Sample records for mukaiyama aldol reactions

  1. Mukaiyama Aldol Reactions in Aqueous Media

    PubMed Central

    Kitanosono, Taku; Kobayashi, Sh?

    2013-01-01

    Mukaiyama aldol reactions in aqueous media have been surveyed. While the original Mukaiyama aldol reactions entailed stoichiometric use of Lewis acids in organic solvents under strictly anhydrous conditions, Mukaiyama aldol reactions in aqueous media are not only suitable for green sustainable chemistry but are found to produce singular phenomena. These findings led to the discovery of a series of water-compatible Lewis acids such as lanthanide triflates in 1991. Our understanding on these beneficial effects in the presence of water will be deepened through the brilliant examples collected in this review. 1 Introduction 2 Rate Enhancement by Water in the Mukaiyama Aldol Reaction 3 Lewis Acid Catalysis in Aqueous or Organic Solvents 3.1 Water-Compatible Lewis Acids 4 Lewis-Base Catalysis in Aqueous or Organic Solvents 5 The Mukaiyama Aldol Reactions in 100% Water 6 Asymmetric Catalysts in Aqueous Media and Water 7 Conclusions and Perspective PMID:24971045

  2. Chiral Brønsted Acid as a True Catalyst: Asymmetric Mukaiyama Aldol and Hosomi-Sakurai Allylation Reactions.

    PubMed

    Sai, Masahiro; Yamamoto, Hisashi

    2015-06-10

    Highly diastereo- and enantioselective Mukaiyama aldol reaction catalyzed by a new chiral Brønsted acid, N-(perfluorooctanesulfonyl)thiophosphoramide, is described. The perfluorooctyl substituent on the sulfonyl group of the catalyst plays an essential role in the stereoselection. The catalyst also allows the asymmetric Hosomi-Sakurai allylation, which has been considerably challenging due to the low reactivity of allylsilanes. (29)Si and (31)P NMR monitoring reveals the characteristic feature of the thiophosphoramide catalyst, acting as a strong Brønsted acid even in the presence of excess silyl nucleophiles, which cannot be found in other related phosphoric acid analogues. PMID:26017677

  3. Efficient Mukaiyama aldol reaction in water with TiO4 tetrahedra on a hydrophobic mesoporous silica surface.

    PubMed

    Shintaku, Hiroshi; Nakajima, Kiyotaka; Kitano, Masaaki; Hara, Michikazu

    2014-11-14

    A new heterogeneous catalyst, hydrophobic TiO4-deposited mesoporous silica, has been designed for the efficient Mukaiyama-aldol condensation, a water-participating Lewis acid-catalyzed reaction between a hydrophobic carbonyl compound and silyl enol ether. The prepared catalyst suspended in water exhibited high catalytic performance as a reusable catalyst for the reaction without a surfactant. PMID:25234202

  4. Pushing the boundaries of vinylogous reactivity: catalytic enantioselective mukaiyama aldol reactions of highly unsaturated 2-silyloxyindoles.

    PubMed

    Curti, Claudio; Sartori, Andrea; Battistini, Lucia; Brindani, Nicoletta; Rassu, Gloria; Pelosi, Giorgio; Lodola, Alessio; Mor, Marco; Casiraghi, Giovanni; Zanardi, Franca

    2015-04-20

    The first example of catalytic, enantioselective hypervinylogous Mukaiyama aldol reaction (HVMAR) involving multiply unsaturated 2-silyloxyindoles is reported. The reaction utilizes a chiral Lewis base-catalyzed Lewis acid-mediated technology to deliver homoallylic 3-polyenylidene 2-oxindoles with extraordinary levels of regio-, enantio-, and geometrical selectivity. This work highlights a subtle yet decisive influence of the indole N-substituents on the propagation of the vinylogous reactivity space of the donor substrates up to ten bonds away from the origin of the vinylogy effect. Analysis of the (13) C NMR chemical shifts of the C-? remote site within homologous silyloxyindole donors enabled rationalization of the results and easy qualitative prediction of the HVMAR reactivity/inertia toward a given aldehyde acceptor. PMID:25735832

  5. Comparison of Cu-ZSM-5 zeolites and Cu-MOF-505 metal-organic frameworks as heterogeneous catalysts for the Mukaiyama aldol reaction: a DFT mechanistic study.

    PubMed

    Yadnum, Sudarat; Choomwattana, Saowapak; Khongpracha, Pipat; Sirijaraensre, Jakkapan; Limtrakul, Jumras

    2013-04-01

    The density functional theory (DFT) model ONIOM(M06L/6-311++G(2df,2p):UFF was employed to reveal the catalytic activity of Cu(II) in the paddle-wheel unit of the metal-organic framework (MOF)-505 material in the Mukaiyama aldol reaction compared with the activity of Cu-ZSM-5 zeolites. The aldol reaction between a silyl enol ether and formaldehyde catalyzed by the Lewis acidic site of both materials takes place through a concerted pathway, in which the formation of the C?C bond and the transfer of the silyl group occurs in a single step. MOF-505 and Cu-ZSM-5 are predicted to be efficient catalysts for this reaction as they strongly activate the formaldehyde carbonyl carbon electrophile, which leads to a considerably lower reaction barrier compared with the gas-phase system. Both MOF-505 and Cu-ZSM-5 catalysts stabilize the reacting species along the reaction coordinate, thereby lowering the activation energy, compared to the gas-phase system. The activation barriers for the MOF-505, Cu-ZSM-5, and gas-phase system are 48, 21, and 61 kJ?mol(-1) , respectively. Our results show the importance of the enveloping framework by stabilizing the reacting species and promoting the reaction. PMID:23436681

  6. A novel, efficient, diastereo- and enantioselective Mukaiyama aldol-based synthesis of a vinyl cyclopentanone core derivative of viridenomycin.

    PubMed

    Batsanov, Andrei S; Knowles, Jonathan P; Lightfoot, Andrew P; Maw, Graham; Thirsk, Carl E; Twiddle, Steven J R; Whiting, Andrew

    2007-12-20

    A strategy has been developed for a rapid seven-step construction of a chiral, nonracemic vinyl cyclopentanone building block as part of a synthetic approach to viridenomycin, using a diastereo- and enantioselective Mukaiyama aldol and intramolecular Knoevenagel condensation as key steps. PMID:18020354

  7. Development of Stereoselective Vinylogous Mukaiyama Aldol Reaction

    E-print Network

    Strathclyde, University of

    H Madindoline A O Me HO Me OH Me Me CHO Citreoviral Khafrefungin OH O O O Me O MeMe CH3(CH2)9 Me OH Debromoflustramine B O O HO O O O OH OMe OH OHOH Me OH OHMeMeMe Me MeMe Me Me OOH O OH HO CO2H O OHO HO OHHO O Me H H O OH OH OH OH OH O O HO HO HO OH O O Me O MeMe C10H21 Me OH Me Me HO OH CO2H OH N H O Br Br OH OH N

  8. The Direct Catalytic Asymmetric Aldol Reaction

    PubMed Central

    Brindle, Cheyenne S.

    2013-01-01

    Asymmetric aldol reactions are a powerful method for the construction of carbon-carbon bonds in an enantioselective fashion. Historically this reaction has been performed in a stoichiometric fashion to control the various aspects of chemo-, diastereo-, regio- and enantioselectivity, however, a more atom economical approach would unite high selectivity with the use of only a catalytic amount of a chiral promoter. This critical review documents the development of direct catalytic asymmetric aldol methodologies, including organocatalytic and metal-based strategies. New methods have improved the reactivity, selectivity and substrate scope of the direct aldol reaction and enabled the synthesis of complex molecular targets PMID:20419212

  9. N-acyl oxazolidin-2-selones promoted aldol reactions

    SciTech Connect

    Li, Zizhong; Wu, R. (Ruilian); Silks, L. A. (Louis A.), III; Michalczyk, R. (Ryszard)

    2001-01-01

    Selenocarbonyls that are housed in a chiral environment have been found to play a pivotal role aldol reactions. We have found that, in general,, the aldol reaction affords the non-Evans aldol syn products. However, the use of glycolate donors with glycoaldehydes, under proper conditions, gave rise to predominately the anti aldol.

  10. Samarium Ion-Promoted Cross-Aldol Reactions and Tandem Aldol/Evans-Tishchenko Reactions.

    PubMed

    Lu, Ling; Chang, Hung-Yu; Fang, Jim-Min

    1999-02-01

    Cross-aldol reactions of carbonyl compounds were achieved by the catalysis of SmI(2) or SmI(3), together with molecular sieves, at ambient temperature. 1,3-Dichloroacetone and 1-chloroacetone can be used as acceptor substrates in the cross-aldol reactions with donor substrates such as acetone, cyclopentanone, and cyclohexanone. The cross-aldol reactions with (R)-glyceraldehyde acetonide gave optically pure compounds 25-32, the stereochemistry of which was in agreement with a chairlike chelate transition state of dipolar mode. SmI(2)-molecular sieves or SmI(3)-molecular sieves also functioned as effective Lewis acids to catalyze tandem aldol/Evans-Tishchenko reactions. The aldol/Evans-Tishchenko reactions of methyl ketones with aldehydes occurred at 0 degrees C to give alpha,gamma-anti diol monoesters 53a-59a. When the reactions were conducted at room temperature, a certain degree of transesterification took place. The aldol/Evans-Tishchenko reactions of ethyl or benzyl ketones with aldehydes yielded alpha,beta-anti-alpha,gamma-anti diol monoesters 60a-65a. However, the aldol/Evans-Tishchenko reactions of cyclic ketones with benzaldehyde occurred with a different stereoselectivity to give alpha,beta-syn-alpha,gamma-anti diol monoesters 66a-76a. The structures of products were determined by chemical and spectroscopic methods including an X-ray diffraction analysis of 72a derived from the reaction of 4-tert-butylcyclohexanone and benzaldehyde. A reaction mechanism involving dissociation-recombination of aldols followed by intramolecular stereoselective hydride shift is proposed, based on some experimental evidence, to explain the dichotomous stereoselectivity using acyclic or cyclic ketones as the reaction substrates. PMID:11674156

  11. Aldol Reactions - Isotope Effects, Mechanism and Dynamic Effects 

    E-print Network

    Vetticatt, Mathew J.

    2011-02-22

    The mechanism of three important aldol reactions and a biomimetic transamination is investigated using a combination of experimental kinetic isotope effects (KIEs), standard theoretical calculations and dynamics ...

  12. Anti-Selective Aldol Reactions with Titanium Enolates of

    E-print Network

    Anti-Selective Aldol Reactions with Titanium Enolates of N-Glycolyloxazolidinethiones Michael T-glycolyloxazolidinethiones has been developed. Enolization of an N-glycolyloxazolidinethione with titanium (IV) chloride successful with a wide variety of aldehydes and protecting groups.2 Additionally, the titanium enolates of N

  13. Investigating ionic effects applied to water based organocatalysed aldol reactions.

    PubMed

    Delaney, Joshua P; Henderson, Luke C

    2011-01-01

    Saturated aqueous solutions of various common salts were examined for their effect on aqueous aldol reactions catalysted by a highly active C(2)-symmetric diprolinamide organocatalyst developed in our laboratory. With respect to the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde, deionised water was always a superior medium to salt solutions though some correlation to increasing anion size and depression in enantiomeric excess could be observed. Additionally, the complete inhibition of catalyst activity observed when employing tap water could be alleviated by the inclusion of ethylenediaminetetraacetate (EDTA) into the aqueous media prior to reaction initiation. Extension of these reaction conditions demonstrated that these ionic effects vary on a case-to-case basis depending on the ketone/aldehyde combination. PMID:22272120

  14. Investigating Ionic Effects Applied to Water Based Organocatalysed Aldol Reactions

    PubMed Central

    Delaney, Joshua P.; Henderson, Luke C.

    2011-01-01

    Saturated aqueous solutions of various common salts were examined for their effect on aqueous aldol reactions catalysted by a highly active C2-symmetric diprolinamide organocatalyst developed in our laboratory. With respect to the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde, deionised water was always a superior medium to salt solutions though some correlation to increasing anion size and depression in enantiomeric excess could be observed. Additionally, the complete inhibition of catalyst activity observed when employing tap water could be alleviated by the inclusion of ethylenediaminetetraacetate (EDTA) into the aqueous media prior to reaction initiation. Extension of these reaction conditions demonstrated that these ionic effects vary on a case-to-case basis depending on the ketone/aldehyde combination. PMID:22272120

  15. Chlorine, an atom economical auxiliary for asymmetric aldol reactions.

    PubMed

    Halperin, Shira D; Britton, Robert

    2013-02-13

    An auxiliary strategy has been developed for asymmetric reactions of aldehydes in which the auxiliary itself is not chiral, but a single chlorine atom introduced via organocatalytic ?-chlorination. The stereodirecting influence of the chlorine atom is then exploited prior to its removal by radical reduction. This strategy is demonstrated in the synthesis of several aldols (92-99% ee) and the natural products (+)-dihydroyashabushiketol and (+)-solistatin. PMID:23370443

  16. Chiral picolylamines for Michael and aldol reactions: probing substrate boundaries.

    PubMed

    Nugent, Thomas C; Bibi, Ahtaram; Sadiq, Abdul; Shoaib, Mohammad; Umar, M Naveed; Tehrani, Foad N

    2012-12-14

    Here we report on inroads concerning increased substrate breadth via the picolylamine organocatalyst template, a vicinal chiral diamine based on a pyridine-primary amine motif. The addition of cyclohexanone to ?-nitrostyrene has many catalyst solutions, but cyclopentanone and isobutyraldehyde additions continue to be challenging. PicAm-3 (10 mol%) readily allows the Michael addition of cyclopentanone or isobutyraldehyde (5.0 equiv.) to ?-nitrostyrene derivatives. By contrast, PicAm-1 (7.0 mol%) is optimal for catalyzing the aldol reaction of cyclohexanone or cycloheptanone (3.3 equiv.) with aromatic aldehydes. Eighteen products are reported and for each reaction type new products are reported (4b-d, 9c). Very good yields and stereoselectivities are generally noted. The reactions, which require an acid additive, proceed via a transient chiral enamine and a mechanistic case is put forth for a bifunctional catalysis model. PMID:23104278

  17. Method of carbon chain extension using novel aldol reaction

    SciTech Connect

    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.

  18. 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.

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

    Microsoft Academic Search

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

    2010-01-01

    The origin of the single chirality of most biomolecules is still a great puzzle. Carbohydrates could form in the formose reaction,\\u000a which is proposed to be autocatalytic and contains aldol reaction steps. Based on our earlier observation of organoautocatalysis\\u000a and spontaneous enantioenrichment in absence of deliberate chiral influences in the aldol reaction of acetone and p-nitrobenzaldehyde\\u000a we suggest that a

  20. A highly efficient organocatalyst for direct aldol reactions of ketones with aldehydes [corrected].

    PubMed

    Tang, Zhuo; Yang, Zhi-Hua; Chen, Xiao-Hua; Cun, Lin-Feng; Mi, Ai-Qiao; Jiang, Yao-Zhong; Gong, Liu-Zhu

    2005-06-29

    L-proline amides derived from various chiral beta-amino alcohols that bear substituents with various electron natures at their stereogenic centers are prepared and evaluated for catalyzing the direct Aldol reaction of 4-nitrobenzaldehyde with acetone. Catalysts with strong electron-withdrawing groups are found to exhibit higher catalytic activity and enantioselectivity than their analogues with electron-donating groups. The presence of 2 mol % catalyst 4g significantly catalyzes the direct Aldol reactions of a wide range of aldehydes with acetone and butanone, to give the beta-hydroxy ketones with very high enantioselectivities ranging from 96% to >99% ee. High diastereoselectivity of 95/5 was observed for the anti Aldol product from the reaction of cyclohexanone, and excellent enantioselectivity of 93% ee was provided for anti Aldol product from the reaction of cyclopentanone. PMID:15969611

  1. Asymmetric reductive aldol-type reaction with carbonyl compounds using dialkyl tartrate as a chiral ligand.

    PubMed

    Isoda, Motoyuki; Sato, Kazuyuki; Tokura, Yoriko; Tarui, Atsushi; Omote, Masaaki; Ando, Akira

    2014-01-01

    An asymmetric reductive aldol-type reaction of ?,?-unsaturated esters with carbonyl compounds using Rh catalyst and Et2Zn was investigated. A chiral zinc complex from ?,?-unsaturated ester was easily generated as the key intermediate from Et2Zn and Wilkinson's catalyst with diisopropyl L-(+)-tartrate to give a variety of enantioenriched ?-hydroxy esters. The reaction was also applied to the intramolecular reductive aldol cyclization. PMID:25273054

  2. Developing novel organocatalyzed aldol reactions for the enantioselective synthesis of biologically active molecules

    PubMed Central

    Bhanushali, Mayur; Zhao, Cong-Gui

    2011-01-01

    Aldol reaction is one of the most important methods for the formation of carbon-carbon bonds. Because of its significance and usefulness, asymmetric versions of this reaction have been realized with different approaches in the past. Over the last decade, the area of organocatalysis has made significant progresses. As one of most studied reactions in organocatalyses, organocatalyzed aldol reaction has emerged as a powerful tool for the synthesis of a large number of useful products in optically enriched forms. In this review, we summarize our efforts on the development of novel organocatalyzed aldol reactions for the enantioselective synthesis of biological active molecules. Literatures closely related to our studies are also covered. PMID:21918584

  3. Synthesis of non-racemic ?-hydroxyphosphonates via asymmetric phospho-aldol reaction.

    PubMed

    Spilling, Christopher D; Malla, Raj K

    2015-01-01

    It has been more than 50 years since the first phospho-aldol reactions of dialkyl phosphites were reported. These efficient P-C bond-forming reactions have become the cornerstone of methods for the synthesis of ?-hydroxyphosphonates and, by numerous available substitution reactions, the synthesis of other ?- and ?-substituted phosphonates and phosphonic acids. Much of the interest in ?- and ?-substituted phosphonates and phosphonic acids has been stimulated by reports of their biological activity, which is often dependent upon their absolute and relative stereochemistry. In this chapter, we review diastereoselective and enantioselective additions of dialkyl phosphites to aldehydes and ketones, otherwise called the phospho-aldol, Pudovik or Abramov reactions. PMID:25467537

  4. Rapid and Efficient Functionalized Ionic Liquid-Catalyzed Aldol Condensation Reactions Associated with Microwave Irradiation

    PubMed Central

    Wang, Chang; Liu, Jing; Leng, Wenguang; Gao, Yanan

    2014-01-01

    Five quaternary ammonium ionic liquid (IL) and two tetrabutylphosphonium ILs were prepared and characterized. An environmentally benign and convenient functionalized ionic liquid catalytic system was thus explored in the aldol condensation reactions of aromatic aldehydes with acetone. The aldol reactions proceeded more efficiently through microwave-assisted heating than through conventional thermal heating. The yield of products obtained under microwave heating for 30 min was approximately 90%, and the ILs can be recovered and reused at least five times without apparent loss of activity. In addition, this catalytic system can be successfully extended to the Henry reactions. PMID:24445262

  5. Hydrophobic Substituent Effects on Proline Catalysis of Aldol Reactions in Water

    PubMed Central

    Zhao, Qingquan; Lam, Yu-hong; Kheirabadi, Mahboubeh; Xu, Chongsong; Houk, K. N.

    2013-01-01

    Derivatives of 4-hydroxyproline with a series of hydrophobic groups in well-defined orientations have been tested as catalysts for the aldol reactions. All of the modified proline catalysts carry out the intermolecular aldol reaction in water and provide high diastereoselectivity and enantioselectivity. Modified prolines with aromatic groups syn to the carboxylic acid are better catalysts than those with small hydrophobic groups (1a is 43.5 times faster than 1f). Quantum mechanical calculations provide transition structures, TS-1awater and TS-1fwater that support the hypothesis that a stabilizing hydrophobic interaction occurs with 1a. PMID:22500641

  6. Aldol reaction catalyzed by a hydrophilic catalyst in aqueous micelle as an enzyme mimic system.

    PubMed

    Zhang, Hefeng; Zhao, Wenshan; Zou, Jun; Liu, Yi; Li, Runtao; Cui, Yuanchen

    2009-05-01

    Chitosan-supported L-proline complex was synthesized and applied as a catalyst for the direct asymmetric aldol reaction in various organic solvents and water as well. It was found that the novel synthesized catalyst was able to efficiently catalyze the aldol reaction in various media. The catalytic capacity and stereoselectivity of the catalyst were obviously improved with the introduction of aqueous micelle, possibly because the micelle functioned as a hydrophobic pocket, like the hydrophobic portion in enzymes. Moreover, the present synthetic catalyst showed performance similar to that of enzymes and could be used as a model of enzyme catalysis to help better understand the mystic mechanism of enzymes. PMID:18655166

  7. 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...

  8. Organocatalytic enantioselective tandem aldol-cyclization reaction of ?-isothiocyanato imides and activated carbonyl compounds

    PubMed Central

    Guang, Jie; Zhao, Cong-Gui

    2011-01-01

    The organocatalytic enantioselective tandem aldol-cyclization reactions of ?-isothiocyanato imides and activated carbonyl compounds, such as isatins, an ?-ketolactone and a 1,2-dione, have been studied with cinchona alkaloid-derived thiourea-catalysts. This methodology provided an easy way to access enantiomerically enriched spirobicyclic thiocarbamates with high yields and good to excellent stereoselectivity, which have been demonstrated to be useful precursors for the synthesis of biologically active molecules. PMID:21921975

  9. Solvent-Induced Reversal of Activities between Two Closely Related Heterogeneous Catalysts in the Aldol Reaction

    SciTech Connect

    Kandel, Kapil [Ames Laboratory; Althaus, Stacey M [Ames Laboratory; Peeraphatdit, Chorthip [Ames Laboratory; Kobayashi, Takeshi [Ames Laboratory; Trewyn, Brian G [Ames Laboratory; Pruski, Marek [Ames Laboratory; Slowing, Igor I [Ames Laboratory

    2013-01-11

    The relative rates of the aldol reaction catalyzed by supported primary and secondary amines can be inverted by 2 orders of magnitude, depending on the use of hexane or water as a solvent. Our analyses suggest that this dramatic shift in the catalytic behavior of the supported amines does not involve differences in reaction mechanism, but is caused by activation of imine to enamine equilibria and stabilization of iminium species. The effects of solvent polarity and acidity were found to be important to the performance of the catalytic reaction. This study highlights the critical role of solvent in multicomponent heterogeneous catalytic processes.

  10. Aldol Reactions - Isotope Effects, Mechanism and Dynamic Effects

    E-print Network

    Vetticatt, Mathew J.

    2011-02-22

    of acetaldehyde and the enamine of acetone. 43 The critical features of this surface are 1. the minimum-energy path involves mainly heavy-atom motion as the geometry approaches and passes through the saddle point, and 2. the orthogonal O-H stretching-type mode... and formaldehyde ............................................................................. 70 TS for reaction of 38 and acetaldehyde .............................................................................. 71 S3 TS for reaction of 38 and acetaldehyde...

  11. Organocatalyzed enantioselective aldol reaction of 1H-pyrrole-2,3-diones

    PubMed Central

    Bhanushali, Mayur

    2011-01-01

    The enantioselective cross aldol reaction of 1-benzyl 4,5-dioxo-2-aryl-4,5-dihydro-1H-pyrrole-3-carboxylates and ketones was studied with proline derivatives or cinchona alkaloid-derived primary amines as the catalysts for the first time. trans-4-Benzoyloxy-L-proline (15) was found to be the best catalyst for acyclic ketones. For cyclohexanone, the best results were achieved with 9-deoxy-9-epi-aminoquinine (18) as the catalyst in the presence of racemic 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (19) as the cocatalyst. Using these protocols, 3-alkyl-3-hydroxy-1H-pyrrol-2(3H)-one derivatives were obtained in excellent yields and good to high ee values (up to 94% ee). PMID:22544980

  12. Direct Access to 6/5/7/5- and 6/7/5/5-Fused Tetracyclic Triterpenoids via Divergent Transannular Aldol Reaction of Lanosterol-Derived Diketone

    PubMed Central

    Ignatenko, Vasily A.; Han, Yong

    2013-01-01

    In an effort to access biologically relevant chemical space, a complex natural product-derived non-symmetrical diketone was prepared as a substrate for divergent transannular aldol reactions. The use of common aldol conditions resulted in predominant syn-addition via pathway a, while the use of alumina provided access to the anti-adduct. Screening of a range of Lewis acids of varying strength unexpectedly resulted in the formation of aldol products with 6/7/5/5-fused molecular skeleton via pathway b. PMID:24161022

  13. Reagent control in the aldol addition reaction of chiral boron enolates with chiral aldehydes. Total synthesis of (3 S,4 S)-Statine

    Microsoft Academic Search

    Cesare Gennari; Daniela Moresca; Anna Vulpetti; Gilles Pain

    1997-01-01

    Boron enolates bearing menthone-derived chiral ligands are capable of fair to excellent diastereocontrol in their reactions with chiral aldehydes. Thioester-derived (better than ketone derived) enolates are able to control aldol stereochemistry irrespective of the aldehyde preferences. With thioacetate-derived chiral enolates and enantiopure N,N-dibenzyl ?-amino aldehydes, either the 3,4-anti or the 3,4-syn aldol adduct can be obtained with very high diastereoselectivity

  14. 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 ?-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. PMID:25640727

  15. Highly Stereoselective and Scalable anti-Aldol Reactions using N-(p-dodecylphenylsulfonyl)-2-Pyrrolidinecarboxamide: Scope and Origins of Stereoselectivities

    PubMed Central

    Yang, Hua; Mahapatra, Subham; Cheong, Paul Ha-Yeon; Carter, Rich G.

    2010-01-01

    A highly enantio- and diastereoselective anti-aldol process (up to >99% ee, >99:1 dr) catalyzed by a proline mimetic – N-(p-dodecylphenylsulfonyl)-2-pyrrolidinecarboxamide – has been developed. Catalyst loading as low as 2 mol% can be employed. Use of industry-friendly solvents for this transformation as well as neat reaction conditions have been demonstrated. The scope of this transformation on a range of aldehydes and ketones is explored. Density Functional Theory computations reveal that the origins of enhanced diastereoselectivity is due to the presence of non-classical hydrogen bonds between the sulfonamide, the electrophile and the catalyst enamine that favor the major Anti-Re aldol TS in the Houk-List model. PMID:20932013

  16. Catalytic anions embedded into avidin: importance of their chirality and the chiral environment on the stereocontrol of the aldol reaction.

    PubMed

    Gauchot, Vincent; Schmitzer, Andreea R

    2014-03-21

    Several catalytic anions bearing a pseudo-dipeptide scaffold, in combination with a biotinylated imidazolium cation, were prepared. The assembly of these salts with avidin resulted in the formation of stable biohybrid catalysts, active in ionic liquid/aqueous media for the aldol reaction. By using natural and non-natural amino alcohols as "side chains" for the proline derivative anion, we studied the cooperativity between the anion and its position in avidin. Taking advantage of the large freedom of movement of the anion inside avidin, we also investigated the substrate scope of this type of biohybrid catalyst. PMID:24559501

  17. Highly enantio- and diastereoselective boron aldol reactions of ?-heterosubstituted thioacetates with aldehydes and silyl imines

    Microsoft Academic Search

    Cesare Gennari; Anna Vulpetti; Gilles Pain

    1997-01-01

    Boron enolates derived from ?-heterosubstituted thioacetates and bearing menthone-derived chiral ligands react with aldehydes to give anti aldols with excellent diastero- and enantiocontrol. Boron enolates derived from tert-butyl ?-halothioacetate and bearing menthone-derived chiral ligands react with imines with excellent diastero- and enantiocontrol to give syn ?-halo-?-aminothioesters, which can be converted to the corresponding aziridines by simple ring closure during LAH

  18. Unexpected Synthesis of 5,6-Dihydropyridin-2(1H)-ones by a Domino Ugi/Aldol/Hydrolysis Reaction Starting from Baylis-Hillman Phosphonium Salts.

    PubMed

    Zeng, Xiao-Hua; Wang, Hong-Mei; Ding, Ming-Wu

    2015-05-01

    A one-pot synthetic approach to 5,6-dihydropyridin-2(1H)-ones has been developed using a domino process involving Ugi, aldol, and hydrolysis reactions, starting with Baylis-Hillman phosphonium salts, primary amines, isocyanides, and arylglyoxals. PMID:25875533

  19. A Combined DFT and NMR Investigation of the Zinc Organometallic Intermediate Proposed in the Syn-Selective Tandem Chain Extension-Aldol Reaction of ?-Keto Esters

    PubMed Central

    Aiken, Karelle S.; Eger, Wilhelm A.; Williams, Craig M.; Spencer, Carley M.

    2012-01-01

    The tandem chain extension-aldol (TCA) reaction of ?-keto esters provides a ?-substituted ?-keto ester with an average syn:anti selectivity of 10:1. It is proposed that the reaction proceeds via a carbon-zinc bound organometallic intermediate potentially bearing mechanistic similarity to the Reformatsky reaction. Evidence, derived from control Reformatsky reactions and a study of the structure of the TCA intermediate utilizing DFT methods and NMR-spectroscopy, suggests the ?-keto group of the TCA intermediate plays a significant role in diastereoselectivity observed in this reaction. Such coordination effects have design implications for future zinc mediated reactions. PMID:22703563

  20. Aromatic aldols and 1,5-diketones as optimized fragrance photocages.

    PubMed

    Griesbeck, Axel G; Hinze, Olga; Görner, Helmut; Huchel, Ursula; Kropf, Christian; Sundermeier, Uta; Gerke, Thomas

    2012-03-01

    Aromatic aldols and 1,5-diketones with abstractable ?-hydrogen atoms are highly photoactive cage molecules for the release of fragrance carbonyl compounds (aldehydes and Michael ketones, respectively). Aldols 3a-d are easily accessible by Mukaiyama addition and are cleaved to form the substrates with high quantum yields under solar radiation. By tuning the properties of the chromophores, a series of ?-damascone cages 5 were developed that can be used for selective and fast (5a,e) or slow (5b,d) release of fragrances under air and solar irradiation. The intermediates of the Norrish II process were observed by laser transient absorption spectroscopy. PMID:22322868

  1. Porous magnesium carboxylate framework: synthesis, X-ray crystal structure, gas adsorption property and heterogeneous catalytic aldol condensation reaction.

    PubMed

    Saha, Debraj; Sen, Rupam; Maity, Tanmoy; Koner, Subratanath

    2012-06-28

    A new three-dimensional alkaline-earth metal-organic framework (MOF) compound, [Mg(Pdc)(H(2)O)](n) (1) (H(2)Pdc = pyridine-2,5-dicarboxylic acid), has been synthesized and structurally characterized by single crystal X-ray diffraction analysis. Compound 1 features a 3D porous framework afforded by the Mg(2)-diad centers through formation of interconnected chair like structural motifs. A nitrogen adsorption study confirms the microporosity of compound 1 with a BET surface area of 211 ± 12 m(2) g(-1). Upon dehydration, the BET surface area of 1 is enhanced to a value of 463 ± 36 m(2) g(-1) due to removal of coordinated water molecule. After rehydration, the compound reverts to its original form as evidenced by powder X-ray diffraction and IR spectroscopic analysis and N(2) sorption measurement. Compound 1 retains its pore structure with a variable BET surface area in several cycles of dehydration and rehydration processes indicating robustness of the framework in [Mg(Pdc)(H(2)O)](n) (1). Compound 1 catalyzes the aldol condensation reactions of various aromatic aldehydes with acetone and cyclohexanone in heterogeneous conditions. Notably, the catalytic activity of the compound is enhanced upon dehydration. The catalyst can be recycled and reused several times without significant loss of activity. PMID:22584602

  2. 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…

  3. Acetaldehyde Aldol Condensation Kinetics J. 8. ANDERSON' and M. S. PETERS

    E-print Network

    Anderson, James B.

    Acetaldehyde Aldol Condensation Kinetics J. 8. ANDERSON' and M. S. PETERS University of Illinois, Urbana, 111. ACETALDEHYDEmay react to form aldol when- ever acetaldehyde and hydroxide ions are present reactions such as the formation of pentaerythrose. The mechanism of the acetaldehyde aldol reaction has been

  4. Evidence for the formation of an enamine species during aldol and Michael-type addition reactions promiscuously catalyzed by 4-oxalocrotonate tautomerase.

    PubMed

    Poddar, Harshwardhan; Rahimi, Mehran; Geertsema, Edzard M; Thunnissen, Andy-Mark W H; Poelarends, Gerrit J

    2015-03-23

    The enzyme 4-oxalocrotonate tautomerase (4-OT), which has a catalytic N-terminal proline residue (Pro1), can promiscuously catalyze various carbon-carbon bond-forming reactions, including aldol condensation of acetaldehyde with benzaldehyde to yield cinnamaldehyde, and Michael-type addition of acetaldehyde to a wide variety of nitroalkenes to yield valuable ?-nitroaldehydes. To gain insight into how 4-OT catalyzes these unnatural reactions, we carried out exchange studies in D2 O, and X-ray crystallography studies. The former established that H-D exchange within acetaldehyde is catalyzed by 4-OT and that the Pro1 residue is crucial for this activity. The latter showed that Pro1 of 4-OT had reacted with acetaldehyde to give an enamine species. These results provide evidence of the mechanism of the 4-OT-catalyzed aldol and Michael-type addition reactions in which acetaldehyde is activated for nucleophilic addition by Pro1-dependent formation of an enamine intermediate. PMID:25728471

  5. 2,4-Dinitrophenol as an effective cocatalyst: greatly improving the activities and enantioselectivities of primary amine organocatalysts for asymmetric aldol reactions.

    PubMed

    Da, Chao-Shan; Che, Li-Ping; Guo, Qi-Peng; Wu, Feng-Chun; Xiao Ma; Jia, Ya-Ning

    2009-03-20

    Seven primary amine organocatalysts 1a-g were readily prepared from natural primary amino acids via two steps and then were used to catalyze the direct asymmetric aldol reaction, but they showed very poor enantioselectivities and activities. As an effective cocatalyst, 2,4-dinitrophenol (DNP) dramatically elevated the activities and enantioselectivities of these very inefficient primary amine organocatalysts. This remedial course to the very inefficient organocatalysts by selection and employment of the optimal cocatalyst was particularly cost-effective and environment-beneficial compared with de novo development of catalysts. The highest efficient organocatalytic system that was composed of 1f and DNP showed high enantioselectivities and good to high diastereoselectivities with a broad spectrum of seven ketones. The linear ketones and cyclopentanone got predominant syn products whereas cyclohexanone mainly gave anti products. PMID:19249831

  6. Asymmetric aldol reactions between acetone and benzaldehydes catalyzed by chiral Zn2+ complexes of aminoacyl 1,4,7,10-tetraazacyclododecane: fine-tuning of the amino-acid side chains and a revised reaction mechanism.

    PubMed

    Itoh, Susumu; Tokunaga, Takuya; Sonoike, Shotaro; Kitamura, Masanori; Yamano, Akihito; Aoki, Shin

    2013-09-01

    We previously reported that chiral Zn(2+) complexes that were designed to mimic the actions of class-I and class-II aldolases catalyzed the enantioselective aldol reactions of acetone and its analogues thereof with benzaldehyde derivatives. Herein, we report the synthesis of new chiral Zn(2+) complexes that contain Zn(2+)-tetraazacyclododecane (Zn(2+)-[12]aneN4) moieties and amino acids that contain aliphatic, aromatic, anionic, cationic, and dipeptide side chains. The chemical and optical yields of the aldol reaction were improved (up to 96?% ee) by using ZnL complexes of L-decanylglycyl-pendant [12]aneN4 (L-ZnL(7)), L-naphthylalanyl-pendant [12]aneN4 (L-ZnL(10)), L-biphenylalanyl-pendant [12]aneN4 (L-ZnL(11)), and L-phenylethylglycyl-pendant [12]aneN4 ligands (L-ZnL(12)). UV/Vis and circular dichroism (CD) titrations of acetylacetone (acac) with ZnL complexes confirmed that a ZnL-(acac)(-) complex was exclusively formed and not the enaminone of ZnL and acac, as we had previously proposed. Moreover, the results of stopped-flow experiments indicated that the complexation of (acac)(-) with ZnL was complete within milliseconds, whereas the formation of an enaminone required several hours. X-ray crystal-structure analysis of L-ZnL(10) and the ZnL complex of L-diphenylalanyl-pendant [12]aneN4 (L-ZnL(13)) shows that the NH2 groups of the amino-acid side chains of these ligands are coordinated to the Zn(2+) center as the fourth coordination site, in addition to three nitrogen atoms of the [12]aneN4 rings. The reaction mechanism of these aldol reactions is discussed and some corrections are made to our previous mechanistic hypothesis. PMID:23780779

  7. Towards catalyst compartimentation in combined chemo- and biocatalytic processes: immobilization of alcohol dehydrogenases for the diastereoselective reduction of a ?-hydroxy ketone obtained from an organocatalytic aldol reaction.

    PubMed

    Rulli, Giuseppe; Heidlindemann, Marcel; Berkessel, Albrecht; Hummel, Werner; Gröger, Harald

    2013-11-01

    The alcohol dehydrogenases (ADHs) from Lactobacillus kefir and Rhodococcus sp., which earlier turned out to be suitable for a chemoenzymatic one-pot synthesis with organocatalysts, were immobilized with their cofactors on a commercially available superabsorber based on a literature known protocol. The use of the immobilized ADH from L. kefir in the reduction of acetophenone as a model substrate led to high conversion (>95%) in the first reaction cycle, followed by a slight decrease of conversion in the second reaction cycle. A comparable result was obtained when no cofactor was added although a water rich reaction media was used. The immobilized ADHs also turned out to be suitable catalysts for the diastereoselective reduction of an organocatalytically prepared enantiomerically enriched aldol adduct, leading to high conversion, diastereomeric ratio and enantioselectivity for the resulting 1,3-diols. However, at a lower catalyst and cofactor amount being still sufficient for biotransformations with "free" enzymes the immobilized ADH only showed high conversion and >99% ee for the first reaction cycle whereas a strong decrease of conversion was observed already in the second reaction cycle, thus indicating a significant leaching effect of catalyst and/or cofactor. PMID:24036136

  8. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) an efficient homogeneous catalyst for aldol condensation reactions. Study of the catalyst recovery and reusability using CO 2

    Microsoft Academic Search

    Iuliana Cota; Francisco Medina; Jesús E. Sueiras; Didier Tichit

    2011-01-01

    In this work it was shown that TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene), a cheap and commercially available guanidine base, efficiently catalyzes aldol condensation reactions yielding interesting products for pharmacological and fragrance industries. This methodology works under solvent-less conditions and affords with very good conversions the corresponding products. Moreover, a simple and effective separation protocol using the CO2 fixation was employed. The catalyst could

  9. 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…

  10. Aldol derivatives of Thioxoimidazolidinones as potential anti-prostate cancer agents.

    PubMed

    Khatik, Gopal L; Kaur, Jasmine; Kumar, Varun; Tikoo, Kulbhushan; Venugopalan, P; Nair, Vipin A

    2011-08-01

    The paper discusses the synthesis and stereochemical aspects of the anti aldol products, 3-(substituted phenyl)-5-[(substituted phenyl) hydroxy methyl]-5-methyl-4-oxo-2-thioxoimidazolidines. The stereochemistry observed in the aldol reactions with benzaldehydes was explained by transition state model of the endocyclic (E)-enolate formed from the rigid 4-oxo-2-thioxoimidazolidine skeleton. Proton NMR and ROESY spectral analyses were carried out to identify the syn and anti conformations of the aldol diastereomers. Configurations of the enantiomers of the representative anti aldol product 3-(4-chlorophenyl)-5-[(4-chlorophenyl) hydroxy methyl]-5-methyl-4-oxo-2-thioxoimidazolidine was determined by single crystal XRD studies. The compounds were screened in vitro against prostate cancer cell lines, PC-3 and LNCaP and the most potent derivatives were identified. PMID:21600678

  11. Total synthesis of (-)-goniotrionin.

    PubMed

    Dias, Luiz C; Ferreira, Marco A B

    2012-04-20

    A stereoselective total synthesis of the reported structure of goniotrionin (4) has been accomplished. The key steps involved the opening of a chiral epoxide, a highly diastereoselective Mukaiyama aerobic oxidative cyclization, a selective 1,2-syn Mukaiyama aldol reaction, and a Noyori reduction. PMID:22443275

  12. A highly efficient and eco-friendly method for the synthesis of 1,3-indandione ring-fused 3-oxindoles bearing two contiguous quaternary stereocenters via an aldol reaction in aqueous media.

    PubMed

    Liu, Xiong-Li; Pan, Bo-Wen; Zhang, Wen-Hui; Yang, Chao; Yang, Jun; Shi, Yang; Feng, Ting-Ting; Zhou, Ying; Yuan, Wei-Cheng

    2015-01-14

    A highly efficient and environmentally benign method for the synthesis of oxindoles featuring two contiguous quaternary carbon centers via an aldol reaction starting from various 3-substituted oxindoles has been established. A wide variety of such featured multi-substituted 1,3-indandione ring-fused 3-oxindole scaffolds were obtained smoothly in good yields (up to 98%) employing the most green of solvents, namely water, as reaction medium. Furthermore, their biological activity has been preliminarily demonstrated by in vitro evaluation against human prostate cancer cells PC-3, human lung cancer cells A549 and human leukemia cells K562 by MTT-based assays, using the commercially available standard drug, cisplatin, as a positive control. Gratifyingly, compounds 3s, 3u, 3y and 3c' exhibited the best levels of in vitro inhibitory activity against human leukemia cells K562, which were almost 2.0, 2.8, 2.5 and 2.2 times, respectively, the activity of the positive control, cisplatin. Compound 3y had 2.7 times the activity of the positive control, cisplatin, against PC-3 cancer cells, and 3s, 3u and 3c' showed levels of in vitro inhibitory activity against PC-3 cancer cells that were comparable to that of cisplatin. Compounds 3s, 3u and 3y had good inhibitory ability against human lung cancer cells A549. The results indicated that 1,3-indandione ring-fused 3-oxindole analogs may be useful leads for further biological screenings. PMID:25382357

  13. Studies in asymmetric ?-lactone synthesis: extensions of the chiral nucleophile catalyzed aldol-lactonization (NCAL) reaction and new transformations of chlorinated ?-lactones

    E-print Network

    Tennyson, Reginald L.

    2001-01-01

    . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . 45 3. 5. 4. Organotin Addition 46 3. 5. 5. Hydride Addition. . . . . 47 Sg2' . . 48 3. 6. 1. Cuprate Addition. . . 48 3. 7. Dyotropic Rearrangements. 3. 7. 1. 7-Lactone Synthesis 49 49 Miscellaneous 4. 1. Decarboxylation 4. 1. 1, Thermal... condensation reaction between lithium ynolates, aldehydes and ketones. For example, they showed that the reaction of ynolate 6 with 5-keto ester 8 gives the bicyclic P-lactone 10, which underwent acid-catalyzed decarboxylation to give cyclohexene 11 in 74...

  14. Determination of the relative configuration of tropinone and granatanone aldols by using TBDMS ethers

    PubMed Central

    Nodzewska, Aneta; Sidorowicz, Katarzyna; Kalicki, Przemyslaw

    2012-01-01

    Summary The relative configurations of tert-butyldimethylsilyl (TBDMS) ethers of all four diastereomers of the aldols of tropinone (8-methyl-8-azabicyclo[3.2.1]octan-3-one), as well as of granatanone (9-methyl-9-azabicyclo[3.3.1]nonan-3-one), were determined from NMR data, and from the observed interconversion of the diastereomers (exo,anti to endo,syn and exo,syn to endo,anti). The exo forms invert to endo isomers in the presence of silica gel. The relative configuration of a new isomer of tropinone aldol accessible synthetically through the direct solventless reaction of tropinone and benzaldehyde in the presence of water was determined as exo,syn by comparison of NMR data of the aldol isomers, in particular vicinal coupling constants and shifts corresponding to the side-chain CH group, with data of related TBDMS derivatives and confirmed by single-crystal X-ray diffraction. PMID:23209525

  15. Asymmetric total synthesis of smyrindiol employing an organocatalytic aldol key step

    PubMed Central

    Fronert, Jeanne; Bisschops, Tom; Boeck, Florian

    2012-01-01

    Summary The first organocatalytic asymmetric synthesis of smyrindiol, by using an (S)-proline catalyzed enantioselective intramolecular aldol reaction as the key step, is described. Smyrindiol was synthesized from commercially available 2,4-dihydroxybenzaldehyde in 15 steps, with excellent stereoselectivity (de = 99%, ee = 99%). In the course of this total synthesis a new and mild coumarin assembly was developed. PMID:23019438

  16. Domino hydroformylation/aldol condensation/hydrogenation catalysis: highly selective synthesis of ketones from olefins.

    PubMed

    Fang, Xianjie; Jackstell, Ralf; Börner, Armin; Beller, Matthias

    2014-11-24

    A general and highly chemo- and regioselective synthesis of ketones from olefins by domino hydroformylation/aldol condensation/hydrogenation reaction has been developed. A variety of olefins are efficiently converted into various ketones in good to excellent yields and regioselectivities in the presence of a specific rhodium phosphine/base-acid catalyst system. PMID:25331557

  17. Synthesis of the C28 through C38 segment of okadaic acid using vinylogous urethane aldol chemistry: Part IV

    Microsoft Academic Search

    John W. Dankwardt; Sharon M. Dankwardt; Richard H. Schlessinger

    1998-01-01

    The synthesis of the C-28 through C-38 segment of the marine natural product okadaic acid was accomplished employing a highly enantio- and diasteroselective aldol condensation reaction of a chiral vinylogous urethane enolate. The stereocenter at C-29 was addressed utilizing a diastereoselective hydroboration reaction.

  18. Manganese ?2-complexes as auxiliaries for stereoselective aldol synthesis of allenyl carbinols.

    PubMed

    Bhowmick, Manishabrata; Lepore, Salvatore D

    2010-11-01

    A convenient and robust manganese auxiliary was linked via an ?(2)-bond to alkynyl esters and ketones using a mild complexation reaction with methylcyclopentadienyl manganese tricarbonyl. This complex readily underwent aldol reactions with exclusive ?-substitution and in good diastereoselectivities especially with aryl ketone substrates. This selectivity has been rationalized using a cyclic transition state model in which the manganese auxiliary plays a critical role in promoting E(O)-geometry of the cumulenolate intermediate. PMID:20936852

  19. Optimization and extensions of the nucleophile catalyzed aldol-lactonization (NCAL) process for bicyclic beta-lactone synthesis: applications to piperidine, pyrrolidine, and gamma-lactam-fused beta-lactones 

    E-print Network

    Oh, Seongho

    2006-08-16

    The intramolecular nucleophile catalyzed aldol-lactonization (NCAL) process was optimized successfully. A variety of C9-acylated cinchona alkaloids were synthesized and used for NCAL reactions with non-activated aldehydes. ...

  20. Cu/MgAl(2)O(4) as bifunctional catalyst for aldol condensation of 5-hydroxymethylfurfural and selective transfer hydrogenation.

    PubMed

    Pupovac, Kristina; Palkovits, Regina

    2013-11-01

    Copper supported on mesoporous magnesium aluminate has been prepared as noble-metal-free solid catalyst for aldol condensation of 5-hydroxymethylfurfural with acetone, followed by hydrogenation of the aldol condensation products. The investigated mesoporous spinels possess high activity as solid-base catalysts. Magnesium aluminate exhibits superior activity compared to zinc and cobalt-based aluminates, reaching full conversion and up to 81?% yield of the 1:1 aldol product. The high activity can be correlated to a higher concentration of basic surface sites on magnesium aluminate. Applying continuous regeneration, the catalysts can be recycled without loss of activity. Focusing on the subsequent hydrogenation of aldol condensation products, Cu/MgAl2 O4 allows a selective hydrogenation and C?O bond cleavage, delivering 3-hydroxybutyl-5-methylfuran as the main product with up to 84?% selectivity avoiding ring saturation. Analysis of the hydrogenation activity reveals that the reaction proceeds in the following order: C?C>C?O>C?O?cleavage>ring hydrogenation. Comparable activity and selectivity can be also achieved utilizing 2-propanol as solvent in the transfer hydrogenation, providing the possibility for partial recycling of acetone and optimization of the hydrogen management. PMID:24038987

  1. Nickel-catalysed reductive aldol cyclisation: scope and mechanistic insight 

    E-print Network

    Fordyce, Euan Alexander Fraser

    2009-01-01

    A highly diastereoselective nickel-catalysed reductive aldol cyclisation is described. Using Ni(acac)2 as a precatalyst and diethylzinc as a stoichiometric reductant, various ?,?-unsaturated carbonyl compounds tethered through an amide or ester...

  2. Copolymer-supported heterogeneous organocatalyst for asymmetric aldol addition in aqueous medium.

    PubMed

    Zhou, Jinqing; Wan, Jinwei; Ma, Xuebing; Wang, Wei

    2012-06-01

    In the current study, a convenient and simple way is presented to synthesize a novel type of supported heterogeneous organocatalyst in 21-81% yield by the copolymerization of 9-amino-9-deoxy-epi-cinchonine organocatalyst with acrylonitrile using AIBN as radical initiator. The chemical compositions (x/y) and weight-average molecular weights of copolymers 1a-d were determined by (1)H NMR and GPC analysis respectively. Their porous and layered structure, and surface morphology were characterized by nitrogen adsorption-desorption, XRD and TEM. In the asymmetric aldol addition of p-nitrobenzaldehyde to cyclohexanone and 1-hydroxy-2-propanone in water, all the supported organocatalysts 1a-d afforded excellent isolated yields (90.2-94.7%) and stereoselectivities (96.8-97.8%ee anti, anti/syn = 91/9). The highest catalytic property (96% yield, anti/syn = 90/10 and 99%ee anti) in water as the sole solvent was achieved under the optimized conditions. Compared with cyclohexanone, cyclopentanone and acetone showed the less desired enantioselectivities in the same aldol reactions. At the end of the aldol reaction, the copolymer-supported organocatalyst 1a was readily recovered in 95-98% yield from reaction mixture by simple filtration using an organic membrane. Even in the fifth run, there was no significant loss in catalytic activity and stereocontrol (94.3% yield, 97.2%ee anti, anti/syn = 90/10). After continuous reuse five times, there was some drop in catalytic activity and stereoselectivity. PMID:22546863

  3. From amino alcohol to aminopolyol: one-pot multienzyme oxidation and aldol addition.

    PubMed

    Peši?, Milja; López, Carmen; López-Santín, Josep; Alvaro, Gregorio

    2013-08-01

    In this work, the successful coupling of enzymatic oxidation and aldol addition reactions for the synthesis of a Cbz-aminopolyol from a Cbz-amino alcohol was achieved for the first time in a multienzymatic one-pot system. The two-step cascade reaction consisted of the oxidation of Cbz-ethanolamine to Cbz-glycinal catalyzed by chloroperoxidase from the fungus Caldariomyces fumago and aldol addition of dihydroxyacetone phosphate to Cbz-glycinal catalyzed by rhamnulose-1-phosphate aldolase expressed as a recombinant enzyme in Escherichia coli, yielding (3R,4S)-5-{[(benzyloxy)carbonyl]amino}-5-deoxy-1-O-phosphonopent-2-ulose. Tools of enzymatic immobilization, reactor configurations, and modification of the reaction medium were applied to highly increase the production of the target compound. While the use of soluble enzymes yielded only 23.6 % of Cbz-aminopolyol due to rapid enzyme inactivation, the use of immobilized ones permitted an almost complete consumption of Cbz-ethanolamine, reaching Cbz-aminopolyol yields of 69.1 and 71.9 % in the stirred-tank and packed-bed reactor, respectively. Furthermore, the reaction production was 18-fold improved when it was catalyzed by immobilized enzymes in the presence of 5 % (v/v) dioxane, reaching a value of 86.6 mM of Cbz-aminopoliol (31 g/L). PMID:23749229

  4. Hydrogen Transfer Reduction of 4- tert-Butylcyclohexanone and Aldol Condensation of Benzaldehyde with Acetophenone on Basic Solids

    Microsoft Academic Search

    J. Lopez; J. Sanchez Valente; J.-M. Clacens; F. Figueras

    2002-01-01

    The liquid-phase reduction of 4-tert-butylcyclohexanone into 4-tert-butylcyclohexanol by reaction with isopropanol at 355 K has been studied on solid bases: mixed oxides obtained by calcination of hydrotalcites, NaBEA zeolites, KF\\/alumina, and La2O3 characterized by calorimetric FTIR adsorption of CO2 and FTIR pyridine adsorption. The aldol condensation of benzaldehyde and acetophenone at 423 K was investigated in parallel to clarify the

  5. Domino-hydroformylation/aldol condensation catalysis: highly selective synthesis of ?,?-unsaturated aldehydes from olefins.

    PubMed

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

    2014-10-01

    A general and highly chemo-, regio-, and stereoselective synthesis of ?,?-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 ?,?-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 ?,?-unsaturated aldehydes. PMID:25179918

  6. Inorganic ammonium salts and carbonate salts are efficient catalysts for aldol condensation in atmospheric aerosols.

    PubMed

    Nozière, Barbara; Dziedzic, Pawel; Córdova, Armando

    2010-04-21

    In natural environments such as atmospheric aerosols, organic compounds coexist with inorganic salts but, until recently, were not thought to interact chemically. We have recently shown that inorganic ammonium ions, NH(4)(+), act as catalysts for acetal formation from glyoxal, a common atmospheric gas. In this work, we report that inorganic ammonium ions, NH(4)(+), and carbonate ions, CO(3)(2-), are also efficient catalysts for the aldol condensation of carbonyl compounds. In the case of NH(4)(+) this was not previously known, and was patented prior to this article. The kinetic results presented in this work show that, for the concentrations of ammonium and carbonate ions present in tropospheric aerosols, the aldol condensation of acetaldehyde and acetone could be as fast as in concentrated sulfuric acid and might compete with their reactions with OH radicals. These catalytic processes could produce significant amounts of polyconjugated, light-absorbing compounds in aerosols, and thus affect their direct forcing on climate. For organic gases with large Henry's law coefficients, these reactions could also result in a significant uptake and in the formation of secondary organic aerosols (SOA). This work reinforces the recent findings that inorganic salts are not inert towards organic compounds in aerosols and shows, in particular, that common ones, such as ammonium and carbonate salts, might even play important roles in their chemical transformations. PMID:20358081

  7. Convergent fabrication of a nanoporous two-dimensional carbon network from an aldol condensation on metal surfaces

    NASA Astrophysics Data System (ADS)

    Landers, John; Chérioux, Frédéric; De Santis, Maurizio; Bendiab, Nedjma; Lamare, Simon; Magaud, Laurence; Coraux, Johann

    2014-12-01

    We report a convergent surface polymerization reaction scheme on Au(111), based on a triple aldol condensation, yielding a carbon-rich, covalent nanoporous two-dimensional network. The reaction is not self-poisoning and proceeds up to a full surface coverage. The deposited precursor molecules 1, 3, 5-tri(4’-acetylphenyl) first form supramolecular assemblies that are converted to the porous covalent network upon heating. The formation and structure of the network and of the intermediate steps are studied with scanning tunneling microscopy, Raman spectroscopy and density functional theory.

  8. A novel and efficient direct aldol condensation from ketones and aromatic aldehydes catalyzed by proline–TEA through a new pathway

    Microsoft Academic Search

    Jun-feng Wang; Meng Lei; Qin Li; Ze-mei Ge; Xin Wang; Run-tao Li

    2009-01-01

    A novel and efficient direct aldol condensation from various ketones and a wide range of aldehydes was catalyzed by l-proline–TEA (triethylamine) in MeOH at room temperature, affording the corresponding (E)-?,?-unsaturated ketones in excellent yields. By using the method, some complicated (E)-?,?-unsaturated ketone C-glycosides were obtained from unmodified ketone C-glycosides and aldehydes. This reaction proceeds through a new pathway, in which

  9. Dual-activation protocol for tandem cross-aldol condensation: An easy and highly efficient synthesis of ?,??-bis(aryl\\/alkylmethylidene)ketones

    Microsoft Academic Search

    Srikant Bhagat; Ratnesh Sharma; Asit K. Chakraborti

    2006-01-01

    Commercially available lithium hydroxide monohydrate (LiOH·H2O) was found to be a novel ‘dual activation’ catalyst for tandem cross-aldol condensation between cyclic\\/acyclic ketones and aromatic\\/heteroaromatic\\/styryl\\/alkyl aldehydes leading to an efficient and easy synthesis of ?,??-bis(aryl\\/alkylmethylidene)ketones at r.t. in short times. The reaction of aryl, heteroaryl, styryl and alkyl aldehydes with acyclic and five\\/six-membered cyclic ketones afforded excellent yields after 2min to

  10. Unified Approach to Isoindolinones and THIQs via Lewis Acid Catalyzed Domino Mukaiyama-Mannich Lactamization/Alkylations: Application in the Synthesis of (±)-Homolaudanosine.

    PubMed

    Dhanasekaran, Sivasankaran; Kayet, Anirban; Suneja, Arun; Bisai, Vishnumaya; Singh, Vinod K

    2015-06-01

    A novel and efficient synthesis of a variety of isoindolinones and tetrahydroisoquinolines via a Lewis acid catalyzed domino Mukaiyama-Mannich lactamization/alkylation is achieved. This transformation comprises a sequential formation of three new bonds through a one-pot, three-component procedure to afford product in moderate to high yields. A concise synthesis of (±)-homolaudanosine (2b) has been achieved using this method. PMID:25992840

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

    PubMed

    Kikhtyanin, Oleg; Chlubná, Pavla; Jindrová, Tereza; Kubi?ka, 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. PMID:24842149

  12. A concise and unified strategy for synthesis of the C1-C18 macrolactone fragments of FD-891, FD-892 and their analogues: formal total synthesis of FD-891.

    PubMed

    Kanoh, Naoki; Kawamata, Ayano; Itagaki, Tomohiro; Miyazaki, Yuta; Yahata, Kenzo; Kwon, Eunsang; Iwabuchi, Yoshiharu

    2014-10-01

    A concise and unified strategy for the synthesis of C1-C18 macrolactone fragments of FD-891 and FD-892 as well as their analogues is reported. The strategy includes a stereoselective vinylogous Mukaiyama aldol reaction (VMAR) using chiral silyl ketene N,O-acetal to construct C6-C7 stereocenters, an E-selective ring closing metathesis to construct a C12-C13 olefin, and stereodivergent construction of a C8-C9 epoxide. PMID:25247478

  13. Anti-selective and regioselective aldol addition of ketones with aldehydes using MgI2 as promoter

    E-print Network

    Paré, Paul W.

    Anti-selective and regioselective aldol addition of ketones with aldehydes using MgI2 as promoter of MgI2 to generate high selectivity of anti-aldol products from unmodified ethyl ketones in high yield-side. q 2004 Elsevier Ltd. All rights reserved. 1. Introduction The stereoselective synthesis of anti

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

    SciTech Connect

    Yu Xiaofang [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China); Yu Xiaobo [China Pharmaceutical University, Nanjing 210009 (China); Wu Shujie; Liu Bo; Liu Heng [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China); Guan Jingqi, E-mail: guanjq@jlu.edu.c [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China); Kan Qiubin, E-mail: catalysischina@yahoo.com.c [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China)

    2011-02-15

    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{sub 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. -- Graphical abstract: Proximal-C-A-SBA-15 with a proximal acid-base distance and maximum-C-A-SBA-15 with a maximum acid-base distance were synthesized by immobilizing lysine onto carboxyl-SBA-15. Display Omitted Research highlights: {yields} Proximal-C-A-SBA-15 with a proximal acid-base distance. {yields} Maximum-C-A-SBA-15 with a maximum acid-base distance. {yields} Compared to maximum-C-A-SBA-15, proximal-C-A-SBA-15 was more active toward aldol condensation reaction between acetone and various aldehydes.

  15. Mathematical model for aldol addition catalyzed by two D-fructose-6-phosphate aldolases variants overexpressed in E. coli.

    PubMed

    Sudar, Martina; Findrik, Zvjezdana; Vasi?-Ra?ki, Dur?a; Clapés, Pere; Lozano, Carles

    2013-09-10

    Two D-fructose-6-phosphate aldolase variants namely, single variant FSA A129S and double variant FSA A129S/A165G, were used as catalysts in the aldol addition of dihydroxyacetone (DHA) to N-Cbz-3-aminopropanal. Mathematical model for reaction catalyzed by both enzymes, consisting of kinetic and mass balance equations, was developed. Kinetic parameters were estimated from the experimental data gathered by using the initial reaction rate method. The model was validated in the batch and continuously operated ultrafiltration membrane reactor (UFMR). The same type of kinetic model could be applied for both enzymes. The operational stability of the aldolases was assessed by measuring enzyme activity during the experiments. FSA A129S/A165G had better operational stability in the batch reactor (half-life time 26.7 h) in comparison to FSA A129S (half-life time 5.78 h). Both variants were unstable in the continuously operated UFMR in which half-life times were 1.99 and 3.64 h for FSA A129S and FSA A129S/A165G, respectively. PMID:23876482

  16. De Novo Computational Design of Retro-Aldol Enzymes

    Microsoft Academic Search

    Lin Jiang; Eric A. Althoff; Fernando R. Clemente; Lindsey Doyle; Daniela Röthlisberger; Alexandre Zanghellini; Jasmine L. Gallaher; Jamie L. Betker; Fujie Tanaka; Carlos F. Barbas; Donald Hilvert; Kendall N. Houk; Barry L. Stoddard; David Baker

    2008-01-01

    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

  17. Asymmetric synthesis of anti-aldol segments via a nonaldol route: synthetic applications to statines and (-)-tetrahydrolipstatin.

    PubMed

    Ghosh, Arun K; Shurrush, Khriesto; Kulkarni, Sarang

    2009-06-19

    An asymmetric synthesis of anti-aldol segments via a nonaldol route is described. The strategy involves a highly diastereoselective synthesis of functionalized tetrahydrofuran derivatives from optically active 4-phenylbutyrolactone. Treatment of the tetrahydrofuran derivatives with a Lewis acid and acetic anhydride provided the corresponding ring-opened styrene derivatives. Oxidative cleavage of the styrene derivatives provided access to the anti-aldol segments. The utility of this methodology was demonstrated by the synthesis of statine derivatives and pancreatic lipase inhibitor, (-)-tetrahydrolipstatin. PMID:19438217

  18. Zeolites as catalysts in organic reactions. Claisen-Schmidt condensation of acetophenone with benzaldehyde

    Microsoft Academic Search

    M. J. Climent; H. Garcia; J. Primo; A. Corma

    1990-01-01

    HY zeolites catalyze the crossed aldol condensation of acetophenone with benzaldehyde, in benzene at 80 °C, to give trans- and cis-chalcones. Together with these expected products, 3,3-diphenylpropiophenone is also produced. In the analogous basic condensation, using phase transfer catalysis, the Michael adduct was not detected, and besides chalcone a small percentage of the Cannizzaro reaction product was observed.

  19. Efficient construction of polycyclic derivatives via a highly selective CuI-catalyzed domino reductive-aldol cyclization.

    PubMed

    Deschamp, Julia; Riant, Olivier

    2009-03-19

    A versatile methodology for the diastereo- and enantioselective domino reductive-aldol cyclizations is reported. By using a copper (I)/diphosphane ligand, various five- and six-membered rings were generated with good to excellent diastereo- and enantioselectivities (cis:trans up to 100:0 and ee up to 95%). PMID:19220061

  20. An Exercise on Structure Elucidation Based on a Tricky Aldol Reaction

    ERIC Educational Resources Information Center

    Sierra, Manuel Gonzalez; Pellegrinet, Silvina C.; Colombo, Maria I.; Ruveda, Edmundo A.

    2008-01-01

    An exercise on structure elucidation for advanced undergraduate students is described. To determine the structure of an unknown product, students are required to use spectra together with an organic chemistry mechanism. This exercise exemplifies the procedure commonly used in research, thus helping students develop problem-solving skills. In…

  1. Direct Catalytic Asymmetric Aldol-Type Reaction of Aldehydes with Ethyl

    E-print Network

    Wang, Jianbo

    and Jianbo Wang* Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education-C bond formation under catalytic condi- tion remains a challenging task in modern organic synthesis

  2. ALDOL- AND MANNICH-TYPE REACTIONS VIA IN SITU OLEFIN MIGRATION IN IONIC LIQUID. (R828129)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  3. SOLVENT AND COUNTERION EFFECT ON THE REACTION OF ARYLMETHANEPHOSPHONATE CARBANION METAL COMPLEXES WITH SCHIFF BASES

    Microsoft Academic Search

    Marko Kirilov; Jordanka Petrova

    1980-01-01

    The influence of solvent and metal ion on the reaction of diethyl esters of phenyl-, 4-methylphenyl- and 4-chlorophenylmethanephosphonic acid la-c and N-benzylidene aniline in the presence of alkaline amides or butyllithium is studied. A strong effect of the counterion on the stereochemistry of the aldol stage of the reaction is established. Complete stereochemical control of the reaction is observed with

  4. Cobalt-catalysed alkylative aldol cyclisations using trialkylaluminium reagents: Rhodium-catalysed carbometallation of ynamides in the preparation of multisubstituted enamides 

    E-print Network

    Rudkin, Mairi Ellen

    2010-01-01

    The cobalt-catalysed alkylative aldol cyclisations of ?,?-unsaturated amides with an appendant ketone were studied using a range of trialkylaluminium reagents. Investigations revealed that Co(acac)2·2H2O acts as an ...

  5. (S)-4-Trimethylsilyl-3-butyn-2-ol as an auxiliary for stereocontrolled synthesis of salinosporamide analogs with modifications at positions C2 and C5.

    PubMed

    Blasdel, Landy K; Lee, DongEun; Sun, Binyuan; Myers, Andrew G

    2013-12-15

    Analogs of salinosporamide A with variations of the C2 and C5 substituents are prepared in 8-10 steps using as the first and key transformation a diastereoselective Mukaiyama aldol reaction between the chiral 5-tert-butyldimethylsiloxy-3-methyl-1H-pyrrole-2-carboxylic ester depicted and various aldehyde substrates, promoted by tert-butyldimethylsilyl triflate. In this transformation, the 4-trimethylsilyl-3-butyn-2-ol ester functions to direct the formation of predominantly one of four possible diastereomeric aldol products. Introduction of the C2 appendage by a later-stage, stereocontrolled alkylation reaction permits the construction of analogs variant at this position. Results from in vitro and cell-based assays of proteasomal inhibition are reported. Mass spectrometric studies provide mechanistic details of proteasomal modification by salinosporamide A and analogs. PMID:24269479

  6. (S)-4-Trimethylsilyl-3-butyn-2-ol as an auxiliary for stereocontrolled synthesis of salinosporamide analogs with modifications at positions C2 and C5

    PubMed Central

    Blasdel, Landy K.; Lee, DongEun; Sun, Binyuan; Myers, Andrew G.

    2013-01-01

    Analogs of salinsporamide A with variations of the C2 and C5 substituents are prepared in 8–10 steps using as the first and key transformation a diastereoselective Mukaiyama aldol reaction between the chiral 5-tert-butyldimethylsiloxy-3-methyl-1H-pyrrole-2-carboxylic ester depicted and various aldehyde substrates, promoted by tert-butyldimethylsilyl triflate. In this transformation, the 4-trimethylsilyl-3-butyn-2-ol ester functions to direct the formation of predominantly one of four possible diastereomeric aldol products. Introduction of the C2 appendage by a later-stage, stereocontrolled alkylation reaction permits the construction of analogs variant at this position. Results from in vitro and cell-based assays of proteasomal inhibition are reported. Mass spectrometric studies provide mechanistic details of proteasomal modification by salinosporamide A and analogs. PMID:24269479

  7. Asymmetric Epoxide Cyclisation Route to the F-pyran Fragment of the Altohyrtins and Key Aldol Studies

    Microsoft Academic Search

    James C. Anderson; Benjamin P. McDermott; Edward J. Griffin

    2000-01-01

    The evolution of an asymmetric synthesis of a differentially protected F-pyran ring of the altohyrtins is described, which relies on a key intramolecular cyclisation of a C43 hydroxyl group onto a C38–C39 epoxide. The C38–C39 epoxide stereochemistry was achieved through optimisation of substrate control. Key aldol studies towards coupling the F-pyran ring with an E-pyran ring precursor was investigated, but

  8. Intramolecular aldol cyclization of l- lyxo-Hexos-5-ulose derivatives: A new diastereoselective synthesis of d- chiro-Inositol

    Microsoft Academic Search

    Giorgio Catelani; Antonino Corsaro; Felicia D'Andrea; Manuela Mariani; Venerando Pistarà

    2002-01-01

    The DBU-promoted intramolecular aldol condensation of two partially protected l-lyxo-hexos-5-ulose derivatives (8 and 9), in turn obtained starting from methyl ?-d-galactopyranoside, takes place with fairly good yield and complete diastereoselectivity to give 2l-(2,3,6\\/4,5)-pentahydroxycyclohexanone derivatives, 10 and 11. The stereoselective reduction of inosose 10 with sodium triacetoxyborohydride leads, after catalytic debenzylation, to d-chiro-inositol (1), while the sodium borohydride reduction furnishes, with

  9. A novel acyclic oligomycin A derivative formed via retro-aldol rearrangement of oligomycin A.

    PubMed

    Lysenkova, Lyudmila N; Turchin, Konstantin F; Korolev, Alexander M; Bykov, Evgenyi E; Danilenko, Valery N; Bekker, Olga B; Trenin, Alexey S; Elizarov, Sergei M; Dezhenkova, Lyubov G; Shtil, Alexander A; Preobrazhenskaya, Maria N

    2012-08-01

    The antibiotic oligomycin A in the presence of K(2)CO(3) and n-Bu(4)NHSO(4) in chloroform in phase-transfer conditions afforded a novel derivative through the initial retro-aldol fragmentation of the 8,9 bond, followed by further transformation of the intermediate aldehyde. NMR, MS and quantum chemical calculations showed that the novel compound is the acyclic oligomycin A derivative, in which the 8,9 carbon bond is disrupted and two polyfunctional branches are connected with spiroketal moiety in positions C-23 and C-25. The tri-O-acetyl derivative of the novel derivative was prepared. The acyclic oligomycin A derivative retained the ability to induce apoptosis in tumor cells at low micromolar concentrations, whereas its antimicrobial potencies decreased substantially. The derivative virtually lost the inhibitory activity against F(0)F(1) ATP synthase-containing proteoliposomes, strongly suggesting the existence of the target(s) beyond F(0)F(1) ATP synthase that is important for the antitumor potency of oligomycin A. PMID:22617550

  10. 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.

  11. Controlling reaction specificity in pyridoxal phosphate enzymes.

    PubMed

    Toney, Michael D

    2011-11-01

    Pyridoxal 5'-phosphate enzymes are ubiquitous in the nitrogen metabolism of all organisms. They catalyze a wide variety of reactions including racemization, transamination, decarboxylation, elimination, retro-aldol cleavage, Claisen condensation, and others on substrates containing an amino group, most commonly ?-amino acids. The wide variety of reactions catalyzed by PLP enzymes is enabled by the ability of the covalent aldimine intermediate formed between substrate and PLP to stabilize carbanionic intermediates at C? of the substrate. This review attempts to summarize the mechanisms by which reaction specificity can be achieved in PLP enzymes by focusing on three aspects of these reactions: stereoelectronic effects, protonation state of the external aldimine intermediate, and interaction of the carbanionic intermediate with the protein side chains present in the active site. This article is part of a Special Issue entitled: Pyridoxal Phosphate Enzymology. PMID:21664990

  12. Controlling reaction specificity in pyridoxal phosphate enzymes

    PubMed Central

    Toney, Michael D.

    2012-01-01

    Pyridoxal 5'-phosphate enzymes are ubiquitous in the nitrogen metabolism of all organisms. They catalyze a wide variety of reactions including racemization, transamination, decarboxylation, elimination, retro-aldol cleavage, Claisen condensation, and others on substrates containing an amino group, most commonly ?-amino acids. The wide variety of reactions catalyzed by PLP enzymes is enabled by the ability of the covalent aldimine intermediate formed between substrate and PLP to stabilize carbanionic intermediates at C? of the substrate. This review attempts to summarize the mechanisms by which reaction specificity can be achieved in PLP enzymes by focusing on three aspects of these reactions: stereoelectronic effects, protonation state of the external aldimine intermediate, and interaction of the carbanionic intermediate with the protein side chains present in the active site. PMID:21664990

  13. 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

    2013-08-01

    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 ?-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. PMID:23834195

  14. 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.…

  15. [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. PMID:11766403

  16. Expanding the scope of the nucleophile catalyzed aldol lactonization (NCALl) process and transformations of the resulting beta-lactones

    E-print Network

    Matla, Andrea Slava

    2009-05-15

    decarboxylation of ?-lactones (Scheme 1.2).5 N MeO OHH N H H catalyst, 1.5a: (Quinidine) 9 N MeO H HO N H catalyst,1.5b: (Quinine) 9 H 5 Scheme 1.2 1.10 (45%) O H O O Ph O O H Cl PhO TEA O O H Ph O? O O OPh -CO2 O Ph 1.6 1.7 1.8 1.9(75%) Although... an unstable ?-lactone which undergoes a retro [2+2] to decarboxylate.16 Using ?,?- unsaturated aldehydes and ketones, they isolate the desired 1,3,4-trisubstitued cyclopentnes in moderate yields. The intermediate ?-lactone is proposed to form via an aldol...

  17. Solidphase aldol condensations mediated by zinc acetate and 2,2?-bipyridine under weakly basic conditions

    Microsoft Academic Search

    Ulrich Sensfuss

    2003-01-01

    A new, efficient and convenient method for the synthesis of resin-bound ?,?-unsaturated ketones is described. Reaction of polystyrene-linked benzaldehydes with methyl ketones or tetralone in the presence of zinc acetate, 2,2?-bipyridine and an amidine base at elevated temperature gave resin-bound (E)-enones in high purity. These were transformed into thioethers by reaction with thiophenol.

  18. 'Super Silyl' Group for Diastereoselective Sequential Reactions: Access to Complex Chiral Architecture in One Pot

    SciTech Connect

    Boxer, Matthew B.; Yamamoto, Hisashi (UC)

    2008-04-02

    We have shown that the tris(trimethylsilyl)silyl (TTMSS) silyl enol ether of acetaldehyde undergoes aldehyde cross-aldol reactions with high selectivity and the extremely low catalyst loading (0.05 mol % of HNTf{sub 2}) allows for one-pot sequential reactions where acidic or basic nucleophiles can be subsequently added. Various ketone-derived silyl enol ethers, Grignard reagents, and dienes succeeded, generating relatively complex molecular architectures in a single step. This represents the first case where, in a single pot, highly acidic conditions followed by very basic conditions were tolerated to give products with high diastereoselectivities and good yields.

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

    PubMed

    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 C(9)-C(15) 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

  20. A General and Enantioselective Approach to Pentoses: A Rapid Synthesis of PSI-6130, the Nucleoside Core of Sofosbuvir

    E-print Network

    MacMillan, David W. C.

    enabled by a chiral amine in conjunction with copper(II) catalysis. A subsequent Mukaiyama aldol coupling of a variety of C-nucleosides and fluorinated pentoses. Finally, this work has facilitated expedient syntheses elaborated pentoses serve as cofactors crucial to enzyme function.1 It is not surprising, therefore

  1. Modelling the reaction course of N -acetylneuraminic acid synthesis from N -acetyl- d -glucosamine—new strategies for the optimisation of neuraminic acid synthesis

    Microsoft Academic Search

    Vera Zimmermann; Hans-Georg Hennemann; Thomas Daußmann; Udo Kragl

    2007-01-01

    In this work, a model describing the complete enzyme catalysed synthesis of N-acetylneuraminic acid (Neu5Ac) from N-acetyl-d-glucosamine (GlcNAc) is presented. It includes the combined reaction steps of epimerisation from GlcNAc to N-acetyl-d-mannosamine (ManNAc) and the aldol condensation of ManNAc with sodium pyruvate yielding Neu5Ac. The model is expedient to\\u000a predict the reaction course for various initial and feed concentrations and

  2. Tris(pentafluorophenyl)borane: a special boron Lewis acid for special reactions.

    PubMed

    Erker, Gerhard

    2005-06-01

    Tris(pentafluorophenyl)borane is best known for its role as an excellent activator component in homogeneous Ziegler-Natta chemistry. However, the special properties of B(C6F5)3 have made this strong boron Lewis acid an increasingly used catalyst or stoichiometric reagent in organic and organometallic chemistry. This includes catalytic hydrometallation reactions, alkylations and catalyzed aldol-type reactions. B(C6F5)3 catalyzes tautomerizations and can sometimes stabilize less favoured tautomeric forms by adduct formation. It induces some rather unusual reactions of early metal acetylide complexes and can help in stabilizing uncommon coordination geometries of carbon. The growing number of such examples indicates an increasing application potential of the useful Lewis acid B(C6F5)3 aside from its established role in olefin polymerization catalysis. PMID:15909033

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

    NASA Astrophysics Data System (ADS)

    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.

    2015-04-01

    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 methylglyoxal have the potential to produce significant organic aerosol mass and therefore could potentially impact chemical, optical and/or cloud-forming properties of aerosols, especially if the products partition to the aerosol surface.

  4. Synthesis, Resolution, and Aldol Reactions of a Planar-Chiral Lewis Acid Complex Shih-Yuan Liu, Ivory D. Hills,1 and Gregory C. Fu*

    E-print Network

    Fu, Gregory C.

    , the distinguishing feature of which was a interaction between the Lewis acid and the carbonyl group (Figure 1 turned our attention to other frameworks, including (5-1,2-azaborolyl)iron derivatives. In this Communication, we report the generation of an enantiopure (5-1,2-azaborolyl)iron adduct,10 and we establish

  5. Synthetic studies toward the brasilinolides: controlled assembly of a protected C1–C38 polyol based on fragment union by complex aldol reactions

    E-print Network

    Paterson, Ian; Housden, Michael P.; Cordier, Christopher J.; Burton, Paul M.; Mühlthau, Friedrich A.; Loiseleur, Olivier

    2015-04-14

    , with potential therapeutic applications to autoimmune diseases and fungal infections, and in the prophylaxis of organ transplant rejection.4 Each member of the brasilinolide family contains several distinctive structural features, including some 26 stereocen...

  6. Studies in asymmetric ?-lactone synthesis: extensions of the chiral nucleophile catalyzed aldol-lactonization (NCAL) reaction and new transformations of chlorinated ?-lactones 

    E-print Network

    Tennyson, Reginald L.

    2001-01-01

    -lactones were accomplished to further extend the utility of these products. In addition, 4-(trichloromethyl)-2-oxetanone was transformed into a variety of amino acid precursors. The first synthesis of the natural amino acid, 2-amino-5-methyl-6-hydroxyhex-4...

  7. Ternary copper(II)-polypyridyl enantiomers: aldol-type condensation, characterization, DNA-binding recognition, BSA-binding and anticancer property.

    PubMed

    Ng, Chew-Hee; Wang, Wai-San; Chong, Kok-Vei; Win, Yip-Foo; Neo, Kian-Eang; Lee, Hong-Boon; San, Swee-Lan; Raja Abd Rahman, Raja Noor Zaliha; Leong, Weng Kee

    2013-07-28

    Chiral enantiomers [Cu(phen)(L-threo)(H2O)]NO3 1 and [Cu(phen)(D-threo)(H2O)]NO3 2 (threo = threoninate) underwent aldol-type condensation with formaldehyde, with retention of chirality, to yield their respective enantiomeric ternary copper(II) complexes, viz. L- and D-[Cu(phen)(5MeOCA)(H2O)]NO3·xH2O (3 and 4; phen = 1,10-phenanthroline; 5MeOCA = 5-methyloxazolidine-4-carboxylate; x = 0-3) respectively. These chiral complexes were characterized by FTIR, elemental analysis, circular dichroism, UV-Visible spectroscopy, fluorescence spectroscopy (FL), molar conductivity measurement, ESI-MS and X-ray crystallography. Analysis of restriction enzyme inhibition by these four complexes revealed modulation of DNA binding selectivity by the type of ligand, ligand modification and chirality. Their interaction with bovine serum albumin was investigated by FL and electronic spectroscopy. With the aid of the crystal structure of BSA, spectroscopic evidence suggested their binding at the cavity containing Trp134 with numerous Tyr residues in subdomain IA. The products were more antiproliferative than cisplatin against cancer cell lines HK-1, MCF-7, HCT116, HSC-2 and C666-1 except HL-60, and were selective towards nasopharyngeal cancer HK-1 cells over normal NP69 cells of the same organ type. PMID:23728518

  8. Synthesis of two subunits of the macrolide domain of the immunosuppressive agent sanglifehrin a and assembly of a macrolactone precursor. application of masamune anti-aldol condensation.

    PubMed

    Suttisintong, Khomson; White, James D

    2015-02-20

    Asymmetric anti-aldol coupling of a norephedrine-derived ester with an ?-chiral aldehyde was used to synthesize a carboxylic acid representing the C13-C19 segment of the macrocyclic domain present in the immunosuppressive agent sanglifehrin A. Felkin addition set configuration at the C14-C17 stereotetrad in this unit in which hydroxyl functions at C15 and C17 were masked as an internal ketal. The carboxyl group of this segment was coupled to the N-terminus of the tripeptide portion (C1-N12) of sanglifehrin A macrolactone to assemble the C1-C19 domain. Synthesis of the C20-C25 subunit of sanglifehrin A containing a (23S) alcohol was completed via asymmetric allylation of (E)-3-iodo-2-methylprop-2-enal followed by oxidative cleavage of the terminal vinyl appendage and a Takai olefination with pinacol dichloromethylboronate. Esterification of this alcohol with a C1-C19 carboxylic acid furnished an open C1-C25 macrolactone precursor, but this substance failed to undergo macrocyclization via intramolecular Suzuki-Miyaura coupling. PMID:25584782

  9. Investigation of thermochemistry associated with the carbon-carbon coupling reactions of furan and furfural using ab initio methods.

    PubMed

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

    2014-06-26

    Upgrading 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 low molecular weight carbohydrates obtained from the pyrolysis via Diels-Alder type reactions in the gas phase to 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 ?-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. PMID:24902118

  10. Synthetic Strategies Toward Tetrahydrofurans Involving Double Diastereoselective Nucleophile-Promoted Aldol-Lactonizations and Subsequent Applications to Bioactive Natural Products 

    E-print Network

    Arendt, Kevin M.

    2011-08-08

    to many of the cell lines, including human lung cancer NCI-H460, than the anticancer medications. This data encourages the use of the haterumalides as lead compounds in the development of novel anticancer drugs. Table 1.1. Cytotoxicity... OF TABLES TABLE Page 1.1 Cytotoxicity of haterumalide NA methyl ester, cisplatin, adriamycin with IC50 values (?M) ..........................................................6 3.1 Theoretical outcome for NCAL reactions...

  11. Adsorption and Reaction of Acetaldehyde on Stoichiometric and Defective SrTiO?(100) Surfaces

    SciTech Connect

    Wang, Li Q.; Ferris, Kim F.; Azad, Samina; Engelhard, Mark H.; Peden, Charles HF.

    2004-02-05

    The adsorption and reaction of acetaldehyde (CH{sub 3}CHO), on stoichiometric (TiO{sub 2}-terminated) and reduced SrTiO{sub 3}(100) surfaces, have been investigated using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Acetaldehyde adsorbs molecularly on the stoichiometric SrTiO{sub 3}(100) surface that contains predominantly Ti{sup 4+} cations. The Ti{sup 4+} sites on the stoichiometric SrTiO{sub 3}(100) surface are not sufficiently active for surface reactions such as aldol condensation, as opposed to the Ti{sup 4+} ions on the TiO{sub 2}(001) surface. However, decomposition and redox reactions of acetaldehyde occur in the presence of surface defects created by Ar{sup +} sputtering. The decomposition products following reactions of acetaldehyde on the defective surface include H{sub 2}, C{sub 2}H{sub 4}, CO, C{sub 4}H{sub 6}, and C{sub 4}H{sub 8}. Reductive coupling, to produce C{sub 2}H{sub 4} and C{sub 4}H{sub 8} is the main reaction pathway for decomposition of acetaldehyde on the sputter reduced SrTiO{sub 3}(100) surface.

  12. Design and synthesis of chiral Zn2+ complexes mimicking natural aldolases for catalytic C-C bond forming reactions in aqueous solution.

    PubMed

    Itoh, Susumu; Sonoike, Shotaro; Kitamura, Masanori; Aoki, Shin

    2014-01-01

    Extending carbon frameworks via a series of C-C bond forming reactions is essential for the synthesis of natural products, pharmaceutically active compounds, active agrochemical ingredients, and a variety of functional materials. The application of stereoselective C-C bond forming reactions to the one-pot synthesis of biorelevant compounds is now emerging as a challenging and powerful strategy for improving the efficiency of a chemical reaction, in which some of the reactants are subjected to successive chemical reactions in just one reactor. However, organic reactions are generally conducted in organic solvents, as many organic molecules, reagents, and intermediates are not stable or soluble in water. In contrast, enzymatic reactions in living systems proceed in aqueous solvents, as most of enzymes generally function only within a narrow range of temperature and pH and are not so stable in less polar organic environments, which makes it difficult to conduct chemoenzymatic reactions in organic solvents. In this review, we describe the design and synthesis of chiral metal complexes with Zn2+ ions as a catalytic factor that mimic aldolases in stereoselective C-C bond forming reactions, especially for enantioselective aldol reactions. Their application to chemoenzymatic reactions in aqueous solution is also presented. PMID:24481060

  13. Chromium-Catalyzed Homoaldol Equivalent Reaction, Indium-Mediated Cycloisomerization, and Palladium-Catalyzed Cross-Coupling Reaction

    E-print Network

    Kang, Jun

    2011-10-21

    that are not possible by a conventional aldol process. Mild hydrolysis of the vinyl acetate and reduction of the homoaldol adducts generated diols and lactols in high yield (99%). Further manipulation including stereoselective epoxidation and cyclopropanation...

  14. Manganese 2 -Complexes as Auxiliaries

    E-print Network

    Lepore, Salvatore D.

    reaction with methylcyclopentadienyl manganese tricarbonyl. This complex readily underwent aldol reactions by Franck-Neumann demonstrating that alkynyl esters 2 -complexed to methylcyclopentadienyl manganeseManganese 2 -Complexes as Auxiliaries for Stereoselective Aldol Synthesis of Allenyl Carbinols

  15. Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2009-05-01

    We don't often stop to think about it, but underlying many of our everyday activities are chemical reactions. From the cooking of an egg to the growth of a child, chemical reactions make things happen. Although many of the reactions that support our lives

  16. Adsorption and Reaction of Acetaldehyde on Stoichiometric and Defective SrTiO{sub 3}(100) Surfaces

    SciTech Connect

    Wang, Li Q.; Ferris, Kim F.; Azad, Samina; Engelhard, Mark H.; Peden, Charles HF.

    2004-02-05

    The adsorption and reaction of acetaldehyde (CH{sub 3}CHO), on stoichiometric (TiO{sub 2}-terminated) and reduced SrTiO{sub 3}(100) surfaces, have been investigated using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Acetaldehyde adsorbs molecularly on the stoichiometric SrTiO{sub 3}(100) surface that contains predominantly Ti{sup 4+} cations. The Ti{sup 4+} sites on the stoichiometric SrTiO{sub 3}(100) surface are not sufficiently active for surface reactions such as aldol condensation, as opposed to the Ti{sup 4+} ions on the TiO{sub 2}(001) surface. However, decomposition and redox reactions of acetaldehyde occur in the presence of surface defects created by Ar{sup +} sputtering. The decomposition products following reactions of acetaldehyde on the defective surface include H{sub 2}, C{sub 2}H{sub 4}, CO, C{sub 4}H{sub 6} and C{sub 4}H{sub 8}. Reductive coupling, to produce C{sub 2}H{sub 4} and C{sub 4}H{sub 8}, is the main reaction pathway for decomposition of acetaldehyde on the sputter reduced SrTiO{sub 3}(100) surface.

  17. The Reactions of Acetone with the Surfaces of Uranium Dioxide Single Crystal and Thin Film

    SciTech Connect

    King,R.; Senanayake, S.; Chong, S.; Idriss, H.

    2007-01-01

    The reaction of acetone, as an example of a carbonyl compound, is studied over UO2 (1 1 1) single crystal and thin film surfaces. Over the stoichiometric single crystal surface, acetone is molecularly and weakly adsorbed with a computed activation energy for desorption in the range of 95-65 kJ/mol with pre-exponential factors between 1011 and 1013 s-1. On the contrary, acetone reacts very strongly on the O-defected single crystal and thin film surfaces. In addition to total decomposition evidence of aldolization and cyclization reactions were seen. The thin film of UO2 was studied by synchrotron light, providing high resolution photoelectron spectroscopy in the core level, and high sensitivity in the both the core and valence band regions. The U5f line was considerably enhanced at grazing angle when compared to that obtained at normal angle for the O-defected surface, showing that the surface is more reduced than the next layers. The U 4f lines indicated the presence of U cations in lower oxidation states than +4 for the O-defected surface. These lines were considerably attenuated upon adsorption of acetone, due to surface oxidation by C{double_bond}O bond dissociation. The reaction pathway for acetone on the O-defected surface is presented, and compared to that of the previously studied acetaldehyde molecule.

  18. Applications of High-Temperature Aqueous Media for Synthetic Organic Reactions.

    PubMed

    An, Jingyi; Bagnell, Laurence; Cablewski, Teresa; Strauss, Christopher R.; Trainor, Robert W.

    1997-04-18

    Preparative organic synthesis was investigated in aqueous media at temperatures up to 300 degrees C. Experiments were conducted with a recently disclosed pressurized microwave batch reactor (MBR) or in conventionally heated autoclaves. Thirty-six examples are presented. Among these, methods were developed for a Fischer synthesis, an intramolecular aldol condensation that was scaled up, decarboxylation of indole-2-carboxylic acid, Rupe rearrangement of 1-ethynyl-1-cyclohexanol, isomerization of carvone to carvacrol, and conversion of phenylacetylene to acetophenone. The applicability of high-temperature water was also demonstrated for biomimetic processes important in food, flavor, and aroma chemistry and for tandem reactions such as formation of 2-methyl-2,3-dihydrobenzofuran from allyl phenyl ether. When addition of acid or base was necessary, less agent was usually required for high-temperature processes than for those at and below boiling, and the reactions often proceeded more selectively. In some instances the requirement was orders of magnitude lower, with obvious consequences for safe, economic processing and for lowering costs of effluent disposal. The diversity of reactions indicates that high-temperature aqueous media could play an increasingly important role in the development of new preparative processes. PMID:11671590

  19. Named Reactions

    NSDL National Science Digital Library

    This Web site lists 95 of the most important named reactions in organic chemistry. Each is linked to a Web page that gives the primary reference and equations for one or more recent literature examples that illustrate the use of the reaction.

  20. Reaction Time

    NSDL National Science Digital Library

    New York Hall of Science

    1999-01-01

    In this activity, learners explore reaction time and challenge themselves to improve their coordination. Do you want to move faster? Catch that ball that you never seem to see in time? Use a simple test to help you improve your reaction (or response) time.

  1. Chemical Reactions

    NSDL National Science Digital Library

    Mrs. Hicken

    2009-05-04

    We are going go over a general view of reactions to prepare us for our unit on Chemical Reactions! Have fun learning! WARNING: If you are caught looking at ANY other site, without permission, you will be sent to the ALC, and you will not participate in any other computer activities for the rest of the year. Get your worksheet and begin! Overview Take this quiz and have me come over and sign off on your worksheet when you have completed the quiz! Overview Quiz Next let's take a look at what effect the rate of a chemical reaction. Rates of Reactions Another quiz, another check off by me! Rates of Reactions Quiz Now how do we measure how fast a ...

  2. Enzyme Reactions

    NSDL National Science Digital Library

    Maryland Virtual High School

    The enzyme reaction rate activity allows students to simulate the effects of variables such as temperature and pH on the reaction rate of the enzyme catalase. This computer simulation is best used after the students have done a wet lab experiment. The value of the simulation is that it requires the students to interpret and analyze the graphical representation of data and it enables the running of mutiple experiments in a short amount of time.

  3. Mechanisms and stereoselectivities of the Rh(i)-catalyzed carbenoid carbon insertion reaction of benzocyclobutenol with diazoester.

    PubMed

    Wang, Yanyan; Wang, Yang; Zhang, Wenjing; Zhu, Yanyan; Wei, Donghui; Tang, Mingsheng

    2015-06-21

    In this study, a density functional theory (DFT) study has been carried out to investigate the mechanisms of Rh(i)-catalyzed carbenoid carbon insertion into a C-C bond reaction between benzocyclobutenol (R1) and diazoester (R2). The calculated results indicate that the reaction proceeds through five stages: deprotonation of R1, cleavage of the C-C bond, carbenoid carbon insertion, intramolecular aldol reaction, and protonation of the alkoxyl-Rh(i) intermediate. We have suggested and studied two possible pathways according to different coordination patterns (including ketone-type and enol-type coordination forms) in the fourth stage and found that the enol-type pathway is favorable, making the coordination mode of the Rh(i) center in the oxa-?-allyl Rh(i) intermediate clear in this reaction system. Moreover, four possible protonation channels have been calculated in the fifth stage, and the computational results show that the H2O-assisted proton transfer channel is the most favorable. The first step of the third stage is rate-determining, and the first steps in stages 3 and 4 play important roles in determining the stereoselectivities. Moreover, the analyses of distortion/interaction, natural bond orbital (NBO), and molecular orbital (MO) have been performed to better understand this title reaction. Furthermore, the pathway corresponding to the RR configurational product is the most favorable path, which is consistent with the experimental result. This work should be helpful for understanding the detailed reaction mechanism and the origin of stereoselectivities of the title reaction and thus could provide valuable insights into rational design of more efficient catalysts for this type of reactions. PMID:25984684

  4. 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.

  5. Formamidine Reactions

    E-print Network

    Griffin, E. L.

    1913-05-15

    of Hantzsch. (1), and the method of Uhlenhuth (2) was found to be not very much more satisfactory owing to the fact that the methyl lsoxazolon broKe down too much on heating Better results were obtained when the oxime of acetoacetic ester was obtained...,C ~ CH RNrOM-SHR = CH.C - C::CHHKR * li , II I H-0- CO U-0- CO * E2sTHx since methyl lsoxazolon is made by the reaction of hydroxylamine hydrochlorid on acetoacetic ester, it was thought that it might be possible to maKe the amldo methylene...

  6. Unusual pyrimidine participation: efficient stereoselective synthesis of potent dual orexin receptor antagonist MK-6096.

    PubMed

    Chung, John Y L; Zhong, Yong-Li; Maloney, Kevin M; Reamer, Robert A; Moore, Jeffrey C; Strotman, Hallena; Kalinin, Alexei; Feng, Ronnie; Strotman, Neil A; Xiang, Bangping; Yasuda, Nobuyoshi

    2014-11-21

    An asymmetric synthesis of dual orexin receptor antagonist MK-6096 (1) is described. Key steps for the trans-2,5-disubstituted piperidinyl ether fragment include a biocatalytic transamination, a trans-selective Mukaiyama aldol, and a regioselective pyridyl SNAr process. The pyrimidyl benzoic acid was synthesized via a Negishi coupling and a nitrile hydrolysis. Coupling of the two fragments via a catalytic T3P-mediated amidation completed the synthesis. Unusual behaviors in the hydrolysis of pyrimidyl benzonitrile and the amide coupling of the pyrimidyl benzoic acid are also described. PMID:25365229

  7. General Biology 1, Reactions 1 CHEMICAL REACTIONS *

    E-print Network

    Prestwich, Ken

    General Biology 1, Reactions 1 CHEMICAL REACTIONS * Note: This is the first of a two-part set of notes. This set will review chemical reactions and the next will overview enzymes. What you learn and ribozymes. At their heart, organisms are complex chemical engines. However, many of the chemical reactions

  8. Intro Biology, Reactions 1 CHEMICAL REACTIONS *

    E-print Network

    Prestwich, Ken

    Intro Biology, Reactions 1 CHEMICAL REACTIONS * Note: This is the first of a two-part set of notes. This set will review chemical reactions and the next will overview enzymes. What you learn in these two and ribozymes. At their heart, organisms are complex chemical engines. However, many of the chemical reactions

  9. Catalysis of Photochemical Reactions.

    ERIC Educational Resources Information Center

    Albini, A.

    1986-01-01

    Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)

  10. Oxygen-dependent fragmentation reactions during the degradation of 1-deoxy-D-erythro-hexo-2,3-diulose.

    PubMed

    Voigt, Michael; Smuda, Mareen; Pfahler, Christoph; Glomb, Marcus A

    2010-05-12

    With this work, we report on further insights into the chemistry of 1-deoxy-D-erythro-hexo-2,3-diulose (1-deoxyglucosone, 1-DG). This alpha-dicarbonyl plays an important role as a highly reactive intermediate in the Maillard chemistry of hexoses. Degradation of 1-DG in the presence of the amino acid l-alanine led to the formation of several products. Lactic acid and glyceric acid were found to be major degradation products. Their formation was dependent on the presence of oxygen. Therefore, a mechanism is postulated based on oxidation leading to a tricarbonyl intermediate. Carbonyl cleavage of this structure should then give rise to carboxylic acids. This mechanism was supported by the isotope distribution observed during degradation of different (13)C-labeled D-glucose isotopomers. Furthermore, we identified 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (gamma-pyranone) to be capable of rehydration forming 1-DG to a minor extent and therefore leading to the same degradation products. The formation of carboxylic acids from gamma-pyranone was also dependent on the presence of oxygen in agreement with the postulated oxidative fragmentation. Finally, we investigated the formation of aldehydes expected as retro-aldol products formed within the degradation of 1-DG. Results seemed to rule out this reaction as an important degradation pathway under the conditions investigated herein. PMID:20441226

  11. Enantioselective copper-catalysed reductive Michael cyclisations 

    E-print Network

    Oswald, Claire Louise

    2010-01-01

    Hydrometalation of ?,?-unsaturated carbonyl compounds provides access to reactive metal enolates, which can then be trapped by a suitable electrophile. The coppercatalysed reductive aldol reaction involves hydrometalation ...

  12. Iodine Clock Reaction

    NSDL National Science Digital Library

    This site allows the user to vary initial solution concentration and temperature for the iodine clock reaction. A simulation of the reaction lets reaction times be measured. The data can then be used to determine the order of reaction for the various components.

  13. Organic Reactions in Aqueous Media (by Chao-Jun Li and Tak-Hang Chan)

    NASA Astrophysics Data System (ADS)

    Rosan, Reviewed Alan M.

    2000-06-01

    This concise book joins the series of Wiley Interscience special topic publications. In seven chapters it selectively reviews the burgeoning literature on organic reactions conducted in water or in aqueous media as a reaction cosolvent, nicely complementing another recent book on the subject by Grieco. Following a short introduction there are six chapters that vary in length from 10 to 50 pages; they cover pericyclic reactions, nucleophilic additions and substitutions, metal-mediated reactions, transition metal-catalyzed reactions, oxidation and reduction reactions, and industrial applications. These chapters, each of which is prefaced with a short provocative quotation, also vary in depth, containing from 11 to more than 180 references. The literature is complete through 1996 and commendably includes citations of original papers by Barbier, Faraday, Frankland, Grignard, Kolbe, Lapworth, and Reformatsky as well as references to selected U.S. and foreign patents and the Russian literature. There is a subject index but no author index. This book is timely and effective. From the title, one might expect a broad discussion of the unique properties of water and water-soluble components (salts, surfactants, etc.) that would be thought to bear on organic reactivity. The first chapter opens by noting that water is the most abundant volatile material in comets and briefly describes those properties that suggest its utility as a solvent or cosolvent, summarizing the potential technical, economic, and environmental advantages. Also described are the remarkable changes in density, conductance, heat capacity, dielectric constant, and ionization constant that accompany the transition to the critical point, but the emphasis here is on the effect of water under non-critical conditions. Discussion of the structure of liquid water and the role of hydrogen bonding in mediating molecular recognition events is abbreviated. In fact, the term "hydrogen bond" is surprisingly absent from the index. The text does not explicitly include a discussion of what has come to be broadly termed biphasic reaction conditions. Understandably, enzymatic reactions are beyond the scope of the presentation. This book has a decidedly applied character with an understated environmental theme, and the authors succinctly present the extraordinary effects of water on the kinetics, efficiency, and stereoselectivity of a large number of diverse reactions. In addition to their emphasis on the historically significant aqueous Diels-Alder reaction, discovered in 1980, and the literature regarding reactions of various nucleophilic organometals, the authors are to be commended for gathering together a wide and diverse body of information: it is clear that many of the examples shown are gems buried among larger bodies of work. Thus the book does an excellent job of culling and surveying a vast amount of data. There is, however, less emphasis on organizing the mechanistic bases underlying these often dramatic effects. For example, the apparent lack of generality of the effect of water on rate and selectivity in pericyclic reactions calls for some theoretical foundation. The singularly effective use of aqueous TlOH in the Suzuki reaction is cited without comment. On the other hand, the authors' concept of a mechanistic triad that incorporates to various degrees anion, radical, or covalent character in the carbon-carbon bond-forming step between various organometals and carbonyl substrates is appealing and suggests the need for future sophisticated experimental design. The most interesting sections are those dealing with synthesis and industrial applications. Unfortunately the latter is also the shortest chapter. The synthetic examples are timely and well chosen and include water-promoted Heck, Stille, Suzuki, and aldol reactions. There is an extensive, highly informative listing and survey of the use of water-soluble phosphines (both achiral and chiral) and an excellent discussion of the diastereoselectivity that often accompanies carbonyl attack by indium, tin, and

  14. Fractal Reaction Kinetics

    NASA Astrophysics Data System (ADS)

    Kopelman, Raoul

    1988-09-01

    Classical reaction kinetics has been found to be unsatisfactory when the reactants are spatially constrained on the microscopic level by either walls, phase boundaries, or force fields. Recently discovered theories of heterogeneous reaction kinetics have dramatic consequences, such as fractal orders for elementary reactions, self-ordering and self-unmixing of reactants, and rate coefficients with temporal ``memories.'' The new theories were needed to explain the results of experiments and supercomputer simulations of reactions that were confined to low dimensions or fractal dimensions or both. Among the practical examples of ``fractal-like kinetics'' are chemical reactions in pores of membranes, excitation trapping in molecular aggregates, exciton fusion in composite materials, and charge recombination in colloids and clouds. Diffusion-controlled reactions with geometrical constraints, as found in heterogeneous kinetics, may be described by reactions on fractal domains. The hallmarks of ``fractal-like'' reactions are anomalous reaction orders and time-dependent reaction rate ``constants.'' These anomalies stem from the nonrandomness of the reactant distributions in low dimensions. For homo-bimolecular reactions (A + A --> Pr) the distribution is partially ordered, for example, quasi-periodic. However, for hetero-bimolecular reactions (A + B --> Pr) the reactants segregate. Theory, simulations, and experiments are interrelated through the formalism of fractal reaction kinetics (42).

  15. Microscale Thermite Reactions.

    ERIC Educational Resources Information Center

    Arnaiz, Francisco J.; Aguado, Rafael; Arnaiz, Susana

    1998-01-01

    Describes the adaptation of thermite (aluminum with metal oxides) reactions from whole-class demonstrations to student-run micro-reactions. Lists detailed directions and possible variations of the experiment. (WRM)

  16. Anaphylaxis-Like Reactions

    MedlinePLUS

    ... antibody) is involved. These reactions are called anaphylactoid (meaning anaphylaxis-like) reactions. While the immune system must ... Find Programs & Services Make a Donation Find a Location Connect With Us View Events Calendar Read the ...

  17. Chemical Reactions and Stoichiometry

    NSDL National Science Digital Library

    2012-07-31

    In this activity, students explore reactions in which chemical bonds are formed and broken. Students experiment with changing the temperature and the concentration of the atoms in order to see how these affect reaction rates. They also learn how to communicate what happens during a chemical reaction by writing the ratios of reactants and products, known as stoichiometry.

  18. Explaining competitive reaction effects

    Microsoft Academic Search

    Peter S. H. Leeflang; Dick R. Wittink

    2001-01-01

    Changes in promotional expenditure decisions for a brand, as in other marketing decisions, should be based on the expected impact on purchase and consumption behavior as well as on the likely reactions by competitors. Purchase behavior may be predicted from estimated demand functions. Competitive reactions can be anticipated based on estimated reaction functions, which show how changes in an instrument

  19. Reaction coordinates for electron transfer reactions

    SciTech Connect

    Rasaiah, Jayendran C. [Department of Chemistry, University of Maine, Orono, Maine 04469 (United States); Zhu Jianjun [Department of Chemistry, State University of New York, Stonybrook, New York 11790 (United States) and Department of Chemistry, Henan Normal University, Xinxiang, Henan (China)

    2008-12-07

    The polarization fluctuation and energy gap formulations of the reaction coordinate for outer sphere electron transfer are linearly related to the constant energy constraint Lagrangian multiplier m in Marcus' theory of electron transfer. The quadratic dependence of the free energies of the reactant and product intermediates on m and m+1, respectively, leads to similar dependence of the free energies on the reaction coordinates and to the same dependence of the activation energy on the reorganization energy and the standard reaction free energy. Within the approximations of a continuum model of the solvent and linear response of the longitudinal polarization to the electric field in Marcus' theory, both formulations of the reaction coordinate are expected to lead to the same results.

  20. Reaction efficiency effects on binary chemical reactions.

    PubMed

    Lazaridis, Filippos; Savara, Aditya; Argyrakis, Panos

    2014-09-14

    We study the effect of the variation of reaction efficiency in binary reactions. We use the well-known A + B ? 0 model, which has been extensively studied in the past. We perform simulations on this model where we vary the efficiency of reaction, i.e., when two particles meet they do not instantly react, as has been assumed in previous studies, but they react with a probability ?, where ? is in the range 0 < ? < 1. Our results show that at small ? values the system is reaction limited, but as ? increases it crosses over to a diffusion limited behavior. At early times, for small ? values, the particle density falls slower than for larger ? values. This fall-off goes over a crossover point, around the value of ? = 0.50 for high initial densities. Under a variety of conditions simulated, we find that the crossover point was dependent on the initial concentration but not on the lattice size. For intermediate and long times simulations, all ? values (in the depleted reciprocal density versus time plot) converge to the same behavior. These theoretical results are useful in models of epidemic reactions and epidemic spreading, where a contagion from one neighbor to the next is not always successful but proceeds with a certain probability, an analogous effect with the reaction probability examined in the current work. PMID:25217900

  1. Applications of B-Lactones: Utility of Spiroepoxy-B-Lactones and Development of a Double Diastereoselective Nucleophile Catalyzed, Aldol-Lactonization Process Leading to !-Lactone Fused Carbocycles and Tetrahydrofurans 

    E-print Network

    Morris, Kay A.

    2011-10-21

    process. With our interest aimed at haterumalide NA, a modified Negishi cross coupling between zincates and dichloroolefins was also revisited. The stringent anhydrous reaction conditions led to reexamination of initial leads, which provided user...

  2. Anaphylactic reactions to cinoxacin.

    PubMed

    Stricker, B H; Slagboom, G; Demaeseneer, R; Slootmaekers, V; Thijs, I; Olsson, S

    1988-12-01

    During 1981 to mid-1988 three cases of anaphylactic shock after treatment with the quinolone derivative cinoxacin were reviewed by the Netherlands Centre for Monitoring of Adverse Reactions to Drugs and 17 cases of an anaphylactic type of reaction notified to the World Health Organisation Collaborating Centre for International Drug Monitoring. In five out of six patients for whom data were available the reaction began shortly after taking a single capsule of a second or next course of treatment. Cinoxacin is related to nalidixic acid, and one patient previously treated with that agent subsequently had an anaphylactoid reaction to cinoxacin and later developed a skin reaction to nalidixic acid. There were no deaths, and patients treated as an emergency with plasma expanders or with adrenaline and corticosteroids generally recovered promptly and uneventfully. In view of the potentially fatal consequences of anaphylactic reactions to cinoxacin and other quinolones doctors should take care when prescribing these drugs. PMID:3147004

  3. HETEROCYCLES, Vol. 62, 2004, pp. 167 -172 Received, 24th July, 2003, Accepted, 25th September, 2003, Published online, 4th November, 2003

    E-print Network

    Williams, David R.

    , 2003, Published online, 4th November, 2003 ALDOL REACTIONS OF UNSUBSTITUTED -LACTAMS. STUDIES@indiana.edu Abstract ­ Aldol reactions of the lithium enolate of N-(4-methoxybenzyloxy)azetidin-2-one (1) were examined for the de novo construction of the 4-membered system.1,2 The potential of this reactive ring as a synthetic

  4. Reaction-diffusion textures

    Microsoft Academic Search

    Andrew P. Witkin; Michael Kass

    1991-01-01

    We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

  5. Immediate Contact Reactions

    Microsoft Academic Search

    David Basketter; Arto Lahti

    \\u000a Immediate contact reactions comprise a diverse spectrum of inflammatory skin reactions of both immune and nonimmune origin\\u000a and involving several often poorly characterized mechanisms and which can be caused by an enormous variety of chemicals and\\u000a proteins. Reactions range from sensory effects through local weal and flare to a more generalized response, but all generally\\u000a characterized by a rapid onset

  6. Weathering Reactions and Soil-Groundwater Reactions

    NSDL National Science Digital Library

    David M. Sherman

    This 11-page PDF document is part of an environmental geochemistry course taught by Dr. David Sherman at the University of Bristol. The lecture explores the weathering reactions that convert primary minerals into quartz or phyllosilicate clays and iron oxide hydroxides, and the mineral-water reactions that buffer pH and the dissolved ion concentration of groundwater. Also discussed is the manner in which phyllosilicate clays, iron oxides and hydroxides sorb pollutants via ion exchange and adsorption. Helpful diagrams and illustrations accompany the text.

  7. Desosamine in multicomponent reactions.

    PubMed

    Achatz, Sepp; Dömling, Alexander

    2006-12-15

    Desosamine occurring ubiquitously in natural products is introduced into isocyanide based multicomponent reaction chemistry. Corresponding products are of potential interest for the design of novel antibiotics. PMID:17070045

  8. Radical reactions of borohydrides.

    PubMed

    Kawamoto, Takuji; Ryu, Ilhyong

    2014-12-28

    Borohydrides are an important class of reagents in both organic and inorganic chemistry. Though popular as hydride-transfer reagents for reduction, since earlier work from the 1970s, borohydride reagents have also been known to serve as hydrogen-transfer reagents. In pursuit of greener tin hydride substitutes, recent progress has been made to mediate radical C-C bond forming reactions, including Giese reactions, radical carbonylation and addition to HCHO reactions, with borohydride reagents. This review article focuses on state-of-the-art borohydride based radical reactions, also covering earlier work, kinetics and some DFT calculations with respect to the hydrogen transfer mechanism. PMID:25349957

  9. Sleeve reaction chamber system

    DOEpatents

    Northrup, M. Allen (Berkeley, CA); Beeman, Barton V. (San Mateo, CA); Benett, William J. (Livermore, CA); Hadley, Dean R. (Manteca, CA); Landre, Phoebe (Livermore, CA); Lehew, Stacy L. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

    2009-08-25

    A chemical reaction chamber system that combines devices such as doped polysilicon for heating, bulk silicon for convective cooling, and thermoelectric (TE) coolers to augment the heating and cooling rates of the reaction chamber or chambers. In addition the system includes non-silicon-based reaction chambers such as any high thermal conductivity material used in combination with a thermoelectric cooling mechanism (i.e., Peltier device). The heat contained in the thermally conductive part of the system can be used/reused to heat the device, thereby conserving energy and expediting the heating/cooling rates. The system combines a micromachined silicon reaction chamber, for example, with an additional module/device for augmented heating/cooling using the Peltier effect. This additional module is particularly useful in extreme environments (very hot or extremely cold) where augmented heating/cooling would be useful to speed up the thermal cycling rates. The chemical reaction chamber system has various applications for synthesis or processing of organic, inorganic, or biochemical reactions, including the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction.

  10. Anaphylactic reactions to cinoxacin

    Microsoft Academic Search

    B. H. Stricker; G. Slagboom; R. Demaeseneer; V. Slootmaekers; I. Thijs; S. Olsson

    1988-01-01

    During 1981 to mid-1988 three cases of anaphylactic shock after treatment with the quinolone derivative cinoxacin were reviewed by the Netherlands Centre for Monitoring of Adverse Reactions to Drugs and 17 cases of an anaphylactic type of reaction notified to the World Health Organisation Collaborating Centre for International Drug Monitoring. In five out of six patients for whom data were

  11. Nuclear Reaction Data Centers

    SciTech Connect

    McLane, V.; Nordborg, C.; Lemmel, H.D.; Manokhin, V.N.

    1988-01-01

    The cooperating Nuclear Reaction Data Centers are involved in the compilation and exchange of nuclear reaction data for incident neutrons, charged particles and photons. Individual centers may also have services in other areas, e.g., evaluated data, nuclear structure and decay data, reactor physics, nuclear safety; some of this information may also be exchanged between interested centers. 20 refs., 1 tab.

  12. Fractal reaction kinetics.

    PubMed

    Kopelman, R

    1988-09-23

    Classical reaction kinetics has been found to be unsatisfactory when the reactants are spatially constrained on the microscopic level by either walls, phase boundaries, or force fields. Recently discovered theories of heterogeneous reaction kinetics have dramatic consequences, such as fractal orders for elementary reactions, self-ordering and self-unmixing of reactants, and rate coefficients with temporal "memories." The new theories were needed to explain the results of experiments and supercomputer simulations of reactions that were confined to low dimensions or fractal dimensions or both. Among the practical examples of "fractal-like kinetics" are chemical reactions in pores of membranes, excitation trapping in molecular aggregates, exciton fusion in composite materials, and charge recombination in colloids and clouds. PMID:17820893

  13. Watermarking 3D Meshes in the Mesh Spectral Domain Akio Mukaiyama1

    E-print Network

    Ohbuchi, Ryutarou

    504 20s distcap 686 1368 6m19s bunny1 1197 2390 33m16s bunny2 2218 4432 2h54m40s 3t [Osada01] 1r 2r [0, 1] ( ) ( )1 1 1 2 2 1 2 31 1r r r r r= - + - +P t t t (8) 2 2 bunny1. (2 ) 2. bunny2 2218 4432 22s 0s bunny4 13990 27976 15m04s 7s bunny5 25849 51694 44m57s 20s 2

  14. Nuclear Reactions and Reactor Safety

    E-print Network

    Onuchic, José

    Nuclear Reactions and Reactor Safety DO NOT LICK We haven't entirely nailed down what element nuclear chain reaction, 1938 #12;Nuclear Chain Reactions Do nuclear chain reactions lead to runaway explosions? or ? -Controlled nuclear chain reactions possible: control energy release/sec -> More

  15. Some Reactions of Formamidines

    E-print Network

    Malleis, Otto Oscar

    1913-05-15

    trichloride on a mixture of a formanilide and amine. 3,- The reaction of orthoformic-ester on a primary amine. OCsHs / HalOeHs . ICdHs HC- OOaHs • = 3C«HsOH + HC^ \\ HEHCeHs MOeHs OOaHs The substituted product in case of aniline is diphenyl- formamidine... as hydrochloride b.- Piorates o.- Chloroplatinates. 2.- Reaction with compounds containing methylene hydrogen. a.- Reaction of oyanacetio ethyl ester with a substi­ tuted formamidine. OH OH I R I CHa * HO = 0 * HCHH R ^ R M a I * HER I COOCaHs COOCa...

  16. Untoward penicillin reactions

    PubMed Central

    Guthe, T.; Idsöe, O.; Willcox, R. R.

    1958-01-01

    The literature on untoward reactions following the administration of penicillin is reviewed. These reactions, including a certain number of deaths which have been reported, are of particular interest to health administrations and to WHO in view of the large-scale programmes for controlling the treponematoses which are now under way—programmes affecting millions of people in many parts of the world. The most serious problems are anaphylactic sensitivity phenomena and superinfection or cross-infection with penicillin-resistant organisms, and the reactions involved range in intensity from the mildest to the fatal; the incidence of the latter is estimated at 0.1-0.3 per million injections. The authors point out that with increasing use of penicillin, more persons are likely to become sensitized and the number of reactions can therefore be expected to rise. The best prevention against such an increase is the restriction of the unnecessary use of penicillin. PMID:13596877

  17. Iodine Clock Reaction.

    ERIC Educational Resources Information Center

    Mitchell, Richard S.

    1996-01-01

    Describes a combination of solutions that can be used in the study of kinetics using the iodine clock reaction. The combination slows down degradation of the prepared solutions and can be used successfully for several weeks. (JRH)

  18. Reactor for exothermic reactions

    DOEpatents

    Smith, L.A. Jr.; Hearn, D.; Jones, E.M. Jr.

    1993-03-02

    A liquid phase process is described for oligomerization of C[sub 4] and C[sub 5] isoolefins or the etherification thereof with C[sub 1] to C[sub 6] alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120 to 300 F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

  19. Polymerase Chain Reaction

    NSDL National Science Digital Library

    2009-09-08

    This interactive activity adapted from the University of Nebraska's Library of Crop Technologies depicts steps in the polymerase chain reaction (PCR) technique and explains how it is used to efficiently copy sections of DNA for analysis.

  20. Reactor for exothermic reactions

    DOEpatents

    Smith, Jr., Lawrence A. (Bellaire, TX); Hearn, Dennis (Houston, TX); Jones, Jr., Edward M. (Friendswood, TX)

    1993-01-01

    A liquid phase process for oligomerization of C.sub.4 and C.sub.5 isoolefins or the etherification thereof with C.sub.1 to C.sub.6 alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120.degree. to 300.degree. F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

  1. Bad Reaction to Cosmetics?

    MedlinePLUS

    ... Cosmetics Dietary Supplements Drugs Food Medical Devices Nutrition Radiation-Emitting Products Tobacco Products Vaccines, Blood & Biologics Articulos en Espanol Bad Reaction to Cosmetics? Tell FDA Search the Consumer Updates ...

  2. Chemisorption And Precipitation Reactions

    EPA Science Inventory

    The transport and bioavailability of chemical components within soils is, in part, controlled by partitioning between solids and solution. General terms used to describe these partitioning reactions include chemisorption and precipitation. Chemisorption is inclusive of the suit...

  3. Phototoxic and Photoallergic Reactions

    Microsoft Academic Search

    Margarida Gonçalo

    \\u000a Phototoxic and photoallergic reactions represent skin reactions to the sun, in the presence of photoactive chemicals applied\\u000a on the skin or taken systemically. They have a highly polymorphic clinical presentation – photocontact urticaria, eczema on\\u000a sun-exposed areas sometimes with erythema multiforme, exaggerated sunburn, linear phytophotodermatitis, pseudoporphyria, photoonycholysis,\\u000a dyschromia, and lupus erythematosus. Also, skin cancers are increasingly associated with exposure to

  4. Glucose reversion reaction kinetics.

    PubMed

    Pilath, Heidi M; Nimlos, Mark R; Mittal, Ashutosh; Himmel, Michael E; Johnson, David K

    2010-05-26

    The reversion reactions of glucose in mildly acidic aqueous solutions have been studied, and the kinetics of conversion to disaccharides has been modeled. The experiments demonstrate that, at high sugar loadings, up to 12 wt % of the glucose can be converted into reversion products. The reversion products observed are primarily disaccharides; no larger oligosaccharides were observed. Only disaccharides linked to the C1 carbon of one of the glucose residues were observed. The formation of 1,6-linked disaccharides was favored, and alpha-linked disaccharides were formed at higher concentrations than beta-linked disaccharides. This observation can be rationalized on the basis of steric effects. At temperatures >140 degrees C, the disaccharides reach equilibrium with glucose and the reversion reaction competes with dehydration reactions to form 5-hydroxymethylfurfural. As a result, disaccharide formation reaches a maximum at reaction times <10 min and decreases with time. At temperatures <130 degrees C, disaccharide formation reaches a maximum at reaction times >30 min. As expected, disaccharide formation exhibits a second-order dependence upon glucose concentration. Levoglucosan formation is also observed; because it shows a first-order dependence upon glucose concentration, its formation is more significant at low concentrations (10 mg mL(-1)), whereas disaccharide formation dominates at high concentrations (200 mg mL(-1)). Experiments conducted using glucose and its disaccharides were calibrated with readily available standards. The kinetic parameters for hydrolysis of some glucodisaccharides could be compared to published literature values. From these experiments, the kinetics and activation energies for the reversion reactions have been calculated. The rate parameters can be used to model the formation of the disaccharides as a function of reaction time and temperature. A new and detailed picture of the molecular mechanism of these industrially important reversion reactions has been developed. PMID:20429509

  5. The Bílik Reaction

    Microsoft Academic Search

    Ladislav Petruš; Mária Petrušová; Zuzana Hricovíniová

    The introduction of the Bílik reaction, the molybdic acid catalyzed interconversion of epimeric aldoses, is an important milestone\\u000a in carbohydrate chemistry. The essentials of this unique, stereospecific carbon-skeleton rearrangement of epialdoses are presented.\\u000a Emphasis is laid on the latest developments in the area, namely the mutual interconversion of 2-ketoses and 2-C-(hydroxymethyl)aldoses, a reaction that is exploited for the preparation of

  6. Ligase Chain Reaction

    Microsoft Academic Search

    Carla Osiowy

    \\u000a Nucleic acid amplification technologies have greatly facilitated medical diagnostics for genetic and infectious diseases through\\u000a the exquisite sensitivity and specificity associated with these methods. Polymerase chain reaction (PCR) (see\\u000a Chapter 6) ushered in these technologies and was soon accompanied by numerous newly developed amplification techniques, including\\u000a ligase chain reaction (LCR). These nucleic acid amplification techniques result in the exponential increase

  7. Optimization and extensions of the nucleophile catalyzed aldol-lactonization (NCAL) process for bicyclic beta-lactone synthesis: applications to piperidine, pyrrolidine, and gamma-lactam-fused beta-lactones

    E-print Network

    Oh, Seongho

    2006-08-16

    as the b-ketoamide after reaction with methoxymethylamine 60 with 2-pyridone as catalyst (Scheme 14). Scheme 14 H N H H N MeO TMSO H O O OH O N(OMe)Me OH O R N(OMe)Me O O 2 55 (1 mol %) THF, -78 ?C LAH THF, -78 ?C (20%) i) HN(OMe)Me ii) H- i) HN(OMe)Me ii...

  8. Classes of Chemical Reactions Reactions in aqueous media

    E-print Network

    Zakarian, Armen

    Classes of Chemical Reactions Reactions in aqueous media · Precipitation reactions · Acid + electrolytes: a substance that conducts an electric current when dissolved in water Acids are donors of H+ (this is a definition) HBr ! H3O+ + Br¯ or HBr ! H+ + Br¯ Equations for Aqueous Ionic Reactions

  9. Chemical ReactionsChemical Reactions between the Componentsbetween the Components

    E-print Network

    Beauchamp, Jack

    1 Chemical ReactionsChemical Reactions between the Componentsbetween the Components of MolecularMethodology We induce chemical reactions in molecular aggregates by collisionally activating the clusters of AMP to ATP by CID: Julian, RJ and J.L. Beauchamp IJMS 2003, 227(1), 147-159. Reaction of Gas

  10. Improved Synthesis of the ABCDE Fragment of Brevetoxin A

    E-print Network

    focused on the application of our anti-glycolate aldol reaction6 to establish four stereo- genic centers strategy was employed rather than the anti-glycolate aldol approach. To this end, the sodium enolate, the primary alcohol of the resultant diol was selectively protected as the triisopropylsilyl ether. Oxidation

  11. Applied Catalysis A: General 392 (2011) 5768 Contents lists available at ScienceDirect

    E-print Network

    Auerbach, Scott M.

    2011-01-01

    Keywords: Nitrogen-substituted zeolite MgO­ZrO2 Aldol condensation High-throughput reactor Shape-selective base catalyst a b s t r a c t The aldol condensation reactions of furfural/hydroxymethylfurfural (furfurals) with acetone/propanal in water­methanol solvents were studied over the solid base catalysts Mg

  12. Nanoparticle Reactions on Chip

    NASA Astrophysics Data System (ADS)

    Köhler, J. M.; Kirner, Th.; Wagner, J.; Csáki, A.; Möller, R.; Fritzsche, W.

    The handling of heterogenous systems in micro reactors is difficult due to their adhesion and transport behaviour. Therefore, the formation of precipitates and gas bubbles has to be avoided in micro reaction technology, in most cases. But, micro channels and other micro reactors offer interesting possibilities for the control of reaction conditions and transport by diffusion and convection due to the laminar flow caused by small Reynolds numbers. This can be used for the preparation and modification of objects, which are much smaller than the cross section of microchannels. The formation of colloidal solutions and the change of surface states of nano particles are two important tasks for the application of chip reactors in nanoparticle technology. Some concepts for the preparation and reaction of nanoparticles in modular chip reactor arrangements will be discussed.

  13. Cutaneous reactions to vaccinations.

    PubMed

    Rosenblatt, Adena E; Stein, Sarah L

    2015-01-01

    Vaccinations are important for infectious disease prevention; however, there are adverse effects of vaccines, many of which are cutaneous. Some of these reactions are due to nonspecific inflammation and irritation at the injection site, whereas other reactions are directly related to the live attenuated virus. Rarely, vaccinations have been associated with generalized hypersensitivity reactions, such as erythema multiforme, Stevens-Johnson syndrome, urticaria, acute generalized exanthematous pustulosis, and drug hypersensitivity syndrome. The onset of certain inflammatory dermatologic conditions, such as lichen planus, granuloma annulare, and pemphigoid, were reported to occur shortly after vaccine administration. Allergic contact dermatitis can develop at the injection site, typically due to adjuvant ingredients in the vaccine, such as thimerosal and aluminum. Vaccinations are important to promote development of both individual and herd immunity. Although most vaccinations are considered relatively safe, there may be adverse effects associated with any vaccine. Cutaneous manifestations make up a large portion of the types of reactions associated with vaccines. There are many different reasons for the development of a cutaneous reaction to a vaccination. Some are directly related to the injection of a live attenuated virus, such as varicella or vaccinia (for immunity to smallpox), whereas others cause more nonspecific erythema and swelling at the injection site, as a result of local inflammation or irritation. Vaccinations have also been associated in rare reports with generalized hypersensitivity reactions, such as erythema multiforme, Stevens-Johnson syndrome, urticaria, acute generalized exanthematous pustulosis, and drug hypersensitivity syndrome. There have been case reports associating the administration of a vaccine with the new onset of a dermatologic condition, such as lichen planus, granuloma annulare, and Sweet syndrome. Finally, allergic contact dermatitis can develop at the injection site, typically due to adjuvant ingredients in the vaccine, such as thimerosal and aluminum. PMID:25889134

  14. Inorganic Reaction Mechanisms. Part I

    ERIC Educational Resources Information Center

    Cooke, D. O.

    1976-01-01

    Provides a collection of data on the mechanistic aspects of inorganic chemical reactions. Wherever possible includes procedures for classroom demonstration or student project work. The material covered includes gas phase reactions, reactions in solution, mechanisms of electron transfer, the reaction between iron III and iodine, and hydrolysis. (GS)

  15. Sulfided heterogeneous, bimetallic RuMo catalysts derived from mixtures of Ru sub 3 (CO) sub 12 (or RuCl sub 3 ) and a molybdenum heteropolyanion. The reactions of ethanol with tetrahydroquinoline

    SciTech Connect

    Koo, Sang-Man; Ryan, D.; Laine, R.M.

    1992-01-01

    Efforts have been made to develop Ru/Mo bimetallic catalyst systems for hydrodenitrogenation (HDN) of tetrahydroquinoline (THQ)- In the course of these studies, it was discovered that in ethanol, under H{sub 2} and in the presence Of CS2, Precatalyst solutions containing Ru (as Ru{sub 3} (CO){sub 12} or RuCl{sub 3}) and Mo (as the H{sub 3}PMO{sub 12}0{sub 40} heteropolyanion (HPA)) decompose to form bimetallic, sulfided particles. Particle diameters run from 0.1 to 5 {mu}m depending on the rate of stirring. Catalyst particles with sizes ranging from 0.1--1 {mu}m can be prepared reproducibly. BET measured surface areas for these size particles ranged from 2 to 20 m2/g. These sulfided particles were found to catalyze, at temperatures of 200--250{degrees}C and hydrogen pressures of 200--1000 psig H{sub 2}, the N-ethylation of THQ to form NEt-THQ; rather than the formation of propylcyclohexane or propylbenzene, reaction products expected for HDN of THQ. Monometallic heterogeneous catalysts prepared from the individual precatalyst complexes, under identical conditions, show minimal activity for N-ethylation by comparison with the bimetallic catalyst. In the absence of H{sub 2}, the reaction proceeds such that THQ is converted to Q, N-EtTHQ, N-C{sub 6}H{sub 9}-THQ, and N-C{sub 6}H{sub 13}-THQ. The latter products appear to arise via acetaldehyde, formed as an intermediate by dehydrogenation of ethanol. Acetaldehyde either condenses with THQ to form N-Et-THQ, or self condenses (aldol condensation) prior to reaction with THQ thereby giving higher homolog alkylation products.

  16. Sulfided heterogeneous, bimetallic RuMo catalysts derived from mixtures of Ru{sub 3}(CO){sub 12} (or RuCl{sub 3}) and a molybdenum heteropolyanion. The reactions of ethanol with tetrahydroquinoline

    SciTech Connect

    Koo, Sang-Man; Ryan, D.; Laine, R.M.

    1992-09-01

    Efforts have been made to develop Ru/Mo bimetallic catalyst systems for hydrodenitrogenation (HDN) of tetrahydroquinoline (THQ)- In the course of these studies, it was discovered that in ethanol, under H{sub 2} and in the presence Of CS2, Precatalyst solutions containing Ru [as Ru{sub 3} (CO){sub 12} or RuCl{sub 3}] and Mo [as the H{sub 3}PMO{sub 12}0{sub 40} heteropolyanion (HPA)] decompose to form bimetallic, sulfided particles. Particle diameters run from 0.1 to 5 {mu}m depending on the rate of stirring. Catalyst particles with sizes ranging from 0.1--1 {mu}m can be prepared reproducibly. BET measured surface areas for these size particles ranged from 2 to 20 m2/g. These sulfided particles were found to catalyze, at temperatures of 200--250{degrees}C and hydrogen pressures of 200--1000 psig H{sub 2}, the N-ethylation of THQ to form NEt-THQ; rather than the formation of propylcyclohexane or propylbenzene, reaction products expected for HDN of THQ. Monometallic heterogeneous catalysts prepared from the individual precatalyst complexes, under identical conditions, show minimal activity for N-ethylation by comparison with the bimetallic catalyst. In the absence of H{sub 2}, the reaction proceeds such that THQ is converted to Q, N-EtTHQ, N-C{sub 6}H{sub 9}-THQ, and N-C{sub 6}H{sub 13}-THQ. The latter products appear to arise via acetaldehyde, formed as an intermediate by dehydrogenation of ethanol. Acetaldehyde either condenses with THQ to form N-Et-THQ, or self condenses (aldol condensation) prior to reaction with THQ thereby giving higher homolog alkylation products.

  17. Introducing the Wittig Reaction.

    ERIC Educational Resources Information Center

    Armstead, D. E. F.

    1979-01-01

    An experiment is described which provides a simple example of the application of the Wittig reaction to the synthesis of unsaturated compounds. The experiment was designed with British HNC chemistry students in mind, but it is also suitable as a project-type exercise for final year GCE A-level students. (Author/BB)

  18. Organic Reactions and Biofuels

    NSDL National Science Digital Library

    The Advanced Technology Environmental and Energy Center (ATEEC) provides this classroom activity on organic reactions and biofuels. The goal of the lesson is to react methanol with waste oil to synthesize biodiesel. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.

  19. Polymerase chain reaction system

    DOEpatents

    Benett, William J.; Richards, James B.; Stratton, Paul L.; Hadley, Dean R.; Milanovich, Fred P.; Belgrader, Phil; Meyer, Peter L.

    2004-03-02

    A portable polymerase chain reaction DNA amplification and detection system includes one or more chamber modules. Each module supports a duplex assay of a biological sample. Each module has two parallel interrogation ports with a linear optical system. The system is capable of being handheld.

  20. Radiobiology of tissue reactions.

    PubMed

    Dörr, W

    2015-06-01

    Tissue effects of radiation exposure are observed in virtually all normal tissues, with interactions when several organs are involved. Early reactions occur in turnover tissues, where proliferative impairment results in hypoplasia; late reactions, based on combined parenchymal, vascular, and connective tissue changes, result in loss of function within the exposed volume; consequential late effects develop through interactions between early and late effects in the same organ; and very late effects are dominated by vascular sequelae. Invariably, involvement of the immune system is observed. Importantly, latent times of late effects are inversely dependent on the biologically equieffective dose. Each tissue component and - importantly - each individual symptom/endpoint displays a specific dose-effect relationship. Equieffective doses are modulated by exposure conditions: in particular, dose-rate reduction - down to chronic levels - and dose fractionation impact on late responding tissues, while overall exposure time predominantly affects early (and consequential late) reactions. Consequences of partial organ exposure are related to tissue architecture. In 'tubular' organs (gastrointestinal tract, but also vasculature), punctual exposure affects function in downstream compartments. In 'parallel' organs, such as liver or lungs, only exposure of a significant (organ-dependent) fraction of the total volume results in clinical consequences. Forthcoming studies must address biomarkers of the individual risk for tissue reactions, and strategies to prevent/mitigate tissue effects after exposure. PMID:25816259

  1. Chemical Reactions at Surfaces

    SciTech Connect

    Michael Henderson and Nancy Ryan Gray

    2010-04-14

    Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The program this year will cover a broad range of topics, including heterogeneous catalysis and surface chemistry, surfaces in environmental chemistry and energy conversion, reactions at the liquid-solid and liquid-gas interface, electronic materials growth and surface modification, biological interfaces, and electrons and photons at surfaces. An exciting program is planned, with contributions from outstanding speakers and discussion leaders from the international scientific community. The conference provides a dynamic environment with ample time for discussion and interaction. Attendees are encouraged to present posters; the poster sessions are historically well attended and stimulate additional discussions. The conference provides an excellent opportunity for junior researchers (e.g. graduate students or postdocs) to present their work and interact with established leaders in the field.

  2. Categorizing Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2009-07-10

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the second of four Science Objects in the Chemical Reactions SciPack. It provides an

  3. Rates of Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    1900-01-01

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the third of four Science Objects in the Chemical Reactions SciPack. It demonstrates

  4. Paradoxical reactions to benzodiazepines

    PubMed Central

    Hall, R. C. W.; Zisook, S.

    1981-01-01

    1 The overall incidence of paradoxical responses to the benzodiazepines is extremely small, but a few controlled studies have been carried out which define the population at risk. 2 Such reactions tend to be idiosyncratic except possibly in patients with pre-rage personality, and do not seem to be associated with any predictable clinical indications. PMID:6133541

  5. Reaction Formulation: A Bibliography.

    ERIC Educational Resources Information Center

    Pedrini, D. T.; Pedrini, Bonnie C.

    Reaction formation was studied by Sigmund Freud. This defense mechanism may be related to repression, substitution, reversal, and compensation (or over-compensation). Alfred Adler considered compensation a basic process in his individual psychology. Anna Freud discussed some defense mechanisms, and Bibring, Dwyer, Huntington, and Valenstein…

  6. Printing enzymatic reactions.

    PubMed

    Tian, Junfei; Shen, Wei

    2011-02-01

    We used relief and planographic printing methods to print the catalytic effect of an enzyme, but not the enzyme molecules, onto paper. Printing enzymatic reactions have applications in bioactive papers, low-cost diagnostics, anti-counterfeiting devices and advanced packaging materials. These methods can create novel printing effects on commodity surfaces for advanced applications. PMID:21109893

  7. A World of Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2009-07-10

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the first of four Science Objects in the Chemical Reactions SciPack. It explains tha

  8. Photoneutron reactions in astrophysics

    SciTech Connect

    Varlamov, V. V., E-mail: Varlamov@depni.sinp.msu.ru; Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.; Stopani, K. A. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)

    2014-12-15

    Among key problems in nuclear astrophysics, that of obtaining deeper insight into the mechanism of synthesis of chemical elements is of paramount importance. The majority of heavy elements existing in nature are produced in stars via radiative neutron capture in so-called s- and r processes, which are, respectively, slow and fast, in relation to competing ?{sup ?}-decay processes. At the same time, we know 35 neutron-deficient so-called bypassed p-nuclei that lie between {sup 74}Se and {sup 196}Hg and which cannot originate from the aforementioned s- and r-processes. Their production is possible in (?, n), (?, p), or (?, ?) photonuclear reactions. In view of this, data on photoneutron reactions play an important role in predicting and describing processes leading to the production of p-nuclei. Interest in determining cross sections for photoneutron reactions in the threshold energy region, which is of particular importance for astrophysics, has grown substantially in recent years. The use of modern sources of quasimonoenergetic photons obtained in processes of inverse Compton laser-radiation scattering on relativistic electronsmakes it possible to reveal rather interesting special features of respective cross sections, manifestations of pygmy E1 and M1 resonances, or the production of nuclei in isomeric states, on one hand, and to revisit the problem of systematic discrepancies between data on reaction cross sections from experiments of different types, on the other hand. Data obtained on the basis of our new experimental-theoretical approach to evaluating cross sections for partial photoneutron reactions are invoked in considering these problems.

  9. Neutrons from Piezonuclear Reactions

    E-print Network

    F. Cardone; G. Cherubini; R. Mignani; W. Perconti; A. Petrucci; F. Rosetto; G. Spera

    2008-11-16

    We report the results obtained by cavitating water solutions of iron salts (iron chloride and iron nitrate) with different concentrations at different ultrasound powers. In all cases we detected a neutron radiation well higher than the background level. The neutron production is perfectly reproducible and can at some extent be controlled. These evidences for neutron emission generated by cavitation support some preliminary clues for the possibility of piezonuclear reactions (namely nuclear reactions induced by pressure and shock waves) obtained in the last ten years. We have been able for the first time to state some basic features of such a neutron emission induced by cavitation, namely: 1) a marked threshold behavior in power, energy and time; 2) its occurring without a concomitant production of gamma radiation.

  10. Concordant Chemical Reaction Networks

    E-print Network

    Shinar, Guy

    2011-01-01

    We describe a large class of chemical reaction networks, those endowed with a subtle structural property called concordance. We show that the class of concordant networks coincides precisely with the class of networks which, when taken with any weakly monotonic kinetics, invariably give rise to kinetic systems that are injective --- a quality that, among other things, precludes the possibility of switch-like transitions between distinct positive steady states. We also provide persistence characteristics of concordant networks, instability implications of discordance, and consequences of stronger variants of concordance. Some of our results are in the spirit of recent ones by Banaji and Craciun, but here we do not require that every species suffer a degradation reaction. This is especially important in studying biochemical networks, for which it is rare to have all species degrade.

  11. Reaction Time 2: Zap!

    NSDL National Science Digital Library

    Science Netlinks

    2003-06-19

    This Science NetLinks lesson is the second of a two-part series that encourages students to think about their own learning and the strategies that best help them learn new skills and ideas. In this lesson, students build upon what they have already learned by participating in another online reaction-time activity--this one testing their visual and auditory abilities, both separately and together.

  12. The Gewald multicomponent reaction

    Microsoft Academic Search

    Yijun Huang; Alexander Dömling

    2011-01-01

    The Gewald reaction of sulfur, cyanoacetic acid derivatives, and oxo-component (G-3CR) yielding highly substituted 2-aminothiophene\\u000a derivatives has seen diverse applications in combinatorial and medicinal chemistry. Its products are of great use in pharmaceutical\\u000a industry mainly as small molecular weight inhibitors. We herein review synthetic scope and variations, usage, and structural\\u000a biology of Gewald products.

  13. Reactions of intermetallic clusters

    Microsoft Academic Search

    R. W. Farley; A. W. Castleman Jr.

    1990-01-01

    Reaction of bismuth--alkali clusters with closed-shell HX acids provides insight into the structures, formation, and stabilities of these intermetallic species. HC1 and HI are observed to quantitatively strip Bi{sub {ital x}}Na{sub {ital y}} and Bi{sub {ital x}}K{sub {ital y}}, respectively, of their alkali component, leaving bare bismuth clusters as the only bismuth-containing species detected. Product bismuth clusters exhibit the same

  14. Reactions of intermetallic clusters

    Microsoft Academic Search

    R. W. Farley; A. W. Castleman

    1990-01-01

    Reaction of bismuth–alkali clusters with closed-shell HX acids provides insight into the structures, formation, and stabilities of these intermetallic species. HC1 and HI are observed to quantitatively strip BixNay and BixKy, respectively, of their alkali component, leaving bare bismuth clusters as the only bismuth-containing species detected. Product bismuth clusters exhibit the same distribution observed when pure bismuth is evaporated in

  15. Gravitational Radiation Reaction

    E-print Network

    Yasushi Mino; Misao Sasaki; Takahiro Tanaka

    1997-12-12

    We consider the radiation reaction to the motion of a point-like particle of mass $m$ and specific spin $S$ traveling on a curved background. Assuming $S=O(Gm)$ and $Gm\\ll L$ where $L$ is the length scale of the background curvature, we divide the spacetime into two regions; the external region where the metric is approximated by the background metric plus perturbations due to a point-like particle and the internal region where the metric is approximated by that of a black hole plus perturbations due to the tidal effect of the background curvature, and use the technique of the matched asymptotic expansion to construct an approximate metric which is valid over the entire region. In this way, we avoid the divergent self-gravity at the position of the particle and derive the equations of motion from the consistency condition of the matching. The matching is done to the order necessary to include the effect of radiation reaction of $O(Gm)$ with respect to the background metric as well as the effect of spin-induced force. The reaction term of $O(Gm)$ is found to be completely due to tails of radiation, that is, due to curvature scattering of gravitational waves. In other words, the reaction force is found to depend on the entire history of the particle trajectory. Defining a regularized metric which consists of the back- ground metric plus the tail part of the perturbed metric, we find the equations of motion reduce to the geodesic equation on this regularized metric, except for the spin-induced force which is locally expressed in terms of the curvature and spin tensors. Some implications of the result and future issues are briefly discussed.

  16. Photochemical reaction dynamics

    SciTech Connect

    Moore, B.C. [Lawrence Berkeley Laboratory, Livermore, CA (United States)

    1993-12-01

    The purpose of the program is to develop a fundamental understanding of unimolecular and bimolecular reaction dynamics with application in combustion and energy systems. The energy dependence in ketene isomerization, ketene dissociation dynamics, and carbonyl substitution on organometallic rhodium complexes in liquid xenon have been studied. Future studies concerning unimolecular processes in ketene as well as energy transfer and kinetic studies of methylene radicals are discussed.

  17. Procedures for Decomposing a Redox Reaction into Half-Reaction

    ERIC Educational Resources Information Center

    Fishtik, Ilie; Berka, Ladislav H.

    2005-01-01

    A simple algorithm for a complete enumeration of the possible ways a redox reaction (RR) might be uniquely decomposed into half-reactions (HRs) using the response reactions (RERs) formalism is presented. A complete enumeration of the possible ways a RR may be decomposed into HRs is equivalent to a complete enumeration of stoichiometrically…

  18. On-surface reactions.

    PubMed

    Lindner, Robert; Kühnle, Angelika

    2015-06-01

    On-surface synthesis constitutes a rapidly growing field of research due to its promising application for creating stable molecular structures on surfaces. While self-assembled structures rely on reversible interactions, on-surface synthesis provides the potential for creating long-term stable structures with well-controlled properties, for example superior electron transport for future molecular electronic devices. On-surface synthesis holds the promise for preparing insoluble compounds that cannot be produced in solution. Another highly exciting aspect of on-surface synthesis is the chance to discover new reaction pathways due to the two-dimensional confinement of the reaction educts. In this review, we discuss the current state-of-the-art and classify the reactions that have been successfully performed so far. Special emphasis is put on electrically insulating surfaces, as these substrates pose particular challenges for on-surface synthesis while at the same time bearing high potential for future use, for example, in molecular electronics. PMID:25965579

  19. Chemical Reactions in DSMC

    NASA Astrophysics Data System (ADS)

    Bird, G. A.

    2011-05-01

    DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

  20. Factors augmenting allergic reactions.

    PubMed

    Niggemann, B; Beyer, K

    2014-12-01

    Elicitors of anaphylactic reactions are any sources of protein with allergenic capacity. However, not all allergic reactions end up in the most severe form of anaphylaxis. Augmenting factors may explain why certain conditions lead to anaphylaxis. Augmenting factors may exhibit three effects: lowering the threshold, increasing the severity, and reversing acquired clinical tolerance. Common augmenting factors are physical exercise, menstruation, NSAIDs, alcohol, body temperature, acute infections, and antacids. Therapeutic options may address causative, preventive, pragmatic, or symptomatic considerations: avoid the eliciting food, take an antihistamine before any situation with a possible risk of augmentation, separate food and sport (at least for 2 h), and carry an adrenaline autoinjector at all times. Individual patterns include summation effects and specific patterns. In conclusion, in the case of a suggestive history but a negative oral challenge, one should consider the possible involvement of augmenting factors; after anaphylactic reactions, always ask for possible augmentation and other risk factors during the recent past; if augmentation is suspected, oral food challenges should be performed in combination with augmenting factors; and in the future, standardized challenge protocols including augmenting factors should be established. PMID:25306896

  1. Adverse reactions after smallpox vaccination.

    PubMed

    Feery, B J

    1977-08-01

    Nine hundred and thirty-eight reports of adverse reactions of smallpox vaccination in Australia between 1960 and 1976 have been analysed according to the type of reaction, and the age and sex of vaccinee. In an estimated 5,000,000 vaccinations, the reaction rate was 188/million, and the death rate 1-5/million. Generalized vaccinia was the most common reaction. The more serious reactions--eczema vaccinatum, progressive vaccinia, and neurological and cardiac complications--accounted for 7-4% of the reports. A small number of rarely reported non-specific inflammatory reactions is also included. There was a marked difference in the number of reactions reported in females and males (the female-male ratio was 1-6:1), and this difference increased with age. Paradoxically, of eight reports of cardiac complications, seven concerned males. The administration of vaccinial immune globulin was usually followed by a rapid resolution of the adverse reactions. PMID:20557

  2. ChemTeacher: Decomposition Reactions

    NSDL National Science Digital Library

    2011-01-01

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Decomposition Reactions page includes resources for teaching students about identifying and predicting decomposition reactions.

  3. ChemTeacher: Combination Reactions

    NSDL National Science Digital Library

    2011-01-01

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Combination Reactions page includes resources for teaching students about identifying and predicting combination reactions.

  4. Hydrazine decomposition and other reactions

    NASA Technical Reports Server (NTRS)

    Armstrong, Warren E. (Inventor); La France, Donald S. (Inventor); Voge, Hervey H. (Inventor)

    1978-01-01

    This invention relates to the catalytic decomposition of hydrazine, catalysts useful for this decomposition and other reactions, and to reactions in hydrogen atmospheres generally using carbon-containing catalysts.

  5. The Vitamin C Clock Reaction

    NASA Astrophysics Data System (ADS)

    Wright, Stephen W.

    2002-01-01

    An iodine clock reaction that gives a colorless to black result similar to that of the familiar Landolt iodate-bisulfite clock reaction is described. The vitamin C clock reaction uses chemicals that are readily available on the retail market: vitamin C, tincture of iodine, 3% hydrogen peroxide, and laundry starch. Orange juice may be used as the vitamin C source to give an orange to black reaction.

  6. Integrated enzymatic reactions and analysis

    Microsoft Academic Search

    Ernst Wehtje; Patrick Adlercreutz; Bo Mattiasson

    1992-01-01

    Summary  Enzymatic reactions were performed in a modified auto-injector unit of a Shimadzu HPLC system. The reactions were analyzed\\u000a by automated injections directly into the HPLC separation system. Two reactions were studied, and the enzymes mandelonitrile\\u000a lyase and ?-chymotrypsin were immobilized by adsorption onto a solid support, e.g., Celite and Chromosorb. The reactions were\\u000a performed in various organic solvents e.g., diisopropyl

  7. Nucleophilic Substitution and Elimination Reactions

    NSDL National Science Digital Library

    Dan Berger

    These pages show the basic mechanism for nucleophilic substition and elimination reactions of alkyl halides. The mechanisms for alcohols are similar. Animated GIFs and controllable Flash animations illustrate SN1, SN2, E1 and E2 reactions. The Flash animations were constructed using AM1 reaction path calculations.

  8. Autocatalysis in the formose reaction

    Microsoft Academic Search

    R. F. Socha; A. H. Weiss; M. M. Sakharov

    1980-01-01

    It has been found that carbohydrates naturally present in ppm quantities in paraformaldehyde are the cause of the autocatalysis in the formose reaction of paraformaldehyde solutions. Paraformaldehyde sublimed into Ca(OH)2 suspension was not transformed to sugars by formose reaction, only to methanol and formate by Cannizzaro reaction. A minute trace of glycolaldehyde — 3 ppm — was sufficient to initiate

  9. Ultrafast Laser Spectroscopyof Chemical Reactions

    E-print Network

    Zewail, Ahmed

    Ultrafast Laser Spectroscopyof Chemical Reactions - Joseph L. Kneeand AhmedH. Zewail California of chemical physics is to understand how chemi- cal reactions complete their journey from reactants to prod at the molecular level. The making of new bonds (and the breaking of old ones) in elementary chemical reactions

  10. Magnetic Effects in Chemical Reactions

    Microsoft Academic Search

    Anatolii L Buchachenko

    1976-01-01

    The Review discusses in what elementary chemical reactions the intrinsic angular momentum of electrons and nuclei is conserved and in what reactions it is not conserved, how weak electron-nuclear magnetic interaction and an external magnetic field influence the conservation of angular momentum and what are the consequences of this effect, and what magnetic effects occur in chemical reactions, as well

  11. Insect bite reactions.

    PubMed

    Singh, Sanjay; Mann, Baldeep Kaur

    2013-01-01

    Insects are a class of living creatures within the arthropods. Insect bite reactions are commonly seen in clinical practice. The present review touches upon the medically important insects and their places in the classification, the sparse literature on the epidemiology of insect bites in India, and different variables influencing the susceptibility of an individual to insect bites. Clinical features of mosquito bites, hypersensitivity to mosquito bites Epstein-Barr virus NK (HMB-EBV-NK) disease, eruptive pseudoangiomatosis, Skeeter syndrome, papular pruritic eruption of HIV/AIDS, and clinical features produced by bed bugs, Mexican chicken bugs, assassin bugs, kissing bugs, fleas, black flies, Blandford flies, louse flies, tsetse flies, midges, and thrips are discussed. Brief account is presented of the immunogenic components of mosquito and bed bug saliva. Papular urticaria is discussed including its epidemiology, the 5 stages of skin reaction, the SCRATCH principle as an aid in diagnosis, and the recent evidence supporting participation of types I, III, and IV hypersensitivity reactions in its causation is summarized. Recent developments in the treatment of pediculosis capitis including spinosad 0.9% suspension, benzyl alcohol 5% lotion, dimethicone 4% lotion, isopropyl myristate 50% rinse, and other suffocants are discussed within the context of evidence derived from randomized controlled trials and key findings of a recent systematic review. We also touch upon a non-chemical treatment of head lice and the ineffectiveness of egg-loosening products. Knockdown resistance (kdr) as the genetic mechanism making the lice nerves insensitive to permethrin is discussed along with the surprising contrary clinical evidence from Europe about efficacy of permethrin in children with head lice carrying kdr-like gene. The review also presents a brief account of insects as vectors of diseases and ends with discussion of prevention of insect bites and some serious adverse effects of mosquito coil smoke. PMID:23442453

  12. Low Energy Nuclear Reactions?

    E-print Network

    CERN. Geneva; Faccini, R.

    2014-01-01

    After an introduction to the controversial problem of Low Energy Nuclear Reactions (LENR) catalyzed by neutrons on metallic hydride surfaces we present the results of an experiment, made in collaboration with ENEA Labs in Frascati, to search neutrons from plasma discharges in electrolytic cells. The negative outcome of our experiment goes in the direction of ruling out those theoretical models expecting LENR to occur in condensed matter systems under specific conditions. Our criticism on the theoretical foundations of such models will also be presented.

  13. Gravitational radiation reaction

    E-print Network

    Takahiro Tanaka

    2005-10-04

    We give a short personally-biased review on the recent progress in our understanding of gravitational radiation reaction acting on a point particle orbiting a black hole. The main motivation of this study is to obtain sufficiently precise gravitational waveforms from inspiraling binary compact stars with a large mass ratio. For this purpose, various new concepts and techniques have been developed to compute the orbital evolution taking into account the gravitational self-force. Combining these ideas with a few supplementary new ideas, we try to outline a path to our goal here.

  14. Reactions of the Formamidines

    E-print Network

    Myers, Tennyson

    1912-06-01

    common of which are; - 1. Heating formanilide. 2* Action of phosphorous trichloride on a mixture of a form- anilide and amine. ?># The reaction of orthoformicester on a primary amine, or- thoformic ester. And aniline giving diphenylformamidine... amidine, the benzol can bo distilled off and the hydrochloride broken up with HaOH; or if this is not practicable the NaOH can be added directly, the benzol may bo distilled off with steam, and the amidine filtered off dried and recry3tallized from...

  15. Geometric description of chemical reactions

    E-print Network

    Hernando Quevedo; Diego Tapias

    2013-01-02

    We use the formalism of Geometrothermodynamics to describe chemical reactions in the context of equilibrium thermodynamics. Any chemical reaction in a closed system is shown to be described by a geodesic in a $2-$dimensional manifold that can be interpreted as the equilibrium space of the reaction. We first show this in the particular cases of a reaction with only two species corresponding to either two ideal gases or two van der Waals gases. We then consider the case of a reaction with an arbitrary number of species. The initial equilibrium state of the geodesic is determined by the initial conditions of the reaction. The final equilibrium state, which follows from a thermodynamic analysis of the reaction, is shown to correspond to a coordinate singularity of the thermodynamic metric which describes the equilibrium manifold.

  16. Geometric description of chemical reactions

    E-print Network

    Quevedo, Hernando

    2013-01-01

    We use the formalism of Geometrothermodynamics to describe chemical reactions in the context of equilibrium thermodynamics. Any chemical reaction in a closed system is shown to be described by a geodesic in a $2-$dimensional manifold that can be interpreted as the equilibrium space of the reaction. We first show this in the particular cases of a reaction with only two species corresponding to either two ideal gases or two van der Waals gases. We then consider the case of a reaction with an arbitrary number of species. The initial equilibrium state of the geodesic is determined by the initial conditions of the reaction. The final equilibrium state, which follows from a thermodynamic analysis of the reaction, is shown to correspond to a coordinate singularity of the thermodynamic metric which describes the equilibrium manifold.

  17. Coalescence reactions of fullerenes

    NASA Astrophysics Data System (ADS)

    Yeretzian, Chahan; Hansen, Klavs; Diederich, François; Whetten, Robert L.

    1993-03-01

    This article reviews recent work in Los Angeles on elementary processes in fullerene vapors. The production of fullerene molecules typically involves extreme high-temperature conditions and processes which are poorly understood at date [1 3]. Once generated, these molecules may represent the most stable molecules known [4,5]. In a recent work [C. Yeretzian et al., Nature 359, 44 (1992)] we presented clear evidence for coalescence reactions between fullerene molecules. Mass spectrometric measurements on hot, dense vapors of small fullerenes (C60 and C70) reveal the formation of stable higher fullerenes which are multiples of the initial masses. These processes are shown to occur in the gas-phase rather than in the solid film and their dependences on laser fluence and He-gas pressure are investigated. Three distinct reactions are proposed—coalescence, emission and capture—to account for the observed distributions at higher fullerene sizes. Specifically, the heat of coalescence is released through emission of small, even-numbered fragments which, in a very dense vapor, are efficiently captured by other coalesced fullerenes. These findings have implications for the long-time stability of the fullerene vapor, and for the mechanism of fullerene formation and growth, and may open new ways to the synthesis of selected higher fullerenes and encapsulation compounds.

  18. Microwave initiated reactions: Pechmann coumarin synthesis, Biginelli reaction, and acylation

    Microsoft Academic Search

    Maghar S. Manhas; Subhendu N. Ganguly; Somdatta Mukherjee; Amit K. Jain; Ajay K. Bose

    2006-01-01

    An energy-efficient protocol has been developed for solvent-free reactions that are mildly exothermic but not spontaneous. The exothermic reaction mixture—on several g-scale—is exposed for about 30s to low power (about 200W) microwaves and then the microwave oven is switched off. After this short burst of energy, the exothermic reaction gets initiated and proceeds on its own to completion. A number

  19. Peripherality of breakup reactions

    NASA Astrophysics Data System (ADS)

    Capel, P.; Nunes, F. M.

    2007-05-01

    The sensitivity of elastic breakup to the interior of the projectile wave function is analyzed. Breakup calculations of loosely bound nuclei (B8 and Be11) are performed with two different descriptions of the projectile. The descriptions differ strongly in the interior of the wave function, but exhibit identical asymptotic properties, namely the same asymptotic normalisation coefficient, and phase shifts. Breakup calculations are performed at intermediate energies (40 70 MeV/nucleon) on lead and carbon targets as well as at low energy (26 MeV) on a nickel target. No dependence on the projectile description is observed. This result confirms that breakup reactions are peripheral in the sense that they probe only the external part of the wave function. These measurements are thus not directly sensitive to the total normalization of the wave function, i.e., spectroscopic factor.

  20. ISMP Adverse Drug Reactions

    PubMed Central

    2013-01-01

    The purpose of this feature is to heighten awareness of specific adverse drug reactions (ADRs), discuss methods of prevention, and promote reporting of ADRs to the US Food and Drug Administration’s (FDA’s) MedWatch program (800-FDA-1088). If you have reported an interesting, preventable ADR to MedWatch, please consider sharing the account with our readers. Write to Dr. Shuster at ISMP, 200 Lakeside Drive, Suite 200, Horsham, PA 19044 (phone: 215-947-7797; fax: 215-914-1492; e-mail: joel.shuster@temple.edu). Your report will be published anonymously unless otherwise requested. This feature is provided by the Institute for Safe Medication Practices (ISMP) in cooperation with the FDA’s MedWatch program and Temple University School of Pharmacy. ISMP is an FDA MedWatch partner. PMID:24421415

  1. Hypersensitivity reaction with deferasirox.

    PubMed

    Sharma, Atul; Arora, Ekta; Singh, Harmanjit

    2015-01-01

    Thalassemias comprise a group of hereditary blood disorders. Thalassemia major presents with anemia within the first 2 years of life requiring frequent blood transfusions for sustaining life. Regular blood transfusions lead to iron overload-related complications. Prognosis of thalassemia has improved because of the availability of iron-chelating agents. Oral iron chelators are the mainstay of chelation therapy. Deferasirox is a new-generation oral iron chelator for once daily usage. We herein describe a patient of beta thalassemia major who developed an allergic manifestation in the form of erythematous pruritic skin rashes to the oral iron chelator deferasirox. This is a rare adverse reaction reported with deferasirox that led to a therapeutic dilemma in this particular case. PMID:25969661

  2. Hydrocracking reactions and catalysis

    SciTech Connect

    Dolbear, G.E. [G.E. Dolbear and Associates, Diamond Bar, CA (United States)

    1995-12-31

    Hydrocracking processes convert aromatic gas oils into high quality gasoline, diesel, and turbine stocks. In doing this, they saturate aromatic rings, crack naphthenes and paraffins, and saturate olefins formed during cracking. The organic chemistry of these steps is well known. Catalysts for hydrocracking contain components for both the hydrogenation and cracking reactions. Hydrogenation activity is provided by Pd or promoted molybdenum or tungsten sulfides. Cracking takes place on strong acid sites in zeolites or amorphous silica aluminas. Specialty catalysts including narrow pore zeolites are used in dewaxing tube oil stocks. Basic nitrogen compounds such as quinoline can poison the acid sites. They are usually removed in a pretreating step, typically with a nickel/molybdenum sulfide catalyst that also removes sulfur.

  3. Formaldehyde reactions in dark clouds

    NASA Technical Reports Server (NTRS)

    Sen, A. D.; Anicich, V. G.; Federman, S. R.

    1992-01-01

    The low-pressure reactions of formaldehyde (H2CO) with D(+), D2(+), D3(+), and He(+) are studied by the ion-cyclotron resonance technique. These reactions are potential loss processes for formaldehyde in cores of dark interstellar clouds. The deuterated reactants represent direct analogs for protons. Rate coefficients and branching ratios of product channels have been measured. Charge transfer is observed to be the dominant reaction of H2CO with D(+), D2(+), and He(+) ions. Only the D3(+) reaction exhibits a proton-transfer channel. All reactions proceed at rate coefficients near the collision limit. Proton-deuteron exchange reactions are found to be inefficient processes in the formaldehyde system.

  4. Immediate hypersensitivity reaction with mango.

    PubMed

    Shah, Ashok; Gera, Kamal

    2014-01-01

    Hypersensitivity to the fruit mango is extremely rare and can exhibit either as immediate or delayed reactions. Since 1939, only 22 patients (10 with immediate type I reactions and 12 with delayed) have been documented with allergy to mango. History of atopy and geographical region may influence the type of reaction. Immediate reactions occurred most often in patients with history of atopy, while delayed reactions developed in non-atopic individuals. Clustering of delayed hypersensitivity reports from Australia and immediate reactions from Europe has been documented. We report a 50-year-old man with immediate type I hypersensitivity to mango, who developed cough, wheezing dyspnoea, generalised itching and abdominal discomfort after ingestion of mango. Life threatening event can also happen making it imperative to diagnose on time, so as to prevent significant morbidity and potential mortality. PMID:25133813

  5. Radiation reaction in various dimensions

    Microsoft Academic Search

    D. V. Gal

    We discuss the radiation reaction problem for an electric charge moving in flat space-time of arbitrary dimensions. It is shown that four is the unique dimension where a local differential equation exists accounting for the radiation reaction and admitting a consistent mass-renormalization (the Dirac-Lorentz equation). In odd dimensions the Huygens principle does not hold; as a result, the radiation reaction

  6. Racemization in Prins Cyclization Reactions

    PubMed Central

    Jasti, Ramesh

    2008-01-01

    Isotopic labeling experiments were performed in order to elucidate a new mechanism for racemization in Prins cyclization reactions. The loss in optical activity for these reactions was shown to occur by 2-oxonia-Cope rearrangements by way of a (Z)-oxocarbenium ion intermediate. Reaction conditions such as solvent, temperature, and the nucleophile employed played a critical role in whether an erosion in enantiomeric excess was observed. Additionally, certain structural features of Prins cyclization precursors were also shown to be important for preserving optical purity in these reactions. PMID:17031979

  7. Speeding chemical reactions by focusing

    E-print Network

    A. M. Lacasta; L. Ramirez-Piscina; J. M. Sancho; K. Lindenberg

    2012-12-13

    We present numerical results for a chemical reaction of colloidal particles which are transported by a laminar fluid and are focused by periodic obstacles in such a way that the two components are well mixed and consequently the chemical reaction is speeded up. The roles of the various system parameters (diffusion coefficients, reaction rate, obstacles sizes) are studied. We show that focusing speeds up the reaction from the diffusion limited rate (t to the power -1/2) to very close to the perfect mixing rate, (t to the power -1).

  8. Speeding chemical reactions by focusing

    E-print Network

    Lacasta, A M; Sancho, J M; Lindenberg, K

    2012-01-01

    We present numerical results for a chemical reaction of colloidal particles which are transported by a laminar fluid and are focused by periodic obstacles in such a way that the two components are well mixed and consequently the chemical reaction is speeded up. The roles of the various system parameters (diffusion coefficients, reaction rate, obstacles sizes) are studied. We show that focusing speeds up the reaction from the diffusion limited rate (t to the power -1/2) to very close to the perfect mixing rate, (t to the power -1).

  9. Reaction Mechanisms Effects of Bending Excitation on the Reaction of

    E-print Network

    Zare, Richard N.

    less energy. They do not obviously map onto the reaction coordinate. Moreover, it is known from-frequency vibrations are more easily populated at thermal temperatures. To date, the influence of bending vibrations as a prototype and for its practical importance to combustion and atmospheric chemis- try. This reaction

  10. Activity : Fusion Reactions

    NSDL National Science Digital Library

    2007-12-12

    This activity gives students an opportunity to learn about the elements created in the cores of high-mass stars by fusion reactions. They will discover that all stars start by burning hydrogen and end up creating many heavier elements inside their cores, elements that will be released into space when it dies in a supernova explosion. Students associate a layer with an element that is being produced by the high-mass star. This will illustrate that as the temperature of the star increases with depth, the ash of each burning stage becomes the fuel for the next stage. Surrounding the core of iron nuclei is a layer of silicon fusion, then magnesium, then neon, then oxygen, then carbon, then helium, and lastly, in the relatively cool periphery of the core, hydrogen fuses into helium. Students will draw their own version of the onion-like nature of the core of a star based on the model and explain the process that occurs at each layer.

  11. Two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1998-05-05

    A vertical two chamber reaction furnace is described. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 C and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  12. Participants' Reactions to Computerized Testing.

    ERIC Educational Resources Information Center

    Moe, Kim C.; Johnson, Marilyn F.

    This study investigated participants' reactions to computerized testing and assessed the practicability of this testing method in the classroom. A sample of 315 secondary-level students took a computerized and a printed version of a standardized aptitude test battery and a survey assessing their reactions to the computerized testing. Overall…

  13. Neutron capture reactions in astrophysics

    SciTech Connect

    Kaeppeler, F.

    1985-01-15

    About 2/3 of the chemical elements in nature were formed in neutron capture reactions. During the life of a star there are certain evolutionary stages where neutrons are available to build up the elements beyond iron which cannot be synthesized by charged particle reactions.

  14. Isosinglet approximation for nonelastic reactions

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.

    1972-01-01

    Group theoretic relations are derived between different combinations of projectile and secondary particles which appear to have a broad range of application in spacecraft shielding or radiation damage studies. These relations are used to reduce the experimental effort required to obtain nuclear reaction data for transport calculations. Implications for theoretical modeling are also noted, especially for heavy-heavy reactions.

  15. Statistical Factors in Complexation Reactions.

    ERIC Educational Resources Information Center

    Chung, Chung-Sun

    1985-01-01

    Four cases which illustrate statistical factors in complexation reactions (where two of the reactants are monodentate ligands) are presented. Included are tables showing statistical factors for the reactions of: (1) square-planar complexes; (2) tetrahedral complexes; and (3) octahedral complexes. (JN)

  16. Entropy Effects in Chelation Reactions.

    ERIC Educational Resources Information Center

    Chung, Chung-Sun

    1984-01-01

    The entropy change for a reaction in aqueous solution can be evaluated as a combination of entropy factors. Valuable insight or understanding can be obtained from a detailed examination of these factors. Several entropy effects of inorganic chemical reactions are discussed as examples. (Author/JN)

  17. Foreign body reaction to biomaterials

    Microsoft Academic Search

    James M. Anderson; Analiz Rodriguez; David T. Chang

    2008-01-01

    The foreign body reaction composed of macrophages and foreign body giant cells is the end-stage response of the inflammatory and wound healing responses following implantation of a medical device, prosthesis, or biomaterial. A brief, focused overview of events leading to the foreign body reaction is presented. The major focus of this review is on factors that modulate the interaction of

  18. Reaction of tellurimides with thiourea

    SciTech Connect

    Naddaka, V.I.; Avanesyan, K.V.; Cherkinskaya, M.L.; Minkin, V.I.

    1987-10-20

    The authors establish that N-(p-tolylsulfonyl)di(p-methoxyphenyl)tellurimide, N-(trichloroacetyl)di(p-methoxyphenyl)tellurimide, and N-(phenylsulfonyl)diphenyltellurimide readily oxidize thiourea to cyanamide. The reaction products also include diaryl tellurides, the corresponding amides, and sulfur. The reaction path is attributed to the fact that thiourea participates in the thiol form. Infrared spectra are analyzed.

  19. Polymerase Chain Reaction Assay and

    E-print Network

    Paris-Sud XI, Université de

    , warm, and windy season, between January and May, localized epidemics of meningococcal meningitis occurPolymerase Chain Reaction Assay and Bacterial Meningitis Surveillance in Remote Areas, Niger Fati reference laboratory for meningitis in Niger used polymerase chain reaction (PCR) to enhance

  20. Theory of hybrid nuclear reactions

    SciTech Connect

    Udagawa, T.

    1983-01-01

    A theory of hybrid nuclear reactions, which are partially direct and partially compound, is presented. We review first the formulation of the theory, based on the optical theorem, and then its applications to a few example reactions. Discussions will be given on the physical picture (deep peripheral nature) of such hybrid processes emerging from the numerical studies. 25 references, 10 figures.

  1. The Variance Reaction Time Model

    ERIC Educational Resources Information Center

    Sikstrom, Sverker

    2004-01-01

    The variance reaction time model (VRTM) is proposed to account for various recognition data on reaction time, the mirror effect, receiver-operating-characteristic (ROC) curves, etc. The model is based on simple and plausible assumptions within a neural network: VRTM is a two layer neural network where one layer represents items and one layer…

  2. Domino reactions triggered by hydroformylation.

    PubMed

    Petricci, Elena; Cini, Elena

    2013-01-01

    HF reaction represents a selective method for the synthesis of aldehydes starting from alkenes. Because of versatile aldehydes reactivity, it is possible to perform different domino protocols based on contemporary HF, including Michael's reaction, reductive amination, cyclopropanation, lactonization, and many others. This overview reports on the last 5 years' results obtained on this field. PMID:23912442

  3. Radiation recall reaction following gemcitabine

    Microsoft Academic Search

    Gerald Fogarty; David Ball; Danny Rischin

    2001-01-01

    A case of dermatitis and myositis in the upper thorax following administration of gemcitabine in a 65-year-old woman with metastatic non small cell lung cancer (NSCLC) is described. The reaction and time course suggest a radiation recall phenomenon. This report joins a small but increasing number of radiation recall events related to gemcitabine. The possibility of a radiation recall reaction

  4. "Greening up" the Suzuki Reaction

    ERIC Educational Resources Information Center

    Aktoudianakis, Evangelos; Chan, Elton; Edward, Amanda R.; Jarosz, Isabel; Lee, Vicki; Mui, Leo; Thatipamala, Sonya S.; Dicks, Andrew P.

    2008-01-01

    This article describes the rapid, green synthesis of a biaryl compound (4-phenylphenol) via a Pd(0)-catalyzed Suzuki cross-coupling reaction in water. Mild reaction conditions and operational simplicity makes this experiment especially amenable to both mid- and upper-level undergraduates. The methodology exposes students to purely aqueous…

  5. Adverse reactions to drug additives.

    PubMed

    Simon, R A

    1984-10-01

    There is a long list of additives used by the pharmaceutical industry. Most of the agents used have not been implicated in hypersensitivity reactions. Among those that have, only reactions to parabens and sulfites have been well established. Parabens have been shown to be responsible for rare immunoglobulin E-mediated reactions that occur after the use of local anesthetics. Sulfites, which are present in many drugs, including agents commonly used to treat asthma, have been shown to provoke severe asthmatic attacks in sensitive individuals. Recent studies indicate that additives do not play a significant role in "hyperactivity." The role of additives in urticaria is not well established and therefore the incidence of adverse reactions in this patient population is simply not known. In double-blind, placebo-controlled studies, reactions to tartrazine or additives other than sulfites, if they occur at all, are indeed quite rare for the asthmatic population, even for the aspirin-sensitive subpopulation. PMID:6491109

  6. [Anaphylactic reaction following hair bleaching].

    PubMed

    Babilas, P; Landthaler, M; Szeimies, R-M

    2005-12-01

    Ammonium persulphate is a potent bleach and oxidizing agent that is commonly present in hair bleaches. Because bleaching is so commonly performed, hairdressers often develop allergic contact dermatitis to ammonium persulphate. In addition to this delayed reaction, asthma and rhinitis may develop as immediate reactions in those exposed to the fumes. Severe anaphylactic reactions are rare. We report a 24-year-old woman who acquired dermatitis following contact with bleaching substances while working as a hairdresser. After changing her profession, the dermatitis disappeared. Following the private use of a hairdressing bleach containing ammonium persulphate, she suffered a severe anaphylactic reaction with unconsciousness. The patient also developed an anaphylactic reaction three hours following patch testing with the hairdresser battery. The rub test with ammonium persulphate (2.5%) in a 1:100 solution was positive. PMID:15688222

  7. Concordant Chemical Reaction Networks and the Species-Reaction Graph

    E-print Network

    Shinar, Guy

    2012-01-01

    In a recent paper it was shown that, for chemical reaction networks possessing a subtle structural property called concordance, dynamical behavior of a very circumscribed (and largely stable) kind is enforced, so long as the kinetics lies within the very broad and natural class of weakly monotonic kinetics. In particular, multiple equilibria are precluded, as are degenerate positive equilibria. Moreover, under certain circumstances, also related to concordance, all real eigenvalues associated with a positive equilibrium are negative. Although concordance of a reaction network can be decided by readily available computational means, we show here that, when a nondegenerate network's Species Reaction Graph satisfies certain mild conditions, concordance and its dynamical consequences are ensured. These conditions are weaker than earlier ones invoked to establish kinetic system injectivity, which, in turn, is just one ramication of network concordance. Because the Species Reaction Graph resembles pathway depiction...

  8. Nuclear Reactions for Astrophysics and Other Applications

    SciTech Connect

    Escher, J E; Burke, J T; Dietrich, F S; Scielzo, N D; Ressler, J J

    2011-03-01

    Cross sections for compound-nuclear reactions are required for many applications. The surrogate nuclear reactions method provides an indirect approach for determining cross sections for reactions on unstable isotopes, which are difficult or impossible to measure otherwise. Current implementations of the method provide useful cross sections for (n,f) reactions, but need to be improved upon for applications to capture reactions.

  9. Reactions at supercritical conditions: Applications and fundamentals

    Microsoft Academic Search

    Phillip E. Savage; Sudhama Gopalan; Thamid I. Mizan; Christopher J. Martino; Eric E. Brock

    1995-01-01

    Supercritical fluids possess properties that make them attractive as media for chemical reactions. Conducting chemical reactions at supercritical conditions affords opportunities to manipulate the reaction environment (Solvent properties) by manipulating pressure, to enhance the solubilities of reactants and products, to eliminate interphase transport limitations on reaction rates, and to integrate reaction and separation unit operations. Supercritical conditions may be advantageous

  10. Tuff reaction vessel experiment

    SciTech Connect

    Bazan, F.; Rego, J.H.

    1986-06-01

    A laboratory leaching test has been performed as part of a project to evaluate the suitability of tuff rocks at Yucca Mountain, Nevada, as a site for a high-level nuclear waste repository. Glass samples of the kind that will be used to store nuclear waste were placed in water inside tuff vessels, and then the tuff vessels were placed in water inside Teflon containers. Glass-component leach rates and migration through the tuff were measured for samples of the ATM-8 actinide glass, which is a PNL 76-68 based glass with low levels of {sup 99}Tc, {sup 237}Np, {sup 238}U, and {sup 239}Pu to simulate wastes. Disc samples of this glass were leached at 90{sup 0}C to 30, 90, and 1983 days inside tuff vessels using a natural groundwater (J-13 well-water) as the leachant. Some samples were held by 304L stainless steel supports to evaluate the effect of this metal on the release rate of glass constituents. At the end of each leaching interval, the J-13 water present inside and outside the rock vessel was analyzed for glass components in solution. On the basis of these analyses, B, Mo, and Tc, appear to migrate through the rock at rates that depend on the porosity of each vessel and the time of reaction. U, Np, and Pu were found only in the inner leachate. Na, Si, and Sr are present in the rock as well as in the J-13 water, and the addition of these elements from the glass could not be determined. Normalized elemental mass loss values for B, Mo, and Tc were calculated using the combined concentrations of the inner and outer leachates and assuming a negligible retention on the rock. The maximum normalized release was 2.3 g/m{sup 2} for Tc. B, Mo, Tc, and Np were released linearly with respect to each other, with B and Mo released at about 85% of the Tc rate, and Np at 5-10% of the Tc rate. Plutonium was found at low levels in the inner leachate but was strongly sorbed on the steel and Teflon supports. Neptunium was sorbed to a lesser extent.

  11. Electron transfer reactions. Reactions of epoxyketones and benzoylaziridines with potassium

    Microsoft Academic Search

    Konda Ashok; Ravinara K. Tikare; Prashant V. Kamat; Manapurathu V. George

    1990-01-01

    The results of our studies on the reaction of some epoxyketones and aziridines with potassium in tetrahydrofuran (THF) are\\u000a presented. Treatment of trans-l,3-diphenyl-2,3-epozypropan-1-one (1a.) with, potassium, for example, gives a mixture of acetophenone (9), the chalcone 4a, the dihydrochalcone 14a, the cyclopentene isomers 20a and 21a, the hydroxy acid 10a and benzoic acid 6, whereas the reaction of 1a with

  12. Freeze Enhanced Halate Halide Reactions

    NASA Astrophysics Data System (ADS)

    Newberg, J. T.; Weaver, K.; Broderick, A.

    2014-12-01

    Relatively little is known about halate ion species (XO3-; X = I, Br, Cl) in atmospheric condensed phases. It was initial thought that iodate was a terminal stable species upon iodide oxidation. However, it is becoming increasingly recognized that reactions involving iodate can lead to reactive iodine, and this chemistry is accelerated under acidic conditions. The environmental concentrations and chemistry of bromate and chlorate are largely unexplored in environmental ices. We present results from a series of aqueous phase halate ion reactions with halides under acidic conditions, showing that the kinetics are strongly enhanced upon freezing. The products of these reactions are reactive halogens, which have important implications to marine boundary layer chemistry.

  13. Ketene reactions with tertiary amines.

    PubMed

    Allen, Annette D; Andraos, John; Tidwell, Thomas T; Vukovic, Sinisa

    2014-01-17

    Tertiary amines react rapidly and reversibly with arylketenes in acetonitrile forming observable zwitterions, and these undergo amine catalyzed dealkylation forming N,N-disubstituted amides. Reactions of N-methyldialkylamines show a strong preference for methyl group loss by displacement, as predicted by computational studies. Loss of ethyl groups in reactions with triethylamine also occur by displacement, but preferential loss of isopropyl groups in the phenylketene reaction with diisopropylethylamine evidently involves elimination. Quinuclidine rapidly forms long-lived zwitterions with arylketenes, providing a model for catalysis by cinchona and related alkaloids in stereoselective additions to ketenes. PMID:24359525

  14. Siloxy alkynes in annulation reactions.

    PubMed

    Qian, Hui; Zhao, Wanxiang; Sun, Jianwei

    2014-12-01

    Siloxy alkynes are a family of versatile species in organic synthesis. This account reviews the annulation reactions of siloxy alkynes for the synthesis of a variety of carbo- and heterocyclic products. With various dipolarophiles or dipolarophile-like reaction partners, siloxy alkynes are capable of forming small (three- to six-membered) rings. Recently, we have expanded the scope to the synthesis of medium- and large-ring lactones, enabled by the design of new amphoteric molecules as well as a new ring-expansion strategy. These annulation reactions provide not only practically useful syntheses of cyclic molecules, but also important understanding of the fundamental reactivity of siloxy alkynes. PMID:25171137

  15. Catalytic Organometallic Reactions of Ammonia

    PubMed Central

    Klinkenberg, Jessica L.

    2012-01-01

    Until recently, ammonia had rarely succumbed to catalytic transformations with homogeneous catalysts, and the development of such reactions that are selective for the formation of single products under mild conditions has encountered numerous challenges. However, recently developed catalysts have allowed several classes of reactions to create products with nitrogen-containing functional groups from ammonia. These reactions include hydroaminomethylation, reductive amination, alkylation, allylic substitution, hydroamination, and cross-coupling. This Minireview describes examples of these processes and the factors that control catalyst activity and selectivity. PMID:20857466

  16. Lowering barriers in surface reactions through concerted reaction mechanisms Sung Sakong,1

    E-print Network

    Ulm, Universität

    Lowering barriers in surface reactions through concerted reaction mechanisms Sung Sakong,1: Surface chemistry, reaction mechanisms, density functional calculations, methanol, hydrogen I. INTRODUCTION Chemical reactions at surfaces are of outstanding tech- nological importance since they correspond

  17. Reaction to Global Change Budget

    Microsoft Academic Search

    R. Jones

    1990-01-01

    A recent hearing of the Subcommittee on Veterans Administration\\/Department of Housing and Urban Development and Independent Agencies of the Senate Committee on Appropriations provided an early glimpse of congressional reaction to the administration's global change research budget.

  18. Severe cutaneous adverse drug reactions

    PubMed Central

    Verma, Rajesh; Vasudevan, Biju; Pragasam, Vijendran

    2013-01-01

    Severe cutaneous drug reactions are one of the commonest medical challenges presenting to an emergency room in any hospital. The manifestations range from maculopapular rash to severe systemic symptoms like renal failure and cardiovascular compromise. Toxic epidermal necrolysis, erythroderma, drug rash with eosinophilia and systemic symptoms, acute generalised exanthematous pustulosis and drug induced vasculitis are the common cutaneous drug reactions which can have severe morbidity and even mortality. Careful history taking of the lag period after drug intake and associated symptoms, along with detailed examination of the skin, mucosa and various systems, help in early diagnosis of these reactions. Early stoppage of the incriminating drug, specific therapy including corticosteroids, cyclosporine and intravenous immunoglobulin depending on the case along with supportive therapy and local measures help in salvaging most patients. An overview of these important cutaneous drug reactions along with their management is being reviewed in this article. PMID:24600147

  19. Method for conducting exothermic reactions

    DOEpatents

    Smith, L. Jr.; Hearn, D.; Jones, E.M. Jr.

    1993-01-05

    A liquid phase process for oligomerization of C[sub 4] and C[sub 5] isoolefins or the etherification thereof with C[sub 1] to C[sub 6] alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120 to 300 F. wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

  20. Solar-thermal reaction processing

    DOEpatents

    Weimer, Alan W; Dahl, Jaimee K; Lewandowski, Allan A; Bingham, Carl; Raska Buechler, Karen J; Grothe, Willy

    2014-03-18

    In an embodiment, a method of conducting a high temperature chemical reaction that produces hydrogen or synthesis gas is described. The high temperature chemical reaction is conducted in a reactor having at least two reactor shells, including an inner shell and an outer shell. Heat absorbing particles are included in a gas stream flowing in the inner shell. The reactor is heated at least in part by a source of concentrated sunlight. The inner shell is heated by the concentrated sunlight. The inner shell re-radiates from the inner wall and heats the heat absorbing particles in the gas stream flowing through the inner shell, and heat transfers from the heat absorbing particles to the first gas stream, thereby heating the reactants in the gas stream to a sufficiently high temperature so that the first gas stream undergoes the desired reaction(s), thereby producing hydrogen or synthesis gas in the gas stream.

  1. Method for conducting exothermic reactions

    DOEpatents

    Smith, Jr., Lawrence (Bellaire, TX); Hearn, Dennis (Houston, TX); Jones, Jr., Edward M. (Friendswood, TX)

    1993-01-01

    A liquid phase process for oligomerization of C.sub.4 and C.sub.5 isoolefins or the etherification thereof with C.sub.1 to C.sub.6 alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120.degree. to 300.degree. F. wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

  2. Radiation Reaction in Quantum Vacuum

    E-print Network

    Keita Seto

    2014-11-02

    From the development of the electron theory by H. A. Lorentz in 1906, many authors have tried to reformulate this model named "radiation reaction". P. A. M. Dirac derived the relativistic-classical electron model in 1938, which is now called the Lorentz-Abraham-Dirac model. But this model has the big difficulty of the run-away solution. Recently, this equation has become important for ultra-intense laser-electron (plasma) interactions. Therefore, it is desirable to stabilize this model of the radiation reaction for estimations. Via my recent research, I found a stabilized model of radiation reaction in quantum vacuum. This leads us to an updated Fletcher-Millikan's charge to mass ratio including radiation, de/dm, derived as the 4th order tensor measure. In this paper, I will discuss the latest update of the model and the ability of the equation of motion with radiation reaction in quantum vacuum via photon-photon scatterings.

  3. Pericyclic reactions in organic synthesis

    E-print Network

    Robinson-Surry, Julia M. (Julia Mae)

    2011-01-01

    Part I of this thesis describes a formal, metal-free, [2 + 2 + 2] cycloaddition strategy based on a cascade of two pericyclic processes. An intramolecular propargylic ene reaction of a 1,6-diyne is used to generate a ...

  4. Allergic adverse reactions to sulfonamides

    Microsoft Academic Search

    Geneviève Choquet-Kastylevsky; Thierry Vial; Jacques Descotes

    2002-01-01

    Antimicrobial sulfonamides were the first antimicrobial agents used effectively to treat infectious diseases. However, because\\u000a they may cause severe adverse drug reactions (ADRs) and because more effective agents have since been developed, sulfonamides\\u000a now are used for only a few indications in specific groups, such as AIDS patients. Skin reactions, from benign rash to potentially\\u000a lethal toxidermias, are the most

  5. Reaction Dynamics at Liquid Interfaces

    NASA Astrophysics Data System (ADS)

    Benjamin, Ilan

    2015-04-01

    The liquid interface is a narrow, highly anisotropic region, characterized by rapidly varying density, polarity, and molecular structure. I review several aspects of interfacial solvation and show how these affect reactivity at liquid/liquid interfaces. I specifically consider ion transfer, electron transfer, and SN2 reactions, showing that solvent effects on these reactions can be understood by examining the unique structure and dynamics of the liquid interface region.

  6. Theory of chemical reaction dynamics. Volume 4

    SciTech Connect

    Baer, M.

    1985-01-01

    This book examines some of the basic principles behind chemical reaction kinetics. Topics considered include generalized transition state theory, statistical dynamics, the theory of reactions at a solid surface, and the theory of reactions in solution.

  7. LATE REACTION, PERSISTENT REACTION AND DOUBTFUL ALLERGIC REACTION: THE PROBLEMS OF INTERPRETATION

    PubMed Central

    Sarma, Nilendu

    2009-01-01

    The standard method of patch test reading is to read the test site for any positive allergy at 48 hr and then again at 72/96 hr. A late reading on the seventh day is also advised to exclude the irritant reaction (IR) and to notice some delayed development of allergic reaction. However, multiple visits are often difficult for the patient; therefore, this late reading is sometimes omitted. Here a case of plantar hyperkeratosis, due to allergic contact dermatitis, is reported with some insight into interpretation of the patch test. The patient showed delayed patch test reaction to formaldehyde and colophony, which has never been reported before. PMID:20049272

  8. Annulation reactions of allenyl esters: an approach to bicyclic diones and medium-sized rings.

    PubMed

    Bhat, Bilal A; Maki, Samantha L; St Germain, Elijah J; Maity, Pradip; Lepore, Salvatore D

    2014-10-01

    A flexible approach to construct sterically congested bicyclo-alkenedione frameworks is reported. Under the action of potassium carbonate, ?-sulphonyl cycloalkanones are added to functionalized allenyl esters, leading to a lactone intermediate that is subsequently reduced to initiate an intramolecular aldol cyclization to [3.2.1], [3.3.1], and [4.3.1] bicycles. Oxidation then affords bicyclic diones in good three-step yields. Under exceptionally mild conditions, these bicycles are converted to highly functionalized medium-sized rings through a Grob-type fragmentation. PMID:25184784

  9. Chemical reaction equilibrium in nanoporous materials: NO dimerization reaction in carbon slit nanopores

    E-print Network

    Lisal, Martin

    Chemical reaction equilibrium in nanoporous materials: NO dimerization reaction in carbon slit of confinement on chemical reaction equilibrium in nanoporous materials. We use the reaction ensemble Monte Carlo of confinement on chemical properties, particularly on chemical reaction equilibria. A chemical reaction

  10. Inorganic Reaction Mechanisms Part II: Homogeneous Catalysis

    ERIC Educational Resources Information Center

    Cooke, D. O.

    1976-01-01

    Suggests several mechanisms for catalysis by metal ion complexes. Discusses the principal factors of importance in these catalysis reactions and suggests reactions suitable for laboratory study. (MLH)

  11. Reaction rates for mesoscopic reaction-diffusion kinetics

    E-print Network

    Stefan Hellander; Andreas Hellander; Linda Petzold

    2015-01-28

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework, frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a mixed boundary condition at the reaction radius of two molecules. We also establish fundamental limits for the range of mesh resolutions for which this approach yields accurate results, and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics.

  12. Total synthesis of diterpenoid steenkrotin?a.

    PubMed

    Pan, Saiyong; Xuan, Jun; Gao, Beiling; Zhu, An; Ding, Hanfeng

    2015-06-01

    A concise and diastereoselective total synthesis of the diterpenoid (±)-steenkrotin?A is described for the first time. The strategy mainly features three key ring formations: 1)?a rhodium-catalyzed O?H bond insertion followed by an intramolecular carbonyl-ene reaction to build up the tetrahydrofuran subunit; 2)?sequential SmI2 -mediated Ueno-Stork and ketyl-olefin cyclizations to construct the [5,7] spirobicyclic skeleton; and 3)?an intramolecular aldol condensation/vinylogous retro-aldol/aldol sequence to form the final six-membered ring with inversion of the relative configuration at the C7 position. PMID:25891977

  13. Reaction bonding of ceramics by gas-metal reactions

    SciTech Connect

    Derby, B. [Univ. of Oxford (United Kingdom)

    1995-09-01

    Reaction bonding may offer the potential for low final shrinkage ceramic processing using composite reactive metal and ceramic filler green bodies. However the process is shown to consist of two distinct steps of initial reaction leading to volume expansion followed by a second sintering step, often at a higher temperature, which leads to shrinkage. By careful choice of green compact composition and relative density it is possible to achieve zero final shrinkage. Control of the process to achieve zero-shrinkage is difficult because the initial powder milling leads to some metal pre-oxidation.

  14. Potential reactions among indoor pollutants

    NASA Astrophysics Data System (ADS)

    Weschler, Charles J.; Shields, Helen C.

    Reactions among indoor pollutants can produce products that, otherwise, might not be present in an indoor environment. To be relevant in an indoor setting, a chemical reaction must occur within a time interval shorter than or comparable to the residence time for a packet of indoor air. At typical air exchange rates, the reactions that meet this criterion include those of ozone with nitric oxide, nitrogen dioxide, and selected unsaturated hydrocarbons; thermal decomposition of peroxyacyl nitrates; numerous free radical reactions; and selected heterogeneous processes. Stable products include aldehydes, ketones, carboxylic acids and various organic nitrates. These reactions also generate free radicals, starting with the nitrate radical, Criegree biradicals, and peroxyacyl radicals, and leading to the hydroxyl, alkyl, alkylperoxy, hydroperoxy, and alkoxy radicals. Such radicals can react with other indoor species yielding additional aldehydes, ketones, carboxylic acids, dinitrates and peroxyacyl nitrates. Some of the potential products are known or suspected to be irritating (e.g. methacrolein, nonanoic acid, 1,2-propanediol dinitrate, peroxybenzoyl nitrate, and radical anions of the type [Cl… NO 2] -) However, some of these same products are difficult to detect using the sampling and analysis techniques currently applied to indoor air.

  15. Nonlocality in deuteron stripping reactions.

    PubMed

    Timofeyuk, N K; Johnson, R C

    2013-03-15

    We propose a new method for the analysis of deuteron stripping reactions, A(d,p)B, in which the nonlocality of nucleon-nucleus interactions and three-body degrees of freedom are accounted for in a consistent way. The model deals with equivalent local nucleon potentials taken at an energy shifted by ?40??MeV from the "E(d)/2" value frequently used in the analysis of experimental data, where E(d) is the incident deuteron energy. The "E(d)/2" rule lies at the heart of all three-body analyses of (d, p) reactions performed so far with the aim of obtaining nuclear structure properties such as spectroscopic factors and asymptotic normalization coefficients that are crucial for our understanding of nuclear shell evolution in neutron- and proton-rich regions of the nuclear periodic table and for predicting the cross sections of stellar reactions. The large predicted shift arises from the large relative kinetic energy of the neutron and proton in the incident deuteron in those components of the n+p+A wave function that dominate the (d, p) reaction amplitude. The large shift reduces the effective d-A potentials and leads to a change in predicted (d, p) cross sections, thus affecting the interpretation of these reactions in terms of nuclear structure. PMID:25166525

  16. Quantifying mixing using equilibrium reactions

    SciTech Connect

    Wheat, Philip M. [Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, Arizona 85287-6106 (United States); Posner, Jonathan D. [Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, Arizona 85287-6106 (United States); Department of Chemical Engineering, Arizona State University, Tempe, Arizona 85287-6106 (United States)

    2009-03-15

    A method of quantifying equilibrium reactions in a microchannel using a fluorometric reaction of Fluo-4 and Ca{sup 2+} ions is presented. Under the proper conditions, equilibrium reactions can be used to quantify fluid mixing without the challenges associated with constituent mixing measures such as limited imaging spatial resolution and viewing angle coupled with three-dimensional structure. Quantitative measurements of CaCl and calcium-indicating fluorescent dye Fluo-4 mixing are measured in Y-shaped microchannels. Reactant and product concentration distributions are modeled using Green's function solutions and a numerical solution to the advection-diffusion equation. Equilibrium reactions provide for an unambiguous, quantitative measure of mixing when the reactant concentrations are greater than 100 times their dissociation constant and the diffusivities are equal. At lower concentrations and for dissimilar diffusivities, the area averaged fluorescence signal reaches a maximum before the species have interdiffused, suggesting that reactant concentrations and diffusivities must be carefully selected to provide unambiguous, quantitative mixing measures. Fluorometric equilibrium reactions work over a wide range of pH and background concentrations such that they can be used for a wide variety of fluid mixing measures including industrial or microscale flows.

  17. Reaction Exposed: The Big Chill!

    NSDL National Science Digital Library

    CREAM GK-12 Program, Engineering Education Research Center, College of Engineering and Architecture,

    Students investigate the endothermic reaction involving citric acid, sodium bicarbonate and water to produce carbon dioxide, water and sodium citrate. In the presence of water [H2O], citric acid [C6H8O7] and sodium bicarbonate [NaHCO3] (also known as baking soda) react to form sodium citrate [Na3C6H5O7], water [H2O], and carbon dioxide [CO2]. Students test a stoichiometric version of the reaction followed by testing various perturbations on the stoichiometric version in which each reactant (citric acid, sodium bicarbonate, and water) is strategically doubled or halved to create a matrix of the effect on the reaction. By analyzing the test matrix data, they determine the optimum quantities to use in their own production companies to minimize material cost and maximize CO2 production. They use their test data to "scale-up" the system from a quart-sized ziplock bag to a reaction tank equal to the volume of their classroom. They collect data on reaction temperature and CO2 production.

  18. Surface reactions of natural glasses

    SciTech Connect

    White, A.F.

    1986-12-31

    Reactions at natural glass surfaces are important in studies involving nuclear waste transport due to chemical control on ground water in host rocks such as basalt and tuff, to potential diffusion into natural hydrated glass surfaces and as natural analogs for waste glass stability. Dissolution kinetics can be described by linear surface reaction coupled with cation interdiffusion with resulting rates similar to those of synthetic silicate glasses. Rates of Cs diffusion into hydrated obsidian surfaces between 25{sup 0} and 75{sup 0}C were determined by XPS depth profiles and loss rates from aqueous solutions. Calculated diffusion coefficients were ten others of magnitude more rapid than predicted from an Arrhenius extrapolation of high temperature tracer diffusion data due to surface hydration reactions.

  19. Vitamin B12 catalysed reactions.

    PubMed

    Giedyk, Maciej; Goliszewska, Katarzyna; Gryko, Dorota

    2015-05-26

    Vitamin B12 (cobalamin, ) is one of a few naturally occurring organometallic molecules. As a cofactor for adenosylcobalamin-dependent and methylcobalamin-dependent enzymes, it plays a crucial role in biological processes, including DNA synthesis and regulation, nervous system function, red blood cell formation, etc. Enzymatic reactions, such as isomerisation, dehalogenation, and methyl transfer, rely on the formation and cleavage of the Co-C bond. Because it is a natural, nontoxic, environmentally benign cobalt complex, cobalamin () has been successfully utilised in organic synthesis as a catalyst for Co-mediated reactions. This tutorial review concisely describes cobalamin-catalysed organic reactions that hold promise for environmentally friendly cobalt catalysis, leaving the reader with basic knowledge and the ability to harness the catalytic potential of this fascinating molecule. PMID:25945462

  20. Radiation reaction in quantum vacuum

    NASA Astrophysics Data System (ADS)

    Seto, Keita

    2015-02-01

    Since the development of the radiating electron theory by P. A. M. Dirac in 1938 [P. A. M. Dirac, Proc. R. Soc. Lond. A 167, 148 (1938)], many authors have tried to reformulate this model, called the "radiation reaction". Recently, this equation has become important for ultra-intense laser-electron (plasma) interactions. In our recent research, we found a stabilized model of the radiation reaction in quantum vacuum [K. Seto et al., Prog. Theor. Exp. Phys. 2014, 043A01 (2014)]. It led us to an updated Fletcher-Millikan charge-to-mass ratio including radiation. In this paper, I will discuss the generalization of our previous model and the new equation of motion with the radiation reaction in quantum vacuum via photon-photon scatterings and also introduce the new tensor d{E}^{? ? ? ? }/dm, as the anisotropy of the charge-to-mass ratio.

  1. Reaction theory for exotic nuclei

    SciTech Connect

    Bonaccorso, Angela [INFN, Sez. di Pisa, 56127 Pisa. (Italy)

    2014-05-09

    Exotic nuclei are usually defined as those with unusual N/Z ratios. They can be found in the crust of neutron stars enbedded in a sea of electrons or created in laboratory by fragmentation of a primary beam (in-flight method) or of the target (ISOL method). They are extremely important for nuclear astrophysics, see for example Ref.[1]. Furthermore by studying them we can check the limits of validity of nuclear reaction and structure models. This contribution will be devoted to the understanding of how by using reaction theory and comparing to the data we can extract structure information. We shall discuss the differences between the mechanisms of transfer and breakup reactions, an we will try to explain how nowadays it is possible to do accurate spectroscopy in extreme conditions.

  2. Radiation reaction in various dimensions

    E-print Network

    D. V. Gal'tsov

    2001-12-12

    We discuss the radiation reaction problem for an electric charge moving in flat space-time of arbitrary dimensions. It is shown that four is the unique dimension where a local differential equation exists accounting for the radiation reaction and admitting a consistent mass-renormalization (the Dirac-Lorentz equation). In odd dimensions the Huygens principle does not hold; as a result, the radiation reaction force depends on the whole past history of a charge (radiative tail). We show that the divergence in the tail integral can be removed by the mass renormalization only in the 2+1 theory. In even dimensions higher than four, divergences can not be removed by a renormalization.

  3. Capture Reactions In The CNO Cycles

    SciTech Connect

    Uberseder, Ethan; Goerres, Joachim; Wiescher, Michael [Department of Physics and Joint Institute for Nuclear Astrophysics University of Notre Dame, Notre Dame, IN 46556 (United States)

    2009-01-28

    Proton capture reactions in the CNO cycles define the energy production, nucleosynthesis and timescale of stellar hydrogen burning in massive stars. This paper investigates present uncertainties and inconsistencies in the low energy cross section and reaction rates of critical CNO reactions. The results indicate that new measurements are necessary to reduce the present uncertainties in the reaction rates of the CNO process.

  4. Foreign Body Reactions to Plastic Implants

    Microsoft Academic Search

    David E. Ocumpaugh; Henry L. Lee

    1970-01-01

    There are three types of foreign body reactions to plastic implants: 1) reactions due to physical characteristics of the implant, 2) reactions due directly to chemical properties of the implant, and 3) immune reactions. Responses which vary with the physical properties of the implant are epithelial encapsulation of the plastic, epithelial keratinization in cutaneous implants, thickening of the connective tissue

  5. REACTIONS BETWEEN REFRACTORY OXIDES AND GRAPHITE

    Microsoft Academic Search

    K. L. Komarek; A. Coucoulas; N. Klinger

    1963-01-01

    Reactions of alumina, magnesia, spinel, and beryllia with graphite were ; studied in vacuum by measuring the amount of carbon monoxide formed. Two types ; of reactions were observed: a diffusion-controlled reaction with alumina, ; beryllia, and thoria, and a phase boundary-controlled reaction with magnesia, ; beryllia, spinel, and titania. The following activation energies were obtained: ; 316 kcal for

  6. Experimental Demonstrations in Teaching Chemical Reactions.

    ERIC Educational Resources Information Center

    Hugerat, Muhamad; Basheer, Sobhi

    2001-01-01

    Presents demonstrations of chemical reactions by employing different features of various compounds that can be altered after a chemical change occurs. Experimental activities include para- and dia-magnetism in chemical reactions, aluminum reaction with base, reaction of acid with carbonates, use of electrochemical cells for demonstrating chemical…

  7. Diels-Alder Reaction 91 Diels-Alder Reaction

    E-print Network

    Jasperse, Craig P.

    : the boiling point for the xylene solvent is 138º; the actual temperature is actually somewhat 1 2 3 4 5 6 1 2-Alder Reaction 92 hotter than that, because the dissolved solutes elevate the boiling point to some degree. Once. Maleic anhydride (2) will function as the dienophile. Xylene (dimethylbenzene) is used as a high-boiling

  8. Learning to Predict Chemical Reactions

    PubMed Central

    Kayala, Matthew A.; Azencott, Chloé-Agathe; Chen, Jonathan H.

    2011-01-01

    Being able to predict the course of arbitrary chemical reactions is essential to the theory and applications of organic chemistry. Approaches to the reaction prediction problems can be organized around three poles corresponding to: (1) physical laws; (2) rule-based expert systems; and (3) inductive machine learning. Previous approaches at these poles respectively are not high-throughput, are not generalizable or scalable, or lack sufficient data and structure to be implemented. We propose a new approach to reaction prediction utilizing elements from each pole. Using a physically inspired conceptualization, we describe single mechanistic reactions as interactions between coarse approximations of molecular orbitals (MOs) and use topological and physicochemical attributes as descriptors. Using an existing rule-based system (Reaction Explorer), we derive a restricted chemistry dataset consisting of 1630 full multi-step reactions with 2358 distinct starting materials and intermediates, associated with 2989 productive mechanistic steps and 6.14 million unproductive mechanistic steps. And from machine learning, we pose identifying productive mechanistic steps as a statistical ranking, information retrieval, problem: given a set of reactants and a description of conditions, learn a ranking model over potential filled-to-unfilled MO interactions such that the top ranked mechanistic steps yield the major products. The machine learning implementation follows a two-stage approach, in which we first train atom level reactivity filters to prune 94.00% of non-productive reactions with a 0.01% error rate. Then, we train an ensemble of ranking models on pairs of interacting MOs to learn a relative productivity function over mechanistic steps in a given system. Without the use of explicit transformation patterns, the ensemble perfectly ranks the productive mechanism at the top 89.05% of the time, rising to 99.86% of the time when the top four are considered. Furthermore, the system is generalizable, making reasonable predictions over reactants and conditions which the rule-based expert does not handle. A web interface to the machine learning based mechanistic reaction predictor is accessible through our chemoinformatics portal (http://cdb.ics.uci.edu) under the Toolkits section. PMID:21819139

  9. Radiation reaction in quantum mechanics

    E-print Network

    Atsushi Higuchi

    1998-12-15

    The Lorentz-Dirac radiation reaction formula predicts that the position shift of a charged particle due to the radiation reaction is of first order in acceleration if it undergoes a small acceleration. A semi-classical calculation shows that this is impossible at least if the acceleration is due to a time-independent potential. Thus, the Lorentz-Dirac formula gives an incorrect classical limit in this situation. The correct classical limit of the position shift at the lowest order in acceleration is obtained by assuming that the energy loss at each time is given by the Larmor formula.

  10. Direct Reactions of Borromean Nuclei

    SciTech Connect

    Shimoura, S. [Center for Nuclear Study (CNS), University of Tokyo, Wako branch at RIKEN, Wako, Saitama 351-0198 (Japan)

    2008-04-29

    There are so-called Borromean nuclei on the drip-line in the nuclear chart, where any two-body subsystem has no bound state. The exotic structure and responses of Borromean nuclei have been studied by measurements of three-body (final-state) channels produced via direct reactions. Measurement of the three-body decay of the isospin partner of light drip-line nuclei populated by the charge exchange reaction is discussed as a means for studying the neutron halo structure. Experimental efforts to study nuclei beyond the drip-line, where many-body resonances may appear, are also presented.

  11. Reaction Dynamics and Multifragmentation in Fermi Energy Heavy Ion Reactions

    E-print Network

    R. Wada; T. Keutgen; K. Hagel; Y. G. Ma; J. Wang; M. Murray; L. Qin; P. Smith; J. B. Natowitz; R. Alfarro; J. Cibor; M. Cinausero; Y. El Masri; D. Fabris; E. Fioretto; A. Keksis; M. Lunardon; A. Makeev; N. Marie; E. Martin; A. Martinez-Davalos; A. Menchaca-Rocha; G. Nebbia; G. Prete; V. Rizzi; A. Ruangma; D. V. Shetty; G. Souliotis; P. Staszel; M. Veselsky; G. Viesti; E. M. Winchester; S. J. Yennello; Z. Majka; A. Ono

    2003-08-27

    The reaction systems, 64Zn + 58Ni, 64Zn + 92Mo, 64Zn + 197Au, at 26A, 35A and 47A MeV, have been studied both in experiments with a 4$\\pi$ detector array, NIMROD, and with Antisymmetrized Molecular Dynamics model calculations employing effective interactions corresponding to soft and stiff equations of state (EOS). Direct experimental observables, such as multiplicity distributions, charge distributions, energy spectra and velocity spectra, have been compared in detail with those of the calculations and a reasonable agreement is obtained. The velocity distributions of $\\alpha$ particles and fragments with Z >= 3 show distinct differences in calculations with the soft EOS and the stiff EOS. The velocity distributions of $\\alpha$ particle and Intermediate Mass Fragments (IMF's) are best described by the stiff EOS. Neither of the above direct observables nor the strength of the elliptic flow are sensitive to changes in the in-medium nucleon-nucleon (NN) cross sections. A detailed analysis of the central collision events calculated with the stiff EOS revealed that multifragmentation with cold fragment emission is a common feature predicted for all reactions studied here. A possible multifragmentation scenario is presented; after the preequilibrium emission ceases in the composite system, cold light fragments are formed in a hotter gas of nucleons and stay cold until the composite system underdoes multifragmentation. For reaction with 197Au at 47A MeV a significant radial expansion takes place. For reactions with 58Ni and 92Mo at 47A MeV semi-transparency becomes prominent. The differing reaction dynamics drastically change the kinematic characteristics of emitted fragments. This scenario gives consistent explanations for many existing experimental results in the Fermi energy domain.

  12. Thermodynamics of Enzyme-Catalyzed Reactions Database

    National Institute of Standards and Technology Data Gateway

    SRD 74 Thermodynamics of Enzyme-Catalyzed Reactions Database (Web, free access)   The Thermodynamics of Enzyme-Catalyzed Reactions Database contains thermodynamic data on enzyme-catalyzed reactions that have been recently published in the Journal of Physical and Chemical Reference Data (JPCRD). For each reaction the following information is provided: the reference for the data, the reaction studied, the name of the enzyme used and its Enzyme Commission number, the method of measurement, the data and an evaluation thereof.

  13. Cyclic Peptidomimetics and Pseudopeptides from Multicomponent Reactions

    Microsoft Academic Search

    Ludger A. Wessjohann; Cristiano Rhoden; Daniel Rivera; Otilie Vercillo

    \\u000a Multicomponent reactions (MCRs) that provide in the final product amides are suitable to produce peptides and peptide-like\\u000a moieties. The Passerini and Staudinger reactions provide one amide bond, and the Ugi-four-component reaction generates two\\u000a amides from three or even four (or more) components, respectively. The Ugi-reaction thus is most important to produce peptides\\u000a and peptoids while the Passerini reaction is useful

  14. Cyclic Peptidomimetics and Pseudopeptides from Multicomponent Reactions

    Microsoft Academic Search

    Ludger A. Wessjohann; Cristiano R. B. Rhoden; Daniel G. Rivera; Otilie Eichler Vercillo

    2010-01-01

    Multicomponent reactions (MCRs) that provide in the final product amides are suitable to produce peptides and peptide-like moieties. The Passerini and Staudinger reactions provide one amide bond, and the Ugi-four-component reaction generates two amides from three or even four (or more) components, respectively. The Ugi-reaction thus is most important to produce peptides and peptoids while the Passerini reaction is useful

  15. Carbene reactions produced by recoil excitation methods

    E-print Network

    Lowery, Kirby

    1968-01-01

    and CTCT. Reactions of CTF with 1, 3-butadiene, aliene, and cyclohexene were studied. Also, products of the Diels-Alder retrogression reaction of cyclohexene were observed when high energy tritium atoms reacted with cyclohexene. A qualitative discussion.... Experimental III. 'Reaction of Tritium-Labeled Monofluorocarbene with Higher Olefins 31 IV. Reactions of F -La'baled Monofluorocarbene V. Formation of Monochlorocarbene-Clgg VI. Formation of Monobromoc"rbene-Br VII. Diels-Alder Retrogression Reaction...

  16. Anaphylactic reactions to tolperisone (Mydocalm).

    PubMed

    Ribi, Camillo; Vermeulen, Christophe; Hauser, Conrad

    2003-06-28

    Four patients with anaphylaxis attributed to the intake of the centrally acting muscle relaxant tolperisone hydrochloride (Mydocalm) were observed at the Emergency Department of the Geneva University Hospital between November 2001 and March 2003. All patients were middle-aged women who took tolperisone for chronic muscular pain. All reactions occurred within an hour after oral intake of this drug frequently prescribed in Switzerland. The severity of anaphylaxis ranged from urticarial reactions to shock with arterial hypotension. Prick-to-prick skin testing performed in one patient with a tablet of tolperisone diluted in water was negative. Its globally restricted commercialisation may explain the lack of reports on such adverse effects in the MedLine database. Anaphylactic reactions to this drug, however, are mentioned in other sources such as the Swiss Drug Compendium and the WHO drug reaction database. Together, these findings suggest that anaphylaxis to tolperisone is not uncommon and should be known to physicians in countries where this drug is available. PMID:12947534

  17. Employer Reactions to Job Development.

    ERIC Educational Resources Information Center

    Zadny, Jerry J.

    1980-01-01

    Surveys of Portland and San Francisco employers about their reactions to job development activity found most were favorable or indifferent to being contacted by representatives serving the disabled. The hiring of state vocational rehabilitation agency clients increased with the number of employees and the number of positions filled. (Author)

  18. Knoevenagel Reaction of Unprotected Sugars

    NASA Astrophysics Data System (ADS)

    Scherrmann, Marie-Christine

    The Knoevenagel reaction of unprotected sugars was investigated in the 1950s using zinc chloride as promoter. The so-called Garcia Gonzalez reaction had been almost forgotten for 50 years, until the emergence of new water tolerant catalysts having Lewis acid behavior. The reaction was thus reinvestigated and optimal conditions have been found to prepare trihydroxylated furan derivatives from pentose or ?-tetrahydrofuranylfuran from hexoses with non-cyclic ?-keto ester or ?-diketones. Other valuable compounds such as ?-linked tetrahydrobenzofuranyl glycosides or hydroxyalkyl-3,3,6,6,-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione can be obtained using cyclic ?-dicarbonylic derivatives. Apart from one report in the 1950s, the Knoevenagel reaction of unprotected carbohydrate in basic condition has been studied only in the mid-1980s to prepare C-glycosyl barbiturates from barbituric acids and, later on, from non-cyclic ?-diketones, ?-C-glycosidic ketones. The efficient method exploited to prepare such compounds has found an industrial development in cosmetics.

  19. Polarization phenomena in hadronic reactions

    NASA Astrophysics Data System (ADS)

    Abramov, V. V.

    2014-01-01

    Predictions are made in the framework of the effective color field ( ECF) model for polarization observables in , A + A ? ? X and p + Pb ? pX reactions. The predictions can be checked in the polarization experiments at IHEP (SPASCHARM), JINR (NICA) and BNL (RHIC). Estimates of quark masses and anamolous chromomagnetic quark moments are given.

  20. Interfacial Reaction Studies Using ONIOM

    NASA Technical Reports Server (NTRS)

    Cardelino, Beatriz H.

    2003-01-01

    In this report, we focus on the calculations of the energetics and chemical kinetics of heterogeneous reactions for Organometallic vapor phase epitaxy (OMVPE). The work described in this report builds upon our own previous thermochemical and chemical kinetics studies. The first of these articles refers to the prediction of thermochemical properties, and the latter one deals with the prediction of rate constants for gaseous homolytic dissociation reactions. The calculations of this investigation are at the microscopic level. The systems chosen consisted of a gallium nitride (GaN) substrate, and molecular nitrogen (N2) and ammonia (NH3) as adsorbants. The energetics for the adsorption and the adsorbant dissociation processes were estimated, and reaction rate constants for the dissociation reactions of free and adsorbed molecules were predicted. The energetics for substrate decomposition was also computed. The ONIOM method, implemented in the Gaussian98 program, was used to perform the calculations. This approach has been selected since it allows dividing the system into two layers that can be treated at different levels of accuracy. The atoms of the substrate were modeled using molecular mechanics6 with universal force fields, whereas the adsorbed molecules were approximated using quantum mechanics, based on density functional theory methods with B3LYP functionals and 6-311G(d,p) basis sets. Calculations for the substrate were performed in slabs of several unit cells in each direction. The N2 and NH3 adsorbates were attached to a central location at the Ga-lined surface.

  1. Photochemical reactions for commercial synthesis

    Microsoft Academic Search

    Guillet

    1985-01-01

    Photochemical reactions are conducted using floating polymer beads on the surface of a moving body of water. The polymer bead is impregnated with a reactant, floated on the water in direct sunlight so as to expose the reactant to solar radiation, collected at a downstream location, treated to remove product from the polymer, and then the bead can be recycled.

  2. HADES results in elementary reactions

    NASA Astrophysics Data System (ADS)

    Ramstein, B.; Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, K.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Yu. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.

    2014-11-01

    Recent results obtained with the HADES experimental set-up at GSI are presented with a focus on dielectron production and strangeness in pp and quasi-free np reactions. Perspectives related to the very recent experiment using the pion beam at GSI are also discussed.

  3. Homeostasis in Chemical Reaction Pathways

    E-print Network

    Malyshev, V A; Zamyatin, A A

    2011-01-01

    We consider stochastic models of chemical reaction networks with time dependent input rates and several types of molecules. We prove that, in despite of strong time dependence of input rates, there is a kind of homeostasis phenomenon: far away from input nodes the mean numbers of molecules of each type become approximately constant (do not depend on time).

  4. Homeostasis in Chemical Reaction Pathways

    E-print Network

    V. A. Malyshev; A. D. Manita; A. A. Zamyatin

    2011-12-25

    We consider stochastic models of chemical reaction networks with time dependent input rates and several types of molecules. We prove that, in despite of strong time dependence of input rates, there is a kind of homeostasis phenomenon: far away from input nodes the mean numbers of molecules of each type become approximately constant (do not depend on time).

  5. Metal implants and surface reactions

    Microsoft Academic Search

    S. G. Steinemann

    1996-01-01

    A metal in living tissue is prone to corrosion. The interaction of the foreign body with the tissue involves the redox reaction (an electron exchange) at the interface, the hydrolysis (a proton exchange) of oxidehydrates as products of corrosion, and the formation of metal-organic complexes in the electrolyte. Denatured tissue in contact with the foreign body is the consequence. But

  6. Medications and Drug Allergic Reactions

    MedlinePLUS

    ... a medication. These include: body size, genetics, body chemistry or the presence of an underlying disease. Also, having an allergy to one drug predisposes an individual to have an allergy to another unrelated drug. Contrary to popular myth, a family history of a reaction to a specific drug does ...

  7. Hypersensitivity reactions to HIV therapy

    PubMed Central

    Chaponda, Mas; Pirmohamed, Munir

    2011-01-01

    Many drugs used for the treatment of HIV disease (including the associated opportunistic infections) can cause drug hypersensitivity reactions, which vary in severity, clinical manifestations and frequency. These reactions are not only seen with the older compounds, but also with the newer more recently introduced drugs. The pathogenesis is unclear in most cases, but there is increasing evidence to support that many of these are mediated through a combination of immunologic and genetic factors through the major histocompatibility complex (MHC). Genetic predisposition to the occurrence of these allergic reactions has been shown for some of the drugs, notably abacavir hypersensitivity which is strongly associated with the class I MHC allele, HLA-B*5701. Testing before the prescription of abacavir has been shown to be of clinical utility, has resulted in a change in the drug label, is now recommended in clinical guidelines and is practiced in most Western countries. For most other drugs, however, there are no good methods of prevention, and clinical monitoring with appropriate (usually supportive and symptomatic) treatment is required. There is a need to undertake further research in this area to increase our understanding of the mechanisms, which may lead to better preventive strategies through the development of predictive genetic biomarkers or through guiding the design of drugs less likely to cause these types of adverse drug reactions. PMID:21480946

  8. Reactions to threatening health messages

    PubMed Central

    2012-01-01

    Background Threatening health messages that focus on severity are popular, but frequently have no effect or even a counterproductive effect on behavior change. This paradox (i.e. wide application despite low effectiveness) may be partly explained by the intuitive appeal of threatening communication: it may be hard to predict the defensive reactions occurring in response to fear appeals. We examine this hypothesis by using two studies by Brown and colleagues, which provide evidence that threatening health messages in the form of distressing imagery in anti-smoking and anti-alcohol campaigns cause defensive reactions. Methods We simulated both Brown et al. experiments, asking participants to estimate the reactions of the original study subjects to the threatening health information (n = 93). Afterwards, we presented the actual original study outcomes. One week later, we assessed whether this knowledge of the actual study outcomes helped participants to more successfully estimate the effectiveness of the threatening health information (n = 72). Results Results showed that participants were initially convinced of the effectiveness of threatening health messages and were unable to anticipate the defensive reactions that in fact occurred. Furthermore, these estimates did not improve after participants had been explained the dynamics of threatening communication as well as what the effects of the threatening communication had been in reality. Conclusions These findings are consistent with the hypothesis that the effectiveness of threatening health messages is intuitively appealing. What is more, providing empirical evidence against the use of threatening health messages has very little effect on this intuitive appeal. PMID:23171445

  9. Photosynthesis-The Light Reactions

    Microsoft Academic Search

    K. Sauer

    1979-01-01

    During the past three or four years there has been a substantial advance in our knowledge of the light reactions in photosynthesis. This comes at a time of heightened interest in sunlight as a source of energy for our daily needs. The exploration of potential practical applications in this area will be helped by identifying the common features of the

  10. Hysterical Conversion Reactions in Childhood.

    ERIC Educational Resources Information Center

    Goodyear, Ian

    1981-01-01

    Retrospective analysis indicated hysterical conversion reactions are uncommon prior to age five, uncommon in in-patient psychiatric practice, and are more common among girls than among boys. The frequency of previous psychiatric difficulties in both the child and his/her family suggests that symptom formation is but one component in ongoing…

  11. The Pitfalls of Precipitation Reactions.

    ERIC Educational Resources Information Center

    Slade, Peter W.; Rayner-Canham, Geoffrey W.

    1990-01-01

    Described are some of the difficulties presented in these reactions by competing equilibria that are usually ignored. Situations involving acid-base equilibria, solubility product calculations, the use of ammonia as a complexing agent, and semiquantitative comparisons of solubility product values are discussed. (CW)

  12. Matter and Energy in Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    1900-01-01

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the final of four Science Objects in the Chemical Reactions SciPack. It explains how

  13. A Synthetic Reaction Network: Chemical Amplification Using Nonequilibrium Autocatalytic Reactions Coupled in Time

    E-print Network

    Ismagilov, Rustem F.

    A Synthetic Reaction Network: Chemical Amplification Using Nonequilibrium Autocatalytic Reactions reaction network synthesized in a microfluidic device. This chemical network performs chemical 5000-fold by a reaction autocatalytic in Co2+ . The microfluidic network is used to maintain the two chemical reactions

  14. Singular perturbation analysis of a diffusion/reaction system with a fast reaction

    E-print Network

    Seidman, Thomas I.

    are the binary reaction rates. We scale our units so µ = 1 and the diffusion coefficient1 is 1. This reactionSingular perturbation analysis of a diffusion/reaction system with a fast reaction Leonid V three species, two reactions (one of which is fast), and diffusion. Formal asymptotic expansion

  15. Ruthenium nanocatalysis on redox reactions.

    PubMed

    Veerakumar, Pitchaimani; Ramdass, Arumugam; Rajagopal, Seenivasan

    2013-07-01

    Nanoparticles have generated intense interest over the past 20 years due to their high potential applications in different areas such as catalysis, sensors, nanoscale electronics, fuel and solar cells and optoelectronics. As the large fractions of metal atoms are exposed to the surface, the use of metal nanoparticles as nanocatalysts allows mild reaction conditions and high catalytic efficiency in a large number of chemical transformations. They have emerged as sustainable heterogeneous catalysts and catalyst supports alternative to conventional materials. This review focuses on the synthesis, characterization and catalytic role of ruthenium nanoparticles (RuNPs) on the redox reactions of heteroatom containing organic compounds with the green reagent H2O2, a field that has attracted immense interest among the chemical, materials and industrial communities. We intend to present a broad overview of Ru nanocatalysts for redox reactions with an emphasis on their performance, stability and reusability. The growth in the chemistry of organic sulfoxides and N-oxides during last decade was due to their importance as synthetic intermediates for the production of a wide range of chemically and biologically active molecules. Thus design of efficient methods for the synthesis of sulfoxides and N-oxides becomes important. This review concentrates on the catalysis of RuNPs on the H2O2 oxidation of organic sulfides to sulfoxides and amines to N-oxides. The deoxygenation reactions of sulfoxides to sulfides and reduction of nitro compounds to amines are fundamental reactions in both chemistry and biology. Here, we also highlight the catalysis of metal nanoparticles on the deoxygenation of sulfoxides and sulfones and reduction of nitro compounds with particular emphasis on the mechanistic aspects. PMID:23901501

  16. Reactions of arsine with hemoglobin

    SciTech Connect

    Hatlelid, K.M.; Brailsford, C.; Carter, D.E. [Univ. of Arizona, Tucson, AZ (United States)] [Univ. of Arizona, Tucson, AZ (United States)

    1996-02-09

    The mechanism of arsine (AsH{sub 3}) induced hemolysis was studied in vitro using isolated red blood cells (RBCs) from the rat or dog. AsH{sub 3}-induced hemolysis of dog red blood cells was completely blocked by carbon monoxide (CO) preincubation and was reduced by pure oxygen (O{sub 2}) compared to incubations in air. Since CO and O{sub 2} bind to heme and also reduced hemolysis, these results suggested a reaction between AsH{sub 3} and hemoglobin in the hemeligand binding pocket or with the heme iron. Further, sodium nitrite induction of methemoglobin (metHb) to 85% and 34% of total Hb in otherwise intact RBCs resulted in 56% and 16% decreases in hemolysis, respectively, after incubation for 4 h. This provided additional evidence for the involvement of hemoglobin in the AsH{sub 3}-induced hemolysis mechanism. Reactions between AsH{sub 3} and hemoglobin were studied in solutions of purified dog hemoglobin. Spectrophotometric studies of the reaction of AsH{sub 3} with various purified hemoglobin species revealed that AsH{sub 3} reacted with HbO{sub 2} to produce metHb and, eventually, degraded Hb characterized by gross precipitation of the protein. AsH{sub 3} did not alter the spectrum of deoxyHb and did not cause degradation of metHb in oxygen, but bound to and reduced metHb in the absence of oxygen. These data indicate that a reaction of AsH{sub 3} with oxygenated hemoglobin, HbO{sub 2}, may lead to hemolysis, but there are reactions between AsH{sub 3} and metHb that may not be directly involved in the hemolytic process. 17 refs., 6 figs.

  17. Triangular-shaped reaction fronts in a catalytic surface reaction

    NASA Astrophysics Data System (ADS)

    Schaak, A.; Imbihl, R.

    1998-02-01

    The reaction between oxygen adsorbed on a Rh(111) surface and hydrogen has been investigated in titration experiments at low pressure ( p<10 -5 mbar) using photoemisson electron microscopy (PEEM) as spatially resolving method. The reactive removal of the (8×8)-O structure proceeds via a hole-eating mechanism. The shape and velocity of the front depends on the parameter p(H 2), temperature and the exposure time to oxygen. At very high O 2 exposures (?10 6 L) triangular reaction fronts are seen oriented parallel to close-packed rows of the (111) surface. The anisotropic front propagation on the isotropic Rh(111) surface is attributed to elastic stress at the interface between surface phases with different periodicities.

  18. The molecular dynamics of atmospheric reaction

    NASA Technical Reports Server (NTRS)

    Polanyi, J. C.

    1971-01-01

    Detailed information about the chemistry of the upper atmosphere took the form of quantitative data concerning the rate of reaction into specified states of product vibration, rotation and translation for exothermic reaction, as well as concerning the rate of reaction from specified states of reagent vibration, rotation and translation for endothermic reaction. The techniques used were variants on the infrared chemiluminescence method. Emphasis was placed on reactions that formed, and that removed, vibrationally-excited hydroxyl radicals. Fundamental studies were also performed on exothermic reactions involving hydrogen halides.

  19. The Biginelli Reaction Is a Urea-Catalyzed Organocatalytic Multicomponent Reaction.

    PubMed

    Puripat, Maneeporn; Ramozzi, Romain; Hatanaka, Miho; Parasuk, Waraporn; Parasuk, Vudhichai; Morokuma, Keiji

    2015-07-17

    The recently developed artificial force induced reaction (AFIR) method was applied to search systematically all possible multicomponent pathways for the Biginelli reaction mechanism. The most favorable pathway starts with the condensation of the urea and benzaldehyde, followed by the addition of ethyl acetoacetate. Remarkably, a second urea molecule catalyzes nearly every step of the reaction. Thus, the Biginelli reaction is a urea-catalyzed multicomponent reaction. The reaction mechanism was found to be identical in both protic and aprotic solvents. PMID:26066623

  20. Hypersensitivity reactions to vaccine components.

    PubMed

    Heidary, Noushin; Cohen, David E

    2005-09-01

    Vaccines are responsible for the control of many infectious diseases that were once common in the United States, including polio, measles, diphtheria, pertussis (whooping cough), rubella (German measles), mumps, tetanus, and Haemophilus influenzae type b. National efforts to generate collaboration between federal, state, and local governments and public and private health care providers have resulted in record high levels of vaccination coverage in the United States. The high rate of US vaccinations is paralleled by growing concerns about the safety of their delivery. The variety of substances used in vaccines sometimes causes the development of cutaneous reactions in susceptible adults and children. This article will review adverse cutaneous events consistent with hypersensitivity reactions to the following ingredients in vaccines: aluminum, thimerosal, 2-phenoxyethanol, formaldehyde, and neomycin. PMID:16242081

  1. Adverse reactions to FMD vaccine.

    PubMed

    Yeruham, I; Yadin, H; Haymovich, M; Perl, S

    2001-08-01

    A case of adverse post-vaccination allergic reactions, which occurred in a dairy cattle herd 8 days after the annual foot-and-mouth disease (FMD) vaccination, is described. The dermatologic lesions observed in these cattle included: urticaria, exudative and necrotic dermatitis, along with oedema and vesicles on the teats. These reactions occurred in 11.3% of the heifers, in 10% of the first-lactating cows and in 14.6% of the adult cows. The average loss of milk production for an affected cow on this farm was 21.5% per day, for seven consecutive days. The extent of the lesions was apparently related to concurrent diseases such as bovine virus diarrhea - mucosal disease complex (BVD-MD) and Johne's disease and, to a lesser degree, correlated with the age or breed. PMID:11493403

  2. Fractional Reaction-Diffusion Equations

    NASA Astrophysics Data System (ADS)

    Saxena, R. K.; Mathai, A. M.; Haubold, H. J.

    2006-12-01

    In a series of papers, Saxena et al. (2002, 2004a, 2004b) derived solutions of a number of fractional kinetic equations in terms of generalized Mittag-Leffler functions which provide the extension of the work of Haubold and Mathai (1995, 2000). The subject of the present paper is to investigate the solution of a fractional reaction-diffusion equation. The results derived are of general nature and include the results reported earlier by many authors, notably by Jespersen et al. (1999) for anomalous diffusion and del-Castillo-Negrete et al. (2003) for reaction-diffusion systems with Lévy flights. The solution has been developed in terms of the H-function in a compact form with the help of Laplace and Fourier transforms. Most of the results obtained are in a form suitable for numerical computation.

  3. Investigating Reaction-Driven Cracking

    NASA Astrophysics Data System (ADS)

    Kelemen, P. B.; Hirth, G.; Savage, H. M.

    2013-12-01

    Many metamorphic reactions lead to large volume changes, and potentially to reaction-driven cracking [1,2]. Large-scale hydration of mantle peridotite to produce serpentine or talc is invoked to explain the rheology of plate boundaries, the nature of earthquakes, and the seismic properties of slow-spread ocean crust and the 'mantle wedge' above subduction zones. Carbonation of peridotite may be an important sink in the global carbon cycle. Zones of 100% magnesite + quartz replacing peridotite, up to 200 m thick, formed where oceanic mantle was thrust over carbonate-bearing metasediments in Oman. Talc + carbonate is an important component of the matrix in subduction mélanges at Santa Catalina Island , California, and the Sanbagawa metamorphic belt, Japan. Engineered systems to emulate natural mineral carbonation could provide relatively inexpensive CO2 capture and storage [3]. More generally, engineered reaction-driven cracking could supplement or replace hydraulic fracture in geothermal systems, solution mining, and extraction of tight oil and gas. The controls on reaction-driven cracking are poorly understood. Hydration and carbonation reactions can be self-limiting, since they potentially reduce permeability and armor reactive surfaces [4]. Also, in some cases, hydration or carbonation may take place at constant volume. Small changes in volume due to precipitation of solid products increases stress, destabilizing solid reactants, until precipitation and dissolution rates become equal at a steady state stress [5]. In a third case, volume change due to precipitation of solid products causes brittle failure. This has been invoked on qualitative grounds to explain, e.g., complete serpentinization of mantle peridotite [6]. Below ~ 300°C, the available potential energy for hydration and carbonation of olivine could produce stresses of 100's of MPa [2], sufficient to fracture rocks to 10 km depth or more, causing brittle failure below the steady state stress required for constant volume replacement. Natural examples have fracture energy densities due to strain energy density of 100's of MPa [2]. Despite theory and observation, until now lab experiments on peridotite hydration and carbonation have not produced reaction-driven cracking. Slow kinetics and limited reactive surface area in low porosity samples may be the cause. Also, maximum stress may be limited by 'disjoining pressure', above which nano-films along grain boundaries collapse, and crystal growth essentially ceases [7]. To address these issues, we've begun experiments on analog materials with fast reaction rates, e.g., CaO + H2O = Ca(OH)2, to efficiently investigate the role of confining pressure and other factors on reaction-driven fracture events. Intriguingly, commercially available 'demolition mortar', largely CaO, produces stresses of 70 MPa or more around 1 inch bore holes at room T and P [8], even though there is a free surface at the top of the borehole, and hydration in a 'closed' system creates ~ 40% air-filled pore space. [1] Jamtveit et al EPSL 08 [2] Kelemen & Hirth EPSL 12 [3] Kelemen et al AREPS 11 [4] Aharonov et al JGR 98 [5] Fletcher & Merino GCA 01 [6] Macdonald & Fyfe T'phys 85 [7] Espinosa-Marzal & Scherer GSL Special Papers 10 [8] Laefer et al Mag Concrete Res 10

  4. Electromagnetic reactions on light nuclei

    E-print Network

    Sonia Bacca; Saori Pastore

    2014-07-13

    Electromagnetic reactions on light nuclei are fundamental to advance our understanding of nuclear structure and dynamics. The perturbative nature of the electromagnetic probes allows to clearly connect measured cross sections with the calculated structure properties of nuclear targets. We present an overview on recent theoretical ab-initio calculations of electron-scattering and photonuclear reactions involving light nuclei. We encompass both the conventional approach and the novel theoretical framework provided by chiral effective field theories. Because both strong and electromagnetic interactions are involved in the processes under study, comparison with available experimental data provides stringent constraints on both many-body nuclear Hamiltonians and electromagnetic currents. We discuss what we have learned from studies on electromagnetic observables of light nuclei, starting from the deuteron and reaching up to nuclear systems with mass number A=16.

  5. Electroweak reactions with light nuclei

    E-print Network

    Sonia Bacca

    2010-06-01

    The investigation of light nuclei with ab-initio methods provides an optimal setting to probe our knowledge on nuclear forces, because the few-nucleon problem can be solved accurately. Nucleons interact not only in pairs but also via many-body forces. Theoretical efforts need to be taken towards the identification of nuclear observables sensitive to the less known many-nucleon forces. Electromagnetic reactions can potentially provide useful information on this. We present results on photo-absorption and electron scattering off light nuclei, emphasizing the role of three-body forces and the comparison with experimental data. On the other hand, reactions induced by weak probes, like neutrino interactions with nucleonic matter, are relevant to astrophysics and can be calculated with few-body techniques. In this case, since often no experiment is possible, ab-initio predictions provide valuable input for astrophysical simulations.

  6. Propulsive Reaction Control System Model

    NASA Technical Reports Server (NTRS)

    Brugarolas, Paul; Phan, Linh H.; Serricchio, Frederick; San Martin, Alejandro M.

    2011-01-01

    This software models a propulsive reaction control system (RCS) for guidance, navigation, and control simulation purposes. The model includes the drive electronics, the electromechanical valve dynamics, the combustion dynamics, and thrust. This innovation follows the Mars Science Laboratory entry reaction control system design, and has been created to meet the Mars Science Laboratory (MSL) entry, descent, and landing simulation needs. It has been built to be plug-and-play on multiple MSL testbeds [analysis, Monte Carlo, flight software development, hardware-in-the-loop, and ATLO (assembly, test and launch operations) testbeds]. This RCS model is a C language program. It contains two main functions: the RCS electronics model function that models the RCS FPGA (field-programmable-gate-array) processing and commanding of the RCS valve, and the RCS dynamic model function that models the valve and combustion dynamics. In addition, this software provides support functions to initialize the model states, set parameters, access model telemetry, and access calculated thruster forces.

  7. Radiation recall reaction causing cardiotoxicity

    PubMed Central

    2014-01-01

    Radiation recall phenomenon is a tissue reaction that develops within a previously irradiated area, precipitated by the subsequent administration of certain chemotherapeutic agents. It commonly affects the skin, but can also involve internal organs with functional consequences. To our best knowledge, this phenomenon has never been reported as a complication on the heart and should be consider as a potential cause of cardiotoxicity. PMID:24755097

  8. Cascade reactions in multicompartmentalized polymersomes.

    PubMed

    Peters, Ruud J R W; Marguet, Maïté; Marais, Sébastien; Fraaije, Marco W; van Hest, Jan C M; Lecommandoux, Sébastien

    2014-01-01

    Enzyme-filled polystyrene-b-poly(3-(isocyano-L-alanyl-aminoethyl)thiophene) (PS-b-PIAT) nanoreactors are encapsulated together with free enzymes and substrates in a larger polybutadiene-b-poly(ethylene oxide) (PB-b-PEO) polymersome, forming a multicompartmentalized structure, which shows structural resemblance to the cell and its organelles. An original cofactor-dependent three-enzyme cascade reaction is performed, using either compatible or incompatible enzymes, which takes place across multiple compartments. PMID:24254810

  9. Radiation Reaction and Center Manifolds

    Microsoft Academic Search

    Markus Kunze; Herbert Spohn

    2000-01-01

    We study the effective dynamics of a mechanical particle coupled to a wave\\u000afield and subject to the slowly varying potential $V(\\\\eps q)$ with $\\\\eps$\\u000asmall. To lowest order in $\\\\eps$ the motion of the particle is governed by an\\u000aeffective Hamiltonian. In the next order one obtains ``dissipative'' terms\\u000awhich describe the radiation reaction. We establish that this dissipative

  10. Collecting Information on Participant Reactions

    E-print Network

    Taylor-Powell, Ellen; Marshall, Mary G

    1988-01-01

    . College Station, Texas B-1615 ~ / (Blank Pa,ge in Original BHUedD] , ~ -' . " r . -~: ' -; :. ' k COLLECTING INFORMATION ON PARTICIPANT REACTIONS LIBRARY DE 1 4 1988 "JA Ellen Taylor-Powell Mary . Marshall Program and Staff Develop leas A M.... , Sawer, Barbara J. EVALUATING FOR ACCOUNTABILITY. Corvallis, Oregon: Oregon State University Extension Service, 1984. Taylor-Powell, Ellen and Mary G. Marshall. QUESTIONNAIRE DESIGN, ASKING QUESTIONS WITH A PURPOSE. The Texas A&M University System...

  11. Kinetics of NCO + hydrocarbon reactions

    NASA Astrophysics Data System (ADS)

    Park, Joonbum; Hershberger, John F.

    1994-02-01

    The kinetics of NCO reactions with hydrocarbon molecules were investigated using time-resolved infrared diode laser absorption spectroscopy. NCO was probed at 1905.6 cm -1, and HNCO reaction products were probed at 2280.1 cm -1. Rate constants at 296 K were measured to be < 1.0 × 10 -14, (7.04 ± 1.20) × 10 -14, (2.29 ± 0.13) × 10 -13, (6.13 ± 0.32) × 10 -13, (8.78 ± 0.42) × 10 -13, (7.47 ± 0.8) × 10 -14, and (2.85 ± 0.22) × 10 -12 cm 3 molecule -1 s -1, for CH 4, C 2H 6, C 3H 8, n-C 4H 10, n-C 5H 12, C 2H 2, and C 2H 4, respectively. Hydrogen abstraction to form HNCO was observed to be a major product channel for reactions with alkanes and for C 2H 2. For C 2H 2, HNCO is formed in negligible yield, indicating that addition—elimination is the primary mechanism active.

  12. Classical and Quantum Radiation Reaction

    E-print Network

    Giles D. R. Martin

    2008-05-06

    This thesis reports on work undertaken in comparing the effects of the phenomenon of radiation reaction in classical and quantum theories of electrodynamics. Specifically, it is concerned with the prediction of the change in position of a particle due to the inclusion of the self-force in the theory. We calculate this position shift for the classical theory, treating radiation reaction as a perturbation in line with the reduction of order procedure. We calculate the contributions to the position shift in the $\\hbar\\to 0$ limit of quantum field theory to order $e^2$ in the coupling, the order of the classical self-force. These calculations contain the emission and forward scattering one loop processes of quantum electrodynamics. The quantum calculations are completed for the case of a particle represented by a scalar field wave packet and then for a particle represented by the Dirac spinor field. We additionally give an alternative derivation of the scalar results using the interpretation of radiation reaction via a Green's function decomposition, in order to explain and contrast the results achieved.

  13. Reaction Selectivity in Heterogeneous Catalysis

    SciTech Connect

    Somorjai, Gabor A.; Kliewer, Christopher J.

    2009-02-02

    The understanding of selectivity in heterogeneous catalysis is of paramount importance to our society today. In this review we outline the current state of the art in research on selectivity in heterogeneous catalysis. Current in-situ surface science techniques have revealed several important features of catalytic selectivity. Sum frequency generation vibrational spectroscopy has shown us the importance of understanding the reaction intermediates and mechanism of a heterogeneous reaction, and can readily yield information as to the effect of temperature, pressure, catalyst geometry, surface promoters, and catalyst composition on the reaction mechanism. DFT calculations are quickly approaching the ability to assist in the interpretation of observed surface spectra, thereby making surface spectroscopy an even more powerful tool. HP-STM has revealed three vitally important parameters in heterogeneous selectivity: adsorbate mobility, catalyst mobility, and selective site-blocking. The development of size controlled nanoparticles from 0.8 to 10 nm, of controlled shape, and of controlled bimetallic composition has revealed several important variables for catalytic selectivity. Lastly, DFT calculations may be paving the way to guiding the composition choice for multi-metallic heterogeneous catalysis for the intelligent design of catalysts incorporating the many factors of selectivity we have learned.

  14. Reaction of steam with molybdenum is studied

    NASA Technical Reports Server (NTRS)

    Kilpatrick, M.; Lott, S.

    1967-01-01

    Comprehensive report studies the reaction of flowing steam with refractory metals /in particular molybdenum/, in the temperature range of 1100 degrees C. The reaction products are hydrogen gas and molybdenum oxide vapor.

  15. ChemTeacher: Double Replacement Reactions

    NSDL National Science Digital Library

    2011-01-01

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Double Replacement Reactions page includes resources for teaching students about identifying and predicting double replacement reactions.

  16. ChemTeacher: Half-Reactions

    NSDL National Science Digital Library

    2011-01-01

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Half-Reactions page includes resources for teaching students about understanding half-reactions.

  17. Heavy atom isotope effects on enzymatic reactions

    NASA Astrophysics Data System (ADS)

    Paneth, Piotr

    1994-05-01

    The theory of isotope effects, which has proved to be extremely useful in providing geometrical details of transition states in a variety of chemical reactions, has recently found an application in studies of enzyme-catalyzed reactions. These reactions are multistep in nature with few steps being partially rate-limiting, thus interpretation of these isotope effects is more complex. The theoretical framework of heavy-atom isotope effects on enzymatic reactions is critically analyzed on the basis of recent results of: carbon kinetic isotope effects on carbonic anhydrase and catalytic antibodies; multiple carbon, deuterium isotope effects on reactions catalyzed by formate decarboxylase; oxygen isotope effects on binding processes in reactions catalyzed by pyruvate kinase; and equilibrium oxygen isotope effect on binding an inhibitor to lactate dehydrogenase. The advantages and disadvantages of reaction complexity in learning details of formal and molecular mechanisms are discussed in the examples of reactions catalyzed by phosphoenolpyruvate carboxylase, orotidine decarboxylase and glutamine synthetase.

  18. Theoretical studies on bimolecular reaction dynamics

    PubMed Central

    Clary, David C.

    2008-01-01

    This perspective discusses progress in the theory of bimolecular reaction dynamics in the gas phase. The examples selected show that definitive quantum dynamical computations are providing insights into the detailed mechanisms of chemical reactions. PMID:18626015

  19. Effective radii of deuteron induced reactions

    E-print Network

    Shintaro Hashimoto; Masanobu Yahiro; Kazuyuki Ogata; Kosho Minomo; Satoshi Chiba

    2011-04-08

    The continuum-discretized coupled-channels method (CDCC) for exclusive reactions and the eikonal reaction theory (ERT) as an extension of CDCC to inclusive reactions are applied to deuteron induced reactions. The CDCC result reproduces experimental data on the reaction cross section for $d+^{58}$Ni scattering at 200 MeV/nucleon and ERT does data on the neutron-stripping cross section for inclusive $^7$Li$(d,n)$ reaction at 40 MeV. For deuteron induced reactions at 200 MeV/nucleon, target-dependence of the reaction, elastic-breakup, nucleon-stripping, nucleon-removal, complete- and incomplete-fusion cross sections is clearly explained by simple formulae. Accuracy of the Glauber model is also investigated.

  20. ChemTeacher: Single Replacement Reactions

    NSDL National Science Digital Library

    2012-07-23

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Single Replacement Reactions page includes resources for teaching students about identifying and predicting single replacement reactions.

  1. Astrophysical Reaction Rates From Statistical Model Calculations

    Microsoft Academic Search

    Thomas Rauscher; Friedrich-Karl Thielemann

    2000-01-01

    Theoretical reaction rates in the temperature range 0.01×109?T(K)?10.0×109 are calculated in the statistical model (Hauser–Feshbach formalism) for targets with 10?Z?83 (Ne to Bi) and for a mass range reaching the neutron and proton driplines. Reactions considered are (n, ?), (n, p), (n, ?), (p, ?), (p, ?), (?, ?), and their inverse reactions. Reaction rates as a function of temperature

  2. Reaction of potassium superoxide with nitrogen oxide

    Microsoft Academic Search

    T. P. Firsova; E. Ya. Filatov

    1974-01-01

    1.A study was made of the reaction of technical potassium superoxide with nitrogen oxide (both pure and diluted with argon).2.The process proceeds at considerable speeds at the start, with a subsequent rapid slowing up and then a complete cessation of the reaction.3.The reaction goes with the formation of potassium nitrite as the main reaction product and potassium nitrate as the

  3. A fluorogenic ‘click’ reaction of azidoanthracene derivatives

    Microsoft Academic Search

    Fang Xie; Krishnamoorthy Sivakumar; Qingbing Zeng; Michael A. Bruckman; Blake Hodges; Qian Wang

    2008-01-01

    Fluorogenic reactions have broad applications in biolabeling, combinatorial synthesis of fluorescent dyes, and materials development. It was recently reported that the highly selective and efficient Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction can be employed in designing new types of fluorogenic reactions. In this study, we report a fluorogenic reaction using anthracene azides as starting materials. The fluorescence of the anthryl core

  4. Visualization of chemical reaction dynamics: Toward understanding complex polyatomic reactions

    PubMed Central

    SUZUKI, Toshinori

    2013-01-01

    Polyatomic molecules have several electronic states that have similar energies. Consequently, their chemical dynamics often involve nonadiabatic transitions between multiple potential energy surfaces. Elucidating the complex reactions of polyatomic molecules is one of the most important tasks of theoretical and experimental studies of chemical dynamics. This paper describes our recent experimental studies of the multidimensional multisurface dynamics of polyatomic molecules based on two-dimensional ion/electron imaging. It also discusses ultrafast photoelectron spectroscopy of liquids for elucidating nonadiabatic electronic dynamics in aqueous solutions. PMID:23318678

  5. Relay cross metathesis reactions of vinylphosphonates.

    PubMed

    Malla, Raj K; Ridenour, Jeremy N; Spilling, Christopher D

    2014-01-01

    Dimethyl (?-substituted) vinylphosphonates do not readily undergo cross metathesis reactions with Grubbs catalyst and terminal alkenes. However, the corresponding mono- or diallyl vinylphosphonate esters undergo facile cross metathesis reactions. The improved reactivity is attributed to a relay step in the cross metathesis reaction mechanism. PMID:25246952

  6. Method of controlling fusion reaction rates

    DOEpatents

    Kulsrud, Russell M. (Princeton, NJ); Furth, Harold P. (Princeton, NJ); Valeo, Ernest J. (Princeton Junction, NJ); Goldhaber, Maurice (Bayport, NY)

    1988-01-01

    A method of controlling the reaction rates of the fuel atoms in a fusion reactor comprises the step of polarizing the nuclei of the fuel atoms in a particular direction relative to the plasma confining magnetic field. Fusion reaction rates can be increased or decreased, and the direction of emission of the reaction products can be controlled, depending on the choice of polarization direction.

  7. A novel capillary polymerase chain reaction machine

    E-print Network

    Chiou, Jeffrey Tsungshuan

    2001-01-01

    I built a novel prototype capillary polymerase chain reaction machine. The purpose was to perform a single reaction as fast as possible with a reaction volume - 100 nl. The PCR mix is in the form of a 1 /1 droplet that ...

  8. Multicomponent reactions are accelerated in water.

    PubMed

    Pirrung, Michael C; Sarma, Koushik Das

    2004-01-21

    Two multicomponent reactions, the Ugi and Passerini reactions, are accelerated by the use of aqueous solutions. The rate enhancements compared to those by organic solvents can approach 300-fold. Reactions performed in water offer another advantage that products are often insoluble, permitting direct isolation by precipitation. The methods were applied to the preparation of three small combinatorial libraries. PMID:14719923

  9. REACTION PHYSICAL PLANT MODULE WORK ORDER ------------------------------------------------2

    E-print Network

    Zimmerman, Steven C.

    1 REACTION PHYSICAL PLANT MODULE USER MENU WORK ORDER;2 ADD WORK ORDER: 1. Logon to Reaction 2. Go to Physical Plant Add Work Order. Or Click Here 3. Enter SEARCH WORK ORDER: 1. Logon to Reaction 2. Go to Physical Plant Search Work Order. Or Click Here 3

  10. Reaction-Map of Organic Chemistry

    ERIC Educational Resources Information Center

    Murov, Steven

    2007-01-01

    The Reaction-Map of Organic Chemistry lists all the most commonly studied reactions in organic chemistry on one page. The discussed Reaction-Map will act as another learning aide for the students, making the study of organic chemistry much easier.

  11. Reaction of citric acid with calcite

    Microsoft Academic Search

    M. H. Al-Khaldi; H. A. Nasr-El-Din; S. Mehta; A. D. Al-Aamri

    2007-01-01

    The reaction of citric acid with calcite was investigated using the rotating disk apparatus. The effects of disk rotational speed, system pressure, and presence of magnesium and ferric ions on this reaction were examined. Scanning electron microscope (SEM) was also used to characterize the surface of the calcite disks at the end of each experiment.The reaction of citric acid and

  12. Triggered amplification by hybridization chain reaction

    E-print Network

    Pierce, Niles A.

    Triggered amplification by hybridization chain reaction Robert M. Dirks and Niles A. Pierce chain reaction (HCR), in which stable DNA monomers assemble only upon exposure to a target DNA fragment termed hybridization chain reaction (HCR). This class of mech- anisms suggests the possibility

  13. Texturing Surfaces Using Reaction-Diffusion

    E-print Network

    North Carolina at Chapel Hill, University of

    Texturing Surfaces Using Reaction-Diffusion TR9~ ·035 June 1994 Greg Tt·rk Department of Computer Opportunity/ Affirmative Action Institution. #12;Texturing Surfaces Using Reaction-Diffusion by Greg Turk. Texruring Surfaces Using Reaction-Diffusion (under the direction of Henry Fuchs). Abstract This dissenation

  14. Alkylchlorosilane reactions at the silica surface

    Microsoft Academic Search

    M. L. Hair; C. P. Tripp

    1995-01-01

    This paper reviews recent work on the reaction of alkyltrichlorosilanes with a pure silica surface. In the absence of moisture these reactions do not occur at temperatures below 300°C. Specifically, it is shown that octadecyltrichlorosilane (OTS) in carbon tetrachloride solution does not react with the surface at room temperature. Reaction does occur with molecular water which is either adsorbed on

  15. Adverse Reactions to Food: Allergies and Intolerances

    Microsoft Academic Search

    Massimo Montalto; Luca Santoro; Ferruccio D’Onofrio; Valentina Curigliano; Antonella Gallo; Dina Visca; Giovanni Cammarota; Antonio Gasbarrini; Giovanni Gasbarrini

    2008-01-01

    All the anomalous reactions secondary to food ingestion are defined as ‘adverse reactions to food’. In 1995 the European Academy of Allergology and Clinical Immunology suggested a classification on the basis of the responsible pathogenetic mechanism; according to this classification, non-toxic reactions can be divided into ‘food allergies’ when they recognize immunological mechanisms, and ‘food intolerances’ when there are no

  16. 'GREENER' CHEMICAL SYNTHESES USING ALTERNATE REACTION CONDITIONS

    EPA Science Inventory

    Microwave (MW) irradiation in conjunction with water as reaction media has proven to be a greener chemical approach for expeditious N-alkylation reactions of amines and hydrazines wherein the reactions under mildly basic conditions afford tertiary amines and double N-alkylation t...

  17. THEORY OF CHEMICAL REACTION ANTONIO LAGANA

    E-print Network

    Auzinsh, Marcis

    THEORY OF CHEMICAL REACTION DYNAMICS Edited by: ANTONIO LAGANA Department of Chemistry University Theoretical treatment of the dynamics of chemical reactions has undergone a spectacular development during the NATO Advanced Research Work- shop on the Theory of the Dynamics of Chemical Reactions in Balatonf

  18. GENERALIZED TOPOLOGIES: HYPERGRAPHS, CHEMICAL REACTIONS, AND

    E-print Network

    Flamm, Christoph

    GENERALIZED TOPOLOGIES: HYPERGRAPHS, CHEMICAL REACTIONS, AND BIOLOGICAL EVOLUTION Christoph Flamm1;INTRODUCTION Investigations into general principles underlying chemical reaction networks, molecular [21, 66, 62, 31, 59, 56, 22, 60]. Chemical Reaction Networks. We start from a fixed set X of molecular

  19. Leaderless deterministic chemical reaction networks Monir Hajiaghayi

    E-print Network

    Doty, David

    Leaderless deterministic chemical reaction networks David Doty Monir Hajiaghayi Abstract This paper is deterministically computable by a stochastic chemical reaction network (CRN) if and only if the graph of f in a well-mixed solution, the language of chemical reaction networks (CRNs) is an attractive choice. A CRN

  20. Collisions, Chemical Reactions, and Transport Chemistry 223

    E-print Network

    Ronis, David M.

    Collisions, Chemical Reactions, and Transport Chemistry 223 David Ronis McGill University 1 for a number of practical con- siderations; e.g., if a chemical reaction takes place every time a molecule hits, introduced earlier. Aside from the previously mentioned example of chemical reaction on a surface, another

  1. Physics 112 Equilibrium in Chemical Reactions

    E-print Network

    Young, A. Peter

    Physics 112 Equilibrium in Chemical Reactions Peter Young I. FORMALISM This is a considerably that it is indeed a minimum. In this handout we discuss chemical reactions, which take place not at constant volume next give some examples of chemical reactions which we will use to illustrate the theory in what

  2. New reaction tester accurate within 56 microseconds

    NASA Technical Reports Server (NTRS)

    Brown, H.

    1972-01-01

    Testing device measures simple and disjunctive reaction time of human subject to light stimuli. Tester consists of reaction key, logic card, panel mounted neon indicators, and interconnecting wiring. Device is used for determining reaction times of patients undergoing postoperative neurological therapy.

  3. The reaction-diffusion approach to morphogenesis

    Microsoft Academic Search

    Rui Dilao

    2005-01-01

    Morphogenesis is the ensemble of processes that determines form, shape and patterns in organisms. Based on a reaction-diffusion theoretical setting and some prototype reaction schemes, we make a review of the models and experiments that support possible mechanisms of morphogenesis. We present specific case studies from chemistry (Belousov-Zhabotinsky reaction) and biology (formation of wing eyespots patterns in butterflies). We show

  4. Radiation Reaction and Center Manifolds Markus Kunze

    E-print Network

    Radiation Reaction and Center Manifolds Markus Kunze Mathematisches Institut der Universit¨at K the radiation reaction. We establish that this dissipative dynamics has a center manifold which is repulsive At the beginning of this century, in the context of the Maxwell­Lorentz equa­ tions, radiation reaction was one

  5. Radiative Capture Reactions of Astrophysical Interest

    E-print Network

    Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University

    capture can occur either by a compound nucleus reaction or by a direct process. The compound reaction Chourasia and Prof. Rogers, for their valuable lectures. From there I solidified my knowledge in physics reactions 12 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2 Direct

  6. CROSS SECTION FOR THE ASTROPHYSICAL 14C(n, )15C REACTION VIA THE INVERSE REACTION

    E-print Network

    Horváth, Ákos

    -induced CNO cycles of stellar evolution phases beyond the main sequence. The chain of reactions in primordialCROSS SECTION FOR THE ASTROPHYSICAL 14C(n, )15C REACTION VIA THE INVERSE REACTION A´ . Horva´th,1 Received 2001 July 9; accepted 2002 January 18 ABSTRACT The 14C(n, )15C reaction is important in neutron

  7. Density functional study of chemical reaction equilibrium for dimerization reactions in slit and cylindrical nanopores

    E-print Network

    Lisal, Martin

    Density functional study of chemical reaction equilibrium for dimerization reactions in slit a theoretical study of the effects of confinement on chemical reaction equilibrium in slit and cylindrical equilibrium, for which much less is known. The behavior of chemical reactions in confinement spans a wide

  8. M. Bahrami ENSC 461 (S 11) Chemical Reactions 1 Chemical Reactions

    E-print Network

    Bahrami, Majid

    M. Bahrami ENSC 461 (S 11) Chemical Reactions 1 Chemical Reactions When analyzing reacting systemsHm. For example octane is C8H18. Combustion: is a chemical reaction during which a fuel is oxidized and a large.28 #12;M. Bahrami ENSC 461 (S 11) Chemical Reactions 2 Where N is the number of moles and M is the molar

  9. A Method for IncorporatingA Method for Incorporating Chemical Reactions intoChemical Reactions into

    E-print Network

    Politècnica de Catalunya, Universitat

    A Method for IncorporatingA Method for Incorporating Chemical Reactions intoChemical Reactions Vilarrasa, Francesca De Gaspari, Orlando Silva, Jesús Carrera #12;Introduction "Chemical reactions" in CODE), CO3 2-, OH- 5 Chemical reactions: CaCO3(s) + H+ = Ca2+ + HCO3 - CO2(aq) = CO2(g) H+ + HCO3 - = H2

  10. Timing in chemical reaction networks Chemical reaction networks (CRNs) formally model chem-

    E-print Network

    Doty, David

    Timing in chemical reaction networks David Doty Abstract Chemical reaction networks (CRNs) formally the interactions of molecular species in a well-mixed solution is that of (fi- nite) chemical reaction networks (CRNs), i.e., finite sets of chemical reactions such as A+B A+C. When the behavior of individual

  11. Hydrothermal reactions of fly ash

    SciTech Connect

    Brown, P.W.

    1991-01-01

    The reactions which occur when fly ash is treated under hydrothermal conditions will be investigated. Formation of four classes of compounds, which bracket likely fly ash compositional ranges, have been selected for study. These are calcium silicate hydrates, calcium silicosulfates, calcium aluminosulfates, and alkali aluminosilicates. The specific compounds fabricated will be determined and their stability regions assessed. As a part of stability assessment, the extent to which selected hazardous species are sequestered will be determined. Finally, the cementing properties of these compounds will be established.

  12. Photochemical reactions for commercial synthesis

    SciTech Connect

    Guillet, J. E.

    1985-06-25

    Photochemical reactions are conducted using floating polymer beads on the surface of a moving body of water. The polymer bead is impregnated with a reactant, floated on the water in direct sunlight so as to expose the reactant to solar radiation, collected at a downstream location, treated to remove product from the polymer, and then the bead can be recycled. The process can be used to collect and store solar energy in chemical form, or for conducting photochemical synthesis to produce useful chemical products.

  13. Chemical reactions at aqueous interfaces

    NASA Astrophysics Data System (ADS)

    Vecitis, Chad David

    2009-12-01

    Interfaces or phase boundaries are a unique chemical environment relative to individual gas, liquid, or solid phases. Interfacial reaction mechanisms and kinetics are often at variance with homogeneous chemistry due to mass transfer, molecular orientation, and catalytic effects. Aqueous interfaces are a common subject of environmental science and engineering research, and three environmentally relevant aqueous interfaces are investigated in this thesis: 1) fluorochemical sonochemistry (bubble-water), 2) aqueous aerosol ozonation (gas-water droplet), and 3) electrolytic hydrogen production and simultaneous organic oxidation (water-metal/semiconductor). Direct interfacial analysis under environmentally relevant conditions is difficult, since most surface-specific techniques require relatively `extreme' conditions. Thus, the experimental investigations here focus on the development of chemical reactors and analytical techniques for the completion of time/concentration-dependent measurements of reactants and their products. Kinetic modeling, estimations, and/or correlations were used to extract information on interfacially relevant processes. We found that interfacial chemistry was determined to be the rate-limiting step to a subsequent series of relatively fast homogeneous reactions, for example: 1) Pyrolytic cleavage of the ionic headgroup of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorbed to cavitating bubble-water interfaces during sonolysis was the rate-determining step in transformation to their inorganic constituents carbon monoxide, carbon dioxide, and fluoride; 2) ozone oxidation of aqueous iodide to hypoiodous acid at the aerosol-gas interface is the rate-determining step in the oxidation of bromide and chloride to dihalogens; 3) Electrolytic oxidation of anodic titanol surface groups is rate-limiting for the overall oxidation of organics by the dichloride radical. We also found chemistry unique to the interface, for example: 1) Adsorption of dilute PFOS(aq) and PFOA(aq) to acoustically cavitating bubble interfaces was greater than equilibrium expectations due to high-velocity bubble radial oscillations; 2) Relative ozone oxidation kinetics of aqueous iodide, sulfite, and thiosulfate were at variance with previously reported bulk aqueous kinetics; 3) Organics that directly chelated with the anode surface were oxidized by direct electron transfer, resulting in immediate carbon dioxide production but slower overall oxidation kinetics. Chemical reactions at aqueous interfaces can be the rate-limiting step of a reaction network and often display novel mechanisms and kinetics as compared to homogeneous chemistry.

  14. Nanomotors Propelled by Chemical Reactions

    NASA Astrophysics Data System (ADS)

    Kapral, Raymond

    2013-12-01

    Molecular motors, like their macroscopic counterparts, consume energy and convert it to work; however, unlike macroscopic motors, they are subject to strong fluctuations and do not rely on inertia for their operation. In this chapter, the dynamics of synthetic chemically-powered nanomotors and mechanisms by which they operate are described. The focus is on motors that propel themselves by utilizing fuel in the environment to generate their own concentration gradients through chemical reactions. Macroscopic diffusiophoretic mechanisms for such motions are discussed, as well as microscopic and mesoscopic descriptions of motor dynamics.

  15. Cutaneous Adverse Reactions of Amiodarone

    PubMed Central

    Jaworski, Krzysztof; Walecka, Irena; Rudnicka, Lidia; Gnatowski, Maciej; Kosior, Dariusz A.

    2014-01-01

    Dermatological complications of amiodarone are commonly encountered problems in therapy. The incidence in the population of patients with prolonged use of amiodarone reaches nearly 75% according to various sources. Nevertheless, they are often misdiagnosed or overlooked. The aim of this review is to present the current state of knowledge about skin changes induced by amiodarone, including phototoxic and photoallergic reactions, as well as hyperpigmentation. In most cases, the adverse effects are reversible and disappear after discontinuation of the drug. Although the dermatological complications usually do not influence the outcome of the therapy and rarely cause discontinuation of treatment, they have a great impact on patient quality of life. PMID:25413691

  16. Microbial analysis using Sharma's reaction

    NASA Astrophysics Data System (ADS)

    Ali, Zulfiqur; Hodson, Bruce; Timmins, James; Keith, Stephen

    1999-02-01

    The photoreaction of thionine with NAD(P)H leads to the formation of non-fluorescent semi and lecuothionine. This has been previously used for the development of enzymatic assays. We show that the fluorescence of thionine is quenched in the presence of Nocardia corallin. We ascribe this decrease in fluorescence to the presence of NAD(P)H present on the walls and in the body of the cells as described by Sharma. We therefore demonstrate that it is possible to measure, in situ, NAD(P)H in Nocardia corallin in a simple and inexpensive manner and that this finding extends the analytical application of Sharma's reaction to other organisms.

  17. Plasmochemical reactions in inhomogeneous solids

    SciTech Connect

    Volkova, A.V.; Zorin, N.L.

    1987-11-01

    To test for hot plasmas in inhomogeneous solids and the scope for plasmochemical reactions, it is necessary to demonstrate neutron emission. The authors have performed such experiments. They examined type D-4 polyarylate and polyurethanes synthesized from polyethylene glycol adipate and 4,4'-diphenyl-methane diisocyanate (PU-1) and on the basis of copolymers of ethylene oxide and propylene oxide with contents of ethylene oxide in the initial copolymer of 20%, together with 4,4'-diphenylmethane diisocyanate and ethylene diamine (PU-2).

  18. Incidents of chemical reactions in cell equipment

    SciTech Connect

    Baldwin, N.M.; Barlow, C.R. [Uranium Enrichment Organization, Oak Ridge, TN (United States)

    1991-12-31

    Strongly exothermic reactions can occur between equipment structural components and process gases under certain accident conditions in the diffusion enrichment cascades. This paper describes the conditions required for initiation of these reactions, and describes the range of such reactions experienced over nearly 50 years of equipment operation in the US uranium enrichment program. Factors are cited which can promote or limit the destructive extent of these reactions, and process operations are described which are designed to control the reactions to minimize equipment damage, downtime, and the possibility of material releases.

  19. Thermochemical modeling of thermite-type reactions

    SciTech Connect

    Behrens, R.G.; Hansen, G.P.

    1985-01-01

    Purpose of this work was to use thermodynamic modeling to study the chemistry associated with the synthesis of TiB/sub 2/, SiC, and TiC by thermite-type reactions. Side reactions (including vaporization reactions) compete with the primary reaction and thus decrease the yield of a desired product. The relative importance of side reactions is governed in part by the thermodynamic stabilities of byproducts relative to the stabilities of the major products. The computer program SOLGASMIX was used to compute condensed phase stability diagrams for the four chemical systems.

  20. [Differentiation of nonspecific serological reactions in brucellosis].

    PubMed

    Khristoforov, L

    1979-01-01

    Differentiation of non-specific agglutination was performed by the complement binding reaction, Coombs' reaction, Hajdu reaction, the surface fixation and agglutination reaction and the reaction of complement binding with heterologic antigens. For that purpose the following were used: 1) Serums--antiglobulin against cattle globulin, 5720 serum of various animals which had manifested non-specific agglutination with brucella antigen and brucella serums of experimentally infected sheep, of naturally infected swine and of cattle--received from abroad. 2) Antigens--of Br. abortus 99, of bacteria heterologic to brucellae: Proteus vulgaris, Listeria monocytogenes, Staphylococcus albus, Escherichia coli, Streptococcus pyogenes, S. abortus ovis, for O and OH agglutination, water extraction antigens--for complement binding and concentrated suspensions of all bacteria used in brucellose and non-brucellose serum absorption. Highest number of non-specific reactions were observed in cattle serums and lowest--in goat serums. Titers with heterologic antigens were higher than these with brucella antigens. Often the serum having non-specific agglutiantion reacted not only with one, but with more heterologic antigens. Non-specific complement binding reactions were not produced in complete antibodies with the brucella antigen. Heterologic brucella antigens were exhausted more fully than heterologic complement binding antibodies. In their effectiveness (differentiation of non-specific agglutination with brucella antigen in cattle serum) the serological reactions studied rank as follows: complement binding reaction, slow agglutination with serums absorbed by heterologic antigens, surface fixation reaction, Coombs' reaction, and Hadju agglutination. PMID:120633

  1. Allergic reactions to local glyceryl trinitrate administration.

    PubMed

    Kounis, N G; Zavras, G M; Papadaki, P J; Soufras, G D; Poulos, E A; Goudevenos, J; Alangoussis, A; Antonakopoulos, K; Frangides, C; Peristeropoulou, S A; Koutsojannis, C

    1996-12-01

    To assess the exact cause and extent of transdermal glyceryl trinitrate (GTN)-induced allergic reactions, a study of continuous and intermittent use of GTN patches was conducted in 320 patients with New York Heart Association (NYHA) class II and III angina pectoris. Three commercially available GTN patch systems were used. Twenty-one patients (6.5%) developed cutaneous reactions. In 17 patients (5.3%), the reactions were confined to the area of application and were characterised as irritant reactions. Four patients (1.2%) developed both localised and remote from the area of application lesions and one patient developed a generalised anaphylactic reaction. The rate of discontinuation of therapy was 3.4%. The irritant skin reactions were mainly due to contaminants and additives. Changing to a different transdermal system reduced the incidence of local reactions--a particularly desirable effect in patients who respond well to GTN therapy. PMID:9039714

  2. An Iodine Fluorescence Quenching Clock Reaction

    NASA Astrophysics Data System (ADS)

    Weinberg, Richard B.

    2007-05-01

    A fluorescent clock reaction is described that is based on the principles of the Landolt iodine reaction but uses the potent fluorescence quenching properties of triiodide to abruptly extinguish the ultraviolet fluorescence of optical brighteners present in liquid laundry detergents. The reaction uses easily obtained household products. One variation illustrates the sequential steps and mechanisms of the reaction; other variations maximize the dramatic impact of the demonstration; and a variation that uses liquid detergent in the Briggs Rauscher reaction yields a striking oscillating luminescence. The iodine fluorescence quenching clock reaction can be used in the classroom to explore not only the principles of redox chemistry and reaction kinetics, but also the photophysics of fluorescent pH probes and optical quenching.

  3. Reactions of hydrocarbon radicals and biradicals.

    PubMed

    Pilling, Michael J

    2013-05-01

    Experimental measurements of the rate coefficients for several types of gas phase radical reactions are reviewed. They include radical isomerization and dissociation, radical + radical association, and unimolecular reactions of peroxy radicals. Some reactions of methylene in its lowest singlet state are also considered. The links to theories of chemical reaction rates and especially of capture rates for radical + radical reactions are examined. Many of the reactions involve formation of adducts, which can isomerize and dissociate. Such reactions frequently involve energy distributions of the adducts that are far from Boltzmann, and the interpretation of measurements requires the use of master equation techniques. The basis of these methods and the use of matrix diagonalization and eigenvector/eigenvalue analysis to extract phenomenological rate coefficients are discussed. The relevance of the measurements to applications in atmospheric chemistry and, especially, in combustion is briefly considered. PMID:23570237

  4. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1994-01-01

    Quantum mechanical methods have been used to compute potential energy surfaces for chemical reactions. The reactions studied were among those believed to be important to the NASP and HSR programs and included the recombination of two H atoms with several different third bodies; the reactions in the thermal Zeldovich mechanism; the reactions of H atom with O2, N2, and NO; reactions involved in the thermal De-NO(x) process; and the reaction of CH(squared Pi) with N2 (leading to 'prompt NO'). These potential energy surfaces have been used to compute reaction rate constants and rates of unimolecular decomposition. An additional application was the calculation of transport properties of gases using a semiclassical approximation (and in the case of interactions involving hydrogen inclusion of quantum mechanical effects).

  5. Competing reaction channels in IR-laser-induced unimolecular reactions

    SciTech Connect

    Berman, M.R.

    1981-01-01

    The competing reaction channels in the unimolecular decomposition of two molecules, formaldehyde and tetralin were studied. A TEA CO/sub 2/ laser was used as the excitation source in all experiments. The dissociation of D/sub 2/CO was studied by infrared multiphoton dissociation (MPD) and the small-molecule nature of formaldehyde with regard to MPD was explored. The effect of collisions in MPD were probed by the pressure dependence of the MPD yield and ir fluorescence from multiphoton excited D/sub 2/CO. MPD yield shows a near cubic dependence in pure D/sub 2/CO which is reduced to a 1.7 power dependence when 15 torr of NO is added. The peak amplitude of 5 ..mu..m ir fluorescence from D/sub 2/CO is proportional to the square of the D/sub 2/CO pressure in pure D/sub 2/CO or in the presence of 50 torr of Ar. Results are explained in terms of bottlenecks to excitation at the v = 1 level which are overcome by a combination of vibrational energy transfer and rotational relaxation. The radical/molecule branching ratio in D/sub 2/CO MPD was 0.10 +- 0.02 at a fluence of 125 J/cm/sup 2/ at 946.0 cm/sup -1/. The barrier height to molecular dissociation was calculated to be 3.6 +- 2.0 kcal/mole below the radical threshold or 85.0 +- 3.0 kcal/mole above the ground state of D/sub 2/CO. In H/sub 2/CO, this corresponds to 2.5 +- 2.0 kcal/mole below the radical threshold or 83.8 +- 3.0 kcal/mole above the ground state. Comparison with uv data indicate that RRKM theory is an acceptable description of formaldehyde dissociation in the 5 to 10 torr pressure range. The unimolecular decomposition of tetralin was studied by MPD and SiF/sub 4/ - sensitized pyrolysis. Both techniques induce decomposition without the interference of catalytic surfaces. Ethylene loss is identified as the lowest energy reaction channel. Dehydrogenation is found to result from step-wise H atom loss. Isomerization via disproportionation is also identified as a primary reaction channel.

  6. The proton-proton reaction and related reactions in an intense magnetic field

    Microsoft Academic Search

    Chih Kang Chou

    1971-01-01

    The reaction rates for the proton-proton reaction and the related electron capture reaction in a strongly magnetized relativistic electron gas of arbitrary degree of degeneracy are computed. The proton-proton reaction rates are unaffected by the presence of the magnetic field for field strengths up to the critical valueHq=m2c3\\/eh=4.414×1013G. For fields greater thanHq, the proton-proton reaction rates are enhanced linearly with

  7. Neutron capture reactions in astrophysics

    NASA Astrophysics Data System (ADS)

    Käppeler, F.

    1985-01-01

    About 2/3 of the chemical elements in nature were formed in neutron capture reactions. During the life of a star there are certain evolutionary stages where neutrons are available to build up the elements beyond iron which cannot be synthesized by charged particle reactions. The observed abundance pattern allows to distinguish a rapid and a slow neutron capture process (r- and s-process). The r-process taking place far from the valley of stability is difficult to investigate because of the required extrapolation of nuclear properties to extreme neutron rich nuclei. The s-process, on the other hand, proceeds along the valley of stability. Therefore, the involved isotopes are accessible to laboratory measurements. This information allows for quantitative calculation of s-process abundances and other parameters which represent constraints for stellar models. Two examples are outlined: (i) the s-process branching at A=147, 148 yields a rather accurate value for the neutron density. (ii) Comparison of s-process abundances with observations of stellar atmospheres are particularly interesting for the unstable isotopes 93Zr, 99Tc and 147Pm. Their deficiency with respect to stable neighbors may yield estimates for the transport time from the stellar interior to the surface.

  8. Nuclear reactions from lattice QCD

    DOE PAGESBeta

    Briceno, Raul A.; Davoudi, Zohreh; Luu, Thomas C.

    2015-02-01

    One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some ofmore »the low- energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.« less

  9. Nuclear Reactions from Lattice QCD

    E-print Network

    Raúl A. Briceño; Zohreh Davoudi; Thomas C. Luu

    2014-11-25

    One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low- energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.

  10. Nuclear reactions from lattice QCD

    NASA Astrophysics Data System (ADS)

    Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.

    2015-02-01

    One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, quantum chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three-nucleon (and higher) interactions in a consistent manner. Currently, lattice quantum chromodynamics (LQCD) provides the only reliable option for performing calculations of some of the low-energy hadronic observables. With the aim of bridging the gap between LQCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from LQCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.

  11. Chemical Reactions in Supercritical Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Wai, Chien M.; Hunt, Fred; Ji, Min; Chen, Xiaoyuan

    1998-12-01

    Utilizing supercritical fluids as environmentally benign solvents for chemical synthesis is one of the new approaches in the "greening" of chemistry. Carbon dioxide is the most widely used gas for supercritical fluid studies because of its moderate critical constants, nontoxic nature, and availability in pure form. One unique property of supercritical carbon dioxide (sc-CO2) is its high solubility for fluorinated compounds. Thus sc-CO2 can be used to replace Freons that are conventionally used as solvents for synthesis of perfluoro-polymers. Another property of sc-CO2 is its miscibility with gases such as H2. Heterogeneous reactions involving these gases may become homogeneous reactions in sc-CO2. Reactions in sc-CO2 may offer several advantages including controlling phase behavior and products, increasing speed of reactions, and obtaining specific reaction channels. This paper describes the following nine types of chemical reactions reported in the literature utilizing sc-CO2 as a solvent to illustrate the unique properties of the supercritical fluid reaction systems: (i) hydrogenation and hydroformylation, (ii) synthesis of organometallic compounds, (iii) metal chelation and extraction, (iv) preparation of inorganic nanoparticles, (v) stereo-selectivity of lipase-catalyzed reactions, (vi) asymmetric catalytic hydrogenation, (vii) polymerization, (viii) Diels-Alder reaction, and (ix) free radical reactions.

  12. Concise route to defined stereoisomers of the hydroxy acid of the chondramides

    PubMed Central

    Schmauder, Anke; Müller, Sven; Maier, Martin E.

    2011-01-01

    The use of Kobayashi vinylogous aldol reaction in the reaction with acetaldehyde led to anti-aldol product 11. After reductive removal of the chiral auxiliary, the primary alcohol was converted to the allyliodide 14. This compound could be engaged in an Evans alkylation reaction, leading eventually to hydroxy acid 19. Inclusion of a Mitsunobu inversion reaction on the sequence starting with ent-11 led to hydroxy ester 30, featuring a 6,7-syn-configuration. These hydroxy acids should help to elucidate the correct stereostructure of the chondramide depsipeptides. PMID:22140278

  13. Charge exchange reactions and applications to astrophysics

    SciTech Connect

    Cheoun, Myung-Ki; Ha, Eunja; Kajino, T. [Department of Physics, Soongsil University, Seoul, 156-743 (Korea, Republic of); National Astronomical Observatory, Mitaka, Tokyo 181-8589 (Japan) and Department of Astronomy, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033 (Japan)

    2012-11-12

    Neutrino-induced reactions have been known to play important roles as the neutrino process on the nucleosynthesis in core collapsing supernovae (SNe) explosions because expected neutrino flux and energy are sufficiently high enough to excite many relevant nuclei in spite of small cross sections of the weak interaction. However, we do not have enough data for the neutrino reaction to be exploited in the network calculation. Only a sparse data in the relevant energy range is known, in specific, for {sup 12}C. Therefore we have to rely on theoretical estimation of the reaction, which has two different modes, charge current (CC) and neutral current (NC). In particular, CC reactions are closely related to charge exchange reactions (CEXRs) which are feasible in the experiment, such as, (p,n) or (n,p) reactions. These CEXRs are usually dominated by the Gamow-Teller (GT) transition in the lower energy region. In this respect, any theoretical approaches for the neutrino reaction should be investigated for the CEXR because we have and expect more useful experimental data. After confirming our models to the GT strength deduced from the CEXR, we calculated neutrino-induced reactions in the energy range below the quasielastic region for nuclei of astrophysical importance. Our calculations are carried out with the Quasi-particle Random Phase Approximation (QRPA), which successfully described the nuclear beta decays of relevant nuclei. To describe neutrino-nucleus reactions, general multipole transitions by the weak interaction are considered for CC and NC reactions. Both reactions are described in a theoretical framework. Our results are shown to well reproduce the data from CEXRs and the sparse experimental data related to the neutrino-induced reaction, and further extended for neutrino reactions on various nuclear targets. Parts of the results are reported in this talk.

  14. Organic syntheses employing supercritical carbon dioxide as a reaction solvent

    NASA Technical Reports Server (NTRS)

    Barstow, Leon E. (Inventor); Ward, Glen D. (Inventor); Bier, Milan (Inventor)

    1991-01-01

    Chemical reactions are readily carried out using supercritical carbon dioxide as the reaction medium. Supercritical carbon dioxide is of special value as a reaction medium in reactions for synthesizing polypeptides, for sequencing polypeptides, or for amino acid analysis.

  15. Organic syntheses employing supercritical carbon dioxide as a reaction solvent

    NASA Technical Reports Server (NTRS)

    Barstow, Leon E. (Inventor); Ward, Glen D. (Inventor); Bier, Milan (Inventor)

    1993-01-01

    Chemical reactions are readily carried out using supercritical carbon dioxide as the reaction medium. Supercritical carbon dioxide is of special value as a reaction medium in reactions for synthesizing polypeptides, for sequencing polypeptides, or for amino acid analysis.

  16. Reaction class transition state theory: Hydrogen abstraction reactions by hydrogen atoms as test cases

    SciTech Connect

    Truong, Thanh N. [Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, 315 South 1400 E, room 2020, Salt Lake City, Utah 84112 (United States)] [Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, 315 South 1400 E, room 2020, Salt Lake City, Utah 84112 (United States)

    2000-09-22

    We present a new method called Reaction Class Transition State Theory (RC-TST) for estimating thermal rate constants of a large number of reactions in a class. This method is based on the transition state theory framework within the reaction class approach. Thermal rate constants of a given reaction in a class relative to those of its principal reaction can be efficiently predicted from only its differential barrier height and reaction energy. Such requirements are much less than what is needed by the conventional TST method. Furthermore, we have shown that the differential energetic information can be calculated at a relatively low level of theory. No frequency calculation beyond those of the principal reaction is required for this theory. The new theory was applied to a number of hydrogen abstraction reactions. Excellent agreement with experimental data shows that the RC-TST method can be very useful in design of fundamental kinetic models of complex reactions. (c) 2000 American Institute of Physics.

  17. Estimating the Backup Reaction Wheel Orientation Using Reaction Wheel Spin Rates Flight Telemetry from a Spacecraft

    NASA Technical Reports Server (NTRS)

    Rizvi, Farheen

    2013-01-01

    A report describes a model that estimates the orientation of the backup reaction wheel using the reaction wheel spin rates telemetry from a spacecraft. Attitude control via the reaction wheel assembly (RWA) onboard a spacecraft uses three reaction wheels (one wheel per axis) and a backup to accommodate any wheel degradation throughout the course of the mission. The spacecraft dynamics prediction depends upon the correct knowledge of the reaction wheel orientations. Thus, it is vital to determine the actual orientation of the reaction wheels such that the correct spacecraft dynamics can be predicted. The conservation of angular momentum is used to estimate the orientation of the backup reaction wheel from the prime and backup reaction wheel spin rates data. The method is applied in estimating the orientation of the backup wheel onboard the Cassini spacecraft. The flight telemetry from the March 2011 prime and backup RWA swap activity on Cassini is used to obtain the best estimate for the backup reaction wheel orientation.

  18. Adverse Reactions of Ferric Carboxymaltose

    PubMed Central

    Patil, Navin; Shenoy, Smita; Bairy, K L; Sarma, Yashdeep

    2014-01-01

    The author reports a 55-year-old female diagnosed of chronic kidney disease grade-5 with associated co-morbidities like type 2 diabetes mellitus, diabetic retinopathy and hypothyroidism was admitted for arteriovenous fistula construction. She was started on ferric carboxymaltose for the treatment of anaemia. She was given a test dose before administering the drug intravenously and she did not develop any reaction. The drug ferric carboxymaltose was then administered over a period of one hour. About half an hour after drug administration, the patient developed breathlessness and myalgia. After half hour of the above episode of breathlessness and myalgia she also developed vomiting (one episode). Patient was managed with oxygen therapy, IV fluids and other drugs like corticosteroids, phenaramine maleate and nalbuphine which controlled the above symptoms. PMID:25478369

  19. The OH + HBr reaction revisited

    NASA Technical Reports Server (NTRS)

    Ravishankara, A. R.; Wine, P. H.; Wells, J. R.

    1985-01-01

    Variable-temperature measurements of the rate coefficient /k(1)/ for the reaction OH + HBr yield Br + H2O are presented. The measurements are verified by two techniques: one involved a 266-nm pulsed-laser photolysis of O3/H2O/HBr/He mixtures in conjunction with time-resolved resonance fluorescence detection of OH, the second comprised pulsed laser-induced fluorescence detection of OH following 248-nm pulsed-laser photolysis of H2O2/HBr/Ar mixtures. It is reported that k(1) = (11.9 + or -1.4 x 10 to the -12th (cu cm)/(molecule)(s) independent of temperature. The measurements are compared with other available results.

  20. A reversible nanoconfined chemical reaction.

    PubMed

    Nielsen, Thomas K; Bösenberg, Ulrike; Gosalawit, Rapee; Dornheim, Martin; Cerenius, Yngve; Besenbacher, Flemming; Jensen, Torben R

    2010-07-27

    Hydrogen is recognized as a potential, extremely interesting energy carrier system, which can facilitate efficient utilization of unevenly distributed renewable energy. A major challenge in a future "hydrogen economy" is the development of a safe, compact, robust, and efficient means of hydrogen storage, in particular, for mobile applications. Here we report on a new concept for hydrogen storage using nanoconfined reversible chemical reactions. LiBH4 and MgH2 nanoparticles are embedded in a nanoporous carbon aerogel scaffold with pore size Dmax approximately 21 nm and react during release of hydrogen and form MgB2. The hydrogen desorption kinetics is significantly improved compared to bulk conditions, and the nanoconfined system has a high degree of reversibility and stability and possibly also improved thermodynamic properties. This new scheme of nanoconfined chemistry may have a wide range of interesting applications in the future, for example, within the merging area of chemical storage of renewable energy. PMID:20533850

  1. Radiation Reaction and Center Manifolds

    E-print Network

    Markus; Kunze; Herbert Spohn

    1999-01-12

    We study the effective dynamics of a mechanical particle coupled to a wave field and subject to the slowly varying potential $V(\\eps q)$ with $\\eps$ small. To lowest order in $\\eps$ the motion of the particle is governed by an effective Hamiltonian. In the next order one obtains ``dissipative'' terms which describe the radiation reaction. We establish that this dissipative dynamics has a center manifold which is repulsive in the normal direction and which is global, in the sense that for given data and sufficiently small $\\eps$ the solution stays on the center manifold forever. We prove that the solution of the full system is well approximated by the effective dissipative dynamics on its center manifold.

  2. Radiation reaction for multipole moments

    E-print Network

    P. O. Kazinski

    2006-04-27

    We propose a Poincare-invariant description for the effective dynamics of systems of charged particles by means of intrinsic multipole moments. To achieve this goal we study the effective dynamics of such systems within two frameworks -- the particle itself and hydrodynamical one. We give a relativistic-invariant definition for the intrinsic multipole moments both pointlike and extended relativistic objects. Within the hydrodynamical framework we suggest a covariant action functional for a perfect fluid with pressure. In the case of a relativistic charged dust we prove the equivalence of the particle approach to the hydrodynamical one to the problem of radiation reaction for multipoles. As the particular example of a general procedure we obtain the effective model for a neutral system of charged particles with dipole moment.

  3. Antibody-mediated cofactor-driven reactions

    DOEpatents

    Schultz, Peter G. (Oakland, CA)

    1993-01-01

    Chemical reactions capable of being rate-enhanced by auxiliary species which interact with the reactants but do not become chemically bound to them in the formation of the final product are performed in the presence of antibodies which promote the reactions. The antibodies contain regions within their antigen binding sites which recognize the auxiliary species in a conformation which promotes the reaction. The antigen binding site frequently recognizes a particular transition state complex or other high energy complex along the reaction coordinate, thereby promoting the progress of the reaction along the desired route as opposed to other less favorable routes. Various classes of reaction together with appropriate antigen binding site specificities tailored for each are disclosed.

  4. Antibody-mediated cofactor-driven reactions

    SciTech Connect

    Schultz, P.G.

    1993-06-15

    Chemical reactions capable of being rate-enhanced by auxiliary species which interact with the reactants but do not become chemically bound to them in the formation of the final product are performed in the presence of antibodies which promote the reactions. The antibodies contain regions within their antigen binding sites which recognize the auxiliary species in a conformation which promotes the reaction. The antigen binding site frequently recognizes a particular transition state complex or other high energy complex along the reaction coordinate, thereby promoting the progress of the reaction along the desired route as opposed to other less favorable routes. Various classes of reactions together with appropriate antigen binding site specificities tailored for each are disclosed.

  5. Controlling chemical reactions of a single particle

    E-print Network

    Ratschbacher, Lothar; Sias, Carlo; Köhl, Michael

    2012-01-01

    The control of chemical reactions is a recurring theme in physics and chemistry. Traditionally, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature or pressure. More recently, physical methods such as laser or magnetic field control have emerged to provide completely new experimental possibilities, in particular in the realm of cold collisions. The control of reaction pathways is also a critical component to implement molecular quantum information processing. For these undertakings, single particles provide a clean and well-controlled experimental system. Here, we report on the experimental tuning of the exchange reaction rates of a single trapped ion with ultracold neutral atoms by exerting control over both their quantum states. We observe the influence of the hyperfine interaction on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products. These investigations advance chemistry with single trapped particles towards achi...

  6. Reactions of Rydberg states of molecular hydrogen

    NASA Astrophysics Data System (ADS)

    Pratt, S. T.; Dehmer, J. L.; Dehmer, P. M.; Chupka, W. A.

    1994-07-01

    The Rydberg state reaction H*2+H2?H+3+H+e- was studied by exciting the (X 2?+g)np,v=0,J Rydberg states with n=30-70 by double resonance excitation via the E,F 1?+g,v=0,J=1 level and by detecting the product ions or electrons. The results are consistent with the reaction occurring between the ion core of the Rydberg molecule and the ground state molecule, with the Rydberg electron acting as a spectator. Thus, these reactions can be used to provide information on the analogous ion-molecule reactions, and the possibility of using the Rydberg state reactions to study the rotational state dependence of the corresponding ion-molecule reactions is discussed.

  7. Hymenoptera-Induced Hypersensitivity Reactions and Anaphylaxis

    Microsoft Academic Search

    Mitja Kosnik; Peter Korosec

    \\u000a Most Hymenoptera (honeybees, bumblebees, yellow jackets, hornets, wasps and fire ants) stings lead to a local reaction. Up\\u000a to 7% of population develops systemic allergic reaction to the constituents of venom. Up to 0.5 per one million people die\\u000a per year due to Hymenoptera venom allergy. Risk factors for the most severe reactions are advanced age, concomitant cardiovascular\\u000a diseases, concomitant

  8. Reaction dynamics of synthesis of superheavy elements

    Microsoft Academic Search

    Y. Abe

    2002-01-01

    :   Based on the theory of the compound nucleus reaction, a brief review is given on the special aspects of the reaction dynamics\\u000a in the synthesis of the superheavy elements (SHE), where the fusion probability is the most unknown factor. A new viewpoint\\u000a of the fusion reaction is proposed that it consists of two processes; the first process up to

  9. Reaction torque minimization techniques for articulated payloads

    NASA Technical Reports Server (NTRS)

    Kral, Kevin; Aleman, Roberto M.

    1988-01-01

    Articulated payloads on spacecraft, such as antenna telemetry systems and robotic elements, impart reaction torques back into the vehicle which can significantly affect the performance of other payloads. This paper discusses ways to minimize the reaction torques of articulated payloads through command-shaping algorithms and unique control implementations. The effects of reaction torques encountered on Landsat are presented and compared with simulated and measured data of prototype systems employing these improvements.

  10. Gold-catalyzed carbene transfer reactions.

    PubMed

    Shin, Seunghoon

    2015-01-01

    In homogeneous gold catalysis, generations and reactions of metal carbenes have been one of the most rapidly developing areas because of their diverse reactivity under mild conditions. This review covers recent advances in the gold-catalyzed oxygen atom transfer and carbene transfer reactions to alkynes. Atom transfer to an alkyne enables alkynes to function as metal carbene synthons. Many such reactions fulfill redox neutrality starting from safe and easily handled precursors. PMID:25518973

  11. Efficiently gap-filling reaction networks

    PubMed Central

    2014-01-01

    Background Flux Balance Analysis (FBA) is a genome-scale computational technique for modeling the steady-state fluxes of an organism’s reaction network. When the organism’s reaction network needs to be completed to obtain growth using FBA, without relying on the genome, the completion process is called reaction gap-filling. Currently, computational techniques used to gap-fill a reaction network compute the minimum set of reactions using Mixed-Integer Linear Programming (MILP). Depending on the number of candidate reactions used to complete the model, MILP can be computationally demanding. Results We present a computational technique, called FastGapFilling, that efficiently completes a reaction network by using only Linear Programming, not MILP. FastGapFilling creates a linear program with all candidate reactions, an objective function based on their weighted fluxes, and a variable weight on the biomass reaction: no integer variable is used. A binary search is performed by modifying the weight applied to the flux of the biomass reaction, and solving each corresponding linear program, to try reducing the number of candidate reactions to add to the network to generate a working model. We show that this method has proved effective on a series of incomplete E. coli and yeast models with, in some cases, a three orders of magnitude execution speedup compared with MILP. We have implemented FastGapFilling in MetaFlux as part of Pathway Tools (version 17.5), which is freely available to academic users, and for a fee to commercial users. Download from: biocyc.org/download.shtml. Conclusions The computational technique presented is very efficient allowing interactive completion of reaction networks of FBA models. Computational techniques based on MILP cannot offer such fast and interactive completion. PMID:24972703

  12. A Unified Theory of Chemical Reactions

    E-print Network

    Aubry, S

    2014-01-01

    We propose a new and general formalism for elementary chemical reactions where quantum electronic variables are used as reaction coordinates. This formalism is in principle applicable to all kinds of chemical reactions ionic or covalent. Our theory reveals the existence of an intermediate situation between ionic and covalent which may be almost barrierless and isoenegetic and which should be of high interest for understanding biochemistry.

  13. The Science of Low Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Storms, Edmund

    2007-03-01

    The large literature describing the anomalous behavior attributed to cold fusion or low energy nuclear reactions has been critically described in a recently published book. Over 950 publications are evaluated allowing the phenomenon to be understood. A new class of nuclear reactions has been discovered that are able to generate practical energy without significant radiation or radioactivity. Edmund K Storms, The Science of Low Energy Nuclear Reactions, in press (2006). Also see: http://www.lenr-canr.org/StudentsGuide.htm .

  14. Nuclear structure in deep-inelastic reactions

    SciTech Connect

    Rehm, K.E.

    1986-01-01

    The paper concentrates on recent deep inelastic experiments conducted at Argonne National Laboratory and the nuclear structure effects evident in reactions between super heavy nuclei. Experiments indicate that these reactions evolve gradually from simple transfer processes which have been studied extensively for lighter nuclei such as /sup 16/O, suggesting a theoretical approach connecting the one-step DWBA theory to the multistep statistical models of nuclear reactions. This transition between quasi-elastic and deep inelastic reactions is achieved by a simple random walk model. Some typical examples of nuclear structure effects are shown. 24 refs., 9 figs.

  15. Non-Markovian polymer reaction kinetics

    NASA Astrophysics Data System (ADS)

    Guérin, T.; Bénichou, O.; Voituriez, R.

    2012-07-01

    Describing the kinetics of polymer reactions, such as the formation of loops and hairpins in nucleic acids or polypeptides, is complicated by the structural dynamics of their chains. Although both intramolecular reactions, such as cyclization, and intermolecular reactions have been studied extensively, both experimentally and theoretically, there is to date no exact explicit analytical treatment of transport-limited polymer reaction kinetics, even in the case of the simplest (Rouse) model of monomers connected by linear springs. We introduce a new analytical approach to calculate the mean reaction time of polymer reactions that encompasses the non-Markovian dynamics of monomer motion. This requires that the conformational statistics of the polymer at the very instant of reaction be determined, which provides, as a by-product, new information on the reaction path. We show that the typical reactive conformation of the polymer is more extended than the equilibrium conformation, which leads to reaction times significantly shorter than predicted by the existing classical Markovian theory.

  16. Entropy generation in a chemical reaction

    E-print Network

    E. N. Miranda

    2012-08-10

    Entropy generation in a chemical reaction is analyzed without using the general formalism of non-equilibrium thermodynamics at a level adequate for advanced undergraduates. In a first approach to the problem, the phenomenological kinetic equation of an elementary first order reaction is used to show that entropy production is always positive. A second approach assumes that the reaction is near equilibrium to prove that the entropy generated is always greater than zero, without any reference to the kinetics of the reaction. Finally, it is shown that entropy generation is related to fluctuations in the number of particles at equilibrium, i.e. it is associated to a microscopic process.

  17. Chemical reactions in low-g

    NASA Technical Reports Server (NTRS)

    Grodzka, P. G.; Facemire, B. R.

    1978-01-01

    The Apollo-Soyuz flight experiment, 'Chemical Foams' demonstrated that foams and air/liquid dispersions are much more stable in low-gravity than on the ground. It thus should be possible to conduct unique chemical reactions in space foams. The low-g results and subsequent ground work on the formaldehyde clock reaction indicate that the reaction is strongly influenced by (1) dissociated and undissociated solution species being adsorbed at solid/liquid and gas/liquid surfaces and (2) chemical reaction rates apparently being affected by long-range forces determined by the liquid mass and the extent and nature of all surface interfaces.

  18. Entropy generation in a chemical reaction

    E-print Network

    Miranda, E N

    2012-01-01

    Entropy generation in a chemical reaction is analyzed without using the general formalism of non-equilibrium thermodynamics at a level adequate for advanced undergraduates. In a first approach to the problem, the phenomenological kinetic equation of an elementary first order reaction is used to show that entropy production is always positive. A second approach assumes that the reaction is near equilibrium to prove that the entropy generated is always greater than zero, without any reference to the kinetics of the reaction. Finally, it is shown that entropy generation is related to fluctuations in the number of particles at equilibrium, i.e. it is associated to a microscopic process.

  19. Short synthesis of a benzyl ether-protected building block for the synthesis of carbocyclic galactopyranose mimics.

    PubMed

    Cumpstey, Ian

    2010-05-27

    A versatile intermediate for the synthesis of galactose-mimicking carbasugars was synthesised from tetrabenzyl galactose in five steps and 30% overall yield. The reaction sequence uses an L-proline-mediated aldol reaction as key step. The reaction sequence was run on several grams of material. PMID:20394917

  20. Mesoscale simulation of polymer reaction equilibrium: Combining dissipative particle dynamics with reaction ensemble Monte Carlo.

    E-print Network

    Lisal, Martin

    Mesoscale simulation of polymer reaction equilibrium: Combining dissipative particle dynamics a mesoscale simulation technique, called the reaction ensemble dissipative particle dynamics RxDPD method. Coarse-grained, particle- based mesoscale models that retain only the most essential features

  1. The Proton-Proton Reaction and Related Reactions in an Intense Magnetic Field

    Microsoft Academic Search

    Chih Kang Chou

    1971-01-01

    The reaction rates for the proton-proton reaction and the related electron capture reaction in a strongly magnetized relativistic electron gas of arbitrary degree of degeneracy are computed. The proton-proton reaction rates are unaffected by the presence of the magnetic field for field strengths up to the critical valueH q =m 2 c 3\\/eh=4.414×1013G. For fields greater thanH q , the

  2. Nuclear Reaction Data File for Astrophysics (NRDF/A) in Hokkaido University Nuclear Reaction Data Center

    SciTech Connect

    Kato, Kiyoshi [Division of Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Kimura, Masaaki [Creative Research Institution Sousei, Hokkaido University, Sapporo 001-0021 (Japan); Furutachi, Naoya; Makinaga, Ayano [Meme Media Laboratory, Hokkaido University, Sapporo 060-8628 (Japan); Togashi, Tomoaki [Division of CosmoScience, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Otuka, Naohiko [Nuclear Data Section, Division of Physical and Chemical Science, Department of Nuclear Science and Applications, International Atomic Energy Agency, A-1400 Wien (Austria)

    2010-06-01

    The activities of the Japan Nuclear Reaction Data Centre is explained. The main task of the centre is data compilation of Japanese nuclear reaction data in collaboration of the International Network of Nuclear Reaction Data Centres. As one of recent activities, preparation of a new database (NRDF/A) and evaluation of astronuclear reaction data are reported. Collaboration in the nuclear data activities among Asian countries is proposed.

  3. Hydrothermal reactions of fly ash

    SciTech Connect

    Brown, P.W.

    1992-01-01

    The reactions which occur when fly ash is treated under hydrothermal conditions will be investigated. This will be done for two primary reasons. The first of these is to determine the nature of the phases that form, to assess the stabilities of these phases in the ambient environment and, finally, to assess whether these phases are capable of sequestering hazardous species. The second reason for undertaking this proposed study is that, depending on the composition of the ash and the presence of selected additives, it may be possible under hydrothermal conditions to form compounds which have cementitious properties. Formation of four classes of compounds which bracket likely fly ash compositional ranges, have been selected for study. These are calcium silicate hydrates, calcium silicosulfates, calcium aluminosulfates, and alkali aluminosilicates. The specific compounds fabricated will be determined and their stability regions assessed. As a part of stability assessment, the extent to which selected hazardous species are sequestered seal be determined. Finally, the cementing properties of these compounds will be established.

  4. Allergic reactions to food proteins.

    PubMed

    Ballmer-Weber, Barbara K

    2011-03-01

    Four to eight percent of the population are estimated to be food-allergic. Most food allergies in adolescents and adults are acquired on the basis of cross-reaction to pollen allergens. Theses allergens are ubiquitous in the plant kingdom. Therefore pollen-allergic patients might acquire a multitude of different plant food allergies, and even react to novel foods to which they have never previously been exposed. A curative therapy for food allergy does not yet exist. Food-allergic patients have to rely on strict avoidance diets, The widespread use of industrially processed foods poses a general problem for food-allergic patients. Although the most frequent allergens must be declared openly in the list of ingredients, involuntary contamination with allergy-provoking compounds can occur. The precautionary labelling "may contain" is sometimes applied even if the chance of contamination is very low; on the other hand, foods not declared to contain possible traces of allergenic components may actually contain relevant amounts of allergenic proteins. Switzerland is the only country in Europe with legal regulations on contamination by allergenic food; however, the allowance of 1 g/kg is too high to protect a relevant proportion of food-allergic individuals. PMID:22139568

  5. Rearrangement reactions of lithiated oxiranes.

    PubMed

    Ramachandran, B Ramu; Waithe, Shannon; Pratt, Lawrence M

    2013-11-01

    The first computational study of the rearrangement reactions of oxiranes initiated by lithium dialkylamides is presented. Aside from the well-known carbenoid insertion pathways, both ?-elimination and ?-lithiation have been suggested as the exclusive mechanism by which oxiranes react in the presence of organolithium bases. The products of the former are allyl alcohols (and, in some cases, dienes) and are ketones in the case of the latter. The computational studies reported in this work indicate that both mechanisms could be simultaneously operational. In particular, our work shows that the allyl alcohols from ?-elimination are unlikely to undergo 1,3-hydrogen transfer to the vinyl alcohols and thus to the ketones, suggesting that ketones are formed through the opening of the oxirane ring after ?-substitution. Elimination of LiOH from the lithiated allyl alcohol is found to result in the diene product. Low activation barriers for ?-elimination are offered as the explanation for the few special cases where the allyl alcohol is the dominant or exclusive product. These findings are consistent with the product distributions observed in several experiments. PMID:24079374

  6. 2005 Chemical Reactions at Surfaces

    SciTech Connect

    Cynthia M. Friend

    2006-03-14

    The Gordon Research Conference (GRC) on 2005 Chemical Reactions at Surfaces was held at Ventura Beach Marriott, Ventura California from February 13, 2005 through February 18, 2005. The Conference was well-attended with 124 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. Attached is a copy of the formal schedule and speaker program and the poster program. In addition to these formal interactions, 'free time' was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field.

  7. Reaction asymmetries and the spin orbit interaction

    NASA Astrophysics Data System (ADS)

    Bond, P. D.

    1984-02-01

    The use of reaction asymmetries to deduce spin orbit interactions in heavy ion reactions is discussed. It is suggested that in most cases they are too sensitive to many other phenomena to be useful tools and reanalysis of some existing data demonstrates that large spin orbit interactions are not required to reproduce the observed asymmetries.

  8. Reactions to Stranger and Acquaintance Rape.

    ERIC Educational Resources Information Center

    Tetreault, Patricia A.; Barnett, Mark A.

    1987-01-01

    Investigated reactions to a woman who presumably had been raped by a stranger or an acquaintance. Undergraduates read one of two rape descriptions prior to watching a videotape of the woman who (they were led to believe) had been the victim of the rape. Females and males showed markedly different reactions to stranger and acquaintance rape and…

  9. Statistical model calculations in heavy ion reactions

    Microsoft Academic Search

    A. Gavron

    1980-01-01

    Results of various fusion experiments with heavy ions are compared with predictions of statistical model calculations. In some reactions there is evidence for nonstatistical effects based on significant discrepancies between the calculations and the experimental results. Alternative explanations of these discrepancies are considered. [NUCLEAR REACTIONS HI (xngamma), statistical model calculations.

  10. Experimental Study of Carbon Sequestration Reactions Controlled

    E-print Network

    Demouchy, Sylvie

    Experimental Study of Carbon Sequestration Reactions Controlled by the Percolation of CO2-Rich. Carbonation of ultramafic rocks in geological reservoirs is, in theory, the most efficient way to trap CO2 irreversibly; however, possible feedback effects between carbonation reactions and changes in the reservoir

  11. ChemTeacher: Balancing Redox Reactions

    NSDL National Science Digital Library

    2011-01-01

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Balancing Redox Reactions page includes resources for teaching students about the steps needed to balance oxidation-reduction reactions.

  12. Astrophysical Reaction Rates Obtained By Indirect Techniques

    SciTech Connect

    Tribble, R. E.; Al-Abdullah, T.; Alharbi, A.; Banu, A.; Chen, X.; Clark, H. L.; Fu, C.; Gagliardi, C. A.; Hardy, J. C.; Iacob, V. E.; Lui, Y.-W.; McCleskey, M.; Mukhamedzhanov, A.; Nica, N.; Park, H. I.; Roeder, B.; Simmons, E.; Tabacaru, G.; Tokimoto, Y.; Trache, L. [Cyclotron Institute, Texas A and M University, College Station, TX 77843 (United States)

    2010-08-12

    Indirect techniques have been used to obtain information about reaction rates for several proton capture reactions that occur on short-lived nuclei. The techniques used to carry out the measurements are reviewed and the results obtained are presented. Also future prospects for further measurements with a new facility, T-REX are discussed.

  13. Resonant structures in heavy-ion reactions

    SciTech Connect

    Sanders, S.J.; Henning, W.; Ernst, H.; Geesaman, D.F.; Jachcinski, C.; Kovar, D.G.; Paul, M.; Schiffer, J.P.

    1980-01-01

    An investigation of heavy-ion resonance structures using the /sup 24/Mg(/sup 16/O, /sup 12/C)/sup 28/Si reaction is presented. The data are analyzed in the context of Breit-Wigner resonances added to a direct-reaction background.

  14. Density functional studies of representative pericyclic reactions

    NASA Astrophysics Data System (ADS)

    Carpenter, John E.; Sosa, Carlos P.

    1994-07-01

    Density functional theory (DFT) has traditionally been shunned by computational chemists, but has long seen widespread use in the physics community. Recently, however, DFT has been adopted by the ab initio quantum chemistry community and much activity has been devoted to refining the methodology and exploring the range of its applicability. We investigate the use of DFT (both local (LDF) and non-local (NLDF) spin density approximations) to calculate transition and equilibrium structures for three representative pericyclic reactions: the electrocyclic ring opening reaction of cyclobutene, the [1,5] sigmatropic hydrogen shift reaction in (Z)-1,3-pentadiene, and the Diels-Alder cycloaddition reaction between ethylene and butadiene. LDF theory tends to overemphasize the stability of the ringed structures in each of these reactions. For example, LDF predicts a very low (6 kcal mol -1) barrier to reaction for the Deils-Alder reaction. NLDF theory substantially improves the calculated reaction barrier (20 kcal mol -1), but it is still low with respect to experiment.

  15. Reliability of a Shuttle reaction timer

    NASA Technical Reports Server (NTRS)

    Hays, Russell D.; Mazzocca, Augustus D.; Rashid, Michael; Siconolfi, Steven F.

    1992-01-01

    Reaction, movement, and task times refer to the times needed to initially respond to a stimulus, make the specific movement, and complete the entire task. This study evaluated the reliability of a simple reaction timer designed to mimic a Space Shuttle task (turning on an overhead switch).

  16. The Iodine Clock Reaction and Hypothermia.

    ERIC Educational Resources Information Center

    Gennaro, Gene; Munson, Bruce

    1988-01-01

    Explains an activity which can be used to compare the effect of temperature on the rate of chemical reactions to the metabolic reactions that take place within the body. Outlines directions and materials needed to perform the experiment. Lists a number of the body's defenses against extremely low temperatures. (RT)

  17. Endometrial Reaction to Intrauterine Device in Pregnancy

    Microsoft Academic Search

    Yossef Ezra; Arie Birkenfeld; Itzhak S. Levij

    1989-01-01

    It is generally assumed that the intrauterine device (IUD) exerts its action by altering endometrial receptivity for the implanting embryo. The most frequently encountered endometrial reaction reported in the presence of an IUD is a chronic inflammatory reaction which may be responsible for the alterations in the normal physiology of the human endometrium. In order to evaluate the endometrial response

  18. Reaction Parameters for Heavy-Ion Collisions

    Microsoft Academic Search

    W. W. Wilcke; J. R. Birkelund; H. J. Wollersheim; A. D. Hoover; J. R. Huizenga; W. U. Schroeder; L. E. Tubbs

    1980-01-01

    These tables present reaction parameters for all combinations of 27 projectile and 16 target nuclei in a laboratory bombarding energy range of 1--50 MeV\\/u. The reaction parameters are derived from the Fresnel model of heavy-ion scattering, the droplet model, and the rotating liquid-drop model, or from systematics of experimental data.

  19. Acute dystonic reactions from "street Valium".

    PubMed

    Demetropoulos, S; Schauben, J L

    1987-01-01

    Four patients presented to the emergency department with acute dystonic reactions 36 hours after the ingestion of "Valium tablets" they purchased on the street. Complete reversal of the symptomatology was achieved with the use of intramuscular diphenhydramine. The pathophysiology, epidemiology, and treatment principles for dystonic reactions are discussed. PMID:3624836

  20. The Logical Chain Reaction (aka Mathematical Induction)

    E-print Network

    Pego, Robert

    The Logical Chain Reaction (aka Mathematical Induction) Robert Pego Department of Mathematical infinitum. This is the logical chain reaction -- it proves that A(n) is in fact true for every postitive an infinite chain of implications: A(1) A(2) A(3) . . . A(37) A(38) . . . ad infinitum. The fuse is set

  1. Low Energy Nuclear Reactions: 2007 Update

    Microsoft Academic Search

    Steven B. Krivit

    2007-01-01

    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

  2. Neutron capture reaction rates for stellar nucleosynthesis

    SciTech Connect

    Mengoni, A. [Department of Nuclear Sciences and Applications, Division of Physical and Chemical Sciences, Nuclear Data Section, International Atomic Energy Agency, A-1400 Wagramer Strasse 5, Vienna (Austria)

    2006-03-13

    A short summary of the three fundamental neutron capture reaction processes of interest in stellar nucleosynthesis is presented. Three examples of actual situations in which the capture reaction proceeds through one of these processes are identified and an overview of the experimental data as well as of the model calculations used in the determination of the capture rates are presented.

  3. Spontaneous Reaction Silencing in Metabolic Optimization

    E-print Network

    Spontaneous Reaction Silencing in Metabolic Optimization Takashi Nishikawa1,2 , Natali Gulbahce3 States of America, 4 Center for Cancer Systems Biology, Dana Farber Cancer Institute, Boston, Massachusetts, United States of America Abstract Metabolic reactions of single-cell organisms are routinely

  4. Foreign body reaction after cochlear implantation

    Microsoft Academic Search

    Hye Jin Lim; Eun-So Lee; Hun Yi Park; Yun-Hoon Choung

    2011-01-01

    Cochlear implantation is a widely accepted, safe procedure for patients with severe to profound sensorineuronal hearing loss. While complications are rare, revision surgeries are required for complications like device failure, misplaced electrode, flap necrosis, and wound infection. Foreign body reaction is a rare complication following cochlear implantation. We experienced a case of foreign body reaction after cochlear implantation treated by

  5. Energy Surfaces, Trajectories, and the Reaction Coordinate

    ERIC Educational Resources Information Center

    Hulse, John E.; And Others

    1974-01-01

    Discusses the use of a computer program to describe chemical reactions by the concepts of reaction coordinate and energy profile. Indicates that representation of a collision encounter by a trajectory on the energy surface leads to a precise explanation, rather than schematic, in the teaching chemical kinetics. (CC)

  6. Multicomponent Reactions in Total Synthesis Kevin Allan

    E-print Network

    Stoltz, Brian M.

    · Ugi Reaction · Cycloadditions · Povarov Reaction · Knoevenagel / Hetero-Diels-Alder Cycloaddition · 1-VCH; Weinheim, 2005. Orru, R. V. A.; de Greef, M. Synthesis 2003, 10, 1471-1499. Ugi, I. Pure Appl. Chem. 2001, 73, 187-191. Bienaymé, H.; Hulme, C.; Oddon, G.; Schmitt, P. Chem. Eur. J. 2000, 6, 3321-3329. Ugi, I

  7. SULFUR DIOXIDE OXIDATION REACTIONS IN AQUEOUS SOLUTIONS

    EPA Science Inventory

    This is the final report on a three year project to study the kinetics and mechanisms of some 105 reactions involving the aqueous oxidation of sulfur dioxide and nitrogen oxides in mixed catalyst-oxidant systems at low pH (0-3). The 105 systems involve six redox reaction types: S...

  8. Chemical Principles Revisited: Annotating Reaction Equations.

    ERIC Educational Resources Information Center

    Tykodi, R. J.

    1987-01-01

    Urges chemistry teachers to have students annotate the chemical reactions in aqueous-solutions that they see in their textbooks and witness in the laboratory. Suggests this will help students recognize the reaction type more readily. Examples are given for gas formation, precipitate formation, redox interaction, acid-base interaction, and…

  9. SCF perturbation theory for unimolecular reactions

    Microsoft Academic Search

    Vinzenz Bachler; Gottfried Olbrich; Oskar E. Polansky; Yuh-Kang Pan

    1979-01-01

    A CNDO\\/2 SCF perturbation theory is presented for interpreting the form of CNDO\\/2 potential energy surfaces of unimolecular reactions. The analysis is performed by calculating the energy change ? E arising from a distortion of the molecular geometry along the reaction coordinate. ? E is decomposed into different perturbational contributions which are appropriate for an interpretation of the perturbation energy

  10. Suspected adverse reactions to medicines during 1989

    Microsoft Academic Search

    A Gray; C Evans; A Kidd

    1990-01-01

    There was an increase in reports of suspected adverse reactions to veterinary medicines in 1989 with 329 reports (compared with 206 in 1988), from veterinary surgeons, farmers and the public, comments the Veterinary Medicines Directorate (VMD). Suspected adverse reactions to clostridial\\/pasteurella vaccines in sheep were a dominant feature and important experience was gained both in terms of liaison with the

  11. Miniature reaction chamber and devices incorporating same

    DOEpatents

    Mathies, Richard A. (Moraga, CA); Woolley, Adam T. (Albany, CA)

    2000-10-17

    The present invention generally relates to miniaturized devices for carrying out and controlling chemical reactions and analyses. In particular, the present invention provides devices which have miniature temperature controlled reaction chambers for carrying out a variety of synthetic and diagnostic applications, such as PCR amplification, nucleic acid hybridization, chemical labeling, nucleic acid fragmentation and the like.

  12. The Activated Complex in Chemical Reactions

    Microsoft Academic Search

    Henry Eyring

    1935-01-01

    The calculation of absolute reaction rates is formulated in terms of quantities which are available from the potential surfaces which can be constructed at the present time. The probability of the activated state is calculated using ordinary statistical mechanics. This probability multiplied by the rate of decomposition gives the specific rate of reaction. The occurrence of quantized vibrations in the

  13. Invited Review Biologically Relevant Chemical Reactions of

    E-print Network

    Gates, Kent. S.

    Invited Review Biologically Relevant Chemical Reactions of N7-Alkylguanine Residues in DNA Kent S set out here to provide an overview of the biologically relevant chemical reactions of N7-alkylgua-Catalyzed Depurination 841 3.2. Chemical Mechanism for the Depurination of N7-Alkylguanine Residues 842 3.3. Overview

  14. The Fluid Mechanics of Chemical Reaction

    NASA Astrophysics Data System (ADS)

    Benson, D. A.; Engdahl, N. B.; Bolster, D.

    2014-12-01

    The ability for reactive constituents to mix is often the key limiting factor for the completion of reactions across a huge range of scales in a variety of media. In flowing systems, deformation and shear enhance mixing by bringing constituents into closer proximity, thus increasing reaction potential. Accurately quantifying this enhanced mixing is key to predicting reactions, and typically is done by observing or simulating scalar transport. To eliminate this computationally expensive step, we use a Lagrangian stochastic framework to derive the enhancement to reaction potential by calculating the collocation probability of particle pairs in a heterogeneous flow field accounting for deformations. We relate the enhanced reaction potential to three well-known flow topology metrics (Okubo-Weiss, finite-time Lyapunov exponent, and right Cauchy-Green tensor) and demonstrate that it is best correlated to the largest eigenvalue of the right Cauchy-Green tensor. The reason is that this eigenvalue reflects compression and shear but ignores rotation, which does not enhance mixing. We demonstrate that regions of high shear and/or compression do indeed have higher rates of reaction in particle-tracking reaction simulations, but this is not necessarily seen in traditional Eulerian simulations due to numerical (artificial) mixing and the amplification of these errors by non-linear reactions.

  15. pH & Rate of Enzymatic Reactions.

    ERIC Educational Resources Information Center

    Clariana, Roy B.

    1991-01-01

    A quantitative and inexpensive way to measure the rate of enzymatic reaction is provided. The effects of different pH levels on the reaction rate of an enzyme from yeast are investigated and the results graphed. Background information, a list of needed materials, directions for preparing solutions, procedure, and results and discussion are…

  16. Electron transfer reactions in microporous solids

    NASA Astrophysics Data System (ADS)

    Mallouk, T. E.

    1991-05-01

    We are studying the synthesis of light-induced electron transfer reactions which occur within microporous materials. Some highlights of our progress in the last year are in the fields of (1) electron transfer reactions of donor/acceptor molecules at the zeolite/solution interface; (2) photochemistry of zeolite/TiO2 composites; and (3) photochemistry of layered oxide semiconductors.

  17. ABIOTIC ORGANIC REACTIONS AT MINERAL SURFACES

    EPA Science Inventory

    Abiotic organic reactions, such as hydrolysis, elimination, substitution, redox, and polymerization reactions, can be influenced by surfaces of clay and primary minerals, and of metal oxides. This influence is due to adsorption of the reactants to surface Lewis and Bronsted sites...

  18. Asthma and anaphylactoid reactions to food additives.

    PubMed Central

    Tarlo, S. M.; Sussman, G. L.

    1993-01-01

    Presumed allergic reactions to hidden food additives are both controversial and important. Clinical manifestations include asthma, urticaria, angioedema, and anaphylactic-anaphylactoid events. Most adverse reactions are caused by just a few additives, such as sulfites and monosodium glutamate. Diagnosis is suspected from the history and confirmed by specific challenge. The treatment is specific avoidance. PMID:8499792

  19. Radiation reaction due to magnetic dipole radiation

    Microsoft Academic Search

    Naoki Itoh

    1991-01-01

    The radiation reaction due to magnetic dipole radiation is calculated for a charged-particle system whose magnetic moment changes with time. The explicit expressions for the electric and magnetic fields due to the magnetic dipole radiation reaction are derived, they are found to originate in the fourth-order term in the expansion of the retarded potential, whereas the field due to the

  20. Reactions of alkynylselenonium salts with sodium benzenesulfinate

    Microsoft Academic Search

    Tadashi Kataoka; Yoshihiro Banno; Shin-ichi Watanabe; Tatunori Iwamura; Hiroshi Shimizu

    1997-01-01

    Alkynylselenonium salts 2 and 5 were synthesized and treated with benzenesulfinic acid or its sodium salt in an alcohol. The reactions with sodium benzenesulfinate gave (Z)-?-alkoxyvinylsulfones 6 as main products, while the reactions with benzenesulfinic acid afforded the ?-sulfonylvinylselenonium salts 11 and 12 in good yields.

  1. A Green Multicomponent Reaction for the Organic Chemistry Laboratory: The Aqueous Passerini Reaction

    ERIC Educational Resources Information Center

    Hooper, Matthew M.; DeBoef, Brenton

    2009-01-01

    Water is the ideal green solvent for organic reactions. However, most organic molecules are insoluble in it. Herein, we report a laboratory module that takes advantage of this property. The Passerini reaction, a three-component coupling involving an isocyanide, aldehyde, and carboxylic acid, typically requires [similar to] 24 h reaction times in…

  2. Direct Monte Carlo simulation of chemical reaction systems: Simple bimolecular reactions

    E-print Network

    Anderson, James B.

    Direct Monte Carlo simulation of chemical reaction systems: Simple bimolecular reactions Shannon D and understanding the behavior of gas phase chemical reaction systems. This Monte Carlo method, originated by Bird useful, and the gas dynamics of many systems is more easily predicted and understood by using Monte Carlo

  3. Connecting localized DNA strand displacement reactions.

    PubMed

    Mullor Ruiz, Ismael; Arbona, Jean-Michel; Lad, Amitkumar; Mendoza, Oscar; Aimé, Jean-Pierre; Elezgaray, Juan

    2015-07-23

    Logic circuits based on DNA strand displacement reactions have been shown to be versatile enough to compute the square root of four-bit numbers. The implementation of these circuits as a set of bulk reactions faces difficulties which include leaky reactions and intrinsically slow, diffusion-limited reaction rates. In this paper, we consider simple examples of these circuits when they are attached to platforms (DNA origamis). As expected, constraining distances between DNA strands leads to faster reaction rates. However, it also induces side-effects that are not detectable in the solution-phase version of this circuitry. Appropriate design of the system, including protection and asymmetry between input and fuel strands, leads to a reproducible behaviour, at least one order of magnitude faster than the one observed under bulk conditions. PMID:26168352

  4. Adverse reaction; patent blue turning patient blue.

    PubMed

    Joshi, Meera; Hart, Matthew; Ahmed, Farid; McPherson, Sandy

    2012-01-01

    The authors report a severe anaphylactic reaction to Patent Blue V dye used in sentinel node biopsy for lymphatic mapping during breast cancer surgery to stage the axilla. Patent Blue dye is the most widely used in the UK; however, adverse reactions have been reported with the blue dye previously. This case highlights that reactions may not always be immediately evident and to be vigilant in all patients that have undergone procedures using blue dye. If the patients are not responding appropriately particularly during an anaesthetic, one must always think of a possible adverse reaction to the dye. All surgical patients should give consent for adverse reactions to patent blue dye preoperatively. Alternative agents such as methylene blue are considered. PMID:23203181

  5. Cascade enzymatic reactions for efficient carbon sequestration.

    PubMed

    Xia, Shunxiang; Zhao, Xueyan; Frigo-Vaz, Benjamin; Zheng, Wenyun; Kim, Jungbae; Wang, Ping

    2015-04-01

    Thermochemical processes developed for carbon capture and storage (CCS) offer high carbon capture capacities, but are generally hampered by low energy efficiency. Reversible cascade enzyme reactions are examined in this work for energy-efficient carbon sequestration. By integrating the reactions of two key enzymes of RTCA cycle, isocitrate dehydrogenase and aconitase, we demonstrate that intensified carbon capture can be realized through such cascade enzymatic reactions. Experiments show that enhanced thermodynamic driving force for carbon conversion can be attained via pH control under ambient conditions, and that the cascade reactions have the potential to capture 0.5 mol carbon at pH 6 for each mole of substrate applied. Overall it manifests that the carbon capture capacity of biocatalytic reactions, in addition to be energy efficient, can also be ultimately intensified to approach those realized with chemical absorbents such as MEA. PMID:25708541

  6. Dynamics of Bimolecular Reactions in Solution

    NASA Astrophysics Data System (ADS)

    Orr-Ewing, Andrew J.

    2015-04-01

    Mechanisms of bimolecular chemical reactions in solution are amenable to study on picosecond timescales, both by transient absorption spectroscopy and by computer simulation. The dynamics of exothermic reactions of CN radicals and of Cl and F atoms with organic solutes in commonly used solvents are contrasted with the corresponding dynamics in the gas phase. Many characteristics of the gas-phase reaction dynamics persist in solution, such as efficient energy release to specific vibrational modes of the products. However, additional complexities associated with the presence of the solvent are open to investigation. These features of liquid-phase reactions include the role of solvent-solute complexes, solvent caging, coupling of the product motions to the solvent bath, thermalization of internally excited reaction products, incipient hydrogen bond formation, and involvement of charge-separated states that arise from proton transfer.

  7. Some Concepts in Reaction Dynamics

    NASA Technical Reports Server (NTRS)

    Polannyi, John C.

    1972-01-01

    In 1929 London 1 published a very approximate solution of the Schroedinger equation for a system of chemical interest: H3. To the extent that chemistry can be regarded as existing separately from physics, this was a landmark in the history of chemistry, comparable in importance to the landmark in the history of physics marked by the appearance of the Heitler-London equation for H2. The expression for H3, was, of necessity, even less accurate than that for H2, but chemists, like the habitual poor, were accustomed to this sort of misfortune. Together with the physicists they enjoyed the sensation of living in a renaissance. The physicists still could not calculate a great deal that was of interest to them, and the chemists could calculate less, but both could now dream. It would be too easy to say that their dreams were dreams of unlimited computer time. Their dreams were a lot more productive than that. Two years after London published his equation, H. Eyring and M. Polanyi obtained the first numerical energy surface for H3. They infused the London equation with a measure of empiricism to produce an energy surface which, whether or not it was correct in its details, provided a basis for further speculations of an important sort. The existence of a tangible energy surface in 1931 stimulated speculation along two different lines. The following year Pelzer and Wigner used this London-Eyring-Polanyi (LEP) energy surface for a thermodynamic treatment of the reaction rate in H + H2. This important development reached its full flowering a few years later. In these remarks I shall be concerned with another line of development. A second more-or-less distinct category of speculation that began with (and, indeed, in) the 1931 paper has to do with the dynamics of individual reactive encounters under the influence of specified interaction potentials.

  8. Development of the reaction time accelerating molecular dynamics method for simulation of chemical reaction

    NASA Astrophysics Data System (ADS)

    Takaba, Hiromitsu; Hayashi, Shigekazu; Zhong, Huifeng; Malani, Hema; Suzuki, Ai; Sahnoun, Riadh; Koyama, Michihisa; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Kubo, Momoji; Del Carrpio, Carlos A.; Miyamoto, Akira

    2008-09-01

    We present a novel and efficient method to integrate chemical reactions into molecular dynamics to simulate chemical reaction systems. We have dubbed this method RTAMD, an acronym for reaction time accelerating molecular dynamics. The methodology we propose here requires no more than the knowledge of the empirical intermolecular potentials for the species at play as well as the elementary reaction path among them. Bond formation during the simulation is performed by changing the inter-atomic potentials from those of the non-bonded species to those of the bonded ones, and a reaction is deemed to occur by the distance separating the bond forming atoms. In this way the energy barrier for a reaction is no longer considered; the estimation of the reaction rate, however, is possible by introducing the principles of the transition state theory. The simplicity of the present scheme to simulate chemical reactions enables it to be used in large-scale MD simulations involving a large number of simultaneous chemical reactions and to evaluate kinetic parameters. In this paper, the basic theory of the method is presented and application to simple equiatomic reaction system where the reaction rates were estimated was illustrated.

  9. ReactionMap: an efficient atom-mapping algorithm for chemical reactions.

    PubMed

    Fooshee, David; Andronico, Alessio; Baldi, Pierre

    2013-11-25

    Large databases of chemical reactions provide new data-mining opportunities and challenges. Key challenges result from the imperfect quality of the data and the fact that many of these reactions are not properly balanced or atom-mapped. Here, we describe ReactionMap, an efficient atom-mapping algorithm. Our approach uses a combination of maximum common chemical subgraph search and minimization of an assignment cost function derived empirically from training data. We use a set of over 259,000 balanced atom-mapped reactions from the SPRESI commercial database to train the system, and we validate it on random sets of 1000 and 17,996 reactions sampled from this pool. These large test sets represent a broad range of chemical reaction types, and ReactionMap correctly maps about 99% of the atoms and about 96% of the reactions, with a mean time per mapping of 2 s. Most correctly mapped reactions are mapped with high confidence. Mapping accuracy compares favorably with ChemAxon's AutoMapper, versions 5 and 6.1, and the DREAM Web tool. These approaches correctly map 60.7%, 86.5%, and 90.3% of the reactions, respectively, on the same data set. A ReactionMap server is available on the ChemDB Web portal at http://cdb.ics.uci.edu . PMID:24160861

  10. Extension of a Kinetic-Theory Approach for Computing Chemical-Reaction Rates to Reactions with Charged Particles

    NASA Technical Reports Server (NTRS)

    Liechty, Derek S.; Lewis, Mark J.

    2010-01-01

    Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction rate information) are extended to include reactions involving charged particles and electronic energy levels. The proposed extensions include ionization reactions, exothermic associative ionization reactions, endothermic and exothermic charge exchange reactions, and other exchange reactions involving ionized species. The extensions are shown to agree favorably with the measured Arrhenius rates for near-equilibrium conditions.

  11. Transport-theoretical Description of Nuclear Reactions

    E-print Network

    O. Buss; T. Gaitanos; K. Gallmeister; H. van Hees; M. Kaskulov; O. Lalakulich; A. B. Larionov; T. Leitner; J. Weil; U. Mosel

    2012-02-02

    In this review we first outline the basics of transport theory and its recent generalization to off-shell transport. We then present in some detail the main ingredients of any transport method using in particular the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) implementation of this theory as an example. We discuss the potentials used, the ground state initialization and the collision term, including the in-medium modifications of the latter. The central part of this review covers applications of GiBUU to a wide class of reactions, starting from pion-induced reactions over proton and antiproton reactions on nuclei to heavy-ion collisions (up to about 30 AGeV). A major part concerns also the description of photon-, electron- and neutrino-induced reactions (in the energy range from a few 100 MeV to a few 100 GeV). For this wide class of reactions GiBUU gives an excellent description with the same physics input and the same code being used. We argue that GiBUU is an indispensable tool for any investigation of nuclear reactions in which final-state interactions play a role. Studies of pion-nucleus interactions, nuclear fragmentation, heavy ion reactions, hyper nucleus formation, hadronization, color transparency, electron-nucleus collisions and neutrino-nucleus interactions are all possible applications of GiBUU and are discussed in this article.

  12. Controlling chemical reactions of a single particle

    E-print Network

    Lothar Ratschbacher; Christoph Zipkes; Carlo Sias; Michael Köhl

    2012-09-26

    The control of chemical reactions is a recurring theme in physics and chemistry. Traditionally, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature or pressure. More recently, physical methods such as laser or magnetic field control have emerged to provide completely new experimental possibilities, in particular in the realm of cold collisions. The control of reaction pathways is also a critical component to implement molecular quantum information processing. For these undertakings, single particles provide a clean and well-controlled experimental system. Here, we report on the experimental tuning of the exchange reaction rates of a single trapped ion with ultracold neutral atoms by exerting control over both their quantum states. We observe the influence of the hyperfine interaction on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products. These investigations advance chemistry with single trapped particles towards achieving quantum-limited control of chemical reactions and indicate limits for buffer gas cooling of single ion clocks.

  13. Quantum Theory of Fast Chemical Reactions

    SciTech Connect

    Light, John C

    2007-07-30

    The aims of the research under this grant were to develop a theoretical understanding and predictive abiility for a variety of processes occurring in the gas phase. These included bimolecular chemical exchange reactions, photodissociation, predissociation resonances, unimolecular reactions and recombination reactions. In general we assumed a knowledge, from quantum chemistry, of the interactions of the atoms and molecular fragments involved. Our focus was primarily on the accurate (quantum) dynamics of small molecular systems. This has been important for many reactions related to combustion and atmospheric chemistry involving light atom transfer reactions and, for example, resonances in dissociation and recombination reactions. The rates of such reactions, as functions of temperature, internal states, and radiation (light), are fundamental for generating models of overall combustion processes. A number of new approaches to these problems were developed inclluding the use of discrete variable representations (DVR's) for evaluating rate constants with the flux-flux correlation approach, finite range approaches to exact quantum scattering calculations, energy selected basis representations, transition state wave packet approaches and improved semiclassical approaches. These (and others) were applied to a number of reactive systems and molecular systems of interest including (many years ago) the isotopic H + H2 exchange reactions, the H2 + OH (and H + H2O) systems, Ozone resonances, van der Waals molecule reactions, etc. A total of 7 graduate students, and 5 post-doctoral Research Associates were supported, at least in part, under this grant and seven papers were published with a total of 10 external collaborators. The majority of the 36 publications under this grant were supported entirely by DOE.

  14. Violent Reactions from Non-Shock Stimuli

    NASA Astrophysics Data System (ADS)

    Sandusky, Harold

    2007-06-01

    Most reactions are thermally initiated, whether from direct heating or dissipation of energy from mechanical, shock, or electrical stimuli. For other than prompt shock initiation, the reaction must be able to spread through porosity or over large surface area to become more violent than just rupturing any confinement. While burning rates are important, high-strain mechanical properties are nearly so, either by reducing existing porosity or generating additional surface area through fracture. The first example is deflagration-to-detonation transition (DDT) in porous beds. During the early stages, weak compressive waves ahead of the convective ignition front will reduce porosity, thereby restricting the spread of combustion and the pressure buildup. If, however, pressure increases faster than can be relieved by loss of confinement, coalescing compressive waves can initiate reaction at hot spots from rapid pore collapse. This compressive reaction can drive a shockwave that transits to detonation, the most violent reaction in any scenario. It has been shown that reaction violence is reduced in DDT experiments if the binder is softened, either by raising the initial temperature or adding a solvent. An example of the role of mechanical properties in enhancing reaction violence through fracturing occurs when cavities in projectile fills collapse during acceleration in the gun barrel, which is referred to as setback. Explosives with soft rubber binders will deform and undergo mild reaction from shear heating within the explosive and adiabatic compression of any gas in the cavity. Stiff explosives are similarly ignited, but also fracture and generate additional surface area for a violent event. The last example to be considered is slow cook-off, where thermal damage can increase burning rate as well as provide porosity to enhance the pressure buildup. As reaction spreads from the zone of thermal run-away, an explosive binder that resists breakup will limit the violence.

  15. A case of a generalized lichenoid tattoo reaction.

    PubMed

    Jacks, Stephanie K; Zirwas, Matthew J; Mosser, Joy L

    2014-08-01

    Cutaneous reactions to tattoos have been increasing in conjunction with the rise in popularity of tattoos. While localized lichenoid reactions to tattoo inks are fairly common, generalized lichenoid reactions are relatively rare. Herein the authors present a case of a generalized lichenoid reaction to a tattoo containing only black ink. They also present a brief discussion of tattoo reactions and treatment options. PMID:25161761

  16. A Case of a Generalized Lichenoid Tattoo Reaction

    PubMed Central

    Zirwas, Matthew J.; Mosser, Joy L.

    2014-01-01

    Cutaneous reactions to tattoos have been increasing in conjunction with the rise in popularity of tattoos. While localized lichenoid reactions to tattoo inks are fairly common, generalized lichenoid reactions are relatively rare. Herein the authors present a case of a generalized lichenoid reaction to a tattoo containing only black ink. They also present a brief discussion of tattoo reactions and treatment options. PMID:25161761

  17. The light reactions of photosynthesis.

    PubMed

    Arnon, D I

    1971-11-01

    Historically, the role of light in photosynthesis has been ascribed either to a photolysis of carbon dioxide or to a photolysis of water and a resultant rearrangement of constituent atoms into molecules of oxygen and glucose (or formaldehyde). The discovery of photophosphorylation demonstrated that photosynthesis includes a light-induced phosphorus metabolism that precedes, and is independent from, a photolysis of water or CO(2). ATP formation could best be accounted for not by a photolytic disruption of the covalent bonds in CO(2) or water but by the operation of a light-induced electron flow that results in a release of free energy which is trapped in the pyrophosphate bonds of ATP. Photophosphorylation is now divided into (a) a non-cyclic type, in which the formation of ATP is coupled with a light-induced electron transport from water to ferredoxin and a concomitant evolution of oxygen and (b) a cyclic type which yields only ATP and produces no net change in the oxidation-reduction state of any electron donor or acceptor. Reduced ferredoxin formed in (a) serves as an electron donor for the reduction of NADP by an enzymic reaction that is independent of light. ATP, from both cyclic and noncyclic photophosphorylation, and reduced NADP jointly constitute the assimilatory power for the conversion of CO(2) to carbohydrates (3 moles of ATP and 2 moles of reduced NADP are required per mole of CO(2)).Investigations, mainly with whole cells, have shown that photosynthesis in green plants involves two photosystems, one (System II) that best uses light of "short" wavelength (lambda < 685 nm) and another (System I) that best uses light of "long" wavelength (lambda > 685 nm). Cyclic photophosphorylation in chloroplasts involves a System I photoreaction. Noncyclic photophosphorylation is widely held to involve a collaboration of two photoreactions: a short-wavelength photoreaction belonging to System II and a long-wavelength photoreaction belonging to System I. Recent findings, however, indicate that noncyclic photophosphorylation may include two short-wavelength, System II, photoreactions that operate in series and are joined by a "dark" electron-transport chain to which is coupled a phosphorylation site. PMID:4400251

  18. Low-energy proton capture reactions

    NASA Astrophysics Data System (ADS)

    Lipoglavsek, M.; Cvetinovic, A.; Gajevic, J.; Likar, A.; Petrovic, T.; Vavpetic, P.

    2014-05-01

    An overview of experimental problems in measuring the cross sections for (p,?) and (p,n) reactions at low energies is given with a specific emphasis on electron screening in metallic targets. Thick target ?-ray and neutron yields are compared for Ni and NiO targets, V and VO2 targets and Mn and MnO targets. The 1H(7Li,?)4He reaction was studied in inverse kinematics with hydrogen loaded into Pd and PdAg alloy foils from gas phase. Based on these results, a new approach to electron screening in nuclear reactions is suggested.

  19. Basic Aspects of Allergy and Hypersensitivity Reactions

    Microsoft Academic Search

    Isabella Pali-Schöll; Erika Jensen-Jarolim

    Key players within immunologically mediated hypersensitivity reactions are allergen-specific IgE or IgG antibodies, immune\\u000a complexes, or lymphocytes. According to these diverse pathophysiological mechanisms behind the clinical appearance, hypersensitivity\\u000a reactions are classified into type I through IV. The focus of this chapter lies on the characterization of type I, i.e. IgE-mediated\\u000a reactions.\\u000a \\u000a In addition to small size and solubility of type

  20. Nuclear chain reaction: forty years later

    SciTech Connect

    Sachs, R.G. (ed.)

    1984-01-01

    The proceedings from a 1982 symposium 40 years after the first controlled nuclear chain reaction took place in Chicago covers four sessions and public discussion. The session covered the history of the chain reaction; peaceful uses in technology, medicine, and biological science; peaceful uses in power generation; and nuclear weapons control. Among the speakers were Eugene Wigner, Glenn Seaborg, Alvin Weinberg, and others who participated in the first chain reaction experiments. The proceedings reflect differences of opinion among the scientists as well as the general public. References, slides, and tables used to illustrate the individual talks are included with the papers.

  1. Rate constant for the Cl + Chloroform reaction

    SciTech Connect

    Brahan, K.M.; Hewitt, A.D.; Boone, G.D. [California State Univ., Fullerton, CA (United States)] [and others

    1995-12-01

    The rate constant for the reaction of Cl with chloroform has been measured relative to the reaction of Cl with methane, methyl chloride, and carbon monoxide using long path FTIR spectroscopy. Our measured rate constant at 298 K and 1 atm of (1.2{plus_minus}0.1)x10{sup -13} cm{sup 3}molecule{sup -1}sec{sup -1} is 50% higher than that recommended for stratospheric modeling; however, it is within experimental error of the values measured by Clyne and Walker and by Watson. The implications of this reaction on the budgets of chloroform and phosgene in the troposphere will be discussed.

  2. Low-energy proton capture reactions

    SciTech Connect

    Lipoglavsek, M.; Cvetinovic, A.; Gajevic, J.; Likar, A.; Vavpetic, P. [Jozef Stefan Institute, Jamova ulica 39, Ljubljana (Slovenia); Petrovic, T. [Jozef Stefan Institute, Jamova ulica 39, Ljubljana, Slovenia and Cosylab d.d., Teslova ulica 30, Ljubljana (Slovenia)

    2014-05-09

    An overview of experimental problems in measuring the cross sections for (p,?) and (p,n) reactions at low energies is given with a specific emphasis on electron screening in metallic targets. Thick target ?-ray and neutron yields are compared for Ni and NiO targets, V and VO{sub 2} targets and Mn and MnO targets. The {sup 1}H({sup 7}Li,?){sup 4}He reaction was studied in inverse kinematics with hydrogen loaded into Pd and PdAg alloy foils from gas phase. Based on these results, a new approach to electron screening in nuclear reactions is suggested.

  3. Serpentinization reaction pathways: implications for modeling approach

    SciTech Connect

    Janecky, D.R.

    1986-01-01

    Experimental seawater-peridotite reaction pathways to form serpentinites at 300/sup 0/C, 500 bars, can be accurately modeled using the EQ3/6 codes in conjunction with thermodynamic and kinetic data from the literature and unpublished compilations. These models provide both confirmation of experimental interpretations and more detailed insight into hydrothermal reaction processes within the oceanic crust. The accuracy of these models depends on careful evaluation of the aqueous speciation model, use of mineral compositions that closely reproduce compositions in the experiments, and definition of realistic reactive components in terms of composition, thermodynamic data, and reaction rates.

  4. Reactions in Droplets in Microfluidic Channels

    PubMed Central

    Song, Helen; Chen, Delai L.; Ismagilov, Rustem F.

    2006-01-01

    Fundamental and applied research in chemistry and biology benefits from opportunities provided by droplet-based microfluidic systems. These systems enable the miniaturization of reactions by compartmentalizing reactions in droplets of femoliter to microliter volumes. Compartmentalization in droplets provides rapid mixing of reagents, control of the timing of reactions on timescales from milliseconds to months, control of interfacial properties, and the ability to synthesize and transport solid reagents and products. Droplet-based microfluidics can help to enhance and accelerate chemical and biochemical screening, protein crystallization, enzymatic kinetics, and assays. Moreover, the control provided by droplets in microfluidic devices can lead to new scientific methods and insights. PMID:17086584

  5. Instrumented staircase for ground reaction measurement.

    PubMed

    Riener, R; Rabuffetti, M; Frigo, C; Quintern, J; Schmidt, G

    1999-07-01

    A staircase was developed to record ground reactions during stair climbing at different slopes (inclinations). Each step is instrumented with six strain-gauge-based force transducers which allow the measurement of three-dimensional ground reaction force and moment as well as the centre of pressure (COP) location. A specific sensor arrangement permits accurate recording, especially of the COP location. The overall design of the staircase and details of a single instrumented step are presented. Static and dynamic characteristics have been evaluated by different experimental procedures. Preliminary results of ground reaction forces are shown. PMID:10696713

  6. LIGAND: chemical database of enzyme reactions

    PubMed Central

    Goto, Susumu; Nishioka, Takaaki; Kanehisa, Minoru

    2000-01-01

    LIGAND is a composite database comprising three sections: ENZYME for the information of enzyme molecules and enzymatic reactions, COMPOUND for the information of metabolites and other chemical compounds, and REACTION for the collection of substrate–product relations. The current release includes 3390 enzymes, 5645 compounds and 5207 reactions. The database is indispensable for the reconstruction of metabolic pathways in the completely sequenced organisms. The LIGAND database can be accessed through the WWW (http://www.genome.ad.jp/dbget/ligand.html ) or may be downloaded by anonymous FTP (ftp://kegg.genome.ad.jp/molecules/ligand/ ). PMID:10592281

  7. Reaction synthesis of heat-resistant materials

    SciTech Connect

    Deevi, S.C.; Sikka, V.K.

    1995-12-31

    Exothermicity associated with the synthesis of aluminides can be utilized to obtain aluminides of transition metals. Combustion synthesis, extrusion, and hot pressing were utilized to obtain dense intermetallics and their composites. Composites were analyzed by X- ray diffraction and microscopy techniques, and tensile properties were measured on button-head and sheet specimens of intermetallics and their composites. Mechanical properties of intermetallics obtained by reaction synthesis and densification compare well with conventionally processed materials. Reaction-synthesis principles were also extended to weld overlays. Possible approaches to obtaining dense products by reaction synthesis and densification are summarized in a schematic illustration. 19 refs., 14 figs., 3 tabs.

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

    SciTech Connect

    Assary, R. S.; Curtiss, L. A. (Center for Nanoscale Materials); ( MSD); (Northwestern Univ.)

    2012-02-01

    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, 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 molecules that is needed to help find more efficient catalysts for the conversion of hexose to useful chemicals.

  9. Toward cell circuitry: Topological analysis of enzyme reaction networks via reaction route graphs

    NASA Astrophysics Data System (ADS)

    Datta, Ravindra; Vilekar, Saurabh A.; Fishtik, Ilie; Dittami, James P.

    2008-05-01

    The first step toward developing complete cell circuitry is to build quantitative networks for enzyme reactions. The conventional King-Altman-Hill (KAH) algorithm for topological analysis of enzyme networks, adapted from electrical networks, is based on “Reaction Graphs” that, unlike electrical circuits, are not quantitative, being straightforward renderings of conventional schematics of reaction mechanisms. Therefore, we propose the use of “Reaction Route (RR) Graphs” instead, as a more suitable graph-theoretical representation for topological analysis of enzyme reaction networks. The RR Graphs are drawn such that they are not only useful for visualizing the various reaction routes or pathways, but unlike Reaction Graphs possess network properties consistent with requisite kinetic, mass balance, and thermodynamic constraints. Therefore, they are better than the conventional Reaction Graphs for topological representation and analysis of enzyme reactions, both via the KAH methodology as well as via numerical matrix inversion. The difference between the two is highlighted based on the example of a single enzyme reaction network for the conversion of 7,8-dihydrofolate and NADPH into 5,6,7,8-tetrahydrofolate and NADP +, catalyzed by the enzyme dihydrofolate reductase.

  10. Two-Dimensional Reaction Free Energy Surfaces of Catalytic Reaction: Effects of Protein Conformational Dynamics on Enzyme Catalysis

    E-print Network

    Xie, Xiaoliang Sunney

    Two-Dimensional Reaction Free Energy Surfaces of Catalytic Reaction: Effects of Protein the reaction free energy surface of the enzyme-catalyzed reaction, as is shown in many biochemistry textbooks Form: October 23, 2007 We introduce a two-dimensional (2D) multisurface reaction free energy

  11. Contact-Allergic Reactions to Cosmetics

    PubMed Central

    Goossens, An

    2011-01-01

    Contact-allergic reactions to cosmetics may be delayed-type reactions such as allergic and photo-allergic contact dermatitis, and more exceptionally also immediate-type reactions, that is, contact urticaria. Fragrances and preservative agents are the most important contact allergens, but reactions also occur to category-specific products such as hair dyes and other hair-care products, nail cosmetics, sunscreens, as well as to antioxidants, vehicles, emulsifiers, and, in fact, any possible cosmetic ingredient. Patch and prick testing to detect the respective culprits remains the golden standard for diagnosis, although additional tests might be useful as well. Once the specific allergens are identified, the patients should be informed of which products can be safely used in the future. PMID:21461388

  12. Enzyme Reactions in Nanoporous, Picoliter Volume Containers

    SciTech Connect

    Siuti, Piro [ORNL; Retterer, Scott T [ORNL; Choi, Chang Kyoung [Michigan Technological University; Doktycz, Mitchel John [ORNL

    2012-01-01

    Advancements in nanoscale fabrication allow creation of small volume reaction containers that can facilitate the screening and characterization of enzymes. A porous, ~19 pL volume vessel has been used in this work to carry out enzyme reactions under varying substrate concentrations. Glucose oxidase and horseradish peroxidase can be contained in these structures and diffusively fed with a solution containing glucose and the fluorogenic substrate Amplex Red through the engineered nanoscale pore structure. Fluorescent microscopy was used to monitor the reaction, which was carried out under microfluidic control. Kinetic characteristics of the enzyme were evaluated and compared with results from conventional scale reactions. These picoliter, nanoporous containers can facilitate quick determination of enzyme kinetics in microfluidic systems without the requirement of surface tethering and can be used for applications in drug discovery, clinical diagnostics and high-throughput screening.

  13. Individual Reactions to Failure in Virtual Teams

    E-print Network

    Diaz, Ismael

    2012-02-14

    This project examines the relationship between team identification and collaboration configuration and how they affect attributions to failure. In a sample of 110 participants, we examined reactions to failure. We manipulated perceptions...

  14. Novel Isotope Effects and Organic Reaction Mechanisms 

    E-print Network

    Kelly, Kelmara K.

    2010-07-14

    A variety of organic reactions provide experimental observations that are not explained by current models of reactivity and selectivity. This dissertation describes a combination of experimental and theoretical studies of ...

  15. The Kinetics of Isotopic Exchange Reactions.

    ERIC Educational Resources Information Center

    Logan, S. R.

    1990-01-01

    Discussed are the kinetic interactions of these chemical processes and the determination of the actual order of such reactions. Included are multiple exchange, catalytic exchange with deuterium, and depletion of the original substrate. (CW)

  16. The Mechanism of the Formaldehyde Clock Reaction.

    ERIC Educational Resources Information Center

    Burnett, M. G.

    1982-01-01

    Provides background information and problems with the formaldehyde clock reaction, including comparisons of experimental clock times reported in the literature and conditions for the reliable use of the formaldehyde clock based on a method discussed. (JN)

  17. Aqueous asymmetric cyclopropanation reactions in polymersome membranes.

    PubMed

    van Oers, Matthijs C M; Abdelmohsen, Loai K E A; Rutjes, Floris P J T; van Hest, Jan C M

    2014-04-21

    Copper-bis(oxazoline) complexes have been immobilised in the hydrophobic domain of a polymersome membrane to perform asymmetric cyclopropanation reactions in aqueous media with enhanced conversions and enantioselectivities. PMID:24457619

  18. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Levin, Eugene

    1993-01-01

    A new global potential energy surface (PES) is being generated for O(P-3) + H2 yields OH + H. This surface is being fit using the rotated Morse oscillator method, which was used to fit the previous POL-CI surface. The new surface is expected to be more accurate and also includes a much more complete sampling of bent geometries. A new study has been undertaken of the reaction N + O2 yields NO + O. The new studies have focused on the region of the surface near a possible minimum corresponding to the peroxy form of NOO. A large portion of the PES for this second reaction has been mapped out. Since state to state cross sections for the reaction are important in the chemistry of high temperature air, these studies will probably be extended to permit generation of a new global potential for reaction.

  19. Reaction specificity in pyridoxal phosphate enzymes.

    PubMed

    Toney, Michael D

    2005-01-01

    Pyridoxal phosphate enzymes catalyze a wide variety of reaction types on amines and amino acids, generally by stabilizing carbanionic intermediates. This makes them very useful in cellular metabolism, but it also creates problems in controlling the reaction pathway that a given enzyme follows, i.e., in controlling reaction specificity. Stereoelectronic effects have been proposed to play a major role in determining the bond to Calpha that gets broken in the external aldimine intermediate that is common to all PLP enzymes. Here, we discuss our work on dialkylglycine decarboxylase aimed at providing direct evidence for stereoelectronic control of external aldimine reactivity. Once a bond to Calpha has been broken to form the carbanionic intermediate, enzymes must also carefully control the fate of this reactive species. Our studies with alanine racemase suggest that the enzyme selectively destabilizes the carbanionic quinonoid intermediate to promote higher racemization specificity by avoiding transamination side reactions. PMID:15581583

  20. Adolescents' Fright Reactions to Television and Films.

    ERIC Educational Resources Information Center

    Cantor, Joanne; Reilly, Sandra

    1982-01-01

    Results demonstrate that adolescents experience enduring fright reactions from scary television shows and films, yet their mothers are often unaware of their responses. Concludes that family communication about how and when a child is frightened is poor. (PD)