacetate with 1:1 acetylenecarboxylate-isocyanides in toluene. These reactions presumably proceed via reaction of the in situ generated 3-acetyl-2H-chromen-2-ones with acetylenecarboxylate-isocyanide zwitterionic intermediates through Michael addition/intramolecular cyclization and double [1,5] acyl shift rearrangement cascade.

  9. Disequilibrium condensation environments in space - A frontier in thermodynamics

    NASA Technical Reports Server (NTRS)

    De, B. R.

    1979-01-01

    The thermal-disequilibrium aspect of the problem of dust-particle formation from a gas phase in an open space environment is discussed in an effort to draw attention to the space condensation environment as an interesting arena for application and extension of the ideas and formalisms of nonequilibrium thermodynamics. It is shown that quasi-steady states with a disequilibrium between the gas-phase kinetic temperature and the condensed-phase internal temperature appear to be the norm of condensation environments in space. Consideration of the case of condensation onto a bulk condensed phase indicates that these quasi-steady states may constitute Prigogine dissipative structures. It is suggested that a proper study of the process of condensation in a space environment should include any effects arising from thermal disequilibrium.

  10. Tunable Magnetic Alignment between Trapped Exciton-Polariton Condensates.

    PubMed

    Ohadi, H; Del Valle-Inclan Redondo, Y; Dreismann, A; Rubo, Y G; Pinsker, F; Tsintzos, S I; Hatzopoulos, Z; Savvidis, P G; Baumberg, J J

    2016-03-11

    Tunable spin correlations are found to arise between two neighboring trapped exciton-polariton condensates which spin polarize spontaneously. We observe a crossover from an antiferromagnetic to a ferromagnetic pair state by reducing the coupling barrier in real time using control of the imprinted pattern of pump light. Fast optical switching of both condensates is then achieved by resonantly but weakly triggering only a single condensate. These effects can be explained as the competition between spin bifurcations and spin-preserving Josephson coupling between the two condensates, and open the way to polariton Bose-Hubbard ladders.

  11. Comparative study during condensation of R152 a and R134 a with presence of non-condensable gas inside a vertical tube

    NASA Astrophysics Data System (ADS)

    Charef, Adil; Feddaoui, M'barek; Najim, Monssif; Meftah, Hicham

    2018-04-01

    A computational study of the liquid film condensation from vapour-gas mixtures of HFC refrigerants inside a vertical tube is performed. The external wall of the tube is subjected to constant temperature. The model uses an implicit finite difference method to solve the governing equations for the liquid film and gas flow together including the boundary and interfacial matching conditions. Parametric computations were realised to examine the effects of inlet Reynolds number, tube length, and inlet temperature of the gas mixtures on the condensation mechanism. A comparative study between the results obtained for studied R152 a and R134 a with presence of non-condensable gas is made. The predicted results indicate that the condensation of R152 a-air corresponds to a higher accumulated condensation m c d and local heat transfer coefficient h T when compared to R134 a-air in the same conditions. Increasing the inlet Reynolds number or the tube length improve the condensation. Additionally, lower non-condensable gas in R152 a - a i r substantially enhances the heat and mass exchanges.

  12. Synchronization crossover of polariton condensates in weakly disordered lattices

    NASA Astrophysics Data System (ADS)

    Ohadi, H.; del Valle-Inclan Redondo, Y.; Ramsay, A. J.; Hatzopoulos, Z.; Liew, T. C. H.; Eastham, P. R.; Savvidis, P. G.; Baumberg, J. J.

    2018-05-01

    We demonstrate that the synchronization of a lattice of solid-state condensates when intersite tunneling is switched on depends strongly on the weak local disorder. This finding is vital for implementation of condensate arrays as computation devices. The condensates here are nonlinear bosonic fluids of exciton-polaritons trapped in a weakly disordered Bose-Hubbard potential, where the nearest-neighboring tunneling rate (Josephson coupling) can be dynamically tuned. The system can thus be tuned from a localized to a delocalized fluid as the number density or the Josephson coupling between nearest neighbors increases. The localized fluid is observed as a lattice of unsynchronized condensates emitting at different energies set by the disorder potential. In the delocalized phase, the condensates synchronize and long-range order appears, evidenced by narrowing of momentum and energy distributions, new diffraction peaks in momentum space, and spatial coherence between condensates. Our paper identifies similarities and differences of this nonequilibrium crossover to the traditional Bose-glass to superfluid transition in atomic condensates.

  13. Condensation Front Migration in a Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Davis, Sanford S.

    2004-01-01

    Condensation front dynamics are investigated in the mid-solar nebula region. A quasi-steady model of the evolving nebula is combined with equilibrium vapor pressure curves to determine evolutionary condensation fronts for selected species. These fronts are found to migrate inwards from the far-nebula to final positions during a period of 10(exp 7) years. The physical process governing this movement is a combination of local viscous heating and luminescent heating from the central star. Two luminescent heating models are used and their effects on the ultimate radial position of the condensation front are discussed. At first the fronts move much faster than the nebular accretion velocity, but after a time the accreting gas and dust overtakes the slowing condensation front.

  14. 40 CFR 405.90 - Applicability; description of the condensed milk subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... subpart are applicable to discharges resulting from the manufacture of condensed whole milk, condensed skim milk, sweetened condensed milk and condensed buttermilk. ... condensed milk subcategory. 405.90 Section 405.90 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY...

  15. Spark gap switch system with condensable dielectric gas

    DOEpatents

    Thayer, III, William J.

    1991-01-01

    A spark gap switch system is disclosed which is capable of operating at a high pulse rate comprising an insulated switch housing having a purging gas entrance port and a gas exit port, a pair of spaced apart electrodes each having one end thereof within the housing and defining a spark gap therebetween, an easily condensable and preferably low molecular weight insulating gas flowing through the switch housing from the housing, a heat exchanger/condenser for condensing the insulating gas after it exits from the housing, a pump for recirculating the condensed insulating gas as a liquid back to the housing, and a heater exchanger/evaporator to vaporize at least a portion of the condensed insulating gas back into a vapor prior to flowing the insulating gas back into the housing.

  16. Employing Magnetic Levitation to Monitor Reaction Kinetics and Measure Activation Energy

    ERIC Educational Resources Information Center

    Benz, Lauren; Cesafsky, Karen E.; Le, Tran; Park, Aileen; Malicky, David

    2012-01-01

    This article describes a simple and inexpensive undergraduate-level kinetics experiment that uses magnetic levitation to monitor the progress and determine the activation energy of a condensation reaction on a polymeric solid support. The method employs a cuvette filled with a paramagnetic solution positioned between two strong magnets. The…

  17. Condensation and Evaporation of Solar System Materials

    NASA Astrophysics Data System (ADS)

    Davis, A. M.; Richter, F. M.

    2003-12-01

    It is widely believed that the materials making up the solar system were derived from a nebular gas and dust cloud that went through an early high-temperature stage during which virtually all of the material was in the gas phase. At one time, it was thought that the entire inner solar nebula was hot, but it is now believed that most material was processed through regions where high temperatures were achieved. Certainly some material, such as presolar grains (cf., Mendybaev et al., 2002a), has never been exposed to high temperatures. As the system cooled, solids and perhaps liquids began to condense, but at some point the partially condensed materials became isolated from the remaining gas. Various lines of evidence support this view. At the largest scale, there is the observation that the Earth, Moon, Mars, and all chondritic meteorites except for the CI chondrites are depleted to varying degrees in the abundances of moderately volatile elements relative to bulk solar system composition. The CI chondrites reflect the bulk composition of the solar system for all but hydrogen, carbon, nitrogen, oxygen, and the rare gases, the most volatile elements (see Chapter 1.03; Palme et al., 1988; McDonough and Sun, 1995; Humayun and Cassen, 2000). The depletions in moderately volatile elements are, to a significant degree, correlated with condensation temperature, suggesting progressive removal of gas as condensation proceeded ( Cassen, 1996). Additional observations that can be explained by partial condensation are that various particularly primitive components of meteorites (e.g., calcium-, aluminum-rich refractory inclusions, and certain metal grains) have mineralogy and/or details of their chemical composition that are remarkably similar to what is calculated for equilibrium condensates from a solar composition gas. For example, the calcium-, aluminum-rich inclusions (CAIs) in chondritic meteorites have compositions very similar to that calculated for the first 5% of total

  18. Enhanced Condensation Heat Transfer On Patterned Surfaces

    NASA Astrophysics Data System (ADS)

    Alizadeh-Birjandi, Elaheh; Kavehpour, H. Pirouz

    2017-11-01

    Transition from film to drop wise condensation can improve the efficiency of thermal management applications and result in considerable savings in investments and operating costs by millions of dollars every year. The current methods available are either hydrophobic coating or nanostructured surfaces. The former has little adhesion to the structure which tends to detach easily under working conditions, the fabrication techniques of the latter are neither cost-effective nor scalable, and both are made with low thermal conductivity materials that would negate the heat transfer enhancement by drop wise condensation. Therefore, the existing technologies have limitations in enhancing vapor-to-liquid condensation. This work focuses on development of surfaces with wettability contrast to boost drop wise condensation, which its overall heat transfer efficiency is 2-3 times film wise condensation, while maintaining high conduction rate through the surface at low manufacturing costs. The variation in interfacial energy is achieved through crafting hydrophobic patterns to the surface of the metal via scalable fabrication techniques. The results of experimental and surface optimization studies are also presented.

  19. Condensation of wet vapors in turbines

    NASA Technical Reports Server (NTRS)

    Kothman, R. E.

    1970-01-01

    Computer program predicts condensation point in wet vapor turbines and analyzes subsequent nucleation and growth processes to determine both moisture content and drop size and number distribution as a function of position. Program includes effects of molecular association on condensation and flow processes and handles both subsonic and supersonic flows.

  20. Condensates in quantum chromodynamics and the cosmological constant

    PubMed Central

    Brodsky, Stanley J.; Shrock, Robert

    2011-01-01

    Casher and Susskind [Casher A, Susskind L (1974) Phys Rev 9:436–460] have noted that in the light-front description, spontaneous chiral symmetry breaking is a property of hadronic wavefunctions and not of the vacuum. Here we show from several physical perspectives that, because of color confinement, quark and gluon condensates in quantum chromodynamics (QCD) are associated with the internal dynamics of hadrons. We discuss condensates using condensed matter analogues, the Anti de Sitter/conformal field theory correspondence, and the Bethe–Salpeter–Dyson–Schwinger approach for bound states. Our analysis is in agreement with the Casher and Susskind model and the explicit demonstration of “in-hadron” condensates by Roberts and coworkers [Maris P, Roberts CD, Tandy PC (1998) Phys Lett B 420:267–273], using the Bethe–Salpeter–Dyson–Schwinger formalism for QCD-bound states. These results imply that QCD condensates give zero contribution to the cosmological constant, because all of the gravitational effects of the in-hadron condensates are already included in the normal contribution from hadron masses.

  1. Atomistic Simulations of Detonation Instabilities in Condensed Phase Systems

    NASA Astrophysics Data System (ADS)

    Kober, Edward; Heim, Andrew; Germann, Timothy; Jensen, Niels

    2007-06-01

    We report the results of simulations of condensed phase detonation phenomena using a model diatomic system: 2AB -> A2 + B2. The initial set of parameters for this system corresponded to the Model 0 set of C. White et al, which exhibits a steady, Chapman-Jouget (CJ) detonation structure with a reaction zone length of 30-100 å. This has a highly compressed CJ state (V/V0˜0.5) that does not consist of discrete molecular species. The potential form was modified so that a more molecular CJ state resulted, consistent with the models for conventional organic explosives. The new system has a less dense CJ state (V/V0˜0.8), and the reaction zone was substantially extended. The reaction rate fits Arrhenius-type kinetics with an activation energy of ˜2 eV, with a minor density dependence. In contrast, the original Model 0 system had a lower activation energy (˜1 eV) with a stronger density dependence. The new system exhibits quite marked two dimensional instability structures with well-defined wavelengths similar to what has been observed for gas-phase detonations and for nitromethane. Depending on the exothermicity and the width of the periodic simulations, these instabilities can result in either detonation failure or quasi-steady propagation. The observed propagation velocities are several per cent higher than CJ values derived from thermodynamic analyses.

  2. Condensation in One-Dimensional Dead-End Nanochannels.

    PubMed

    Zhong, Junjie; Zandavi, Seyed Hadi; Li, Huawei; Bao, Bo; Persad, Aaron H; Mostowfi, Farshid; Sinton, David

    2017-01-24

    Phase change at the nanoscale is at the heart of many biological and geological phenomena. The recent emergence and global implications of unconventional oil and gas production from nanoporous shale further necessitate a higher understanding of phase behavior at these scales. Here, we directly observe condensation and condensate growth of a light hydrocarbon (propane) in discrete sub-100 nm (∼70 nm) channels. Two different condensation mechanisms at this nanoscale are distinguished, continuous growth and discontinuous growth due to liquid bridging ahead of the meniscus, both leading to similar net growth rates. The growth rates agree well with those predicted by a suitably defined thermofluid resistance model. In contrast to phase change at larger scales (∼220 and ∼1000 nm cases), the rate of liquid condensate growth in channels of sub-100 nm size is found to be limited mainly by vapor flow resistance (∼70% of the total resistance here), with interface resistance making up the difference. The condensation-induced vapor flow is in the transitional flow regime (Knudsen flow accounting for up to 13% of total resistance here). Collectively, these results demonstrate that with confinement at sub-100 nm scales, such as is commonly found in porous shale and other applications, condensation conditions deviate from the microscale and larger bulk conditions chiefly due to vapor flow and interface resistances.

  3. Calcium ions function as a booster of chromosome condensation

    PubMed Central

    Phengchat, Rinyaporn; Takata, Hideaki; Morii, Kenichi; Inada, Noriko; Murakoshi, Hideji; Uchiyama, Susumu; Fukui, Kiichi

    2016-01-01

    Chromosome condensation is essential for the faithful transmission of genetic information to daughter cells during cell division. The depletion of chromosome scaffold proteins does not prevent chromosome condensation despite structural defects. This suggests that other factors contribute to condensation. Here we investigated the contribution of divalent cations, particularly Ca2+, to chromosome condensation in vitro and in vivo. Ca2+ depletion caused defects in proper mitotic progression, particularly in chromosome condensation after the breakdown of the nuclear envelope. Fluorescence lifetime imaging microscopy-Förster resonance energy transfer and electron microscopy demonstrated that chromosome condensation is influenced by Ca2+. Chromosomes had compact globular structures when exposed to Ca2+ and expanded fibrous structures without Ca2+. Therefore, we have clearly demonstrated a role for Ca2+ in the compaction of chromatin fibres. PMID:27910894

  4. Calcium ions function as a booster of chromosome condensation.

    PubMed

    Phengchat, Rinyaporn; Takata, Hideaki; Morii, Kenichi; Inada, Noriko; Murakoshi, Hideji; Uchiyama, Susumu; Fukui, Kiichi

    2016-12-02

    Chromosome condensation is essential for the faithful transmission of genetic information to daughter cells during cell division. The depletion of chromosome scaffold proteins does not prevent chromosome condensation despite structural defects. This suggests that other factors contribute to condensation. Here we investigated the contribution of divalent cations, particularly Ca 2+ , to chromosome condensation in vitro and in vivo. Ca 2+ depletion caused defects in proper mitotic progression, particularly in chromosome condensation after the breakdown of the nuclear envelope. Fluorescence lifetime imaging microscopy-Förster resonance energy transfer and electron microscopy demonstrated that chromosome condensation is influenced by Ca 2+ . Chromosomes had compact globular structures when exposed to Ca 2+ and expanded fibrous structures without Ca 2+ . Therefore, we have clearly demonstrated a role for Ca 2+ in the compaction of chromatin fibres.

  5. Modeling the free energy surfaces of electron transfer in condensed phases

    NASA Astrophysics Data System (ADS)

    Matyushov, Dmitry V.; Voth, Gregory A.

    2000-10-01

    We develop a three-parameter model of electron transfer (ET) in condensed phases based on the Hamiltonian of a two-state solute linearly coupled to a harmonic, classical solvent mode with different force constants in the initial and final states (a classical limit of the quantum Kubo-Toyozawa model). The exact analytical solution for the ET free energy surfaces demonstrates the following features: (i) the range of ET reaction coordinates is limited by a one-sided fluctuation band, (ii) the ET free energies are infinite outside the band, and (iii) the free energy surfaces are parabolic close to their minima and linear far from the minima positions. The model provides an analytical framework to map physical phenomena conflicting with the Marcus-Hush two-parameter model of ET. Nonlinear solvation, ET in polarizable charge-transfer complexes, and configurational flexibility of donor-acceptor complexes are successfully mapped onto the model. The present theory leads to a significant modification of the energy gap law for ET reactions.

  6. Supermode-density-wave-polariton condensation with a Bose–Einstein condensate in a multimode cavity

    PubMed Central

    Kollár, Alicia J.; Papageorge, Alexander T.; Vaidya, Varun D.; Guo, Yudan; Keeling, Jonathan; Lev, Benjamin L.

    2017-01-01

    Phase transitions, where observable properties of a many-body system change discontinuously, can occur in both open and closed systems. By placing cold atoms in optical cavities and inducing strong coupling between light and excitations of the atoms, one can experimentally study phase transitions of open quantum systems. Here we observe and study a non-equilibrium phase transition, the condensation of supermode-density-wave polaritons. These polaritons are formed from a superposition of cavity photon eigenmodes (a supermode), coupled to atomic density waves of a quantum gas. As the cavity supports multiple photon spatial modes and because the light–matter coupling can be comparable to the energy splitting of these modes, the composition of the supermode polariton is changed by the light–matter coupling on condensation. By demonstrating the ability to observe and understand density-wave-polariton condensation in the few-mode-degenerate cavity regime, our results show the potential to study similar questions in fully multimode cavities. PMID:28211455

  7. Experimental Investigation of Flow Condensation in Microgravity

    NASA Technical Reports Server (NTRS)

    Lee, Hyoungsoon; Park, Ilchung; Konishi, Christopher; Mudawar, Issam; May, Rochelle I.; Juergens, Jeffery R.; Wagner, James D.; Hall, Nancy R.; Nahra, Henry K.; Hasan, Mohammed M.; hide

    2013-01-01

    Future manned missions to Mars are expected to greatly increase the space vehicle's size, weight, and heat dissipation requirements. An effective means to reducing both size and weight is to replace single-phase thermal management systems with two-phase counterparts that capitalize upon both latent and sensible heat of the coolant rather than sensible heat alone. This shift is expected to yield orders of magnitude enhancements in flow boiling and condensation heat transfer coefficients. A major challenge to this shift is a lack of reliable tools for accurate prediction of two-phase pressure drop and heat transfer coefficient in reduced gravity. Developing such tools will require a sophisticated experimental facility to enable investigators to perform both flow boiling and condensation experiments in microgravity in pursuit of reliable databases. This study will discuss the development of the Flow Boiling and Condensation Experiment (FBCE) for the International Space Station (ISS), which was initiated in 2012 in collaboration between Purdue University and NASA Glenn Research Center. This facility was recently tested in parabolic flight to acquire condensation data for FC-72 in microgravity, aided by high-speed video analysis of interfacial structure of the condensation film. The condensation is achieved by rejecting heat to a counter flow of water, and experiments were performed at different mass velocities of FC-72 and water and different FC-72 inlet qualities. It is shown that the film flow varies from smooth-laminar to wavy-laminar and ultimately turbulent with increasing FC-72 mass velocity. The heat transfer coefficient is highest near the inlet of the condensation tube, where the film is thinnest, and decreases monotonically along the tube, except for high FC-72 mass velocities, where the heat transfer coefficient is enhanced downstream. This enhancement is attributed to both turbulence and increased interfacial waviness. One-ge correlations are shown to

  8. Integral Reactor Containment Condensation Model and Experimental Validation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wu, Qiao; Corradini, Michael

    This NEUP funded project, NEUP 12-3630, is for experimental, numerical and analytical studies on high-pressure steam condensation phenomena in a steel containment vessel connected to a water cooling tank, carried out at Oregon State University (OrSU) and the University of Wisconsin at Madison (UW-Madison). In the three years of investigation duration, following the original proposal, the planned tasks have been completed: (1) Performed a scaling study for the full pressure test facility applicable to the reference design for the condensation heat transfer process during design basis accidents (DBAs), modified the existing test facility to route the steady-state secondary steam flowmore » into the high pressure containment for controllable condensation tests, and extended the operations at negative gage pressure conditions (OrSU). (2) Conducted a series of DBA and quasi-steady experiments using the full pressure test facility to provide a reliable high pressure condensation database (OrSU). (3) Analyzed experimental data and evaluated condensation model for the experimental conditions, and predicted the prototypic containment performance under accidental conditions (UW-Madison). A film flow model was developed for the scaling analysis, and the results suggest that the 1/3 scaled test facility covers large portion of laminar film flow, leading to a lower average heat transfer coefficient comparing to the prototypic value. Although it is conservative in reactor safety analysis, the significant reduction of heat transfer coefficient (50%) could under estimate the prototypic condensation heat transfer rate, resulting in inaccurate prediction of the decay heat removal capability. Further investigation is thus needed to quantify the scaling distortion for safety analysis code validation. Experimental investigations were performed in the existing MASLWR test facility at OrST with minor modifications. A total of 13 containment condensation tests were conducted for

  9. Spin polarized semimagnetic exciton-polariton condensate in magnetic field.

    PubMed

    Król, Mateusz; Mirek, Rafał; Lekenta, Katarzyna; Rousset, Jean-Guy; Stephan, Daniel; Nawrocki, Michał; Matuszewski, Michał; Szczytko, Jacek; Pacuski, Wojciech; Piętka, Barbara

    2018-04-27

    Owing to their integer spin, exciton-polaritons in microcavities can be used for observation of non-equilibrium Bose-Einstein condensation in solid state. However, spin-related phenomena of such condensates are difficult to explore due to the relatively small Zeeman effect of standard semiconductor microcavity systems and the strong tendency to sustain an equal population of two spin components, which precludes the observation of condensates with a well defined spin projection along the axis of the system. The enhancement of the Zeeman splitting can be achieved by introducing magnetic ions to the quantum wells, and consequently forming semimagnetic polaritons. In this system, increasing magnetic field can induce polariton condensation at constant excitation power. Here we evidence the spin polarization of a semimagnetic polaritons condensate exhibiting a circularly polarized emission over 95% even in a moderate magnetic field of about 3 T. Furthermore, we show that unlike nonmagnetic polaritons, an increase on excitation power results in an increase of the semimagnetic polaritons condensate spin polarization. These properties open new possibilities for testing theoretically predicted phenomena of spin polarized condensate.

  10. Condensation of Forced Convection Two-Phase Flow in a Miniature Tube

    NASA Technical Reports Server (NTRS)

    Begg, E.; Faghri, A.; Krustalev, D.

    1999-01-01

    A physical/mathematical model of annular film condensation at the inlet of a miniature tube has been developed. In the model, the liquid flow is coupled with the vapor flow along the liquid-vapor interface through the interfacial temperature, heat flux, shear stress, and pressure jump conditions due to surface tension effects. The model predicts the shape of the liquid-vapor interface along the condenser and leads to the conclusion that there is complete condensation at a certain distance from the condenser inlet. The numerical results show that complete condensation of the incoming vapor is possible at comparatively low heat loads and that this is a special case of a more general condensation regime with two-phase bubbly flow downstream of the initial annular film condensation region. Observations from the flow visualization experiment confirm the existence and qualitative features of annular film condensation leading to the complete condensation phenomenon in a small diameter (3.25 mm) circular tube condenser.

  11. Experiments of Transient Condensation Heat Transfer on the Heat Flux Senor

    NASA Astrophysics Data System (ADS)

    Wang, Xuwen; Liu, Qiusheng; Zhu, Zhiqiang; Chen, Xue

    2015-09-01

    The influence of transient heat transfer in different condensation condition was investigated experimentally in the present paper. Getting condensation heat and mass transfer regularity and characteristics in space can provide theoretical basis for thermodynamic device such as heat pipes, loop heat pipes and capillary pumped loops as well as other fluid management engineering designing. In order to study the condensation process in space, an experimental study has been carried out on the ground for space experiment. The results show that transit heat transfer coefficient of film condensation is related to the condensation film width, the flow condition near the two phase interface and the pressure of the vapor and non-condensable gas in chamber. On the ground, the condensation heat flux on vertical surface is higher than it on horizontal surface. The transit heat flux of film condensation is affected by the temperature of superheated vapor, the temperature of condensation surface and non-condensable gas pressure. Condensation heat flux with vapor forced convection is many times more than it with natural convection. All of heat flux for both vapor forced convection and natural convection condensation in limited chamber declines dramatically over time. The present experiment is preliminary work for our future space experiments of the condensation and heat transfer process onboard the Chinese Spacecraft "TZ-1" to be launched in 2016.

  12. Spacecraft Crew Cabin Condensation Control

    NASA Technical Reports Server (NTRS)

    Carrillo, Laurie Y.; Rickman, Steven L.; Ungar, Eugene K.

    2013-01-01

    A report discusses a new technique to prevent condensation on the cabin walls of manned spacecraft exposed to the cold environment of space, as such condensation could lead to free water in the cabin. This could facilitate the growth of mold and bacteria, and could lead to oxidation and weakening of the cabin wall. This condensation control technique employs a passive method that uses spacecraft waste heat as the primary wallheating mechanism. A network of heat pipes is bonded to the crew cabin pressure vessel, as well as the pipes to each other, in order to provide for efficient heat transfer to the cabin walls and from one heat pipe to another. When properly sized, the heat-pipe network can maintain the crew cabin walls at a nearly uniform temperature. It can also accept and distribute spacecraft waste heat to maintain the pressure vessel above dew point.

  13. Cytoskeletal Reorganization Drives Mesenchymal Condensation and Regulates Downstream Molecular Signaling.

    PubMed

    Ray, Poulomi; Chapman, Susan C

    2015-01-01

    Skeletal condensation occurs when specified mesenchyme cells self-organize over several days to form a distinctive cartilage template. Here, we determine how and when specified mesenchyme cells integrate mechanical and molecular information from their environment, forming cartilage condensations in the pharyngeal arches of chick embryos. By disrupting cytoskeletal reorganization, we demonstrate that dynamic cell shape changes drive condensation and modulate the response of the condensing cells to Fibroblast Growth Factor (FGF), Bone Morphogenetic Protein (BMP) and Transforming Growth Factor beta (TGF-β) signaling pathways. Rho Kinase (ROCK)-driven actomyosin contractions and Myosin II-generated differential cell cortex tension regulate these cell shape changes. Disruption of the condensation process inhibits the differentiation of the mesenchyme cells into chondrocytes, demonstrating that condensation regulates the fate of the mesenchyme cells. We also find that dorsal and ventral condensations undergo distinct cell shape changes. BMP signaling is instructive for dorsal condensation-specific cell shape changes. Moreover, condensations exhibit ventral characteristics in the absence of BMP signaling, suggesting that in the pharyngeal arches ventral morphology is the ground pattern. Overall, this study characterizes the interplay between cytoskeletal dynamics and molecular signaling in a self-organizing system during tissue morphogenesis.

  14. Cytoskeletal Reorganization Drives Mesenchymal Condensation and Regulates Downstream Molecular Signaling

    PubMed Central

    Ray, Poulomi; Chapman, Susan C.

    2015-01-01

    Skeletal condensation occurs when specified mesenchyme cells self-organize over several days to form a distinctive cartilage template. Here, we determine how and when specified mesenchyme cells integrate mechanical and molecular information from their environment, forming cartilage condensations in the pharyngeal arches of chick embryos. By disrupting cytoskeletal reorganization, we demonstrate that dynamic cell shape changes drive condensation and modulate the response of the condensing cells to Fibroblast Growth Factor (FGF), Bone Morphogenetic Protein (BMP) and Transforming Growth Factor beta (TGF-β) signaling pathways. Rho Kinase (ROCK)-driven actomyosin contractions and Myosin II-generated differential cell cortex tension regulate these cell shape changes. Disruption of the condensation process inhibits the differentiation of the mesenchyme cells into chondrocytes, demonstrating that condensation regulates the fate of the mesenchyme cells. We also find that dorsal and ventral condensations undergo distinct cell shape changes. BMP signaling is instructive for dorsal condensation-specific cell shape changes. Moreover, condensations exhibit ventral characteristics in the absence of BMP signaling, suggesting that in the pharyngeal arches ventral morphology is the ground pattern. Overall, this study characterizes the interplay between cytoskeletal dynamics and molecular signaling in a self-organizing system during tissue morphogenesis. PMID:26237312

  15. Transient alkylaminium radicals in n-hexane. Condensed-phase ion-molecule reactions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Werst, D.W.; Trifunac, A.D.

    Time-resolved fluorescence detected magnetic resonance (FDMR) is used to observe alkylaminium radicals formed in n-hexane solutions by electron pulse radiolysis. The ease of observation of aminium radical FDMR signals increases with increasing alkyl substitution of the amine solutes. The results are discussed in terms of the ion-molecule reactions, such as proton transfer, which compete with the electron-transfer processes, i.e, the electron transfer from solute molecules to n-hexane radical cations and geminate recombination.

  16. Soliton resonance in bose-einstein condensate

    NASA Technical Reports Server (NTRS)

    Zak, Michail; Kulikov, I.

    2002-01-01

    A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.

  17. Structure-reactivity modeling using mixture-based representation of chemical reactions.

    PubMed

    Polishchuk, Pavel; Madzhidov, Timur; Gimadiev, Timur; Bodrov, Andrey; Nugmanov, Ramil; Varnek, Alexandre

    2017-09-01

    We describe a novel approach of reaction representation as a combination of two mixtures: a mixture of reactants and a mixture of products. In turn, each mixture can be encoded using an earlier reported approach involving simplex descriptors (SiRMS). The feature vector representing these two mixtures results from either concatenated product and reactant descriptors or the difference between descriptors of products and reactants. This reaction representation doesn't need an explicit labeling of a reaction center. The rigorous "product-out" cross-validation (CV) strategy has been suggested. Unlike the naïve "reaction-out" CV approach based on a random selection of items, the proposed one provides with more realistic estimation of prediction accuracy for reactions resulting in novel products. The new methodology has been applied to model rate constants of E2 reactions. It has been demonstrated that the use of the fragment control domain applicability approach significantly increases prediction accuracy of the models. The models obtained with new "mixture" approach performed better than those required either explicit (Condensed Graph of Reaction) or implicit (reaction fingerprints) reaction center labeling.

  18. Bose-Einstein condensation in atomic alkali gases

    NASA Astrophysics Data System (ADS)

    Dodd, Robert J.

    1998-05-01

    I present a review of the time-independent Gross-Pitaevskii (GP), Bogoliubov, and finite-temperature Hartree-Fock-Bogoliubov (HFB) mean-field theories used to study trapped, Bose-Einstein condensed alkali gases. Numerical solutions of the (zero-temperature) GP equation are presented for attractive (negative scattering length) and repulsive (positive scattering length) interactions. Comparison is made with the Thomas-Fermi and (variational) trial wavefunction appr oximations that are used in the literature to study condensed gases. Numerical calculations of the (zero-temperature) Bogoliubov quasi-particle excitation frequencies are found to be in excellent agreement with the experimental results. The finite-temperature properties of condensed gases are examined using the Popov approximation (of the HFB theory) and a simple two-gas model. Specific, quantitative comparisons are made with experimental results for finite-temperature excitation frequencies. Qualitative comparisons are made between the results of the Popov approximation, two-gas model, and other published models for condensate fraction and thermal density distribution. The time-independent mean-field theories are found to be in excellent agreement with experimental results at relatively low temperatures (high condensate fractions). However, at higher temperatures (and condensate fractions of less than 50%) there are significant discrepancies between experimental data and theoretical calculations. This work was undertaken at the University of Maryland at College Park and was supported in part by the National Science Foundation (PHY-9601261) and the U.S. Office of Naval Research.

  19. Acoustically-Enhanced Direct Contact Vapor Bubble Condensation

    NASA Astrophysics Data System (ADS)

    Boziuk, Thomas; Smith, Marc; Glezer, Ari

    2017-11-01

    Rate-limited, direct contact vapor condensation of vapor bubbles that are formed by direct steam injection through a nozzle in a quiescent subcooled liquid bath is accelerated using ultrasonic (MHz-range) actuation. A submerged, low power actuator produces an acoustic beam whose radiation pressure deforms the liquid-vapor interface, leading to the formation of a liquid spear that penetrates the vapor bubble to form a vapor torus with a significantly larger surface area and condensation rate. Ultrasonic focusing along the spear leads to the ejection of small, subcooled droplets through the vapor volume that impact the vapor-liquid interface and further enhance the condensation. High-speed Schlieren imaging of the formation and collapse of the vapor bubbles in the absence and presence of actuation shows that the impulse associated with the collapse of the toroidal volume leads to the formation of a turbulent vortex ring in the liquid phase. Liquid motions near the condensing vapor volume are investigated in the absence and presence of acoustic actuation using high-magnification PIV and show the evolution of a liquid jet through the center of the condensing toroidal volume and the formation and advection of vortex ring structures whose impulse appear to increase with temperature difference between the liquid and vapor phases. High-speed image processing is used to assess the effect of the actuation on the temporal and spatial variations in the characteristic scales and condensation rates of the vapor bubbles.

  20. Dropwise condensation on hydrophobic bumps and dimples

    NASA Astrophysics Data System (ADS)

    Yao, Yuehan; Aizenberg, Joanna; Park, Kyoo-Chul

    2018-04-01

    Surface topography plays an important role in promoting or suppressing localized condensation. In this work, we study the growth of water droplets on hydrophobic convex surface textures such as bumps and concave surface textures such as dimples with a millimeter scale radius of curvature. We analyze the spatio-temporal droplet size distribution under a supersaturation condition created by keeping the uniform surface temperature below the dew point and show its relationship with the sign and magnitude of the surface curvature. In particular, in contrast to the well-known capillary condensation effect, we report an unexpectedly less favorable condensation on smaller, millimeter-scale dimples where the capillary condensation effect is negligible. To explain these experimental results, we numerically calculated the diffusion flux of water vapor around the surface textures, showing that its magnitude is higher on bumps and lower on dimples compared to a flat surface. We envision that our understanding of millimetric surface topography can be applied to improve the energy efficiency of condensation in applications such as water harvesting, heating, ventilation, and air conditioning systems for buildings and transportation, heat exchangers, thermal desalination plants, and fuel processing systems.

  1. Diagnosis of condensation-induced waterhammer: Case studies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Izenson, M.G.; Rothe, P.H.; Wallis, G.B.

    1988-10-01

    This guidebook provides reference material and diagnostic procedures concerning condensation-induced waterhammer in nuclear power plants. Condensation-induced waterhammer is the most damaging form of waterhammer, and its diagnosis is complicated by the complex nature of the underlying phenomena. In Volume 1, the guidebook groups condensation-induced waterhammers into five event classes which have similar phenomena and levels of damage. Diagnostic guidelines focus on locating the event center where condensation and slug acceleration take place. Diagnosis is described in three stages: an initial assessment, detailed evaluation and final confirmation. Graphical scoping analyses are provided to evaluate whether an event from one of themore » event classes could have occurred at the event center. Examples are provided for each type of waterhammer. Special instructions are provided for walking down damaged piping and evaluating damage due to waterhammer. To illustrate the diagnostic methods and document past experience, six case studies have been compiled in Volume 2. These case studies, based on actual condensation-induced waterhammer events at nuclear plants, present detailed data and work through the event diagnosis using the tools introduced in the first volume. 20 refs., 21 figs., 6 tabs.« less

  2. De Novo Computational Design of Retro-Aldol Enzymes

    PubMed Central

    Jiang, Lin; Althoff, Eric A.; Clemente, Fernando R.; Doyle, Lindsey; Röthlisberger, Daniela; Zanghellini, Alexandre; Gallaher, Jasmine L.; Betker, Jamie L.; Tanaka, Fujie; Barbas, Carlos F.; Hilvert, Donald; Houk, Kendall N.; Stoddard, Barry L.; Baker, David

    2012-01-01

    The creation of enzymes capable of catalyzing any desired chemical reaction is a grand challenge for computational protein design. Using new algorithms that rely on hashing techniques to construct active sites for multistep reactions, we designed retro-aldolases that use four different catalytic motifs to catalyze the breaking of a carbon-carbon bond in a nonnatural substrate. Of the 72 designs that were experimentally characterized, 32, spanning a range of protein folds, had detectable retro-aldolase activity. Designs that used an explicit water molecule to mediate proton shuffling were significantly more successful, with rate accelerations of up to four orders of magnitude and multiple turnovers, than those involving charged side-chain networks. The atomic accuracy of the design process was confirmed by the x-ray crystal structure of active designs embedded in two protein scaffolds, both of which were nearly superimposable on the design model. PMID:18323453

  3. CONVECTION IN CONDENSIBLE-RICH ATMOSPHERES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ding, F.; Pierrehumbert, R. T., E-mail: fding@uchicago.edu

    2016-05-01

    Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case—water vapor in Earth’s present climate—the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO{sub 2} is the condensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamentalmore » ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-convective simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere for both steady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.« less

  4. 40 CFR 721.10146 - Partially fluorinated condensation polymer (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Partially fluorinated condensation... Specific Chemical Substances § 721.10146 Partially fluorinated condensation polymer (generic). (a) Chemical... as partially fluorinated condensation polymer (PMN P-07-87) is subject to reporting under this...

  5. 40 CFR 721.10146 - Partially fluorinated condensation polymer (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Partially fluorinated condensation... Specific Chemical Substances § 721.10146 Partially fluorinated condensation polymer (generic). (a) Chemical... as partially fluorinated condensation polymer (PMN P-07-87) is subject to reporting under this...

  6. 40 CFR 721.10146 - Partially fluorinated condensation polymer (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Partially fluorinated condensation... Specific Chemical Substances § 721.10146 Partially fluorinated condensation polymer (generic). (a) Chemical... as partially fluorinated condensation polymer (PMN P-07-87) is subject to reporting under this...

  7. 40 CFR 721.10146 - Partially fluorinated condensation polymer (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Partially fluorinated condensation... Specific Chemical Substances § 721.10146 Partially fluorinated condensation polymer (generic). (a) Chemical... as partially fluorinated condensation polymer (PMN P-07-87) is subject to reporting under this...

  8. Experimental study of condensate subcooling with the use of a model of an air-cooled condenser

    NASA Astrophysics Data System (ADS)

    Sukhanov, V. A.; Bezukhov, A. P.; Bogov, I. A.; Dontsov, N. Y.; Volkovitsky, I. D.; Tolmachev, V. V.

    2016-01-01

    Water-supply deficit is now felt in many regions of the world. This hampers the construction of new steam-turbine and combined steam-and-gas thermal power plants. The use of dry cooling systems and, specifically, steam-turbine air-cooled condensers (ACCs) expands the choice of sites for the construction of such power plants. The significance of condensate subcooling Δ t as a parameter that negatively affects the engineering and economic performance of steam-turbine plants is thereby increased. The operation and design factors that influence the condensate subcooling in ACCs are revealed, and the research objective is, thus, formulated properly. The indicated research was conducted through physical modeling with the use of the Steam-Turbine Air-Cooled Condenser Unit specialized, multipurpose, laboratory bench. The design and the combined schematic and measurement diagram of this test bench are discussed. The experimental results are presented in the form of graphic dependences of the condensate subcooling value on cooling ratio m and relative weight content ɛ' of air in steam at the ACC inlet at different temperatures of cooling air t ca ' . The typical ranges of condensate subcooling variation (4 ≤ Δ t ≤ 6°C, 2 ≤ Δ t ≤ 4°C, and 0 ≤ Δ t ≤ 2°C) are identified based on the results of analysis of the attained Δ t levels in the ACC and numerous Δ t reduction estimates. The corresponding ranges of cooling ratio variation at different temperatures of cooling air at the ACC inlet are specified. The guidelines for choosing the adjusted ranges of cooling ratio variation with account of the results of experimental studies of the dependences of the absolute pressure of the steam-air mixture in the top header of the ACC and the heat flux density on the cooling ratio at different temperatures of cooling air at the ACC inlet are given.

  9. Modeling the Phase Composition of Gas Condensate in Pipelines

    NASA Astrophysics Data System (ADS)

    Dudin, S. M.; Zemenkov, Yu D.; Shabarov, A. B.

    2016-10-01

    Gas condensate fields demonstrate a number of thermodynamic characteristics to be considered when they are developed, as well as when gas condensate is transported and processed. A complicated phase behavior of the gas condensate system, as well as the dependence of the extracted raw materials on the phase state of the deposit other conditions being equal, is a key aspect. Therefore, when designing gas condensate lines the crucial task is to select the most appropriate methods of calculating thermophysical properties and phase equilibrium of the transported gas condensate. The paper describes a physical-mathematical model of a gas-liquid flow in the gas condensate line. It was developed based on balance equations of conservation of mass, impulse and energy of the transported medium within the framework of a quasi-1D approach. Constitutive relationships are given separately, and practical recommendations on how to apply the research results are provided as well.

  10. Self-propelled sweeping removal of dropwise condensate

    DOE PAGES

    Qu, Xiaopeng; Boreyko, Jonathan; Liu, Fangjie; ...

    2015-06-02

    Dropwise condensation can be enhanced by superhydrophobic surfaces, on which the condensate drops spontaneously jump upon coalescence. However, the self-propelled jumping in prior reports is mostly perpendicular to the substrate. Here, we propose a substrate design with regularly spaced micropillars. Coalescence on the sidewalls of the micropillars leads to self-propelled jumping in a direction nearly orthogonal to the pillars and therefore parallel to the substrate. This in- plane motion in turn produces sweeping removal of multiple neighboring drops. The spontaneous sweeping mechanism may greatly enhance dropwise condensation in a self-sustained manner.

  11. Synthesis and insect antifeedant activities of some substituted styryl 3,4-dichlorophenyl ketones

    NASA Astrophysics Data System (ADS)

    Thirunarayanan, G.; Surya, S.; Srinivasan, S.; Vanangamudi, G.; Sathiyendiran, V.

    2010-01-01

    Sixteen substituted styryl 3,4-dichlorophenyl ketones [ (2E)-1-(3,4-dichlorophenyl)-3-phenyl-2-propen-1-ones] were synthesized using eco-friendly benign stereoselective crossed-aldol reaction. They are characterized by their analytical, infrared, NMR and mass spectral data. The insect antifeedant activities of these chalcones were evaluated using Caster semilooper and Achoea janata L.

  12. A Pauson-Khand approach to the synthesis of ingenol.

    PubMed

    Winkler, Jeffrey D; Lee, Esther C Y; Nevels, LaToya I

    2005-04-14

    [reaction: see text] Pauson-Khand cyclization of dioxanone photoadduct 21 leads to the formation of a single product in good yield. However, retro-aldol fragmentation of the pentacyclic cyclopentenone 22 leads to the formation of 23, with cis C-8/C-10 intrabridgehead stereochemistry, unlike the target compound ingenol 1, which possesses C-8/C-10 trans intrabridgehead stereochemistry.

  13. Fabrication and condensation characteristics of metallic superhydrophobic surface with hierarchical micro-nano structures

    NASA Astrophysics Data System (ADS)

    Chu, Fuqiang; Wu, Xiaomin

    2016-05-01

    Metallic superhydrophobic surfaces have various applications in aerospace, refrigeration and other engineering fields due to their excellent water repellent characteristics. This study considers a simple but widely applicable fabrication method using a two simultaneous chemical reactions method to prepare the acid-salt mixed solutions to process the metal surfaces with surface deposition and surface etching to construct hierarchical micro-nano structures on the surface and then modify the surface with low surface-energy materials. Al-based and Cu-based superhydrophobic surfaces were fabricated using this method. The Al-based superhydrophobic surface had a water contact angle of 164° with hierarchical micro-nano structures similar to the lotus leaves. The Cu-based surface had a water contact angle of 157° with moss-like hierarchical micro-nano structures. Droplet condensation experiments were also performed on these two superhydrophobic surfaces to investigate their condensation characteristics. The results show that the Al-based superhydrophobic surface has lower droplet density, higher droplet jumping probability, slower droplet growth rate and lower surface coverage due to the more structured hierarchical structures.

  14. Distillation of bose-einstein condensates in a double-well potential.

    PubMed

    Shin, Y; Saba, M; Schirotzek, A; Pasquini, T A; Leanhardt, A E; Pritchard, D E; Ketterle, W

    2004-04-16

    Bose-Einstein condensates of sodium atoms, prepared in an optical dipole trap, were distilled into a second empty dipole trap adjacent to the first one. The distillation was driven by thermal atoms spilling over the potential barrier separating the two wells and then forming a new condensate. This process serves as a model system for metastability in condensates, provides a test for quantum kinetic theories of condensate formation, and also represents a novel technique for creating or replenishing condensates in new locations.

  15. [A fluoride-sensor for kink structure in DNA condensation process].

    PubMed

    Liu, Yan-Hui; Zhang, Jing; Chen, Ying-Bing; Li, Yu-Pu; Hu, Lin

    2014-01-01

    Bloomfield has pointed out that the kink structure occurs for sharp bending during DNA condensation process, until now, which has not been proved by experiments. Using UV Spectrophotometer, the effects of fluoride and chlorine on the polyamine-DNA condensation system can be detected. Fluoride and chlorine both belong to the halogen family, but their effects on spermine-DNA condensation system are totally different. Fluoride ions make blue-shift and hyperchromicity appear in the spermine-DNA condensation system, but chlorine ions only make insignificant hyperchromicity happen in this system. Both fluoride ions and chlorine ions only make insignificant hyperchromicity happen in spermidine-DNA condensation system. Based on the distinguished character of fluoride, a fluoride-sensor for "kink" structure in DNA condensation was developed and the second kind of "kink" structure only appear in the spermine-DNA condensation system.

  16. Revealing the dark side of a bright exciton–polariton condensate

    PubMed Central

    Ménard, J. -M.; Poellmann, C.; Porer, M.; Leierseder, U.; Galopin, E.; Lemaître, A.; Amo, A.; Bloch, J.; Huber, R.

    2014-01-01

    Condensation of bosons causes spectacular phenomena such as superfluidity or superconductivity. Understanding the nature of the condensed particles is crucial for active control of such quantum phases. Fascinating possibilities emerge from condensates of light–matter-coupled excitations, such as exciton–polaritons, photons hybridized with hydrogen-like bound electron–hole pairs. So far, only the photon component has been resolved, while even the mere existence of excitons in the condensed regime has been challenged. Here we trace the matter component of polariton condensates by monitoring intra-excitonic terahertz transitions. We study how a reservoir of optically dark excitons forms and feeds the degenerate state. Unlike atomic gases, the atom-like transition in excitons is dramatically renormalized on macroscopic ground state population. Our results establish fundamental differences between polariton condensation and photon lasing and open possibilities for coherent control of condensates. PMID:25115964

  17. Detecting Chromosome Condensation Defects in Gulf War Illness Patients.

    PubMed

    Liu, Guo; Ye, Christine J; Chowdhury, Saroj K; Abdallah, Batoul Y; Horne, Steven D; Nichols, Denise; Heng, Henry H

    2018-04-01

    Gulf War Illness (GWI) impacts 25-30% of gulf war veterans. Due to its heterogeneity in both etiology and symptoms, it has been challenging to establish the commonly accepted case definition for GWI. Equally challenging are the understanding of the general mechanism of GWI and the development of biomarkers useful for its clinical diagnosis and treatment. We have observed that chromosome condensation defects can be detected in GWI patients. To document this phenomenon in GWI, we aim to describe and compare different types of chromosomal condensation defects in GWI patients, if possible. Since chromosomal condensation represents an important step of ensuring genome integrity, condensation defects could be used as a potential biomarker of GWI. Lymphocytes from GWI patients have been used for short term cell culture followed by chromosome slide preparation. Both Giemsa staining and multiple color spectral karyotyping (SKY) were applied to study chromosome aberrations, focusing on different types of condensation defects. At least three subtypes of Defective Mitotic Figures (DMFs) were observed. Some individuals displayed elevated frequencies of DMFs. Another type of condensation defect identified as sticky chromosomes were also observed. Various types of condensation defects have been observed in GWI patients. It is rather surprising that some GWI patients exhibited a high level of chromosomal condensation defects. Previously, the elevated frequency of DMFs was only observed in cancer patients. Since chromosome condensation can be linked to other types of chromosome aberrations, as well as cellular stress conditions, the detailed mechanism and clinical impact should be further studied, especially with increased sample size.

  18. Automatized Assessment of Protective Group Reactivity: A Step Toward Big Reaction Data Analysis.

    PubMed

    Lin, Arkadii I; Madzhidov, Timur I; Klimchuk, Olga; Nugmanov, Ramil I; Antipin, Igor S; Varnek, Alexandre

    2016-11-28

    We report a new method to assess protective groups (PGs) reactivity as a function of reaction conditions (catalyst, solvent) using raw reaction data. It is based on an intuitive similarity principle for chemical reactions: similar reactions proceed under similar conditions. Technically, reaction similarity can be assessed using the Condensed Graph of Reaction (CGR) approach representing an ensemble of reactants and products as a single molecular graph, i.e., as a pseudomolecule for which molecular descriptors or fingerprints can be calculated. CGR-based in-house tools were used to process data for 142,111 catalytic hydrogenation reactions extracted from the Reaxys database. Our results reveal some contradictions with famous Greene's Reactivity Charts based on manual expert analysis. Models developed in this study show high accuracy (ca. 90%) for predicting optimal experimental conditions of protective group deprotection.

  19. Mechanism insight into the cyanide-catalyzed benzoin condensation: a density functional theory study.

    PubMed

    He, Yunqing; Xue, Ying

    2010-09-02

    The reaction mechanism of the cyanide-catalyzed benzoin condensation without protonic solvent assistance has been studied computationally for the first time employing the density functional theory (B3LYP) method in conjunction with 6-31+G(d,p) basis set. Four possible pathways have been investigated. A new proposed pathway on the basis of the Lapworth mechanism is determined to be the dominant pathway in aprotic solvent, in which the formation of the Lapworth's cyanohydrin intermediate is a sequence including three steps assisted by benzaldehyde, clearly manifesting that the reaction can take place in aprotic solvents such as DMSO. In this favorable pathway with six possible transition states located along the potential energy surface, the reaction of the cyanide/benzaldehyde complex with another benzaldehyde to afford an alpha-hydroxy ether is the rate-determining dynamically with the activation free energy barrier of 26.9 kcal/mol, and the step to form cyanohydrin intermediate from alpha-hydroxy ether is partially rate-determining for its relatively significant barrier 20.0 kcal/mol.

  20. 40 CFR 405.110 - Applicability; description of the condensed whey subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... condensed whey subcategory. 405.110 Section 405.110 Protection of Environment ENVIRONMENTAL PROTECTION... Condensed Whey Subcategory § 405.110 Applicability; description of the condensed whey subcategory. The... whey and condensed acid whey. ...