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 N,N'-dioxide-In(OTf)3-catalyzed asymmetric vinylogous Mukaiyama aldol reactions.

    PubMed

    Fu, Kai; Zheng, Jianfeng; Lin, Lili; Liu, Xiaohua; Feng, Xiaoming

    2015-02-01

    Chiral N,N'-dioxide-In(OTf)3 complexes were developed as efficient catalysts to catalyze the vinylogous Mukaiyama aldol reaction of the silyl dienol ester with aldehydes. The corresponding ?-hydroxy-?,?-unsaturated esters were obtained in up to 99% yield and 98% ee. Moreover, the obtained (R)-3v can be easily transformed to natural bioactive products. PMID:25597692

  3. A New Class of Ligands for Aqueous, Lanthanide-Catalyzed, Enantioselective Mukaiyama Aldol Reactions

    PubMed Central

    Mei, Yujiang; Dissanayake, Prabani; Allen, Matthew J.

    2010-01-01

    The development of aqueous methods to generate enantiopure ?-hydroxy carbonyl compounds is an important goal because these subunits compose many bioactive compounds, and the ability to synthesis these groups in water has environmental and cost benefits. In this communication, we report a new class of ligands for aqueous, lanthanide-catalyzed, asymmetric Mukaiyama aldol reactions to synthesize chiral ?-hydroxy ketones. Furthermore, we use luminescence-decay measurements to unveil mechanistic information regarding the catalytic reaction via changes of water-coordination number. The precatalysts presented here yielded ?-hydroxy carbonyls from aliphatic and aryl substrates with outstanding syn:anti ratios and enantiometric excesses of up to 49:1 and 97%. PMID:20806902

  4. 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

  5. CALIX[6]ARENE DERIVATIVES BEARING SULFONATE AND ALKYL GROUPS AS SURFACTANTS IN SC(OTF)3-CATALYZED MUKAIYAMA ALDOL REACTIONS IN WATER. (R822668)

    EPA Science Inventory

    Abstract Amphiphilic calix[6]arene derivatives 1a¯b were found to be efficient surfactants for Sc(OTf)3-catalyzed Mukaiyama aldol reaction of silyl enol ethers with aldehydes in water. The results indicated t...

  6. The First Direct and Enantioselective Cross-Aldol Reaction of Aldehydes Alan B. Northrup and David W. C. MacMillan*

    E-print Network

    MacMillan, David W. C.

    The First Direct and Enantioselective Cross-Aldol Reaction of Aldehydes Alan B. Northrup and David the labora- tories of Evans,1 Heathcock,2 Masamune,3 and Mukaiyama4 has established the aldol reaction as the principal chemical reaction for the stereoselective construction of complex polyol architecture. Recently

  7. Organolanthanide reagents and the Mukaiyama reaction

    SciTech Connect

    Gong, L.

    1989-01-01

    The bis(pentamethylcyclopentadienyl) lutetium halide complex ((C/sub 5/Me/sub 5/)/sub 2/LuCl/center dot/THF) was synthesized and characterized. The crystal structure of this complex shows that the Lu is at the center of a distorted tetrahedron consisting of the centroids of two cyclopentadienyl rings, the oxygen atom of a tetrahydrofuran molecule and a chlorine atom. /sup 1/H NMR studies of toluene-d/sub 8/ solutions of (C/sub 5/Me/sub 5/LuCl(THF) + THF, (TMS/sub 2/CP)/sub 2/LuCl(THF) + THF, and (MeCp)/sub 2/LuCl(THF) + THF at various temperatures showed exchange processes between co- ordinated THF and free THF with average values of ..delta..G/sup ne/ of 13.0 /+-/ 0.3 kcal/mol, 11.1 /+-/ 0.1 kcal/mol and <11 kcal/mol at 0/degree/C, respectively. It has been found that under the influence of a catalytic amount (1--5 mol %) of (TMS/sub 2/Cp)/sub 2/YbCl dimer, silyl enol ethers (R/sub 1/R/sub 2/C = C(OR/sub 3/)OSiMe/sub 3/)) react with benzaldehyde smoothly in dichloromethane at room temperature, giving >99% of the aldol silyl ether (isolated yield: 90%) within 3 h. At /minus/78/degrees/C, the reaction gives kinetically controlled diastereoselectivity, which was not observed in the TiCl/sub 4/-mediated aldol reaction. The use of organoytterbium enolates shows promise result with respect to increased stereoselectivity, and indicates the importance of the bulky ligands on the metal center. In addition, Yb(III) species can retard retroaldol reaction owing to its mild Lewis acidity. 118 refs., 14 figs., 30 tabs.

  8. The Aldol Reaction Andr B. Charette

    E-print Network

    Charette, André

    RX Acetate Aldol Propionate Aldol O OHMe Me Me HO O OH OH OH OH OH O COOH OSugar OH Amphotericin B HThe Aldol Reaction CHM-6315 André B. Charette 2012 I. Introduction II. General mechanistic pictures for aldol (not for alkylation reactions!) + + O BR2 H H Me Me i-Pr2NEt OTf O B H Me H NEt3 Me R R Cl #12

  9. 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

  10. 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.

  11. The First Enantioselective Organocatalytic Mukaiyama-Michael Reaction: A Direct Method for the Synthesis of Enantioenriched -Butenolide Architecture

    E-print Network

    MacMillan, David W. C.

    ),6 further outlining the broad utility of the Mukaiyama-Aldol transform in asymmetric synthesis.7 Surpris anticipated that R, -unsaturated iminium ions arising from chiral amine 1 might be inert to silyloxy furan 1:anti, 85% ee); however, catalytic efficiency was poor (31% yield). On the basis of the assumption

  12. Diastereoselective Synthesis of Tetrahydrofurans via Mead Reductive Cyclization of Keto-?-Lactones Derived from the Tandem Mukaiyama Aldol Lactonization (TMAL) Process

    PubMed Central

    Mitchell, T. Andrew; Romo, Daniel

    2008-01-01

    The development of a diastereoselective, three-step strategy for the construction of substituted tetrahydrofurans from alkenyl aldehydes based on the tandem Mukaiyama aldol-lactonization process and Mead reductive cyclization of keto ?-lactones is reported. Stereochemical outcomes of the TMAL process are consistent with models established for Lewis acid-mediated additions to ?-benzyloxy and ?-silyloxy aldehydes while reductions of the five-membered oxocarbenium ions are consistent with Woerpel’s models. Further rationalization for observed high diastereoselectivity in reductions of ?-silyloxy 5-membered oxocarbenium ions based on stereoelectronic effects are posited. A diagnostic trend for coupling constants of ?-benzyloxy ?-lactones was observed that should enable assignment of the relative configuration of these systems. PMID:17973527

  13. Anti-selective direct catalytic asymmetric aldol reaction of thiolactams.

    PubMed

    Sureshkumar, Devarajulu; Kawato, Yuji; Iwata, Mitsutaka; Kumagai, Naoya; Shibasaki, Masakatsu

    2012-06-15

    An anti-selective direct catalytic asymmetric aldol reaction of thiolactam is described. A soft Lewis acid/hard Brønsted base cooperative catalyst comprised of mesitylcopper/(R,R)-Ph-BPE exhibited high catalytic performance to produce an anti-aldol product with high stereoselectivity. The highly chemoselective nature of the present catalysis allows for the use of enolizable aldehydes as aldol acceptors. The diverse transformations of the thiolactam moiety highlight the synthetic utility of the present anti-aldol protocol. PMID:22667330

  14. A designed amide as an aldol donor in the direct catalytic asymmetric aldol reaction.

    PubMed

    Weidner, Karin; Kumagai, Naoya; Shibasaki, Masakatsu

    2014-06-10

    The direct catalytic asymmetric aldol reaction offers efficient access to ?-hydroxy carbonyl entities. Described is a robust direct catalytic asymmetric aldol reaction of ?-sulfanyl 7-azaindolinylamide, thus affording both aromatic and aliphatic ?-hydroxy amides with high ee?values. The design of this transformation features a cooperative interplay of a soft and a hard Lewis acid, which together facilitate the challenging chemoselective enolization by a hard Brønsted base. PMID:24789121

  15. Asymmetric disulfonimide-catalyzed synthesis of ?-amino-?-ketoester derivatives by vinylogous Mukaiyama-Mannich reactions.

    PubMed

    Wang, Qinggang; van Gemmeren, Manuel; List, Benjamin

    2014-12-01

    An organocatalytic asymmetric synthesis of ?-amino-?-ketoester derivatives has been developed. A chiral disulfonimide (DSI) serves as a highly efficient precatalyst for a vinylogous Mukaiyama-Mannich reaction of readily available dioxinone-derived silyloxydienes with N-Boc-protected imines, delivering products in excellent yields and enantioselectivities. The synthetic utility of this reaction is illustrated in various transformations, including a new C?C bond-forming reaction, which provide useful enantioenriched building blocks. The methodology is applied in a formal synthesis of (-)-lasubin. PMID:25348924

  16. 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 trajectory simulations. This powerful...

  17. l-Proline catalysed asymmetric aldol reactions in PEG400 as recyclable medium and transfer aldol reactions

    Microsoft Academic Search

    S. Chandrasekhar; N. Ramakrishna Reddy; S. Shameem Sultana; Ch. Narsihmulu; K. Venkatram Reddy

    2006-01-01

    l-Proline-catalysed direct asymmetric aldol reaction of acetone with various aldehydes in PEG-400 is described. Recycling of the catalyst and solvent (PEG) was possible up to ten runs without loss of catalyst activity. l-Proline was also found to be an efficient catalyst for the asymmetric transfer aldol reaction between various aldehydes and diacetone alcohol for the first time. Good yields and

  18. Direct catalytic enantio- and diastereoselective ketone aldol reactions of isocyanoacetates.

    PubMed

    de la Campa, Raquel; Ortín, Irene; Dixon, Darren J

    2015-04-13

    A catalytic asymmetric aldol addition/cyclization reaction of unactivated ketones with isocyanoacetate pronucleophiles has been developed. A quinine-derived aminophosphine precatalyst and silver oxide were found to be an effective binary catalyst system and promoted the reaction to afford chiral oxazolines possessing a fully substituted stereocenter with good diastereoselectivities and excellent enantioselectivities. PMID:25735645

  19. Completely stereocontrolled aldol reaction of chiral ?-amino acids.

    PubMed

    Gazvoda, Martin; Höferl-Prantz, Kathrin; Barth, Roland; Felzmann, Wolfgang; Pevec, Andrej; Košmrlj, Janez

    2015-02-01

    A general protocol to independently access stereoisomerically pure ?'-hydroxy-?-amino acid derivatives that is based on dibutylboron triflate-mediated aldol reaction of suitably protected ?-amino acids bearing chiral oxazolidinone auxiliary is reported. The method smoothly afforded syn-aldol (?,?'-syn) products in pure form and excellent isolated yield. Both ?,?-syn and ?,?-anti isomers are readily accessible solely through the choice of the oxazolidinone chirality. This method allows for the preparation of stereoisomeric ?'-hydroxy-?-amino acid derivatives that were previously unreported. PMID:25616036

  20. Enantioselective direct aldol reaction: the blossoming of modern organocatalysis

    Microsoft Academic Search

    Gabriela Guillena; Carmen Nájera; Diego J. Ramón

    2007-01-01

    The use of simple (S)-proline as catalyst for the intermolecular direct aldol reaction at the beginning of this century became a true milestone in the growth of organocatalysis as a useful synthetic strategy. Since then, a plethora of new organocatalytic systems have been developed allowing to reach extraordinary levels of efficiencies, widening the scope of substrates used. Several modifications have

  1. 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

  2. (Diisopinocampheyl)borane-mediated reductive aldol reactions of acrylate esters: enantioselective synthesis of anti-aldols.

    PubMed

    Allais, Christophe; Nuhant, Philippe; Roush, William R

    2013-08-01

    The (diisopinocampheyl)borane promoted reductive aldol reaction of acrylate esters 4 is described. Isomerization of the kinetically formed Z(O)-enolborinate 5Z to the thermodynamic E(O)-enolborinate 5E via 1,3-boratropic shifts, followed by treatment with representative achiral aldehydes, leads to anti-?-methyl-?-hydroxy esters 9 or 10 with excellent diastereo- (up to ?20:1 dr) and enantioselectivity (up to 87% ee). The results of double asymmetric reactions of 5E with several chiral aldehydes are also presented. PMID:23885946

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    The covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with a proline-based derivative is reported. Initially, MWCNTs were oxidized in order to introduce a large number of carboxylic units on their tips followed by N-tert-butoxycarbonyl-2,2'(ethylenedioxy)bis-(ethylamine) conjugation through an amide bond. Then, a proline derivative bearing a carboxylic terminal moiety at the 4-position was coupled furnishing proline-modified MWCNTs. This new hybrid material was fully characterized by spectroscopic and microscopy means and its catalytic activity in the asymmetric aldol reaction between acetone and 4-nitrobenzaldehyde was evaluated for the first time, showing to proceed almost quantitatively in aqueous media. Furthermore, several amino-modified MWCNTs were prepared and examined in the particular aldol reaction. These new hybrid materials exhibited an enhanced catalytic activity in water, contrasting with the pristine MWCNTs as well as the parent organic molecule, which failed to catalyze the reaction efficiently. Furthermore, the modified MWCNTs proved to catalyze the aldol reaction even after three repetitive cycles. Overall, a green approach for the aldol reaction is presented, where water can be employed as the solvent and modified MWCNTs can be used as catalysts, which can be successfully recovered and reused, while their catalytic activity is retained.The covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with a proline-based derivative is reported. Initially, MWCNTs were oxidized in order to introduce a large number of carboxylic units on their tips followed by N-tert-butoxycarbonyl-2,2'(ethylenedioxy)bis-(ethylamine) conjugation through an amide bond. Then, a proline derivative bearing a carboxylic terminal moiety at the 4-position was coupled furnishing proline-modified MWCNTs. This new hybrid material was fully characterized by spectroscopic and microscopy means and its catalytic activity in the asymmetric aldol reaction between acetone and 4-nitrobenzaldehyde was evaluated for the first time, showing to proceed almost quantitatively in aqueous media. Furthermore, several amino-modified MWCNTs were prepared and examined in the particular aldol reaction. These new hybrid materials exhibited an enhanced catalytic activity in water, contrasting with the pristine MWCNTs as well as the parent organic molecule, which failed to catalyze the reaction efficiently. Furthermore, the modified MWCNTs proved to catalyze the aldol reaction even after three repetitive cycles. Overall, a green approach for the aldol reaction is presented, where water can be employed as the solvent and modified MWCNTs can be used as catalysts, which can be successfully recovered and reused, while their catalytic activity is retained. Electronic supplementary information (ESI) available: Experimental details for the synthesis of 5, 8 and 11; 1H & 13C NMR of compounds 8 and 11; ATR-IR spectra, thermographs and TEM imaging of hybrids 10 and 13. See DOI: 10.1039/c4nr06543c

  4. Acetylphosphonate as a Surrogate of Acetate or Acetamide in Organocatalyzed Enantioselective Aldol Reactions

    PubMed Central

    Guang, Jie; Guo, Qunsheng

    2012-01-01

    Highly enantioselective aldol reactions of acetylphosphonates and activated carbonyl compounds was realized with cinchona alkaloid derived catalysts, in which the acetylphosphonate was directly used as an enolate precursor for the first time. The aldol product obtained was converted in situ to its corresponding ester or amide through methanolysis or aminolysis. The overall process may be viewed as formal highly enantioselective acetate or acetamide aldol reactions, which are very difficult to achieve directly with organocatalytic methods. PMID:22650245

  5. An unprecedented, tandem Aldol-Grob reaction sequence

    SciTech Connect

    Kabalka, G.W.; Tejedor, D.; Li, N.S.; Malladi, R.R.; Trotman, S. [Univ. of Tennessee, Knoxville, TN (United States)] [Univ. of Tennessee, Knoxville, TN (United States)

    1998-09-18

    The authors report an unprecedented, tandem Aldol-Grob sequence involving the reaction of ketones with aromatic aldehydes in nonnucleophilic solvents in the presence of boron trifluoride. Although a detailed study of the reaction mechanism has not yet been completed, the consistent formation of (E)-alkene products, as well as the fact that aromatic aldehydes appear to be required, would point toward the intermediacy of a carbocation derivative. A reasonable mechanism would involve the formation of the mixed aldol followed by the formation and subsequent nonsynchronous ring opening of a lactol. The proposed fragmentation is reminiscent of two-step Grob fragmentations that have been reported for N-halo-{alpha}-amino acids and cyclobutane hemiacetals as well as the acid-catalyzed fragmentation of {beta}-hydroxy acetals. The authors examined the effect of various acids on the reaction sequence in order to ascertain which would be most efficient. They conclude that boron trifluoride is the most effective of the acids studied in achieving the new tandem condensation-cleavage sequence.

  6. Development of a general, enantioselective organocatalytic MukaiyamaMichael reaction with a,b-unsaturated aldehydes

    E-print Network

    MacMillan, David W. C.

    ,b-unsaturated aldehydes Christopher J. Borths a,b , Diane E. Carrera a,b , David W.C. MacMillan a,b,* a Merck Center-pyrrolyl silylketene acetals to a,b-unsaturated aldehydes, yielding both, syn and anti Mukaiyama­ Michael.2,3 It is surprising to consider, therefore, that a,b-unsaturated aldehydes have been largely

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

    E-print Network

    Wang, Jianbo

    Direct Catalytic Asymmetric Aldol-Type Reaction of Aldehydes with Ethyl Diazoacetate Wengang Yao of aldehydes with ethyl diazoacetate catalyzed by the chiral complex of BINOL derivatives-Zr(OtBu)4 gave developed.2 We have recently developed a DBU-catalyzed aldol-type condensation of aldehydes with ethyl

  8. Organocatalyzed Asymmetric Aldol Reactions of Ketones and ?,?-Unsaturated ?-Ketoesters and Phenylglyoxal Hydrates.

    PubMed

    Konda, Swapna; Guo, Qun-Sheng; Abe, Manabu; Huang, Huicai; Arman, Hadi; Zhao, John C-G

    2015-01-16

    Enantioselective aldol reactions of acetophenone with ?,?-unsaturated ?-ketoesters and cyclic ketones with phenylglyoxal hydrates were realized with cinchona alkaloid-derived thiourea catalysts. The corresponding aldol products were obtained in high yields and good to excellent diastereoselectivities and enantioselectivities (up to 95% ee). PMID:25490142

  9. Method of carbon chain extension using novel aldol reaction

    DOEpatents

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

    2013-08-13

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

  10. Method of carbon chain extension using novel aldol reaction

    DOEpatents

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

    2013-07-30

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

  11. 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

  12. Zinc(II)-Catalyzed Intermolecular Hydrative Aldol Reactions of 2-En-1-ynamides with Aldehydes and Water to form Branched Aldol Products Regio- and Stereoselectively.

    PubMed

    Jadhav, Appaso Mahadev; Pagar, Vinayak Vishnu; Huple, Deepak B; Liu, Rai-Shung

    2015-03-16

    This work describes zinc(II)-catalyzed hydrative aldol reactions of 2-en-1-ynamides with aldehydes and water to afford branched aldol products regio- and stereoselectively. The anti and syn selectivity can be modulated by the sizes of sulfonamides to yield E- and Z-configured zinc(II) dienolates selectively. This new reaction leads to enantiopure aldol products by using a cheap chiral sulfonamide. The mechanistic analysis reveals that the sulfonamide amides of the substrates can trap a released proton to generate dual acidic sites to activate a carbonyl allylation reaction. PMID:25605573

  13. Stereodivergent approach to the avermectins based on "super silyl" directed aldol reactions.

    PubMed

    Brady, Patrick B; Oda, Susumu; Yamamoto, Hisashi

    2014-08-01

    A stereodivergent approach to the spiroketal fragment of the avermectins is described. The strategy utilizes a sequence of three aldol reactions directed by the tris(trimethylsilyl)silyl "super silyl" group. Central to this strategy is that each aldol reaction can be controlled to allow access to either diastereomer in high stereoselectivity, thereby affording 16 stereoisomers along the same linear skeleton. The aldol products can be transformed into spiroketals, including an advanced intermediate in the total synthesis of avermectin A1a. PMID:25025525

  14. A closer look at spontaneous mirror symmetry breaking in aldol reactions.

    PubMed

    Valero, Guillem; Ribó, Josep M; Moyano, Albert

    2014-12-22

    The aldol reaction between acetone and 4-nitrobenzaldehyde run in the nominal absence of any enantioselective catalyst was monitored by chiral HPLC with the aid of an internal standard. The collected data show the presence of a detectable initial enantiomeric excess of the aldol product in the early stages of the reaction in about 50?% of the experiments. Only a small fraction of the reaction contained the non-racemic aldol product after 24?h. This temporary emergence of natural optical activity could be the signature of a coupled reaction network that leads to a spontaneous mirror-symmetry-breaking process, which originates at very low conversions (i.e., strongly depends on events taking place at the very first stages of the process). The reaction is not autocatalytic in the aldol product, which rules out a simple Frank-type reaction network as the source of the observed symmetry breaking. On the other hand, the isolation and characterisation of a double-aldol adduct suggested a reaction network that involved both indirect autocatalysis and indirect mutual inhibition between the enantiomers of the reaction product. PMID:25346447

  15. 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

  16. 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

  17. An alternative approach to aldol reactions: gold-catalyzed formation of boron enolates from alkynes.

    PubMed

    Körner, Cindy; Starkov, Pavel; Sheppard, Tom D

    2010-05-01

    A new method for enolate generation via the gold-catalyzed addition of boronic acids to alkynes is reported. The formation of boron enolates from readily accessible ortho-alkynylbenzeneboronic acids proceeds rapidly with 2 mol % PPh(3)AuNTf(2) at ambient temperature. The enolates undergo aldol reaction with an aldehyde present in the reaction mixture to give cyclic boronate esters, which can be subsequently transformed into phenols, biaryls, or dihydrobenzofurans via oxidation, Suzuki-Miyaura, or intramolecular Chan-Lam coupling, respectively. A combined gold/boronic acid catalyzed aldol condensation reaction of an alkynyl aldehyde was also successfully achieved. PMID:20380452

  18. 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

  19. 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

  20. The Aldol Reaction of Allenolates with Aldehydes in the Presence of Magnesium Diiodide (MgI2) as Catalyst

    E-print Network

    Paré, Paul W.

    The Aldol Reaction of Allenolates with Aldehydes in the Presence of Magnesium Diiodide (MgI2 couples a,b-unsubstituted acrylate CC bonds with aldehydes via an aldol-type addition, is widely utilized was catalyzed by TiCl4-promoted conjugation followed by electrophilic coupling to a series of aldehyde

  1. 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...

  2. Catalytic asymmetric aldol-type reaction of zinc enolate equivalent of amides.

    PubMed

    Haraguchi, Ryosuke; Matsubara, Seijiro

    2013-07-01

    Treatment of phenyl isocyanate with bis(iodozincio)methane gave a zinciomethylenated product, which acts as an amide-enoate equivalent. It did not react with an aldehyde efficiently, but gave the corresponding adduct in good yield in the presence of an aminoalcohol. Use of a catalytic amount of chiral aminoalcohol led the process to the catalytic asymmetric Aldol-type reaction. PMID:23758119

  3. Asymmetric aldol reactions in poly(ethylene glycol) catalyzed by l-proline

    Microsoft Academic Search

    S. Chandrasekhar; Ch. Narsihmulu; N. Ramakrishna Reddy; S. Shameem Sultana

    2004-01-01

    A rapid l-proline catalyzed direct aldol reaction between various aldehydes and acetone was achieved using PEG as the solvent with comparable enantioselectivities and yields to those obtained in other solvents. Recycling the catalyst and solvent (PEG) was possible 10 times without loss of activity.

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

    EPA Science Inventory

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

  5. A NOVEL CHIRAL GALLIUM LEWIS ACID CATALYST WITH SEMI-CROWN LIGAND IN AQUEOUS ASYMMETRIC MUKAIYAMA ALDOL REACTIONS. (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...

  6. A simplified catalytic system for direct catalytic asymmetric aldol reaction of thioamides; application to an enantioselective synthesis of atorvastatin

    Microsoft Academic Search

    Yuji Kawato; Mitsutaka Iwata; Ryo Yazaki; Naoya Kumagai; Masakatsu Shibasaki

    2011-01-01

    A new catalytic system was developed for the direct catalytic asymmetric aldol reaction of thioamides. The new lithium-free Cu catalyst (second-generation catalyst) exhibited enhanced catalytic efficiency over the previously developed catalyst comprising [Cu(CH3CN)4]PF6\\/Ph-BPE\\/LiOAr (first-generation catalyst), which required a tedious catalyst preparation process. In the reaction with the second-generation catalyst, the intermediate Cu-aldolate functioned as a Brønsted base to generate thioamide

  7. Transition state models for probing stereoinduction in Evans chiral auxiliary-based asymmetric aldol reactions.

    PubMed

    Shinisha, C B; Sunoj, Raghavan B

    2010-09-01

    The use of chiral auxiliaries is one of the most fundamental protocols employed in asymmetric synthesis. In the present study, stereoselectivity-determining factors in a chiral auxiliary-based asymmetric aldol reaction promoted by TiCl(4) are investigated by using density functional theory methods. The aldol reaction between chiral titanium enolate [derived from Evans propionyl oxazolidinone (1a) and its variants oxazolidinethione (1b) and thiazolidinethione (1c)] and benzaldehyde is examined by using transition-state modeling. Different stereochemical possibilities for the addition of titanium enolates to aldehyde are compared. On the basis of the coordination of the carbonyl/thiocarbonyl group of the chiral auxiliary with titanium, both pathways involving nonchelated and chelated transition states (TSs) are considered. The computed relative energies of the stereoselectivity-determining C-C bond formation TSs in the nonchelated pathway, for both 1a and 1c, indicate a preference toward Evans syn aldol product. The presence of a ring carbonyl or thiocarbonyl group in the chiral auxiliary renders the formation of neutral TiCl(3)-enolate, which otherwise is energetically less favored as compared to the anionic TiCl(4)-enolate. Hence, under suitable conditions, the reaction between titanium enolate and aldehyde is expected to be viable through chelated TSs leading to the selective formation of non-Evans syn aldol product. Experimentally known high stereoselectivity toward Evans syn aldol product is effectively rationalized by using the larger energy differences between the corresponding diastereomeric TSs. In both chelated and nonchelated pathways, the attack by the less hindered face of the enolate on aldehyde through a chair-like TS with an equatorial disposition of the aldehydic substituent is identified as the preferred mode. The steric hindrance offered by the isopropyl group and the possible chelation are identified as the key reasons behind the interesting stereodivergence between Evans and non-Evans products normally reported for the title reaction. The application of an activation strain model on the critical TSs has been effective toward rationalizing the origin of stereoselectivity. Improved interaction energy between the reactants is found to be the key stabilizing factor for the lowest energy TS in both chelated and nonchelated pathways. The present study provides newer insights on the role of titanium(IV) toward modulating stereoselectivity in aldol reactions. PMID:20707387

  8. Asymmetric Catalysis Special Feature Part II: Enantioselective direct aldol reactions catalyzed by L-prolinamide derivatives

    Microsoft Academic Search

    Zhuo Tang; Fan Jiang; Xin Cui; Liu-Zhu Gong; Ai-Qiao Mi; Yao-Zhong Jiang; Yun-Dong Wu

    2004-01-01

    L-Prolinamides 2, prepared from L-proline and simple aliphatic and aromatic amines, have been found to be active catalysts for the direct aldol reaction of 4-nitrobenzaldehyde with neat acetone at room temperature. They give moderate enantioselectivities of up to 46% enantiomeric excess (ee). The enantioselectivity increases as the amide N H becomes a better hydrogen bond donor. L-Prolinamides 3, derived from

  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 with kinetic resolution: scope and limitations of ketal- and dithioketal-protected ?-ketoaldehydes.

    PubMed

    Ward, Dale E; Kazemeini, Alieh

    2012-12-01

    The multiplicativity rule suggests that aldol coupling of chiral reactants will proceed with substantial mutual kinetic enantioselection (MKE) (racemic reactants) or via a highly enantioselective kinetic resolution (KR) (one enantiopure reactant) if the relative topicity is highly selective and the ketone enolate and aldehyde each have high diastereoface selectivity. The scope and limitations of that paradigm were explored by determining the stereoselectivities of aldol reactions of ketone 1a (known to give 3,5-trans aldol adducts with high selectivity) with a series of ketal- and dithioketal-protected ?-ketoaldehydes (±)-5 (predicted to have high Felkin diastereoface selectivity). Using racemic reactants, all reactions of the (c-Hex)(2)B enolates (highly anti-selective relative topicity) were remarkably selective and gave the 3,5-trans-3,1"-anti-1",2"-syn adduct, one of eight possible diastereomers, via a diastereoselective (dr > 20) preferential reaction (MKE > 17) of like reactant enantiomers [i.e., (3R)-1a + (R)-5 and (3S)-1a + (S)-5]. Reactions of the corresponding Ti(IV) "ate" enolates (anticipated syn-selective relative topicity) were much less selective, and only those of MOM-protected 1a with dithiolane-protected (±)-5 (i.e., X = S, n = 1) gave high selectivity in favor of the 3,5-trans-3,1"-syn-1",2"-syn adduct via a diastereoselective (dr > 20) preferential reaction (MKE ? 6) of unlike reactant enantiomers [i.e., (3R)-1a + (S)-5 and (3S)-1a + (R)-5]. Analogous reactions of the (c-Hex)(2)B and Ti(IV) "ate" enolates of enantiopure (+)-1a (R = MOM) with (±)-5c (R(2) = Me, X = S, n = 1) occurred with KR to give the corresponding enantiopure adducts with the expected stereoselectivity. The adducts have applications in polyproionate synthesis. PMID:23137001

  11. Enantioselective aldol reaction between isatins and cyclohexanone catalyzed by amino Acid sulphonamides.

    PubMed

    Wang, Jun; Liu, Qi; Hao, Qing; Sun, Yanhua; Luo, Yiming; Yang, Hua

    2015-04-01

    Sulphonamides derived from primary ?-amino acid were successfully applied to catalyze the aldol reaction between isatin and cyclohexanone under neat conditions. More interestingly, molecular sieves, as privileged additives, were found to play a vital role in achieving high enantioselectivity. Consequently, high yields (up to 99%) along with good enantioselectivities (up to 92% ee) and diastereoselectivities (up to 95:5 dr) were obtained. In addition, this reaction was also conveniently scaled up, demonstrating the applicability of this protocol. Chirality 27:314-319, 2015. © 2015 Wiley Periodicals, Inc. PMID:25691447

  12. Practical asymmetric synthesis of ?-hydroxy ?-amino acids via complimentary aldol reactions

    PubMed Central

    Pandya, Bhaumik A.; Dandapani, Sivaraman; Duvall, Jeremy R.; Rowley, Ann; Mulrooney, Carol A.; Ryba, Troy; Dombrowski, Michael; Harton, Marie; Young, Damian W.; Marcaurelle, Lisa A.

    2011-01-01

    Orthogonally protected chiral ?-hydroxy-?-amino acids can be accessed in >100 g quantities from readily available starting materials and reagents in 3–4 steps. These chiral synthons contain two adjacent stereocenters along with suitably protected functional groups (O-TBS, N-Boc) for downstream reactivity. Implementation of two existing aldol technologies allows rapid access to all possible stereoisomers of 1. The guiding principles during reaction optimization were reaction scalability and operational efficiency. Conversion of the amino acids to a variety of chiral building blocks in 1–2 steps demonstrates their synthetic utility. PMID:21822337

  13. Oxazinanones as chiral auxiliaries: synthesis and evaluation in enolate alkylations and aldol reactions.

    PubMed

    Davies, Stephen G; Garner, A Christopher; Roberts, Paul M; Smith, Andrew D; Sweet, Miles J; Thomson, James E

    2006-07-21

    Homochiral beta-amino esters (prepared on multigram scale by lithium amide conjugate addition) are readily transformed into oxazinanones. N-acyl derivatives of oxazinanones undergo stereoselective enolate alkylation reactions, with higher stereoselectivities observed for the enolate alkylation of (R)-N-propanoyl-4-iso-propyl-6,6-dimethyl-oxazinan-2-one than the corresponding Evans oxazolidin-2-one. A C(4)-iso-propyl stereodirecting group within the oxazinanone conveys higher stereoselectivity than the analogous C(4)-phenyl substituent. gem-Dimethyl substitution at C(6) within the oxazinanone framework facilitates exclusive exocyclic cleavage upon hydrolysis to furnish alpha-substituted carboxylic acid derivatives and the parent oxazinanone in good yield. Asymmetric aldol reactions of a range of aromatic and aliphatic aldehydes with the chlorotitanium enolate of (R)-N-propanoyl-4-iso-propyl-6,6-dimethyl-oxazinan-2-one proceed with excellent diastereoselectivity. Hydrolysis of the aldol products affords homochiral alpha-methyl-beta-hydroxy-carboxylic acids. PMID:16826300

  14. Asymmetric Michael-aldol tandem reaction of 2-substituted benzofuran-3-ones and enones: a facile synthesis of griseofulvin analogues.

    PubMed

    Dong, Nan; Li, Xin; Wang, Feng; Cheng, Jin-Pei

    2013-09-20

    A highly enantioselective Michael-aldol tandem reaction with respect to prochiral 2-substituted benzofuran-3-ones and enones by a facile primary amine catalyst was investigated. The approach provides rapid access to the desired pharmaceutically active griseofulvin analogues. PMID:24001214

  15. Organocatalytic Asymmetric Synthesis of Functionalized 1,3,5-Triarylpyrrolidin-2-ones via an Aza-Michael/Aldol Domino Reaction

    PubMed Central

    Joie, Céline; Deckers, Kristina; Enders, Dieter

    2014-01-01

    The organocatalytic asymmetric synthesis of functionalized 1,3,5-triarylpyrrolidin-2-ones bearing three contiguous stereocenters through an aza-Michael/aldol domino reaction of ?-ketoamides with ?,?-unsaturated aldehydes is described. The domino products were further derivatized by aldehyde olefination under one-pot conditions. The reaction proceeds with excellent diastereoselectivities (>20:1) and good to excellent enantioselectivities (60–96% ee). PMID:25278634

  16. Homogeneous silicone modified primary amine-Brønsted acid salt catalyzed aldol reaction: unexpected synergistic effect of polysiloxane with remarkable improvement of efficiency and stereoselectivity

    Microsoft Academic Search

    Li-Wen Xu; Ya-Dong Ju; Li Li; Hua-Yu Qiu; Jian-Xiong Jiang; Guo-Qiao Lai

    2008-01-01

    We have developed a new strategy to improve the stereoselectivity in enamine catalysis by the introduction of super-hydrophobic long-chain silicone\\/polysiloxane as support\\/functional group for a model aldol reaction. The homogeneous direct aldol reaction of cyclic ketones with different aromatic aldehydes catalyzed by polysiloxane-derived primary amines has been reported with high yields, good diastereoselectivity, and up to 99% ee.

  17. 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

  18. Construction of bicyclo[3.2.1]octanes with four stereogenic centers by organocatalytic domino Michael/Aldol reaction.

    PubMed

    Lefranc, A; Gremaud, L; Alexakis, A

    2014-10-17

    An enantio- and diastereoselective organocatalytic domino Michael/Aldol reaction for the direct preparation of synthetically and medicinally relevant bicyclo[3.2.1]octane derivatives with four stereogenic centers, including two quaternary carbons, has been described. The reaction tolerates a large variety of substituents on ?,?-unsaturated 1,2-ketoesters and cyclic 1,3-ketoesters. It allows for the formation of various bicyclo[3.2.1]octanes in good yields (53-98%), diastereoselectivities (1:1 to 5:1 dr), and enantioselectivities (up to 95:5 ee). PMID:25275702

  19. Double diastereoselective SuperQuat glycolate aldol reactions: application to the asymmetric synthesis of polyfunctionalised lactones.

    PubMed

    Davies, Stephen G; Nicholson, Rebecca L; Smith, Andrew D

    2004-11-21

    Polyfunctionalised lactones with up to five contiguous stereocentres may be prepared with high stereocontrol by a double diastereoselective aldol protocol with protected homochiral alpha,beta-dihydroxy- or alpha,beta-gamma-trihydroxyaldehydes and a chiral glycolate oxazolidinone, followed by subsequent O-desilylation and lactonisation. PMID:15534718

  20. Liquid phase aldol condensation reactions with MgO–ZrO 2 and shape-selective nitrogen-substituted NaY

    Microsoft Academic Search

    Wenqin Shen; Geoffrey A. Tompsett; Karl D. Hammond; Rong Xing; Fulya Dogan; Clare P. Grey; W. Curtis Conner; Scott M. Auerbach; George W. Huber

    2011-01-01

    The aldol condensation reactions of furfural\\/hydroxymethylfurfural (furfurals) with acetone\\/propanal in water–methanol solvents were studied over the solid base catalysts MgO–ZrO2, NaY and nitrogen-substituted NaY (Nit-NaY). The reactions were conducted at 120°C and 750psig of He in batch reactors. Nit-NaY exhibited catalytic activity for aldol condensation comparable to MgO–ZrO2 and much higher than that of NaY, indicative of the increased base

  1. Equilibrium between a vinylogous ylide and a phosphonium dienolate zwitterion: vinylogous Wittig olefination versus vinylogous aldol-type reaction

    PubMed Central

    Khong, San N.; Tran, Yang S.; Kwon, Ohyun

    2010-01-01

    This paper describes the equilibrium established between a phosphonium dienolate zwitterion and a vinylogous phosphorus ylide, and their reactions with aldehydes. The reactions between ethyl 2-methyl-2,3-butadienoate and various aldehydes occur through either a phosphonium dienolate or a vinylogous ylide intermediate, depending on the presence/absence of a Lewis acid and the nature of the phosphine. We observed a rare vinylogous Wittig olefination from the reaction between ethyl 2-methyl-2,3-butadienoate and an electron-deficient aromatic aldehyde in the presence of a stoichiometric amount of an electron-deficient triarylphosphine and a catalytic amount of a Lewis acid (e.g., BF3·Et2O). On the other hand, the use of triphenylphosphine, in the absence of a Lewis acid, facilitated vinylogous aldol addition, accompanied by a rare 1,2-aryl phosphorus-to-carbon migration. PMID:21359169

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

    EPA Science Inventory

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

  3. The tandem chain extension aldol reaction used for synthesis of ketomethylene tripeptidomimetics targeting hPEPT1

    PubMed Central

    Thorn, Karina; Nielsen, Carsten Uhd; Jakobsen, Palle; Steffansen, Bente; Zercher, Charles K.; Begtrup, Mikael

    2011-01-01

    The rationale for targeting the human di-/tripeptide transporter hPEPT1 for oral drug delivery has been well established by several drug and prodrug cases. The aim of this study was to synthesize novel ketomethylene modified tripeptidomimetics and to investigate their binding affinity for hPEPT1. Three related tripeptidomimetics of the structure H-Phe-?[COCH2]-Ser(Bz)-Xaa-OH were synthesized applying the tandem chain extension aldol reaction, where amino acid derived ?-keto imides were stereoselectively converted to ?-substituted ?-keto imides. In addition, three corresponding tripeptides, composed of amide bonds, were synthesized for comparison of binding affinities. The six investigated compounds were all defined as high affinity ligands (Ki-values <0.5 mM) for hPEPT1 by measuring the concentration dependent inhibition of apical [14C]Gly-Sar uptake in Caco-2 cells. Consequently, the ketomethylene replacement for the natural amide bond and ?-side chain modifications appears to offer a promising strategy to modify tripeptidic structures while maintaining a high affinity for hPEPT1. PMID:21703856

  4. 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…

  5. Formal homologous aldol reactions: interrupting the Nazarov cyclization via carboalkoxylation of alkynes.

    PubMed

    Wu, Yen-Ku; West, F G

    2014-05-01

    Reactions between 1,4-pentadien-3-ones and aryl acetylenes in the presence of BF3·OEt2 furnish ?-phenacyl cyclopentanones via a domino electrocyclization/carboalkoxylation reaction sequence. The overall process underscores a new mode of interrupted Nazarov trapping, where two new carbon-carbon bonds are installed with concomitant formation of carbonyl functionality. PMID:24735109

  6. Decarboxylative ketone aldol reactions: development and mechanistic evaluation under metal-free conditions.

    PubMed

    Blaquiere, Nicole; Shore, Daniel G; Rousseaux, Sophie; Fagnou, Keith

    2009-08-21

    Malonic acid half thioesters (MAHTs) and malonic acid half oxyesters (MAHOs) are shown to undergo decarboxylative nucleophilic addition reactions with ketone and aldehyde electrophiles in the presence of stoichiometric or catalytic quantities of triethylamine at room temperature. The ability to perform these reactions under metal-free conditions has enabled a detailed mechanistic analysis of the reaction pathway leading to the (1)H NMR spectroscopic characterization of a postnucleophilic addition/predecarboxylation intermediate and experimental evidence for a reversible formation of this intermediate followed by an irreversible decarboxylation. Rate constants for each of the bond forming/bond breaking steps in the reaction pathway were also determined, casting light on the differing reactivity between MAHO and MAHT nucleophiles in these processes. Finally, the mechanistic insights gained through these studies have been employed in the development of a new decarboxylative coumarin synthesis. PMID:20560569

  7. Divergent Stereocontrol of Acid Catalyzed Intramolecular Aldol Reactions of 2,3,7-Triketoesters: Synthesis of Highly Functionalized Cyclopentanones

    PubMed Central

    Truong, Phong; Shanahan, Charles S.; Doyle, Michael P.

    2012-01-01

    The intramolecular acid catalyzed aldol cyclization of 2,3,7-triketoesters formed from ?-keto-?-diazo-?-ketoesters provides highly functionalized cyclopentanones with good diastereoselectivity in high overall yields via kinetically controlled and stereodivergent catalytic processes. Lewis acid catalysis gives high selectivity for the 1,3-anti tetrasubstituted cyclopentanones, whereas Brønsted acid catalysis produces the corresponding 1,3-syn diastereomer. PMID:22738671

  8. 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

  9. Iterative direct aldol strategy for polypropionates: enantioselective total synthesis of (-)-membrenone A and B.

    PubMed

    Alagiri, Kaliyamoorthy; Lin, Shaoquan; Kumagai, Naoya; Shibasaki, Masakatsu

    2014-10-17

    An iterative direct aldol reaction using a C3 propionate unit as an aldol donor offers expeditious access to polyketide assembly in a highly diastereo- and enantioselective manner. An all-syn polyketide array with four consecutive stereogenic centers was efficiently constructed by an aldol reaction of thiopropionamide via soft Lewis acid/hard Brønsted base cooperative catalysis. This iterative aldol strategy led to an enantioselective synthesis of (-)-membrenone A and B. PMID:25259628

  10. Microwave-assisted esterification of N-acetyl-L-phenylalanine using modified Mukaiyama's reagents: A new approach involving ionic liquids.

    PubMed

    Zhao, Hua; Song, Zhiyan; Cowins, Janet V; Olubajo, Olarongbe

    2008-01-01

    Inspired by the concept of ionic liquids (ILs), this study modified the original Mukaiyama's reagent, 2-chloro-1-methylpyridinium iodide (m.p. 200-dec), from ionic solid into liquids by changing its anion. The esterification of N-acetyl-L-phenylalanine was investigated as a model reaction. The microwave irradiation was more effective in esterifying N-acetyl-L-phenylalanine than the conventional reflux method. The original Mukaiyama's reagent was modified into ILs through manipulating its anion. However, only non-nucleophilic anions (such as EtSO(4) (-) and Tf(2)N(-)) were favorable since nucleophilic ones (such as CF(3)COO(-) and CH(3)COO(-)) could exchange with chlorine resulting in non-reactive coupling reagents. Two modified Mukaiyama's compounds (i.e. hydrophilic [2-ClMePy][EtSO(4)] and hydrophobic [2-ClMePy][Tf(2)N]) have been identified as the best ILtype coupling reagents. The esterification reaction was greatly enhanced by using 1- methylimidazole as the base instead of conventional toxic tertiary amines, and by using excess amount of alcohols as solvents instead of dichloromethane. Overall, the method reported is effective and 'greener'. PMID:19325717

  11. Aldehyde Coupling Reactions Enantioselective Organocatalytic

    E-print Network

    MacMillan, David W. C.

    Aldehyde Coupling Reactions Enantioselective Organocatalytic Direct Aldol Reactions of a upon carbohydrate architecture[2] as an important platform for reaction design and methodological advance- ment.[3] Application of the aldol reaction[4] to the synthesis of carbohydrates is well

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

    ERIC Educational Resources Information Center

    Wade, Edmir O.; Walsh, Kenneth E.

    2011-01-01

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

  13. Enantioselective organocatalytic aldehydealdehyde cross-aldol couplings. The broad utility of a-thioacetal aldehydes

    E-print Network

    MacMillan, David W. C.

    Enantioselective organocatalytic aldehyde­aldehyde cross-aldol couplings. The broad utility of a-thioacetal aldehydes R. Ian Storer and David W. C. MacMillan* Division of Chemistry and Chemical Engineering aldol reaction with a-thioacetal aldehydes has been developed. Thioacetal bearing aldehydes readily

  14. Catalytic enantioselective quick route to aldol-tethered 1,6- and 1,7-enynes from ?-unsaturated aldehydes.

    PubMed

    García, Jesús M; Odriozola, José M; Razkin, Jesús; Lapuerta, Irati; Odriozola, Amaiur; Urruzuno, Iñaki; Vera, Silvia; Oiarbide, Mikel; Palomo, Claudio

    2014-11-17

    An effective asymmetric route to functionalized 1,6- and 1,7-enynes has been developed based on a direct cross-aldol reaction between ?-unsaturated aldehydes and propargylic aldehydes (?,?-ynals) promoted by combined ?,?-dialkylprolinol ether/Brønsted acid catalysis. This synergistic activation strategy is key to accessing the corresponding aldol adducts with high stereoselectivity, both enantio- and diastereoselectivity. The aldol reaction also proceeds well with propargylic ketones (?,?-ynones) thus enabling a stereocontrolled access to the corresponding tertiary alcohols. The utility of these adducts, which are difficult to prepare through standard methodology, is demonstrated by their transformation into trisubstituted bicyclic enones using standard Pauson-Khand conditions. PMID:25283152

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

    E-print Network

    Paré, Paul W.

    example of a direct aldehyde­ketone coupling using the secondary amine piperidine as base in the presence 60 (2004) 11829­11835 Scheme 1. Keywords: Piperidine; Anti-aldol reaction; Magnesium iodide; Ethyl

  16. Tandem retro-aldol\\/Wittig\\/Michael and related cascade processes

    Microsoft Academic Search

    Sandra Beltrán-Rodil; James R. Donald; Michael G. Edwards; Steven A. Raw; Richard J. K. Taylor

    2009-01-01

    A number of novel tandem sequences initiated by a retro-aldol process are described along with preliminary scope and limitation studies. These include (i) retro-aldol\\/Wittig trapping\\/intramolecular Michael addition, (ii) retro-aldol\\/aza-Wittig\\/intramolecular imine addition, (iii) retro-aldol\\/Henry\\/intramolecular Michael addition and (iv) retro-aldol\\/Knoevenagel\\/intramolecular Michael addition sequences. A range of novel functionalised cyclopentanes, and related systems, are described which should prove to be useful synthetic building

  17. Base-Catalyzed Direct Aldolization of ?-Alkyl-?-Hydroxy Trialkyl Phosphonoacetates**

    PubMed Central

    Corbett, Michael T.; Uraguchi, Daisuke; Ooi, Takashi; Johnson, Jeffrey S.

    2013-01-01

    Catalytic direct aldol addition of ?-hydroxy trialkyl phosphonacetates to aldehydes affords ?-hydroxy-?-phosphonyloxy ester products. The fully substituted glycolate enolate intermediate is generated in situ under mild conditions via [1,2]-phosphonate-phosphate rearrangement. High enantioselectivity and dramatic enhancement of reaction diastereocontrol is realized via the application of chiral iminophosphorane catalysts. The phosphate products undergo stereoselective nucleophilic displacement reactions. PMID:22474004

  18. Stereoselective synthesis of the monomeric unit of actin binding macrolide rhizopodin.

    PubMed

    Pulukuri, Kiran Kumar; Chakraborty, Tushar Kanti

    2012-06-01

    An efficient, scalable, and stereocontrolled synthesis of the entire carbon framework of an actin binding dimeric macrolide rhizopodin has been accomplished in its protected form. The key features of our synthesis include a titanium catalyzed anti acetal aldol reaction, a substrate controlled diastereoslelective prenyl stannylation, a Mukaiyama aldol reaction, an indium mediated diastereoselective propargylation, and an advanced stage Stille coupling reaction. PMID:22594399

  19. 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

    the spiroketal 77, a substructure of altohyrtin A in 94% yield. Scheme 21 OTIPB 0 = 0 OBn p p 76 1. ) K&Cps, MepH 94% TMS BFs epEts, CHapls -42 C to -15 C Hp' , OBn 0 (82%) subunit of Altohyrtin 77 Rorno and coworkers were able to generate a P...-lactone intermediate. ' Reaction of P-lactone 80 with allyltrimethylsilane and TMSOTf gave the spiro-ketal 81 in 75% yield (Scheme 23). Scheme 23 0 OBn p p 80 allyl-TMS TMSOT(, CHsCN -37 C (75%) 0 Bnp 0 CpeH 81 26 A proposed mechanism was offered...

  20. 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

  1. 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

  2. Development of Catalytic Stereoselective Reductive Aldol Reactions 

    E-print Network

    Joensuu, Pekka Matias

    2008-01-01

    The chemistry of enolates can be considered one of the cornerstone areas in organic chemistry. Regioselective generation of an enolate in the presence of several enolisable sites can often prove to be a difficult task. ...

  3. 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

    methodologies. Three of the strategies pursued involved use of B-lactone scaffolds as intermediates. Extensions of the nucleophile catalyzed, aldol-lactonization (NCAL) reaction were also pursued and targeted toward alternative natural product targets...

  4. Spontaneous aldol and Michael additions of simple enoxytrimethylsilanes in DMSO

    Microsoft Academic Search

    Yves Génisson; Liliane Gorrichon

    2000-01-01

    Activation of simple trimethylsilyl ketene acetals by dipolar aprotic solvents has been evidenced, allowing efficient solvent assisted aldol and Michael additions under extremely simple, mild and metal free conditions.

  5. 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

  6. 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

  7. 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

    &M University. 11 CHAPTER III RESULTS AND DISCUSSION NCAL process Scheme 3.1. Proposed Mechanism For Formation of Bicyclic ?-Lactones.47 In the most general case, the intramolecular nucleophile-catalyzed aldol-lactonization (NCAL) process... provided evidence in favor of a NCAL reaction over a [2 +2] cycloaddition since employing a chiral amine catalyst leads to the formation of bicyclic systems in high enantiomeric purity.9 While the precise details of the NCAL process remains ambiguous...

  8. Size-Selective Lewis Acid Catalysis in a Microporous Metal-Organic Framework with Exposed Mn2+

    E-print Network

    relatively scarce.5,6 While these have included some significant successes in enantioselective catalysis,5a,aswellasthemoredemandingMukaiyama-aldol reaction. Moreover, in each case, a pronounced size-selectivity effect consistent with the pore dimensions catalyst for Lewis acid promoted reactions. To compare the catalytic activity of 1 with that of other metal

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

    E-print Network

    Anderson, James B.

    a dilatometric technique, he studied the acetaldehyde aldol condensation in water solution with sodium hydroxide, Urbana, 111. ACETALDEHYDEmay react to form aldol when- ever acetaldehyde and hydroxide ions are present by hydroxide ions and does not proceed in acidic solutions. The equilibrium point is too far in the aldol

  10. Total synthesis of the proposed structure of astakolactin

    PubMed Central

    Mameda, Keisuke; Fujishiro, Moe; Yoshinaga, Yutaka

    2014-01-01

    Summary The first total synthesis of the proposed structure of astakolactin, a sesterterpene metabolite isolated from the marine sponge Cacospongia scalaris, has been achieved, mainly featuring Johnson–Claisen rearrangement, asymmetric Mukaiyama aldol reaction and MNBA-mediated lactonization. PMID:25383112

  11. Enantioselective synthesis of highly functionalised cyclohexanones starting from R-(?)-carvone

    Microsoft Academic Search

    Tommi M. Meulemans; Gerrit A. Stork; Ben J. M. Jansen; Aede de Groot

    1998-01-01

    Copper (I) catalysed conjugate addition of methylmagnesium iodide to R-(?)-carvone and trapping the enolate as its trimethylsilyl enol ether, followed by a trityl perchlorate (TrClO4) catalysed Mukaiyama-aldol reaction, is an efficient method for the preparation of highly functionalised cyclohexanones which can be used as starting compounds in the total syntheses of enantiomerically pure clerodanes.

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

    ERIC Educational Resources Information Center

    Bennett, George D.

    2006-01-01

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

  13. Total Synthesis of the Spirocyclic Imine Marine Toxin (?)-Gymnodimine and an Unnatural C4-Epimer

    PubMed Central

    Kong, Ke; Moussa, Ziad; Lee, Changsuk

    2011-01-01

    The first total synthesis of the marine toxin (?)-gymnodimine (1) has been accomplished in a convergent manner. A highly diastereo- and enantioselective exo-Diels–Alder reaction catalyzed by a bis-oxazoline Cu(II) catalyst enabled rapid assembly of the spirocyclic core of gymnodimine. The preparation of the tetrahydrofuran fragment utilized a chiral auxiliary based anti-aldol reaction. Two major fragments, spirolactam 56 and tetrahydrofuran 55, were then coupled through an efficient Nozaki–Hiyama–Kishi reaction. An unconventional, ambient temperature t-BuLi-initiated intramolecular Barbier reaction of alkyl iodide 64 was employed to form the macrocycle. A late stage vinylogous Mukaiyama aldol addition of a silyloxyfuran to a complex cyclohexanone 83 appended the butenolide and a few additional steps provided (?)-gymnodimine (1). A diastereomer of the natural product was also synthesized, C4-epi-gymnodimine (90), derived from the vinylogous Mukaiyama aldol addition. PMID:22023219

  14. An Aldol-based Build/Couple/Pair Strategy for the Synthesis of Medium- and Large-Sized Rings: Discovery of Macrocyclic Histone Deacetylase Inhibitors

    PubMed Central

    Marcaurelle, Lisa A.; Comer, Eamon; Dandapani, Sivaraman; Duvall, Jeremy R.; Gerard, Baudouin; Kesavan, Sarathy; Lee, Maurice D.; Liu, Haibo; Lowe, Jason T.; Marie, Jean-Charles; Mulrooney, Carol A.; Pandya, Bhaumik A.; Rowley, Ann; Ryba, Troy D.; Suh, Byung-Chul; Wei, Jingqiang; Young, Damian W.; Akella, Lakshmi B.; Ross, Nathan T.; Zhang, Yan-Ling; Fass, Daniel M.; Reis, Surya A.; Zhao, Wen-Ning; Haggarty, Stephen J.; Palmer, Michelle; Foley, Michael A.

    2010-01-01

    An aldol-based ‘build/couple/pair’ (B/C/P) strategy was applied to generate a collection of stereochemically and skeletally diverse small molecules. In the build phase, a series of asymmetric syn- and anti- aldol reactions were performed to produce four stereoisomers of a Boc protected ?-amino acid. In addition both stereoisomers of O-PMB-protected alaninol were generated to provide a chiral amine coupling partner. In the couple step, eight stereoisomeric amides were synthesized by coupling the chiral acid and amine building blocks. The amides were subsequently reduced to generate the corresponding secondary amines. In the pair phase, three different reactions were employed to enable intramolecular ring-forming processes, namely: nucleophilic aromatic substitution (SNAr), Huisgen [3+2] cycloaddition and ring-closing metathesis (RCM). Despite some stereochemical dependencies, the ring-forming reactions were optimized to proceed with good to excellent yields providing a variety of skeletons ranging in size from 8- to 14-membered rings. Scaffolds resulting from the RCM pairing reaction were diversified on solid-phase to yield a 14,400-membered library of macrolactams. Screening of this library led to the discovery of a novel class of histone deacetylase inhibitors, which display mixed enzyme inhibition and led to increased levels of acetylation in a primary mouse neuron culture. The development of stereo-structure/activity relationships (SSAR) was made possible by screening all 16 stereoisomers of the macrolactams produced through the aldol-based B/C/P strategy. PMID:21067169

  15. Total synthesis of (+)-isatisine a: application of a silicon-directed mukaiyama-type [3 + 2]-annulation.

    PubMed

    Lee, Jihoon; Panek, James S

    2015-03-20

    Complete details of an asymmetric synthesis of (+)-isatisine A (1) are described. The synthesis highlights the use of a highly diastereoselective Mukaiyama-type [3 + 2]-annulation of allylsilane 5 with the unsaturated aldehyde 9a to assemble the functionalized tetrahydrofuran core of isatisine A. A convergent route to the framework of the natural product was established that employed a substrate-controlled indole coupling that was followed by a late-stage intramolecular copper(I)-mediated amidation to complete the assembly of the tetracyclic framework of (+)-isatisine A. In addition, the scope of the [3 + 2]-annulation was evaluated and enhanced utilizing diastereomeric allylsilanes anti-5 and syn-5 to establish an efficient route to stereochemically well-defined tetrahydrofurans. PMID:25739011

  16. The first enantioselective synthesis of imino-deoxydigitoxose and protected imino-digitoxose by using l-threonine aldolase-catalyzed aldol condensation

    Microsoft Academic Search

    Toshihiro Nishiyama; Tetsuya Kajimoto; Swapnil S. Mohile; Noboru Hayama; Teppei Otsuda; Minoru Ozeki; Manabu Node

    2009-01-01

    The first enantioselective synthesis of protected imino-digitoxose (?)-16 was attained starting with a synthetic intermediate of polyoxin C prepared by the l-threonine aldolase-catalyzed aldol condensation of (2S,3S)-2,3-O-isopropyriden-4-penten-1-al 8 and glycine. The strategy took advantage of an intramolecular nucleophilic attack by a Cbz-protected amino group on the hemiacetal carbon, a side reaction in the synthesis of natural products, for the formation

  17. 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

    )................................................ 12 a. Bicyclic ?-Lactones via Aldol-Lactonizations...................... 13 b. Bicyclic ?-Butyrolactones via Aldol-Lactonizations............. 17 4. Pyridine Derivatives.... Cuprate Additions to Bicyclic ?-Lactones................................. 29 2. Application to Merck IND.......................................................... 32 vii CHAPTER...

  18. Organocatalytic Domino Reactions

    Microsoft Academic Search

    Andrea-Nekane Alba; Xavier Companyo; Monica Viciano; Ramon Rios

    2009-01-01

    Since the rediscovery of proline in 2000 as catalyst in aldol reaction by List, Barbas and Lerner and, soon after, the development of iminium catalysis by D. W. C. MacMillan, the emergence of organocatalysis as an important tool in organic synthesis is outstanding. During the last years, several research groups have worked in the development of new and powerful methodologies

  19. Experimental Observations in the Morita Baylis-Hillman Reaction in Methanol

    E-print Network

    Plata, Robert Erik

    2013-05-22

    to afford the 1, the carbon-carbon bond forming ?aldol? step affording 2, and a multistep ?elimination? to afford the product. (This follows the descriptive terminology used by Hill and Issacs.10) However, the multicomponent nature of the MBH reaction... underscores the importance of mechanistic understanding for the rational control of reactions and development of new reactions. There has thus been considerable interest R H O + EWG + Nu: R OH EWG "addition" EWG Nu+ "aldol" EWG Nu+ R O...

  20. New short aliphatic chain ionic liquids: synthesis, physical properties, and catalytic activity in aldol condensations.

    PubMed

    Cota, I; Gonzalez-Olmos, R; Iglesias, M; Medina, F

    2007-11-01

    This paper reports on the synthesis of new short aliphatic chain ionic liquids and the study of the temperature dependence of density, ultrasonic velocities, and ionic conductivity in the range of 278.15-338.15 K. Fourier transform infrared spectra establishes their simple ionic salt structure. Because of their polarity, the ionic liquids are able to dissolve polar solvents and inorganic salts, all of them showing high tolerance in hydroxylic media. The observed temperature trend of the studied properties points out the special packing of these ionic liquids, as well as the strong influence of the steric hindrance among linear aliphatic residues enclosed in anions and cations. One of them showed a very high melting temperature. A collection of slightly basic ionic liquids were used to test their catalytic activity in several aldol condensation reactions of some carbonyl compounds. The best conversions and selectivities were obtained using single ionic liquids, with no synergetic effects being observed when different concentrations of mixed ionic liquids were used as catalysts. In any case, the ionic liquid can also easily be recycled from reaction media, suggesting a promising method of process design for this kind of reaction. PMID:17918990

  1. Creation of acid–base bifunctional catalysis for efficient C C coupling reactions by amines immobilization on SiO 2, silica-alumina, and nano-H-ZSM-5

    Microsoft Academic Search

    Ken Motokura; Nagabhatla Viswanadham; Gudimella Murali Dhar; Yasuhiro Iwasawa

    2009-01-01

    Silica-supported amines (SiO2-NR2) were found to be excellent heterogeneous catalysts for various organic CC coupling reactions, namely cyanation, Michael reaction, and nitro–aldol reaction. A wide variety of substrates, such as aromatic, heteroaromatic, aliphatic, and cyclic carbonyl compounds, can be efficiently converted into the corresponding cyano-O-ethoxycarbonylation products. The SiO2-NR2 also promoted Michael reaction of ethyl cyanoacetae with cyclohexen-1-one and nitro–aldol reaction

  2. Dibenzalacetone by Aldol Condensation 45 ALDOL SYNTHESIS of DIBENZALACETONE, AN ORGANIC SUN SCREEN

    E-print Network

    Jasperse, Craig P.

    Overview: The reaction of an aldehyde with a ketone employing sodium hydroxide as the base is an example a nucleophilic enolate anion. The aldehyde carbonyl is much more electrophilic than that of a ketone that the benzaldehyde is surplus and that the acetone is limiting. This is helpful for several reasons: a. Aldehyde

  3. Asymmetric Aldol Additions: Use of Titanium Tetrachloride and (-)-Sparteine for the Soft Enolization of N-Acyl Oxazolidinones,

    E-print Network

    Asymmetric Aldol Additions: Use of Titanium Tetrachloride and (-)-Sparteine for the Soft- Evans syn product depending on the nature and amount of the base used. With 1 equiv of titanium and are highly effective for the prepara- tion of Evans syn products in asymmetric aldol addi- tions.3 Titanium

  4. Imidazole-Catalyzed Henry Reactions in Aqueous Medium

    Microsoft Academic Search

    Mridula Phukan; Kalyan Jyoti Borah; Ruli Borah

    2008-01-01

    2-Nitroalkanols can be efficiently synthesized using imidazole as a mild Lewis basic catalyst in aqueous medium as well as in organic solvents. The products have been found in good yields without purification (> 95% purity by H NMR) for aromatic aldehydes. Additionally, the very mild reaction conditions prevent the particular side reactions such as aldol condensation, Cannizzaro reaction, or dehydration of

  5. 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.

  6. Catalytic effect of barium ferrite magnetic particles on aldol condensation of acetone

    Microsoft Academic Search

    Haruo Watanabe; Jun'etsu Seto

    1996-01-01

    The catalytic effect of barium ferrite magnetic particles on aldol condensation was studied from the viewpoint of the reduction of this effect. The poisoning caused by different kinds of oxoacid ions was examined, and tungstate and molybdate ions were found to show high effectiveness for the deactivation of the above catalysis. These ions were adsorbed selectively on the side-planes (1100)

  7. Convenient and facile cross-Aldol condensation catalyzed by molecular iodine: An efficient synthesis of ?,??-bis(substituted-benzylidene) cycloalkanones

    Microsoft Academic Search

    Biswanath Das; Ponnaboina Thirupathi; Ibram Mahender; Kongara Ravinder Reddy

    2006-01-01

    Cross-Aldol condensation of aromatic aldehydes with cyclic ketones in the presence of catalytic amount of iodine at room temperature afforded ?,??-bis(substituted-benzylidene) cycloalkanones in high yields.

  8. The effect of acid–base pairing on catalysis: An efficient acid–base functionalized catalyst for aldol condensation

    Microsoft Academic Search

    Ryan K. Zeidan; Mark E. Davis

    2007-01-01

    Acid–base bifunctionalized heterogeneous catalysts may be capable of exhibiting reactivity not achievable with homogeneous catalysts. We investigated the effect of pKa of the acid component of mesoporous solids containing acid–base bifunctionality on their catalytic ability toward aldol condensation between 4-nitrobenzaldehyde and acetone. We found that higher levels of aldol product conversion were obtained when weaker acid components (phosphoric, carboxylic vs

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

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

  10. Copper-catalyzed cascade reactions of ?,?-unsaturated esters with keto esters

    PubMed Central

    Wang, Chongnian; Li, Zengchang

    2015-01-01

    Summary A copper-catalyzed cascade reaction of ?,?-unsaturated esters with keto esters is reported. It features a copper-catalyzed reductive aldolization followed by a lactonization. This method provides a facile approach to prepare ?-carboxymethyl-?-lactones and ?-carboxymethyl-?-lactones under mild reaction conditions.

  11. Single-reactor process for sequential aldol-condensation and hydrogenation of biomass-derived compounds in water

    Microsoft Academic Search

    C. J. Barrett; J. N. Chheda; G. W. Huber; J. A. Dumesic

    2006-01-01

    A bifunctional Pd\\/MgO-ZrO2 catalyst was developed for the single-reactor, aqueous phase aldol-condensation and hydrogenation of carbohydrate-derived compounds, furfural and 5-hydroxymethylfurfural (HMF), leading to large water-soluble intermediates that can be converted to liquid alkanes. The cross aldol-condensation of these compounds with acetone results in formation of water-insoluble monomer (C8–C9) and dimer (C13–C15) product species, which are subsequently hydrogenated in the same

  12. 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…

  13. reactions

    Microsoft Academic Search

    S. Reinker; R. M. Altman; J. Timmer

    Gene regulatory, signal transduction and metabolic networks are major areas of interest in the newly emerging field of systems biology. In living cells, stochastic dynamics play an important role; however, the kinetic parameters of biochemical reactions necessary for modelling these processes are often not accessible directly through experiments. The problem of estimating stochastic reaction constants from molecule count data measured,

  14. 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 ...

  15. Total Synthesis of (+)-Azaspiracid-1. An Exhibition of the Intricacies of Complex Molecule Synthesis

    PubMed Central

    Evans, David A.; Kværnø, Lisbet; Dunn, Travis B.; Beauchemin, André; Raymer, Brian; Mulder, Jason A.; Olhava, Edward J.; Juhl, Martin; Kagechika, Katsuji; Favor, David A.

    2012-01-01

    The synthesis of the marine neurotoxin azaspiracid-1 has been accomplished. The individual fragments were synthesized by catalytic enantioselective processes: A hetero-Diels-Alder reaction to afford the E- and HI-ring fragments, a carbonyl-ene reaction to furnish the CD-ring fragment, and a Mukaiyama aldol reaction to deliver the FG-ring fragment. The subsequent fragment couplings were accomplished by aldol and sulfone anion methodologies. All ketalization events to form the non-acyclic target were accomplished under equilibrating conditions utilizing the imbedded configurations of the molecule to adopt one favored conformation. A final fragment coupling of the anomeric EFGHI-sulfone anion to the ABCD-aldehyde completed the convergent synthesis of (+)-azaspiracid-1. PMID:19006391

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

    PubMed Central

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

    2013-01-01

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

  17. Quantum mechanical investigations on the role of neutral and negatively charged enamine intermediates in organocatalyzed reactions

    NASA Astrophysics Data System (ADS)

    Hubin, Pierre O.; Jacquemin, Denis; Leherte, Laurence; Vercauteren, Daniel P.

    2014-04-01

    The proline-catalyzed aldol reaction is the seminal example of asymmetric organocatalysis. Previous theoretical and experimental studies aimed at identifying its mechanism in order to rationalize the outcome of this reaction. Here, we focus on key steps with modern first principle methods, i.e. the M06-2X hybrid exchange-correlation functional combined to the solvation density model to account for environmental effects. In particular, different pathways leading to the formation of neutral and negatively charged enamine intermediates are investigated, and their reactivity towards two electrophiles, i.e. an aldehyde and a benzhydrylium cation, are compared. Regarding the self-aldol reaction, our calculations confirm that the neutral enamine intermediate is more reactive than the negatively charged one. For the reaction with benzhydrylium cations however, the negatively charged enamine intermediate is more reactive.

  18. 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.

  19. 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.…

  20. Versatile One-Step One-Pot Direct Aldol Condensation Promoted by MgI2 by Han-Xun Wei*1

    E-print Network

    Paré, Paul W.

    at room temperature by simply mixing four components in CH2Cl2, with medium-to-high yields of aldol both as a Lewis acid and an iodine source for a Michael-type addition in which an a,b-ethynyl ketone aldehyde, ketone (or ester), and MgI2 at room temperature under N2 atmosphere. This gave rise

  1. Molecular Mechanism by which One Enzyme Catalyzes Two Reactions

    NASA Astrophysics Data System (ADS)

    Nishimasu, Hiroshi; Fushinobu, Shinya; Wakagi, Takayoshi

    Unlike ordinary enzymes, fructose-1,6-bisphosphate (FBP) aldolase/phosphatase (FBPA/P) catalyzes two distinct reactions : (1) the aldol condensation of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate to FBP, and (2) the dephosphorylation of FBP to fructose-6-phosphate. We solved the crystal structures of FBPA/P in complex with DHAP (its aldolase form) and FBP (its phosphatase form). The crystal structures revealed that FBPA/P exhibits the dual activities through a dramatic conformational change in the active-site architecture. Our findings expand the conventional concept that one enzyme catalyzes one reaction.

  2. 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

  3. Pd/NbOPO? multifunctional catalyst for the direct production of liquid alkanes from aldol adducts of furans.

    PubMed

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

    2014-09-01

    Great efforts have been made to convert renewable biomass into transportation fuels. Herein, we report the novel properties of NbO(x)-based catalysts in the hydrodeoxygenation of furan-derived adducts to liquid alkanes. Excellent activity and stability were observed with almost no decrease in octane yield (>90% throughout) in a 256?h time-on-stream test. Experimental and theoretical studies showed that NbO(x) species play the key role in C-O bond cleavage. As a multifunctional catalyst, Pd/NbOPO4 plays three roles in the conversion of aldol adducts into alkanes: 1)?The noble metal (in this case Pd) is the active center for hydrogenation; 2)?NbO(x) species help to cleave the C-O bond, especially of the tetrahydrofuran ring; and 3)?a niobium-based solid acid catalyzes the dehydration, thus enabling the quantitative conversion of furan-derived adducts into alkanes under mild conditions. PMID:25045056

  4. RUTHENIUM-CATALYZED TANDEM OLEFIN MIGRATION-ALDOL AND MANNICH-TYPE REACTIONS IN WATER AND PROTIC SOLVENT. (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...

  5. Total synthesis of the protected aglycon of fidaxomicin (tiacumicin?B, lipiarmycin?A3).

    PubMed

    Miyatake-Ondozabal, Hideki; Kaufmann, Elias; Gademann, Karl

    2015-02-01

    Fidaxomicin, also known as tiacumicin?B or lipiarmycin?A3, is a novel macrocyclic antibiotic that is used in hospitals for the treatment of Clostridium difficile infections. This natural product has also been shown to have excellent bactericidal activity against multidrug-resistant Mycobacterium tuberculosis. In spite of its attractive biological activity, no total synthesis has been reported to date. The enantioselective synthesis of the central 18-membered macrolactone is reported herein. The key reactions include ring-closing metathesis between a terminal olefin and a dienoate moiety for macrocyclization, a vinylogous Mukaiyama aldol reaction, and a Stille coupling reaction of sterically demanding substrates. The retrosynthesis involves three medium-sized fragments, thus leading to a flexible yet convergent synthetic route. PMID:25431322

  6. '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.

  7. Catalytic and structural properties of co-precipitated Mg–Zr mixed oxides for furfural valorization via aqueous aldol condensation with acetone

    Microsoft Academic Search

    I. Sádaba; M. Ojeda; R. Mariscal; J. L. G. Fierro; M. López Granados

    2011-01-01

    A series of MgO–ZrO2 mixed oxides with different nominal Mg\\/(Mg+Zr) atomic ratios (0, 0.1, 0.3, 0.5, 0.75, 0.85 0.92) were prepared by co-precipitation and calcined at 873K. The catalytic activity in aldol condensation of furfural with acetone was tested in aqueous medium. These solids were systematically characterized by XRD, TEM, XPS, N2 adsorption–desorption isotherms and thermal analysis.MgxZr1?xO2?x solid solution with

  8. Thermodynamics of the formation of atmospheric organic particulate matter by accretion reactions—Part 1: aldehydes and ketones

    NASA Astrophysics Data System (ADS)

    Barsanti, Kelley C.; Pankow, James F.

    The term "accretion reactions" is introduced here to refer to the large collection of reactions by which atmospheric organic molecules can add mass, especially as by combination with other organic molecules. A general thermodynamic approach is developed for evaluating the tendency of atmospheric constituents (e.g., C 10 aldehydes) to undergo accretion reactions (e.g., dimerization) and thereby form less volatile molecules (e.g., aldol condensation products) that may subsequently condense and so contribute to the levels of organic particulate matter (OPM) observed in the atmosphere. As an example, gaseous compounds A and B may contribute to OPM formation by the net overall reaction A g+B g=C liq. This reaction may occur according to any of three kinetic schemes. Scheme I: (1) A g+B g=C g (accretion in the gas phase): then (2) C g=C liq (condensation of the accretion product); Scheme II: (1) B g=B liq (condensation of B); then (2) A g+B liq=C liq (heterogeneous accretion reaction of gaseous A with condensed B); or Scheme III: (1) A g+B g=A liq+B liq (condensation of A and B); then (2) A liq+B liq=C liq (accretion of A with B within the PM phase). For all three schemes, the net overall reaction remains A g+B g=C liq. The overall thermodynamic tendency of the net reaction remains the same regardless of the actual predominating kinetic mechanism. If an accretion reaction between two atmospheric components is to produce significant new OPM, appreciable amounts of the product C must form, and the vapor pressure of C must be relatively low so that a significant proportion of C can condense into the multicomponent liquid OPM phase. This study considers the thermodynamics of accretion reactions of atmospheric aldehydes including: (a) hydration, polymerization (i.e., oligomer formation), hemiacetal/acetal formation; and (b) aldol condensation. It was concluded regarding OPM formation that: (1) the reactions in the first group are not thermodynamically favored, either in the atmosphere, or in the "acid-catalyzed" chamber experiments of Jang and Kamens (Environ. Sci. Technol. 35 (2001b) 4758) with n-butanal, n-hexanal, n-octanal, and n-decanal; (2) aldol condensation is not thermodynamically favored for the conditions of the Jang and Kamens (2001b) experiments with those four aldehydes; (3) the mechanism for any observed OPM formation from n-butanal, n-hexanal, and n-octanal in those experiments remains unknown, and may also have been involved in the "acid-catalyzed" experiments with n-decanal; (4) whether Jang and Kamens (2001b) observed the consequences of aldol condensation in their n-decanal experiments remains unclear due in part to uncertainties in the free energy of formation (? Gf0) values for the aldol products of n-decanal; (5) analogous refinement in the quality of needed ? Gf0 values is required to clarify the potential importance of aldol products of pinonaldehyde in the formation of ambient OPM; and (6) the possibility that photo-assisted mechanisms may compensate for unfavorable thermodyamics in the formation of accretion products in the atmosphere should be considered.

  9. 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

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

    PubMed Central

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

    2013-01-01

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

  11. Lewis acid-mediated reactions of 1-cyclopropyl-2-arylethanone derivatives with allenic ester, ethyl acetoacetate, and methyl acrylate.

    PubMed

    Shi, Min; Tang, Xiang-Ying; Yang, Yong-Hua

    2008-07-18

    TMSOTf-mediated reactions of 2-aryl-1-(1-phenylcyclopropyl)ethanones 1 with allenic esters afford a novel method for the synthesis of 6-methyl-3a,7-diaryl-3,3a-dihydro-2H-benzofuran-4-one derivatives 2 in moderate yields. In addition, we also found that TMSOTf-mediated reactions of 1-cyclopropyl-2-arylethanones with ethyl acetoacetate can provide the corresponding 2,3-dihydrobenzofuran-4-ol and dihydrofuro[2,3-h]chromen-2-one in moderate yields via a sequential reaction involving a nucleophilic ring-opening reaction of the cyclopropane by H2O, one intermolecular aldol type reaction and two intramolecular aldol type reactions, a cyclic transesterification, dehydration, and aromatization. Moreover, by using methyl acrylate to replace allenic ester, the corresponding 7-aryl-3,5,6,7-tetrahydro-2H-benzofuran-4-one and 5-aryl-3,5,6,7-tetrahydro-2 H-benzofuran-4-one can be formed in moderate to high yields in the presence of Bi(OTf)2Cl. Plausible reaction mechanisms have also been provided on the basis of control experiments. PMID:18570403

  12. Effects of water on reactions for waste treatment, organic synthesis, and bio-refinery in sub- and supercritical water.

    PubMed

    Akizuki, Makoto; Fujii, Tatsuya; Hayashi, Rumiko; Oshima, Yoshito

    2014-01-01

    Current research analyzing the effects of water in the field of homogeneous and heterogeneous reactions of organics in sub- and supercritical water are reviewed in this article. Since the physical properties of water (e.g., density, ion product and dielectric constants) can affect the reaction rates and mechanisms of various reactions, understanding the effects that water can have is important in controlling reactions. For homogeneous reactions, the effects of water on oxidation, hydrolysis, aldol condensation, Beckman rearrangement and biomass refining were introduced including recent experimental results up to 100 MPa using special pressure-resistance equipment. For heterogeneous reactions, the effects of ion product on acid/base-catalyzed reactions, such as hydrothermal conversion of biomass-related compounds, organic synthesis in the context of bio-refinery, and hydration of olefins were described and how the reaction paths are controlled by the concentration of water and hydrogen ions was summarized. PMID:23867097

  13. A stereocontrolled approach for the synthesis of 2,5-diaryl-3,4-disubstituted furano lignans through a highly diastereoselective aldol condensation of an ester enolate with an ?-chiral center: total syntheses of (?)-talaumidin and (?)-virgatusin

    Microsoft Academic Search

    Kiran Matcha; Subrata Ghosh

    2008-01-01

    A general stereocontrolled approach for entry into a family of highly biologically active 2,5-diaryl-3,4-disubstituted furano lignans has been developed. The key step involves a diastereoselective aldol-type condensation of an ester enolate having an ?-chiral center with an aromatic aldehyde. The methodology has been illustrated with the total syntheses of (?)-talaumidin and (?)-virgatusin.

  14. The Base-Induced Reaction of Salicylaldehyde with 1-Bromobutane in Acetone: Two Related Examples of Chemical Problem Solving

    NASA Astrophysics Data System (ADS)

    Bendorf, Holly D.; McDonald, Chriss E.

    2003-10-01

    This investigational laboratory experiment emphasizes structure determination using modern spectroscopic techniques. The experiment examines the base-induced reaction of salicylaldehyde with 1-bromobutane in acetone. The product obtained from the reaction depends upon the identity of the base, either carbonate or hydroxide. With carbonate, an SN2 reaction yields the butyl salicyl ether. Reaction with hydroxide results in a dehydrative aldol reaction between salicylaldehyde and acetone that occurs along with the etherification. Students are divided into groups of four. Each student performs his or her own experimental work, running one of the two reactions, and acquiring the proton and carbon NMR, IR, and mass spectra. The students work in groups to propose structures for the products and mechanisms for their formation. The students are also asked to address why the reactions take different courses.

  15. 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.

    2014-11-01

    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 and 1H Nuclear Magnetic Resonance 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, which 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 for 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.

  16. 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

  17. 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

  18. Synthesis of Substituted a-(Hydroxymethyl)-b-iodoacrylates via MgI2-Promoted Stereoselective Aldol Coupling

    E-print Network

    Paré, Paul W.

    -pot coupling reaction under mild conditions, promoted by MgI2, which serves both as a Lewis acid and iodine parameter. We found that the aldehyde and MgI2 had to be mixed in CH2Cl2 at room temperature for 20 min

  19. Origins of asymmetric phosphazene organocatalysis: computations reveal a common mechanism for nitro- and phospho-aldol additions.

    PubMed

    Simón, Luis; Paton, Robert S

    2015-03-01

    We report a hybrid density functional theory-molecular mechanics study of the mechanism of the addition of nitroalkanes and phosphonates to benzaldehyde catalyzed by a chiral phosphacene catalyst developed by Ooi and co-workers. Our results are consistent with a reaction mechanism in which a catalyst molecule simultaneously interacts by hydrogen bonds with the nucleophile and the electrophile, transferring a proton to the aldehyde in concert with carbon-carbon bond formation. Despite the C2 symmetry of this class of organocatalyst, substrate recognition, and asymmetric induction in both reaction classes studied relies on interactions with nonequivalent N-H bonds that break symmetry. The origin of the stereo and diastereoselectivity is discussed in terms of steric effects and of the conformations adopted by the reactants, and the most favorable transition structure results from minimal geometric distortion energies. A rational model for predicting the major stereoisomer of reactions catalyzed by this chiral phosphacene, based on the qualitative assessment of steric interactions, is given. PMID:25658042

  20. 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

  1. Design and Synthesis of Chiral Zn2+ Complexes Mimicking Natural Aldolases for Catalytic C–C Bond Forming Reactions in Aqueous Solution

    PubMed Central

    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

  2. Manganese 2 -Complexes as Auxiliaries

    E-print Network

    Lepore, Salvatore D.

    Manganese 2 -Complexes as Auxiliaries for Stereoselective Aldol Synthesis of Allenyl Carbinols 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

  3. Allergic reactions

    MedlinePLUS

    ... more often in people who have a family history of allergies . Substances that don't bother most people ( ... reaction is getting worse. The person has a history of severe allergic reactions (check for a medical ID ...

  4. Enzyme Reactions

    NSDL National Science Digital Library

    Minerva Deland School

    2011-10-03

    This video shows an enzyme reaction lab. The teacher demonstrates how the enzyme, catalase, reacts with hydrogen peroxide (a substrate found in cells). The teacher first demonstrates a normal enzyme reaction. He or she then goes on to show how manipulating temperature and pH will affect the reaction of an enzyme.

  5. Special Reactions

    NSDL National Science Digital Library

    William C. Robertson, Ph.D.

    2010-03-01

    The basics of chemical reactions were covered in the first chemistry book, including how to write and balance chemical equations that represent those reactions. There is also a quick review of chemical reactions in Chapter 1 of this book. We're going to d

  6. 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

  7. Glucose and fructose decomposition in subcritical and supercritical water: Detailed reaction pathway, mechanisms, and kinetics

    SciTech Connect

    Kabyemela, B.M.; Adschiri, T.; Malaluan, R.M.; Arai, K. [Tohoku Univ., Sendai (Japan). Dept. of Chemical Engineering] [Tohoku Univ., Sendai (Japan). Dept. of Chemical Engineering

    1999-08-01

    The authors are developing a new catalyst-free process of cellulose decomposition in supercritical water. In their initial study on the cellulose decomposition in supercritical water, the main products of cellulose decomposition were found to be oligomers of glucose (cellobiose, cellotriose, etc.) and glucose at short residence times (400 C, 25 MPa, 0.05 s). The kinetics of glucose at these conditions can be useful in understanding the reaction pathways of cellulose. Experiments were performed on the products of glucose decomposition at short residence times to elucidate the reaction pathways and evaluate kinetics of glucose and fructose decomposition in sub- and supercritical water. The conditions were a temperature of 300--400 C and pressure of 25--40 MPa for extremely short residence times between 0.02 and 2 s. The products of glucose decomposition were fructose, a product of isomerization, 1,6-anhydroglucose, a product of dehydration, and erythrose and glyceraldehyde, products of C-C bond cleavage. Fructose underwent reactions similar to glucose except that it did not form 1,6-anhydroglucose and isomerization to glucose is negligible. The mechanism for the products formed from C-C bond cleavage could be explained by reverse aldol condensation and the double-bond rule of the respective enediols formed during the Lobry de Bruyn Alberda van Ekenstein transformation. The differential equations resulting from the proposed pathways were fit to experimental results to obtain the kinetic rate constants.

  8. Reaction Time

    NSDL National Science Digital Library

    2012-06-26

    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.

  9. 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.

  10. 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 ...

  11. Drug Reactions

    MedlinePLUS

    Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions. One problem is ...

  12. 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.

  13. Gas-phase base-catalyzed Claisen-Schmidt reactions of the acetone enolate anion with various para-substituted benzaldehydes.

    PubMed

    Haas, G W; Gross, M L

    1996-01-01

    Substituent effects were determined for the gas-phase base-catalyzed Claisen-Schmidt reaction of the acetone enolate anion and various para-substituted benzaldehydes. Under chemical ionization conditions, the adduct for the reaction was detected and the fraction of adduct that is tetrahedral was determined. The Hammett constants for the substituents correlate the fraction of the adduct population that is tetrahedral. The fraction of tetrahedral intermediate is greatest for those systems in which the negative charge is most highly stabilized. The structures of the adducts are determined on the basis of collisionally activated decomposition mass spectra. These spectra show that both the adducts of the ion-molecule reactions and deprotonated reference compounds, which have a structure that is similar to the tetrahedral intermediate, decompose by elimination of water and by a retro-aldol reaction. The adducts formed from the ion-molecule reactions show a greater propensity to reform the acetone enolate, whereas the deprotonated reference compounds eliminate H2O readily. The reaction constant ? from the Hammett correlation is +1.6, which substantiates that the production of tetrahedral intermediates is facilitated by electron-withdrawing substituents. PMID:24202798

  14. Advances in QM/MM Simulations for Organic and Enzymatic Reactions

    PubMed Central

    2010-01-01

    CONSPECTUS Application of combined quantum and molecular mechanical (QM/MM) methods focuses on predicting activation barriers and the structures of stationary points for organic and enzymatic reactions. Characterization of the factors that stabilize transition structures in solution and in enzyme active sites provides a basis for design and optimization of catalysts. Continued technological advances allowed expansion from prototypical cases to mechanistic studies featuring detailed enzyme and condensed-phase environments with full integration of the QM calculations and configurational sampling. This required improved algorithms featuring fast QM methods, advances in computing changes in free energies including free-energy perturbation (FEP) calculations, and enhanced configurational sampling. In particular, the present Account highlights development of the PDDG/PM3 semiempirical QM method, computation of multidimensional potentials of mean force (PMF), incorporation of on-the-fly QM in Monte Carlo (MC) simulations, and a polynomial quadrature method for efficient modeling of proton-transfer reactions. The utility of this QM/MM/MC/FEP methodology is illustrated for a variety of organic reactions including substitution, decarboxylation, elimination, and pericyclic reactions. Comparison with experimental kinetic results on medium effects has verified the accuracy of the QM/MM approach in the full range of solvents from hydrocarbons to water to ionic liquids. Corresponding results from ab initio and density functional theory (DFT) methods with continuum-based treatments of solvation reveal deficiencies, particularly for protic solvents. Also summarized in this Account are three specific QM/MM applications to biomolecular systems: (1) a recent study that clarified the mechanism for the reaction of 2-pyrone derivatives catalyzed by macrophomate synthase as a tandem Michael-aldol sequence rather than a Diels-Alder reaction; (2) elucidation of the mechanism of action of fatty acid amide hydrolase (FAAH), an unusual Ser-Ser-Lys proteolytic enzyme; and, (3) the construction of enzymes for Kemp elimination of 5-nitrobenzisoxazole that highlights the utility of QM/MM in the design of artificial enzymes. PMID:19728702

  15. Early stage composition of SOA produced by ?-pinene/ozone reaction: ?-Acyloxyhydroperoxy aldehydes and acidic dimers

    NASA Astrophysics Data System (ADS)

    Witkowski, Bart?omiej; Gierczak, Tomasz

    2014-10-01

    Composition of the freshly formed secondary organic aerosol (SOA) generated by ozonolysis of cyclohexene, cyclohexene-d10 (model precursors) and ?-pinene was studied using liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC-ESI/MS2). SOA was generated in the flow-tube reactor under the following conditions: 22 ± 2 °C, 1 atm and reaction time was approx. 30 s. In an attempt to resolve the current ambiguities, regarding the structure of ?-pinene SOA nucleating agents, analytical methods for analysis of ?-acyloxyhydroperoxy aldehydes and oligomers containing carboxylic group were developed to study the potential nucleating agents. Negatively charged m/z 351, 341, 337, 357 and 367 ions corresponding to the acidic oligomers were detected in freshly formed ?-pinene SOA. For the first time, structures and formation mechanism for compounds detected as m/z 337 and 351 ions were proposed. Based on the model precursor analysis (cyclohexene and cyclohexene-d10) it was concluded that these compounds were most likely formed via aldol reaction of the lower molecular weight aerosol components. ?-Acyloxyhydroperoxy aldehydes were studied in the SOA samples using previously developed, novel method, based on the prediction of fragmentation spectrum for the compounds of interest. It was concluded that ?-acyloxyhydroperoxy aldehydes were not formed in significant quantities. Based on the obtained results, possible SOA formation and growth mechanism is discussed.

  16. The effects of interactions between proline and carbon nanostructures on organocatalysis in the Hajos-Parrish-Eder-Sauer-Wiechert reaction

    NASA Astrophysics Data System (ADS)

    Rance, G. A.; Khlobystov, A. N.

    2014-09-01

    The non-covalent interactions of S-(-)-proline with the surfaces of carbon nanostructures (fullerene, nanotubes and graphite) change the nucleophilic-electrophilic and acid-base properties of the amino acid, thus tuning its activity and selectivity in the organocatalytic Hajos-Parrish-Eder-Sauer-Wiechert (HPESW) reaction. Whilst our spectroscopy and microscopy measurements show no permanent covalent bonding between S-(-)-proline and carbon nanostructures, a systematic investigation of the catalytic activity and selectivity of the organocatalyst in the HPESW reaction demonstrates a clear correlation between the pyramidalisation angle of carbon nanostructures and the catalytic properties of S-(-)-proline. Carbon nanostructures with larger pyramidalisation angles have a stronger interaction with the nitrogen atom lone pair of electrons of the organocatalyst, thereby simultaneously decreasing the nucleophilicity and increasing the acidity of the organocatalyst. These translate into lower conversion rates but higher selectivities towards the dehydrated product of Aldol addition.The non-covalent interactions of S-(-)-proline with the surfaces of carbon nanostructures (fullerene, nanotubes and graphite) change the nucleophilic-electrophilic and acid-base properties of the amino acid, thus tuning its activity and selectivity in the organocatalytic Hajos-Parrish-Eder-Sauer-Wiechert (HPESW) reaction. Whilst our spectroscopy and microscopy measurements show no permanent covalent bonding between S-(-)-proline and carbon nanostructures, a systematic investigation of the catalytic activity and selectivity of the organocatalyst in the HPESW reaction demonstrates a clear correlation between the pyramidalisation angle of carbon nanostructures and the catalytic properties of S-(-)-proline. Carbon nanostructures with larger pyramidalisation angles have a stronger interaction with the nitrogen atom lone pair of electrons of the organocatalyst, thereby simultaneously decreasing the nucleophilicity and increasing the acidity of the organocatalyst. These translate into lower conversion rates but higher selectivities towards the dehydrated product of Aldol addition. Electronic supplementary information (ESI) available: Control experiments in the absence of carbon nanostructures and additional spectroscopic measurements and titrations are described in the ESI. See DOI: 10.1039/c4nr04009k

  17. Dimerization and cyclotrimerization of aldehydes: ruthenium catalyzed formation of esters, 1,3,5-trioxanes, and aldol condensation products from aldehydes

    Microsoft Academic Search

    Angela Sorkau; Kerstin Schwarzer; Christoph Wagner; Eike Poetsch; Dirk Steinborn

    2004-01-01

    [RuCl(SiMe3)(CO)(PPh3)2] (1) was found to catalyze dimerization of aldehydes RC(O)H yielding esters RC(O)OCH2R (3) in a Tishchenko type reaction. Aldehydes with ?-hydrogen atoms (R = Me, Et, iPr, iBu) reacted quantitatively within 2 days (5mol% catalyst, 70°C in C6D6) whereas those without ?-hydrogen atoms (R = tBu, Ph) did not react at all. In the case of benzaldehyde (R =

  18. Reaction Time

    NSDL National Science Digital Library

    Michael Horton

    2009-05-30

    This lab is not an inquiry activity. There are some students whose reaction times will not allow them to catch a 12 inch ruler. They may use a dowel, stick, strip of cardboard, etc. Although the students are led to believe that the point of the lab is to

  19. Reaction Time

    NSDL National Science Digital Library

    WGBH Boston

    2003-01-01

    In this activity, learners conduct an experiment to test how fast they can react. Learners try to catch a piece of paper with a ruler printed on it (or a ruler) as quickly as they can. Learners collect data and compare the reaction times of friends and family.

  20. 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.

  1. 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

  2. Metal Reactions

    NSDL National Science Digital Library

    Oregon Museum of Science and Industry

    1997-01-01

    This is written as a static display, but can easily be adapted to a hands-on experiment for learners to conduct. Sodium phosphate, a clear colorless solution, is combined with six different metal ion solutions. Each metal (copper, nickel, iron, silver, cobalt, and barium) forms a different color and texture precipitate. Learners discover that a chemical reaction can be identified by a color change, and formation of a precipitate. They also learn that metals can be identified by their precipitates. For safety reasons, this activity should be conducted as a demonstration for younger audiences.

  3. Thermonuclear reaction rates. II

    Microsoft Academic Search

    W. A. Fowler; G. R. Caughlan; B. A. Zimmerman

    1975-01-01

    A revision and updating of charged particle reactions involving nuclei ; with A less than or approximately equal to 30, except for the $sup ; 2$H(d,$gamma$)⁴He reaction whose reaction rate is very uncertain, is ; presented. Reactions involving neutrons are treated as neutron-producing ; reactions but factors for calculating the reverse reaction rate are provided for ; all reactions. The

  4. Cyclic beta-amino acid derivatives: synthesis via lithium amide promoted tandem asymmetric conjugate addition-cyclisation reactions.

    PubMed

    Davies, Stephen G; Díez, David; Dominguez, Sara H; Garrido, Narciso M; Kruchinin, Dennis; Price, Paul D; Smith, Andrew D

    2005-04-01

    The product distribution upon conjugate addition of homochiral lithium N-benzyl-N-alpha-methylbenzylamide to dimethyl-(E,E)-nona-2,7-dienedioate can be controlled to give either the cyclic 1,2-anti-1,6-anti-beta-amino ester (derived from conjugate addition and intramolecular enolate cyclisation) or the acyclic bis-beta-amino ester derivative (derived from double conjugate addition) in high de. The introduction of a protected nitrogen functionality into the diester skeleton facilitates, after conjugate addition and intramolecular enolate cyclisation, the asymmetric construction of piperidines in high de; variation in the N-protecting group indicates that the highest stereoselectivity is observed with alpha-branched N-substituents. Tandem conjugate addition-aldol reactions can also be achieved stereoselectively, with lithium amide conjugate addition to epsilon- and zeta-oxo-alpha,beta-unsaturated esters giving the corresponding five and six membered cyclic beta-amino esters in high de. N-deprotection by hydrogenolysis of the products arising from these reactions furnishes a range of polyfunctionalised transpentacin and transhexacin derivatives in high de and ee. PMID:15785819

  5. 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

    Summary of Attempted Amide Coupling of Amine 260 and Acid 242.................. 98 20 a-Cylopropylated g-Lactam Fused b-Lactone (272) with NCAL Reaction...........103 21 Work-up Conditions after NCAL Reaction...

  6. Proline catalyzed ?-aminoxylation reaction in the synthesis of biologically active compounds.

    PubMed

    Kumar, Pradeep; Dwivedi, Namrata

    2013-02-19

    The search for new and efficient ways to synthesize optically pure compounds is an active area of research in organic synthesis. Asymmetric catalysis provides a practical, cost-effective, and efficient method to create a variety of complex natural products containing multiple stereocenters. In recent years, chemists have become more interested in using small organic molecules to catalyze organic reactions. As a result, organocatalysis has emerged both as a promising strategy and as an alternative to catalysis with expensive proteins or toxic metals. One of the most successful and widely studied secondary amine-based organocatalysts is proline. This small molecule can catalyze numerous reactions such as the aldol, Mannich, Michael addition, Robinson annulation, Diels-Alder, ?-functionalization, ?-amination, and ?-aminoxylation reactions. Catalytic and enantioselective ?-oxygenation of carbonyl compounds is an important reaction to access a variety of useful building blocks for bioactive molecules. Proline catalyzed ?-aminoxylation using nitrosobenzene as oxygen source, followed by in situ reduction, gives enantiomerically pure 1,2-diol. This molecule can then undergo a variety of organic reactions. In addition, proline organocatalysis provides access to an assortment of biologically active natural products including mevinoline (a cholesterol lowering drug), tetrahydrolipstatin (an antiobesity drug), R(+)-?-lipoic acid, and bovidic acid. In this Account, we present an iterative organocatalytic approach to synthesize both syn- and anti-1,3-polyols, both enantio- and stereoselectively. This method is primarily based on proline-catalyzed sequential ?-aminoxylation and Horner-Wadsworth-Emmons (HWE) olefination of aldehyde to give a ?-hydroxy ester. In addition, we briefly illustrate the broad application of our recently developed strategy for 1,3-polyols, which serve as valuable, enantiopure building blocks for polyketides and other structurally diverse and complex natural products. Other research groups have also applied similar strategies to prepare such bioactive molecules as littoralisone, brasoside and (+)-cytotrienin A. Among the various synthetic approaches reported for 1,3-polyols, our organocatalytic iterative approach appears to be very promising and robust. This method combines the merit of organocatalytic reaction with an easy access to both enantiomerically pure forms of proline, mild reaction conditions, and tolerance to both air and moisture. In this Account, we present the latest applications of organocatalysis and how organic chemists can use this new tool for the total synthesis of complex natural products. PMID:23148510

  7. 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)

  8. On Thermonuclear Reaction Rates

    E-print Network

    H. J. Haubold; A. M. Mathai

    1996-12-02

    Nuclear reactions govern major aspects of the chemical evolution od galaxies and stars. Analytic study of the reaction rates and reaction probability integrals is attempted here. Exact expressions for the reaction rates and reaction probability integrals for nuclear reactions in the case of nonresonant, modified nonresonant, screened nonresonant and resonant cases are given. These are expressed in terms of H-functions, G-functions and in computable series forms. Computational aspects are also discussed.

  9. 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 ...

  10. 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.

  11. The Glyoxal Clock Reaction

    ERIC Educational Resources Information Center

    Ealy, Julie B.; Negron, Alexandra Rodriguez; Stephens, Jessica; Stauffer, Rebecca; Furrow, Stanley D.

    2007-01-01

    Research on the glyoxal clock reaction has led to adaptation of the clock reaction to a general chemistry experiment. This particular reaction is just one of many that used formaldehyde in the past. The kinetics of the glyoxal clock makes the reaction suitable as a general chemistry lab using a Calculator Based Laboratory (CBL) or a LabPro. The…

  12. 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

  13. DOI:10.1039/b409056j T h i s j o u r n a l i s T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4 2 8 9 3O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 9 3 2 8 9 6

    E-print Network

    Paré, Paul W.

    - and enantioselective fashion has been an important topic in modern organic chemistry.1­2 Among these reactions.rsc.org/obc A R T I C L E MgI2-catalyzed halo aldol reaction: a practical approach to (E,b-unsaturated ketones in dichloromethane at 0 °C without the use of any catalyst. The halo aldol reaction

  14. Continuous detonation reaction engine

    NASA Technical Reports Server (NTRS)

    Lange, O. H.; Stein, R. J.; Tubbs, H. E.

    1968-01-01

    Reaction engine operates on the principles of a controlled condensed detonation rather than on the principles of gas expansion. The detonation results in reaction products that are expelled at a much higher velocity.

  15. Pulmonary Transfusion Reactions

    PubMed Central

    Bux, Jürgen; Sachs, Ulrich J. H.

    2008-01-01

    Summary Background In recent years, pulmonary transfusion reactions have gained increasing importance as serious adverse transfusion events. Methods Review of the literature. Results Pulmonary transfusion reactions are not extremely rare and, according to hemovigilance data, important causes of transfusion-induced major morbidity and death. They can be classified as primary with predominant pulmonary injury and secondary as part of another transfusion reaction. Primary reactions include transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO) and transfusion-associated dyspnea (TAD). Secondary pulmonary reactions are often observed in the wake of hemolytic transfusion reactions, hypotensive/anaphylactic reactions, and transfusion-transmitted bacterial infections. Conclusion Knowledge and careful management of cases of pulmonary transfusion reactions are essential for correct reporting to blood services and hemovigilance systems. Careful differentiation between TRALI and TACO is important for taking adequate preventive measures. PMID:21512622

  16. Microfluidic chemical reaction circuits

    DOEpatents

    Lee, Chung-cheng (Irvine, CA); Sui, Guodong (Los Angeles, CA); Elizarov, Arkadij (Valley Village, CA); Kolb, Hartmuth C. (Playa del Rey, CA); Huang, Jiang (San Jose, CA); Heath, James R. (South Pasadena, CA); Phelps, Michael E. (Los Angeles, CA); Quake, Stephen R. (Stanford, CA); Tseng, Hsian-rong (Los Angeles, CA); Wyatt, Paul (Tipperary, IE); Daridon, Antoine (Mont-Sur-Rolle, CH)

    2012-06-26

    New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

  17. 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)

  18. Chemical Reactions (Netorials)

    NSDL National Science Digital Library

    Chemical Reactions: this is a resource in the collection "Netorials". The Netorials cover selected topics in first-year chemistry including: Chemical Reactions, Stoichiometry, Thermodynamics, Intermolecular Forces, Acids & Bases, Biomolecules, and Electrochemistry.

  19. Chemical Reactions and Stoichiometry

    NSDL National Science Digital Library

    The Concord Consortium

    2011-12-11

    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.

  20. Chemical Reactions: Investigating Exothermic and Endothermic Reactions

    NSDL National Science Digital Library

    This activity is an inquiry-based investigation where students discover the indicators of chemical reactions (endothermic and exothermic) by collecting data and using that data to develop a testable question for further experimentation.

  1. High Resolution Reaction Intermediates of rabbit Muscle Fructose-1,6-bisphosphate Aldolase: Substrate Cleavage and Induced Fit

    SciTech Connect

    St-Jean,M.; Lafrance-Vanasse, J.; Liotard, B.; Sygusch, J.

    2005-01-01

    Crystal structures were determined to 1.8-Angstrom resolution of the glycolytic enzyme fructose-1, 6-bis(phosphate) aldolase trapped in complex with its substrate and a competitive inhibitor, mannitol-1, 6-bis(phosphate). The enzyme substrate complex corresponded to the postulated Schiff base intermediate and has reaction geometry consistent with incipient C3-C4 bond cleavage catalyzed by Glu-187, which is adjacent to the Schiff base forming Lys-229. Atom arrangement about the cleaved bond in the reaction intermediate mimics a pericyclic transition state occurring in non-enzymatic aldol condensations. Lys-146 hydrogen bonds the substrate C4 hydroxyl and assists substrate cleavage by stabilizing the developing negative charge on the C4 hydroxyl during proton abstraction. Mannitol-1, 6-bis(phosphate) forms a non-covalent complex in the active site whose binding geometry mimics the covalent carbinolamine precursor. Glu-187 hydrogen bonds the C2 hydroxyl of the inhibitor in the enzyme complex substantiating a proton transfer role by Glu-187 in catalyzing the conversion of the carbinolamine intermediate to Schiff base. Modeling of the acyclic substrate configuration into the active site shows Glu-187, in acid form, hydrogen bonding both substrate C2 carbonyl and C4 hydroxyl, thereby aligning the substrate ketose for nucleophilic attack by Lys-229. The multi-functional role by Glu-187 epitomizes a canonical mechanistic feature conserved in Schiff base forming aldolases catalyzing carbohydrate metabolism. Trapping of tagatose-1, 6-bis(phosphate), a diastereoisomer of fructose-1, 6-bis(phosphate), displayed stereospecific discrimination and reduced ketohexose binding specificity. Each ligand induces homologous conformational changes in two adjacent a-helical regions that promote phosphate binding in the active site.

  2. Reaction efficiency effects on binary chemical reactions

    NASA Astrophysics Data System (ADS)

    Lazaridis, Filippos; Savara, Aditya; Argyrakis, Panos

    2014-09-01

    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.

  3. Mechanisms in knockout reactions

    E-print Network

    D. Bazin; R. J. Charity; R. T. de Souza; M. A. Famiano; A. Gade; V. Henzl; D. Henzlova; S. Hudan; J. Lee; S. Lukyanov; W. G. Lynch; S. McDaniel; M. Mocko; A. Obertelli; A. M. Rogers; L. G. Sobotka; J. R. Terry; J. A. Tostevin; M. B. Tsang; M. S. Wallace

    2009-02-16

    We report on the first detailed study of the mechanisms involved in knockout reactions, via a coincidence measurement of the residue and fast proton in one-proton knockout reactions, using the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results on the reactions $^9$Be($^9$C,$^8$B+X)Y and $^9$Be($^8$B,$^7$Be+X)Y are presented. They are compared with theoretical predictions for both the diffraction and stripping reaction mechanisms, as calculated in the eikonal model. The data shows a clear distinction between the two reaction mechanisms, and the observed respective proportions are very well reproduced by the reaction theory. This agreement supports the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.

  4. Classes of Chemical Reactions Reactions in aqueous media

    E-print Network

    Zakarian, Armen

    Classes of Chemical Reactions Reactions in aqueous media · Precipitation reactions · Acid-Base+ , and Pb2+ #12;Classes of Chemical Reactions Acid-Base Reactions Acid - a substance that is a donor of H Acid-Base Reactions STRONG ACIDS WEAK ACIDS Hydrochloric acid, HCl Hydrofluoric acid, HF Hydrobromic

  5. [Reactions after MMR vaccination].

    PubMed

    Kaaber, K; Samuelsson, I S; Larsen, S O

    1990-06-01

    Four months after introducing routine vaccination against measles, mumps and German measles (MMR-vaccination) in Denmark, a questionnaire study of reactions in vaccinated children was carried out. There were significantly fewer reactions in children who had previously developed immunity to measles, either by having had the disease or by vaccination. The reaction frequency after MMR-vaccination of children immune to measles was no greater than that after other vaccinations. Moreover, for all vaccinations, the frequency of reaction was found to decrease significantly with increasing age. The study suggests that a large proportion of the so-called reactions were not caused by vaccination, but were due to common viral infections occurring at random and concurrently with it. The reactions that arose in connection with MMR-vaccination are considered to be of minor importance when compared with often prolonged and more severe course of these diseases. PMID:2363211

  6. 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

  7. Classic Organic Reactions

    NSDL National Science Digital Library

    Despite the fact that the Classic Organic Reactions Page was designed for commercial purposes, to demonstrate the capabilities of ChemPen chemical structure drawing software for Windows, the page offers a useful resource for chemistry students and professionals. The creator of this page, and author and proprietor of ChemPen, Dr. Hilton Evans, has cited the literature for each reaction. The site contains drawings for over 300 alphabetically listed classic organic reactions. The list begins with the Acetoacetic Ester Condensation and ends with the Zinke-Suhl Reaction.

  8. 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.

  9. CREATED USING THE RSC COMMUNICATION TEMPLATE (VER. 3.1) -SEE WWW.RSC.ORG/ELECTRONICFILES FOR DETAILS ARTICLE TYPE www.rsc.org/xxxxxx | XXXXXXXX

    E-print Network

    Takada, Shoji

    acceptors, we chose ketomalonate 1, which is obtained in a hydrate form, as electronically activated ketone and a synthetically useful ketomalonate 1c as a hydrated form was developed, and either anti- or syn-aldol adducts compounds.1 Among these reactions, catalytic asymmetric aldol reactions of ketone electrophiles afford

  10. Smell the Maillard Reaction

    NSDL National Science Digital Library

    2012-10-03

    In this activity, learners cook amino acids and sugar to explore the range of aromas released. When amino acids and sugars are heated, learners will observe a phenomenon known as the Maillard reaction, also known as the browning reaction. Caution!: Kids, please don't try this at home without the help of an adult. The corn syrup can get very hot, very quickly.

  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. Clock Reaction: Outreach Attraction

    ERIC Educational Resources Information Center

    Carpenter, Yuen-ying; Phillips, Heather A.; Jakubinek, Michael B.

    2010-01-01

    Chemistry students are often introduced to the concept of reaction rates through demonstrations or laboratory activities involving the well-known iodine clock reaction. For example, a laboratory experiment involving thiosulfate as an iodine scavenger is part of the first-year general chemistry laboratory curriculum at Dalhousie University. With…

  13. Applications of Reaction Rate

    ERIC Educational Resources Information Center

    Cunningham, Kevin

    2007-01-01

    This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…

  14. The guaiol color reaction.

    PubMed

    Waddell, Thomas G; Arp, Nathan W; Bodine, Kyle D; Pagni, Richard M

    2002-10-01

    The common and biogenetically important sesquiterpene guaiol yields a deep purple color when treated with electrophilic bromine reagents. This interesting color reaction was observed over fifty years ago, but the chemistry of this process has not been investigated. Herein, we present the chemistry of the guaiol color reaction. PMID:12391567

  15. Oscillating Reactions: Two Analogies

    ERIC Educational Resources Information Center

    Petruševski, Vladimir M.; Stojanovska, Marina I.; Šoptrajanov, Bojan T.

    2007-01-01

    Oscillating chemical reactions are truly spectacular phenomena, and demonstrations are always appreciated by the class. However, explaining such reactions to high school or first-year university students is problematic, because it may seem that no acceptable explanation is possible unless the students have profound knowledge of both physical…

  16. Chemical burn or reaction

    MedlinePLUS

    Chemicals that touch skin can lead to a reaction on the skin, throughout the body, or both. ... leave the person alone and watch carefully for reactions affecting the entire body. Note: If a chemical gets into the eyes, the eyes should be ...

  17. The chemistry and biology of zoanthamine alkaloids and Illicium sesquiterpenes

    E-print Network

    Trzoss, Lynnie L.

    2012-01-01

    aldol reaction would proceed in an enantioselective manner.Enantioselective synthesis of the ABC ring motif of norzoanthamine based on asymmetric Robinson annulation reactions.Enantioselective synthesis of ABC ring motif of norzoanthamine based on asymmetric Robinson annulation reactions

  18. Thiol-catalysed radical-chain redox rearrangement reactions of benzylidene acetals derived from terpenoid diols.

    PubMed

    Dang, Hai-Shan; Roberts, Brian P; Tocher, Derek A

    2003-11-21

    The thiol-catalysed radical-chain redox rearrangement of cyclic benzylidene acetals derived from 1,2- and 1,3-diols of terpene origin has been investigated from both synthetic and mechanistic standpoints. The redox rearrangement was carried out either at ca. 70 degrees C (using Bu(t)ON=NOBu(t) as initiator) or at ca. 130 degrees C (using Bu(t)OOBu(t) as initiator) in the presence of triisopropylsilanethiol or methyl thioglycolate as catalyst; the silanethiol was usually more effective. This general reaction affords the benzoate ester of the monodeoxygenated diol, unless rearrangement of intermediate carbon-centred radicals takes place prior to final trapping by the thiol to give the product, in which case structurally rearranged esters are obtained. For the benzylidene acetals of 1,2-diols prepared by vicinal cis-dihydroxylation of 2-carene, alpha-pinene or beta-pinene, intermediate cyclopropylcarbinyl or cyclobutylcarbinyl radicals are involved and ring opening of these leads ultimately to unsaturated monocyclic benzoates. 1,2-Migration of the benzoate group in the intermediate beta-benzoyloxyalkyl radical sometimes also competes with thiol trapping during the redox rearrangement of benzylidene acetals derived from 1,2-diols. Redox rearrangement of the benzylidene acetal from carane-3,4-diol, obtained by cis-dihydroxylation of 3-carene, does not involve intermediate cyclopropylcarbinyl radicals and leads to benzoate ester in which the bicyclic carane skeleton is retained. The inefficient redox rearrangement of the relatively rigid benzylidene acetal from exo,exo-norbornane-2,3-diol is attributed to comparatively slow chain-propagating beta-scission of the intermediate 2-phenyl-1,3-dioxolan-2-yl radical, probably caused by the development of adverse angle strain in the transition state for this cleavage. Similar angle strain effects are thought to influence the regioselectivities of redox rearrangement of bicyclic [4.4.0]benzylidene acetals resulting from selected 1,3-diols, themselves prepared by reduction of aldol adducts derived from reactions of aldehydes with the kinetic lithium enolates obtained from menthone and from isomenthone. PMID:14664397

  19. Reaction Spectroscopy of ? Hypernuclei

    NASA Astrophysics Data System (ADS)

    Hashimoto, Osamu

    2000-09-01

    Reaction spectroscopy as a tool to investigate ? hypernuclear structure and ?N interaction is discussed showing recent spectroscopic data obtained through the (?+, K+) reaction using a large acceptance high resolution spectrometer (SKS) at KEK 12 GeV PS. High quality spectra of light ? hypernuclei in the p-shell region are compared with the recent DWIA calculation, in which a good agreement are observed. Analysis of the spectral shapes for 16? O and 13? C and their comparison with (K-,?-) data provided information on the splitting of the spin-orbit partner states, suggesting they are small. Future prospects of hypernuclear reaction spectroscopy are also presented.

  20. Reaction pathways in coprocessing

    SciTech Connect

    Stock, L.M.; Ettinger, M.D.; Gatsis, J.G. [Univ. of Chicago, IL (United States)

    1995-12-01

    The reaction pathways in the catalytic coprocessing of Illinois No. 6 and Wyodak coals with Lloydminster and Hondo resids have been investigated at low and high severity. The reactions of a selected set of representative compounds including several different hydrocarbons as well as phenols and alkylated phenols have also been studied to gain perspective on the manner in which structural elements of complex coal molecules transform under the reaction conditions. The results of these investigations will be discussed in this presentation which will focus on the transformations that take place to fragment the very complex coal molecules.

  1. 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.

  2. 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.

  3. 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.

  4. 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...

  5. 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

  6. 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)

  7. Transfusion reaction - hemolytic

    MedlinePLUS

    ... transfusion reaction. Mild symptoms may be treated with: Acetaminophen, a pain reliever to reduce fever and discomfort Fluids given through a vein (intravenous) and other medicines to treat or prevent kidney ...

  8. 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

  9. Thermonuclear reaction rates V

    Microsoft Academic Search

    G. R. Caughlan; W. A. Fowler

    1988-01-01

    Analytic expressions are given for the reaction rates of astrophysically important thermonuclear reactions involving low-mass nuclei (1less than or equal toZless than or equal to14). Numerical values of the rates are tabulated for the temperature range 10⁶less than or equal toTless than or equal to10¹° K. This provides a comprehensive update of our previous publications. copyright 1988 Academic Press, Inc.

  10. Polymerase Chain Reaction

    NSDL National Science Digital Library

    Polymerase chain reaction (PCR) enables researchers to produce millions of copies of a specific DNA sequence in approximately two hours. This automated process bypasses the need to use bacteria for amplifying DNA. This animation from Cold Spring Harbor Laboratory's Dolan DNA Learning Center presents Polymerase Chain Reaction through a series of illustrations of the processes involved. Users may view the animation online (Flash is required) or download it for PC or Mac.

  11. 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

  12. Rates of Hydrothermal Reactions

    Microsoft Academic Search

    Bernard J. Wood; John V. Walther

    1983-01-01

    The rates of reactions of silicates and aqueous fluids follow zero-order kinetics controlled by the reacting surface area with the rate constant given by the equation: log k\\/bumpeq -2900\\/T - 6.85, where T is temperature and where k has the unit's gram-atoms of oxygen per square centimeter per second. This expression appears to hold for all silicates and for reactions

  13. [Cutaneous adverse drug reactions].

    PubMed

    Lebrun-Vignes, B; Valeyrie-Allanore, L

    2015-04-01

    Cutaneous adverse drug reactions (CADR) represent a heterogeneous field including various clinical patterns without specific features suggesting drug causality. Exanthematous eruptions, urticaria and vasculitis are the most common forms of CADR. Fixed eruption is uncommon in western countries. Serious reactions (fatal outcome, sequelae) represent 2% of CADR: bullous reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), DRESS (drug reaction with eosinophilia and systemic symptoms or drug-induced hypersensitivity syndrome) and acute generalized exanthematous pustulosis (AGEP). These forms must be quickly diagnosed to guide their management. The main risk factors are immunosuppression, autoimmunity and some HLA alleles in bullous reactions and DRESS. Most systemic drugs may induce cutaneous adverse reactions, especially antibiotics, anticonvulsivants, antineoplastic drugs, non-steroidal anti-inflammatory drugs, allopurinol and contrast media. Pathogenesis includes immediate or delayed immunologic mechanism, usually not related to dose, and pharmacologic/toxic mechanism, commonly dose-dependent or time-dependent. In case of immunologic mechanism, allergologic exploration is possible to clarify drug causality, with a variable sensitivity according to the drug and to the CADR type. It includes epicutaneous patch testing, prick test and intradermal test. However, no in vivo or in vitro test can confirm the drug causality. To determine the cause of the eruption, a logical approach based on clinical characteristics, chronologic factors and elimination of differential diagnosis is required, completed with a literature search. A reporting to pharmacovigilance network is essential in case of a serious CADR whatever the suspected drug and in any case if the involved drug is a newly marketed one or unusually related to cutaneous reactions. PMID:25458866

  14. Ion-Molecule Reactions

    NASA Astrophysics Data System (ADS)

    Farrar, James

    The observation of ion-molecule reactions has a history that goes back to the beginning of the twentieth century, when J. J. Thomson discovered that operating his positive ray parabola apparatus in a hydrogen atmosphere produced signals at a mass to charge ratio of 3, which he correctly attributed to the species H3 [67.1]. Later studies showed that this species was produced by a reaction between the primary ionization product H2 + and molecular hydrogen. Most ion-molecule reactions proceed without an activation barrier and their cross sections are governed by the long range attractive potential of the approaching reactants (Sect. 64.2.4). Reaction rates based on long range potential capture models [67.2] predict rates in excess of 10-9 cm3molecule-1s-1, corresponding to thermal energy cross sections (Sect. 47.1.7) of 10-16-10-15 cm2. The importance of ion-molecule reactions in such widely diverse areas as planetary atmospheres, (Sect. 84.1), electrical discharges and plasmas (Sect. 87.1.4), particularly in semiconductor processing, in the formation of molecules in interstellar space (Chapt. 82), and in flames and combustion systems (Sect. 88.1), has borne out that prediction. This chapter discusses applications of single-collision scattering methods to the study of reactive collision dynamics of ionic species with neutral partners.

  15. Theoretical Study ofTheoretical Study of ReactionReaction

    E-print Network

    . The program prints out the reaction rate in the Arrhenius form (k = A Tn exp(-Ea/RT)) over the temperature and enthalpy) in the polynomial form for 200-6000K temperature range. The reaction rate and the polynomial form was extended to a mechanism with 35 species and 1012 reactions. Rate constants for 117 elementary reactions

  16. Reaction/Momentum Wheel

    NASA Technical Reports Server (NTRS)

    1997-01-01

    CTA Space Systems, Inc. has been licensed to sell commercially a reaction/momentum wheel originally developed for NASA's scientific satellites. NASA originally identified a need for the wheel in its Small Explorer program. The Submillimeter Wave Astronomy Satellite required extremely low jitter and a reaction/momentum wheel with a torque greater than any comparably sized commercially available wheel to keep the instrument pointed at celestial objects to a high degree of precision. After development, a market assessment by Research Triangle Institute was completed, showing commercial potential for the flywheel technology. A license was granted to CTA in the fall of 1996. The company currently uses the technology in its complete spacecraft fabrication services and has built over 10 reaction/momentum wheels for commercial, scientific, and military customers.

  17. 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

  18. Microbial aldolases as C–C bonding enzymes—unknown treasures and new developments

    Microsoft Academic Search

    Anne K. Samland; Georg A. Sprenger

    2006-01-01

    Aldolases are a specific group of lyases that catalyze the reversible stereoselective addition of a donor compound (nucleophile) onto an acceptor compound (electrophile). Whereas most aldolases are specific for their donor compound in the aldolization reaction, they often tolerate a wide range of aldehydes as acceptor compounds. C–C bonding by aldolases creates stereocenters in the resulting aldol products. This makes

  19. Positron Reaction Microscope

    NASA Astrophysics Data System (ADS)

    Mueller, D. W.; Lee, C.; Vermet, C.; Armitage, S.; Slaughter, D.; Hargrave, L.; Dorn, A.; Brunton, J.; Buckman, S. J.; Sullivan, J. P.

    2012-06-01

    We are developing a positron reaction microscope to measure kinematically complete ionization reactions of atoms and dissociative ionization of simple molecules by positron impact. The experiment is designed to use the slow positron beamline at the ARC Centre for Antimatter Matter Studies (CAMS) node at the Australian National University (ANU). This project is a collaboration among the University of North Texas, CAMS, and the Max Planck Insitute for Kern Phyzik in Heidelberg. Initial measurements and apparatus calibration will be performed using electrons. For positron measurements, the apparatus will be rolled into position on the slow positron beamline at the CAMS site at ANU.

  20. Velocity pump reaction turbine

    DOEpatents

    House, Palmer A. (Walnut Creek, CA)

    1984-01-01

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  1. Velocity pump reaction turbine

    DOEpatents

    House, Palmer A. (Walnut Creek, CA)

    1982-01-01

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  2. Gas Producing Micro-Reaction

    NSDL National Science Digital Library

    2014-01-28

    In this chemistry activity, learners use common chemicals and metals to examine reactions that produce gaseous substances. Learners will identify the gases produced and write a balanced equation for each reaction. Use this activity to also introduce learners to single displacement and double displacement reactions, two types of chemical reactions.

  3. What Is a Reaction Rate?

    ERIC Educational Resources Information Center

    Schmitz, Guy

    2005-01-01

    The definition of reaction rate is derived and demonstrations are made for the care to be taken while using the term. Reaction rate can be in terms of a reaction property, the extent of reaction and thus it is possible to give a definition applicable in open and closed systems.

  4. 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)

  5. A Principal's Reaction

    ERIC Educational Resources Information Center

    Zaretsky, Lindy

    2004-01-01

    This article presents a principal's reaction to Catherine Marshall and Michael Ward's article on research on social justice and training for leadership. The author applauds Marshall and Ward's efforts to address what is undoubtedly among the most fundamentally important issues facing principals today. Marshall and Ward illuminate the importance of…

  6. Exocharmic Reactions up Close

    ERIC Educational Resources Information Center

    Ramette, R. W.

    2007-01-01

    The exocharmic reactions that can be observed microscopically are discussed. The students can discover the optimal concentration of an acidic lead nitrate solution, so that a crystal of potassium iodide, nudged to the edge of a drop, results in glinting golden hexagons of lead iodide.

  7. 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.

  8. 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

  9. Two chamber reaction furnace

    Microsoft Academic Search

    Blaugher; Richard D

    1998-01-01

    A vertical two chamber reaction furnace. 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.

  10. Two chamber reaction furnace

    Microsoft Academic Search

    Blaugher

    1998-01-01

    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

  11. 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

  12. 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.

  13. Chain Reaction Polymerization.

    ERIC Educational Resources Information Center

    McGrath, James E.

    1981-01-01

    The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

  14. Activationless photoionization reactions

    NASA Astrophysics Data System (ADS)

    Burshtein, A. I.; Morozov, V. A.

    1990-01-01

    The notion of an activationless zone appearing due to the space dispersion of the activation energy and vibronic excitation of reaction products is introduced. The effective radius viscosity dependence of pheophytin a quenching by toluquinone is compared with the theory, taking into account a strong interaction between them deep inside the activationless zone. The electron tunnelling probability is determined by fitting to experiment.

  15. 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…

  16. 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.

  17. Reaction Time Sound Explanation

    NSDL National Science Digital Library

    This experiment presents auditory stimuli and requires the participant to respond after hearing target stimuli under different conditions. This experiment gives students the opportunity to determine whether their reaction times are reliably different for tasks that require slightly different decisions. This page provides guidance for faculty who wish to incorporate this activity into their classroom.

  18. Reaction product imaging

    SciTech Connect

    Chandler, D.W. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    Over the past few years the author has investigated the photochemistry of small molecules using the photofragment imaging technique. Bond energies, spectroscopy of radicals, dissociation dynamics and branching ratios are examples of information obtained by this technique. Along with extending the technique to the study of bimolecular reactions, efforts to make the technique as quantitative as possible have been the focus of the research effort. To this end, the author has measured the bond energy of the C-H bond in acetylene, branching ratios in the dissociation of HI, the energetics of CH{sub 3}Br, CD{sub 3}Br, C{sub 2}H{sub 5}Br and C{sub 2}H{sub 5}OBr dissociation, and the alignment of the CD{sub 3} fragment from CD{sub 3}I photolysis. In an effort to extend the technique to bimolecular reactions the author has studied the reaction of H with HI and the isotopic exchange reaction between H and D{sub 2}.

  19. 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

  20. Photoneutron reactions in astrophysics

    NASA Astrophysics Data System (ADS)

    Varlamov, V. V.; Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.; Stopani, K. A.

    2014-12-01

    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 ? --decay processes. At the same time, we know 35 neutron-deficient so-called bypassed p-nuclei that lie between 74Se and 196Hg 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.

  1. Enzyme catalysed tandem reactions.

    PubMed

    Oroz-Guinea, Isabel; García-Junceda, Eduardo

    2013-04-01

    To transfer to the laboratory, the excellent efficiency shown by enzymes in Nature, biocatalysis, had to mimic several synthetic strategies used by the living organisms. Biosynthetic pathways are examples of tandem catalysis and may be assimilated in the biocatalysis field for the use of isolated multi-enzyme systems in the homogeneous phase. The concurrent action of several enzymes that work sequentially presents extraordinary advantages from the synthetic point of view, since it permits a reversible process to become irreversible, to shift the equilibrium reaction in such a way that enantiopure compounds can be obtained from prochiral or racemic substrates, reduce or eliminate problems due to product inhibition or prevent the shortage of substrates by dilution or degradation in the bulk media, etc. In this review we want to illustrate the developments of recent studies involving in vitro multi-enzyme reactions for the synthesis of different classes of organic compounds. PMID:23490810

  2. Cascade reactions in nanoreactors.

    PubMed

    van Oers, M C M; Rutjes, F P J T; van Hest, J C M

    2014-08-01

    In an attempt to mimic the biosynthetic efficiencies of nature and in a search for greener, more sustainable alternatives to nowadays ways of producing chemicals, one-pot cascade reactions have attracted a lot of attention in the past decade. Since most catalysts are not compatible with each other, compartmentalization techniques have often been applied to prevent catalyst inactivation. A various array of nanoreactors have been developed to meet the demand of having a site-isolated catalyst system, while maintaining the catalyst activity. Both multienzyme nanoreactors as well as enzyme/metal catalyst or organocatalyst systems have shown great potential in one-pot cascade reactions and hold promise for future developments in this field. PMID:24832069

  3. 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.

  4. Reactions to dietary tartrazine.

    PubMed

    David, T J

    1987-02-01

    Double blind challenges with tartrazine and benzoic acid were performed in hospital in 24 children whose parents gave a definite history of a purely behavioural immediate adverse reaction to one of these substances. The patients, whose ages ranged from 1.6 to 12.4 years, were on a diet that avoided these items, and in all there was a clear history that any lapse of the diet caused an obvious adverse behavioural reaction within two hours. In no patient was any change in behaviour noted either by the parents or the nursing staff after the administration of placebo or active substances. Twenty two patients returned to a normal diet without problems, but the parents of two children insisted on continuing the diet. While popular belief has it that additives may have harmful behavioural effects, objective verification is required to prevent overdiagnosis. PMID:3548601

  5. Reaction chemistry of cerium

    SciTech Connect

    NONE

    1997-01-01

    It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

  6. Heat Speeds Up Reactions

    NSDL National Science Digital Library

    Maisie Shaw

    2009-01-01

    In this activity, learners investigate the effect of heat on a reaction. Learners first model molecular motion by moving their bodies (running, moving slowly) and pretending to be molecules at different temperatures, then by using groups of cut-out shapes (not provided) which get rearranged when they collide. After this introduction, three glow sticks are activated—one is put in ice water, one in warm water, and one left at room temperature for 15 minutes. A comparison of which glow stick gives off the most light gives an indication of the speed of the molecules and the number of reactions occurring. (The activity was originally written as part of a kit to be checked out of the library, but the kit is not required.)

  7. Pathobiology of transfusion reactions.

    PubMed

    Zimring, James C; Spitalnik, Steven L

    2015-01-24

    Antibody-induced hemolytic transfusion reactions were first described over 300 years ago. Indeed, during its early evolution, transfusion medicine focused almost exclusively on issues in immunohematology to prevent such events. However, despite the best of efforts to avoid them, incompatible transfusions still occur, through both error and an inability to obtain compatible red blood cells for patients who are alloimmunized against multiple antigens. Because transfusing units of incompatible blood is potentially lethal, studies on human volunteers are not ethical. Thus, understanding of hemolytic transfusion reactions is generated through clinical cases, animal models, inference from related human pathologies, or studies using small volumes of transfused red blood cells. Over the past several decades, substantial new knowledge has been accumulated regarding the mechanisms of hemolysis, the metabolism of products of hemolysis, and the effects of both on recipient biology. Using these data sources, this article traces the historical generation of this knowledge and describes recent advances. PMID:25621658

  8. Polymerase Chain Reaction

    NSDL National Science Digital Library

    Teachers' Domain presents this interactive, adapted from the University of Nebraska's Library of Crop Technologies, with reading material and animations to help students learn the basic steps of polymerase chain reaction. Following the introduction, the lesson is divided four parts: Finding and Isolating DNA, Creating the DNA Solution, Begin Thermal Cycling, and Replication. Animations help students visualize each step of the processes described. On the site, visitors will also find a supplemental background essay, discussion questions, and standards alignment from Teachers' Domain.

  9. 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.

  10. Chemical Reactions in DSMC

    SciTech Connect

    Bird, G. A. [GAB Consulting Pty Ltd, 144/110 Sussex Street, Sydney NSW 2000 (Australia)

    2011-05-20

    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.

  11. 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

  12. Reaction Extrema: Extent of Reaction in General Chemistry

    ERIC Educational Resources Information Center

    Vandezande, Jonathon E.; Vander Griend, Douglas A.; DeKock, Roger L.

    2013-01-01

    Nearly 100 years ago de Donder introduced the term "extent of reaction", ?. We build on that work by defining the concept of reagent extrema for an arbitrary chemical reaction, aA + bB [reversible reaction] yY + zZ. The central equation is ?^[subscript i] = -n[subscript i,0]/?[subscript i]. The symbol ?^[subscript i] represents the…

  13. 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.

  14. Zip-lock Bag Reactions

    NSDL National Science Digital Library

    David A. Katz

    2009-07-09

    Students conduct and observe a chemical reaction in a sealable plastic bag. Students then devise and conduct their own experiments to determine the identity of two unknown substances used in the reaction.

  15. Demonstration of the Fenton Reaction

    ERIC Educational Resources Information Center

    Luehrs, Dean C.; Roher, Alex E.

    2007-01-01

    The study demonstrates the Fenton reaction, which is carried out using the Fenton reagent that is used for groundwater and soil remediation. The Fenton reaction can be implicated in DNA damage, Alzheimer's disease, cardiovascular disease and ageing in general.

  16. 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.

  17. ChemTeacher: Decomposition 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 Decomposition Reactions page includes resources for teaching students about identifying and predicting decomposition reactions.

  18. 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.

  19. Polymerase Chain Reaction Assay and

    E-print Network

    Paris-Sud XI, Université de

    Polymerase 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) and the national reference center for menin- gitis in Niger. The polymerase chain reaction (PCR) method

  20. 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.

  1. The Vitamin C Clock Reaction.

    ERIC Educational Resources Information Center

    Wright, Stephen W.

    2002-01-01

    Describes an iodine clock reaction that produces an effect similar to the Landolt clock reaction. This reaction uses supermarket chemicals and avoids iodate, bisulfite, and mercury compounds. Ascorbic acid and tincture of iodine are the main reactants with alternate procedures provided for vitamin C tablets and orange juice. (DDR)

  2. Double Replacement Micro-Reactions

    NSDL National Science Digital Library

    The Science House

    2014-01-28

    In this chemistry activity, learners use common chemicals to examine reactions that occur between two aqueous solutions. Learners will record any color changes or precipitate formation for each reaction as well as write a balanced equation for each. Learners will discover that the driving force for the reaction is the formation of an insoluble product.

  3. 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

  4. 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.

  5. Using Disproportionation Reaction

    E-print Network

    Preparation Of Nanosized Cu O; Cu Cu; O Mixture; Yousef Zeraatkish; Ezat Keshavarzi; Yousef Ghaeb; Kazem Karami; Saman Mousavian

    Abstract: In this study, copper (II) oxide and copper/copper (I) oxide mixture nanoparticles have been prepared via copper disproportionation reaction in non-aqueous solution. The performance of disproportionation reaction in dimethyl solfoxide (DMSO) was used to synthesis a Nano metallic element without any modification for the first time. Copper (I) Iodide (CuI), DMSO and ethylene diamine (en) have been used as copper (I) ion source, solvent and ligand, respectively. In this investigation the experiments were performed at two conditions. The products were characterized using both X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analysis of the solids produced at ambient atmosphere depicts the formation of pure copper (II) oxide (CuO) phase. The results also indicate that the achievement of the process after removal of oxygen and at N2 0 atmosphere yields a mixture of metallic copper (Cu) and copper (I) oxide (Cu2O). The SEM images of both products showed that the particle sizes are less than 100 nm and are spherical in shape.

  6. [Allergic drug reactions in children].

    PubMed

    Añibarro Bausela, B; Berto Salort, J M; García Ara, M C; Díaz Pena, J M; Ojeda Casas, J A

    1992-06-01

    We present a retrospective study of allergic drug reactions seen in our pediatric allergy consulting room during the last 6 years. During this time, 840 patients were examined for suspected adverse drug reactions. Drug allergy was confirmed in 72 cases (8.5%). Of these cases, 29 (40.2%) were considered to be IgE mediated, or immediate hypersensitivity reactions. We have not found significant differences with regards to age, sex, atopic family history or atopia between patients with IgE mediated reactions compared to patients with allergic drug reactions of different mechanisms or to patients without drug allergies. Sulfonamides, streptomycin, beta-lactam and analgesics were the drugs most frequently involved in immediate type reactions. Among non-immediate reactions, fixed eruption by sulfonamides and contact dermatitis due to Mercurochrome were the most frequent. PMID:1386717

  7. 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.

  8. Subdiffusion-reaction processes with A ?B reactions versus subdiffusion-reaction processes with A +B?B reactions

    NASA Astrophysics Data System (ADS)

    Koszto?owicz, Tadeusz; Lewandowska, Katarzyna D.

    2014-09-01

    We consider the subdiffusion-reaction process with reactions of a type A +B?B (in which particles A are assumed to be mobile, whereas B are assumed to be static) in comparison to the subdiffusion-reaction process with A ?B reactions which was studied by Sokolov, Schmidt, and Sagués [Phys. Rev. E 73, 031102 (2006), 10.1103/PhysRevE.73.031102]. In both processes a rule that reactions can only occur between particles which continue to exist is taken into account. Although in both processes a probability of the vanishing of particle A due to a reaction is independent of both time and space variables (assuming that in the system with the A +B?B reactions, particles B are distributed homogeneously), we show that subdiffusion-reaction equations describing these processes as well as their Green's functions are qualitatively different. The reason for this difference is as follows. In the case of the former reaction, particles A and B have to meet with some probability before the reaction occurs in contradiction with the case of the latter reaction. For the subdiffusion process with the A +B?B reactions we consider three models which differ in some details concerning a description of the reactions. We base the method considered in this paper on a random walk model in a system with both discrete time and discrete space variables. Then the system with discrete variables is transformed into a system with both continuous time and continuous space variables. Such a method seems to be convenient in analyzing subdiffusion-reaction processes with partially absorbing or partially reflecting walls. The reason is that within this method we can determine Green's functions without a necessity of solving a fractional differential subdiffusion-reaction equation with boundary conditions at the walls. As an example, we use the model to find the Green's functions for a subdiffusive reaction system (with the reactions mentioned above), which is bounded by a partially absorbing wall. This example shows how the model can be used to analyze the subdiffusion-reaction process in a system with partially absorbing or reflecting thin membranes. Employing a simple phenomenological model, we also derive equations related to the reaction parameters used in the considered models.

  9. Reactions of the Formamidines

    E-print Network

    Myers, Tennyson

    1912-06-01

    . This sesquichloride will react with two molecules of an amine giving one molecmle of a substituted formamidine and one molecule of forma m idine itself. I.HN : CH # NCHC1 # HC1 4 R1TH = HN : CH NH CH NR - 3 HC1 o •c. II. HN : CH NH CHNR - 3 HC1 + HNHR = znH .NHR... on carbodia^idh/ a body of the following type was formed. R - NH ~C 0 C H 3 J^C- CH ^ R N ^ COOR The aminomethylene derivatives of the general form R N H * CH: CXY which can be made by this reaction have been in part described by Claissen % Ann.d. Chem...

  10. Intermolecular reaction screening as a tool for reaction evaluation.

    PubMed

    Collins, Karl D; Glorius, Frank

    2015-03-17

    Synthetic organic chemistry underpins many scientific disciplines. The development of new synthetic methods proceeds with the ultimate intention of providing access to novel structural motifs or providing safer, increasingly efficient, or more economical chemical reactions. To facilitate the identification and application of new methods in solving real synthetic problems, this Account will highlight the benefits of providing a fuller picture of both the scope and limitations of new reactions, with a primary focus on the evaluation of functional group tolerance and stability of a reaction using intermolecular screens. This Account will begin with a discussion on reaction evaluation, specifically considering the suitability of a given reaction for application in target-oriented synthesis. A comparison of desirable and essential criteria when choosing a reaction is given, and a short discussion on the value of negative and qualitative data is provided. The concept of intermolecular reaction screening will be introduced, and a direct comparison with a traditional substrate scope highlights the benefits and limitations of each and thus the complementary nature of these approaches. In recent years, a number of ad hoc applications of intermolecular screens to evaluate the functional group tolerance of a reaction or the stability of functional groups to a given set of reaction conditions have been reported, and will be discussed. More recently, we have developed a formal high-throughput intermolecular screening protocol that can be utilized to rapidly evaluate new chemical reactions. This simple and rapid protocol enables a much broader evaluation of a reaction in terms of functional group tolerance and the stability of chemical motifs to the reaction conditions than is feasible with a typical reaction scope. The development, evaluation, and application of this method within our group will be discussed in detail, with both the potential benefits and limitations highlighted and discussed. In addition, we will discuss more recent applications of intermolecular screens from both industrial and academic groups. Modifications in protocols and applications will be highlighted, including problem based evaluations, assessment of biomolecule compatibility, establishment of relative rate data, and the identification of new reactivity. Such screens have been applied in diverse chemistries including C-H functionalization reactions, frustrated Lewis-pair-catalyzed hydrogenations, heterogeneous catalysis, photoredox catalysis, enantioselective organocatalysis, and polymer science. We feel that the application of intermolecular screens to such a diversity of reactions highlights the practical simplicity of such screens. A summary of the applications and potential utility of intermolecular reaction evaluation is provided. PMID:25699585

  11. ChemTeacher Resource: Oxidation Reduction Reactions

    NSDL National Science Digital Library

    2012-08-02

    This computer resource goes over oxidation reduction reactions and how they are broken down into half reactions. It explains which half reaction is the oxidation reaction and which one is the reduction, then has some summary questions at the end.

  12. Asymmetric Aldol-Ring-Closing Metathesis Strategy for the Enantioselective

    E-print Network

    .; Danishefsky, S. J.; Zheng, Y.-H.; Chou, T.-C.; He, L.; Horwitz, S. B. J. Am. Chem. Soc. 1996, 119, 2733- 5177. FAX: (919) 962-2388. E-mail: mtc@net.chem.unc.edu. (1) Grubbs, R. H.; Miller, S. J., Fu, G. C.; Giles, M. R.; Marshall, E. L.; Procopiou, P. A. J. Chem. Soc. Chem. Commun. 1997, 155-156. Huwe, C. M

  13. Change in Temperature: Exothermic Reaction

    NSDL National Science Digital Library

    James H. Kessler

    2007-01-01

    Learners add calcium chloride to a baking soda solution and observe an increase in temperature along with the production of a gas and a white precipitate. These are all signs of a chemical reaction. Learners can quantify the results of the reaction by using a thermometer to measure the temperature change. Learners also design their own experiment to alter the reaction and measure how it affects the change in temperature.

  14. Nuclear astrophysics from direct reactions

    E-print Network

    C. A. Bertulani

    2009-01-22

    Accurate nuclear reaction rates are needed for primordial nucleosynthesis and hydrostatic burning in stars. The relevant reactions are extremely difficult to measure directly in the laboratory at the small astrophysical energies. In recent years direct reactions have been developed and applied to extract low-energy astrophysical S-factors. These methods require a combination of new experimental techniques and theoretical efforts, which are the subject of this presentation.

  15. Microstructured reactors for catalytic reactions

    Microsoft Academic Search

    Lioubov Kiwi-Minsker; Albert Renken

    2005-01-01

    This review addresses the catalytic reactions performed in microstructured reactors, which are more and more recognized in recent years as a novel approach for chemistry and chemical process industry. They are particularly suited for highly exothermic and fast reactions allowing temperature control and isothermal operation. A brief evaluation of the advantages for gas-phase, liquid-phase, and gas–liquid–solid reactions carried out in

  16. Thermodynamic properties of isomerization reactions

    SciTech Connect

    Frenkel, M.L.; Kabo, G.Ya.; Roganov, G.H.

    1992-10-01

    In handbook form, this book provides both experimental and theoretical data describing thermodynamic properties of groups of isomers of different classes, particularly for organic compound reactions. Data have been derived through chemical equilibria studies, statistical thermodynamics, and to some degree, calorimetry. Data based on equilibria studies are also valuable as a cross-check to thermodynamic functions derived purely from calorimetric measurements. Unique in its presentation, this book systematizes available data and compiles nearly 1,000 isomerization reactions of organic compounds. Contents include: specific aspects of determining the thermodynamic properties of isomerization reactions; qualitative regularities of changes in the enthalpy ad entropy functions of isomerization reactions; and description of tables.

  17. Hypersensitivity reactions to biological drugs.

    PubMed

    Corominas, M; Gastaminza, G; Lobera, T

    2014-01-01

    Strictly speaking, biological drugs are defined as drugs obtained using biotechnology that act on the immune system. They encompass monoclonal antibodies, fusion proteins, and cytokines. Although they are restricted to specific diseases, they have been increasingly used in recent years, with the consequent reporting of adverse reactions, many of which occur during the postmarketing phase. Because of the characteristics of adverse reactions, a new classification has been proposed. Hypersensitivity reactions are beta-type reactions and include infusion reactions and injection site reactions. In some cases, an immune mechanism mediated by IgE, IgG, or T cells is involved. Clinical symptoms vary widely, from skin reactions to anaphylaxis. Diagnostic studies are based on skin tests and in vitro tests (specific IgE, basophil activation test). Most are not standardized and are conducted in small groups of patients, thus making it impossible to obtain sensitivity and specificity values. With some biological drugs, desensitization protocols have proven successful. In this review, we discuss hypersensitivity reactions to biological drugs and the diagnostic tests used to assess these reactions. PMID:25219103

  18. SABIO Reaction Kinetics Database (Homepage)

    NSDL National Science Digital Library

    Scientific Databases and Visualization Group at the EML Research in Heidelberg, Germany

    The SABIO-RK (System for the Analysis of Biochemical Pathways - Reaction Kinetics) is a web-based application based on the SABIO relational database that contains information about biochemical reactions, their kinetic equations with their parameters, and the experimental conditions under which these parameters were measured. It aims to support modellers in the setting-up of models of biochemical networks, but it is also useful for experimentalists or researchers with interest in biochemical reactions and their kinetics. Information about reactions and their kinetics can be exported in SBML (Systems Biology Mark-Up Language) format.

  19. 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).

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

    E-print Network

    Zare, Richard N.

    internuclear axis efficiently couples to the reaction coordinate, that is, the set of motions that transforms enhances the reaction by a factor of approximately 30.[2] The effects of reagent bending vibrations-frequency vibrations are more easily populated at thermal temperatures. To date, the influence of bending vibrations

  1. Dynamic Reaction Figures: An Integrative Vehicle for Understanding Chemical Reactions

    ERIC Educational Resources Information Center

    Schultz, Emeric

    2008-01-01

    A highly flexible learning tool, referred to as a dynamic reaction figure, is described. Application of these figures can (i) yield the correct chemical equation by simply following a set of menu driven directions; (ii) present the underlying "mechanism" in chemical reactions; and (iii) help to solve quantitative problems in a number of different…

  2. Chemoenzymatic Synthesis of Vitamin B5-Intermediate (R)-Pantolactone via Combined Asymmetric Organo- and Biocatalysis.

    PubMed

    Heidlindemann, Marcel; Hammel, Matthias; Scheffler, Ulf; Mahrwald, Rainer; Hummel, Werner; Berkessel, Albrecht; Gröger, Harald

    2015-04-01

    The combination of an asymmetric organocatalytic aldol reaction with a subsequent biotransformation toward a "one-pot-like" process for the synthesis of (R)-pantolactone, which to date is industrially produced by a resolution process, is demonstrated. This process consists of an initial aldol reaction catalyzed by readily available l-histidine followed by biotransformation of the aldol adduct by an alcohol dehydrogenase without the need for intermediate isolation. Employing the industrially attractive starting material isobutanal, a chemoenzymatic three-step process without intermediate purification is established allowing the synthesis of (R)-pantolactone in an overall yield of 55% (three steps) and high enantiomeric excess of 95%. PMID:25710713

  3. Charge Transfer Reactions

    NASA Astrophysics Data System (ADS)

    Dennerl, Konrad

    2010-12-01

    Charge transfer, or charge exchange, describes a process in which an ion takes one or more electrons from another atom. Investigations of this fundamental process have accompanied atomic physics from its very beginning, and have been extended to astrophysical scenarios already many decades ago. Yet one important aspect of this process, i.e. its high efficiency in generating X-rays, was only revealed in 1996, when comets were discovered as a new class of X-ray sources. This finding has opened up an entirely new field of X-ray studies, with great impact due to the richness of the underlying atomic physics, as the X-rays are not generated by hot electrons, but by ions picking up electrons from cold gas. While comets still represent the best astrophysical laboratory for investigating the physics of charge transfer, various studies have already spotted a variety of other astrophysical locations, within and beyond our solar system, where X-rays may be generated by this process. They range from planetary atmospheres, the heliosphere, the interstellar medium and stars to galaxies and clusters of galaxies, where charge transfer may even be observationally linked to dark matter. This review attempts to put the various aspects of the study of charge transfer reactions into a broader historical context, with special emphasis on X-ray astrophysics, where the discovery of cometary X-ray emission may have stimulated a novel look at our universe.

  4. 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.

  5. Two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D. (Evergreen, CO)

    1998-05-05

    A vertical two chamber reaction furnace. 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.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. 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.

  6. 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.

  7. Mechanism of pyrazole formation in [ 13C-2] labeled glycine model systems: N–N bond formation during Maillard reaction

    Microsoft Academic Search

    Varoujan A. Yaylayan; Luke J. W. Haffenden

    2003-01-01

    Studies with 13C-2 labeled glycine in model systems containing 3-hydroxy-2-butanone or glyceraldehyde have indicated that the ?-dicarbonyl compounds, the immediate precursors of pyrazoles, are produced in Maillard model systems through two pathways. One pathway involves dehydration of ?,?-dihydroxy carbonyl compounds with elimination of the ?-hydroxyl group and the other through aldol condensation of an ?-hydroxy carbonyl compound with simple aldehydes

  8. "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…

  9. Parent Reactions to Childhood Phenylketonuria

    Microsoft Academic Search

    Bruce Lord; Colin Wastell; Judy Ungerer

    2005-01-01

    Parents play a prominent role in the early management of phenylketonuria (PKU). This study examines parent trauma reactions to PKU, the nature of parent concerns about PKU, and social relationship variables predicting parent trauma reactions. Questionnaires were completed by 65 mothers and 61 fathers of children aged 3 months to 12 years. Most parents reported mild levels of trauma. Intrusive

  10. Acute dystonic reaction with rivastigmine.

    PubMed

    Dhikav, Vikas; Anand, Kuljeet Singh

    2013-08-01

    Dystonic reactions are adverse extrapyramidal side effects and are common to antipsychotics, antiemetics, and a variety of other drugs. Rivastigmine, an anticholinesterase of carbamate variety, is well tolerated. A case of acute dystonic reaction with rivastigmine patch is being reported. PMID:23561545

  11. Pharmacogenomics of adverse drug reactions

    PubMed Central

    2013-01-01

    Considerable progress has been made in identifying genetic risk factors for idiosyncratic adverse drug reactions in the past 30 years. These reactions can affect various tissues and organs, including liver, skin, muscle and heart, in a drug-dependent manner. Using both candidate gene and genome-wide association studies, various genes that make contributions of varying extents to each of these forms of reactions have been identified. Many of the associations identified for reactions affecting the liver and skin involve human leukocyte antigen (HLA) genes and for reactions relating to the drugs abacavir and carbamazepine, HLA genotyping is now in routine use prior to drug prescription. Other HLA associations are not sufficiently specific for translation but are still of interest in relation to underlying mechanisms for the reactions. Progress on non-HLA genes affecting adverse drug reactions has been less, but some important associations, such as those of SLCO1B1 and statin myopathy, KCNE1 and drug-induced QT prolongation and NAT2 and isoniazid-induced liver injury, are considered. Future prospects for identification of additional genetic risk factors for the various adverse drug reactions are discussed. PMID:23360680

  12. Nuclear Reactions and Reactor Safety

    E-print Network

    Onuchic, José

    successful nuclear power "plant" : 1942 Famous names: J Robert Oppenheimer, Richard Feynman, Enrico Fermi to ask me some questions about the plot! #12;Nuclear Chain Reactions to Nuclear Power Plants And now, we explosions? or ? -Controlled nuclear chain reactions possible: control energy release/sec -> More

  13. 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

  14. Adverse Reactions to Hallucinogenic Drugs.

    ERIC Educational Resources Information Center

    Meyer, Roger E. , Ed.

    This reports a conference of psychologists, psychiatrists, geneticists and others concerned with the biological and psychological effects of lysergic acid diethylamide and other hallucinogenic drugs. Clinical data are presented on adverse drug reactions. The difficulty of determining the causes of adverse reactions is discussed, as are different…

  15. Organocatalytic enantioselective multicomponent reactions (OEMCRs)

    Microsoft Academic Search

    Gabriela Guillena; Diego J. Ramón; Miguel Yus

    2007-01-01

    The achieved level of expertise in organocatalytic processes has allowed synthetic chemists to apply this useful synthetic strategy to enantioselective multicomponent reactions. Although, this new methodology is still in its infancy, the reported results show the possibilities and versatility of this type of reaction, with an extraordinary level of atom efficiency being reached. All examples, from classical Mannich, Biginelli, Michael,

  16. Allergic reactions to insect secretions.

    PubMed

    Pecquet, Catherine

    2013-01-01

    Some products derived from insects can induce allergic reactions. The main characteristics of some products from honeybees, cochineal and silkworms are summarised here. We review allergic reactions from honey-derived products (propolis, wax, royal jelly), from cochineal products (shellac and carmine) and from silk : clinical features, allergological investigations and allergens if they are known. PMID:24449611

  17. Chemistry of heavy ion reactions

    SciTech Connect

    Hoffman, D.C.

    1988-10-01

    The use of heavy ions to induce nuclear reactions was reported as early as 1950. Since that time it has been one of the most active areas of nuclear research. Intense beams of ions as heavy as uranium with energies high enough to overcome the Coulomb barriers of even the heaviest elements are available. The wide variety of possible reactions gives rise to a multitude of products which have been studied by many ingenious chemical and physical techniques. Chemical techniques have been of special value for the separation and unequivocal identification of low yield species from the plethora of other nuclides present. Heavy ion reactions have been essential for the production of the trans-Md elements and a host of new isotopes. The systematics of compound nucleus reactions, transfer reactions, and deeply inelastic reactions have been elucidated using chemical techniques. A review of the variety of chemical procedures and techniques which have been developed for the study of heavy ion reactions and their products is given. Determination of the chemical properties of the trans-Md elements, which are very short-lived and can only be produced an ''atom-at-a-time'' via heavy ion reactions, is discussed. 53 refs., 19 figs.

  18. Endothermic photo-catalytic reactions

    SciTech Connect

    Prengle, H.W. Jr.; Wentworth, W.E.; Polonczyk, K.C.; Saghafi, M.; Wilking, J.A.; Kramer, K.S. (Houston Univ., TX (United States))

    1992-04-01

    The overall objective of this report is to present the results of an investigation to provide guidelines for future experimental work, on solar energy driven endothermic photo-catalytic reactions, and primarily to select candidate synthesis reactions which lead to high $-value products. An intensive literature search was conducted to find properties, market demand, and prices of pertinent chemicals; meeting four criteria: (1) the reaction must be endothermic and favorable; (2) the reaction must be catalytic; (3) the product must be produced from low cost feedstocks; and (4) the product must have a sales price >$1.00/lb. Initial examination of low cost feedstocks to high value products lead to consideration of n-paraffins to aromatics and substituted aromatics. Fifteen candidate endothermic synthesis reactions, meeting the above criteria, are suggested. The ratio of product price by reactant cost indicates {approximately}5--8 for the best possibilities; all can be visualized as starting with low cost paraffin and methanol feedstocks.

  19. Directed Mizoroki-Heck Reactions

    NASA Astrophysics Data System (ADS)

    Oestreich, Martin

    The Mizoroki-Heck reaction is one of the key C-C bond-forming processes in organic synthesis. A prominent variant, which has found broadest application in targeted complex molecule synthesis, is the asymmetric intramolecular Mizoroki-Heck reaction. This methodology has outshone another powerful facet of Mizoroki-Heck chemistry, which has been prospering in recent years, namely directed Mizoroki-Heck reactions. Initially designed to achieve high regiocontrol in intermolecular reactions, this technique has recently been extended to highly diastereoselective and even enantioselective substrate-directed inter- as well as intramolecular Mizoroki-Heck reactions. This summary delineates the evolution of this chemistry from regio- to diastereo- and finally, enantioselective transformations.

  20. Fundamental reaction pathways during coprocessing

    SciTech Connect

    Stock, L.M.; Gatsis, J.G. (Chicago Univ., IL (United States). Dept. of Chemistry)

    1992-12-01

    The objective of this research was to investigate the fundamental reaction pathways in coal petroleum residuum coprocessing. Once the reaction pathways are defined, further efforts can be directed at improving those aspects of the chemistry of coprocessing that are responsible for the desired results such as high oil yields, low dihydrogen consumption, and mild reaction conditions. We decided to carry out this investigation by looking at four basic aspects of coprocessing: (1) the effect of fossil fuel materials on promoting reactions essential to coprocessing such as hydrogen atom transfer, carbon-carbon bond scission, and hydrodemethylation; (2) the effect of varied mild conditions on the coprocessing reactions; (3) determination of dihydrogen uptake and utilization under severe conditions as a function of the coal or petroleum residuum employed; and (4) the effect of varied dihydrogen pressure, temperature, and residence time on the uptake and utilization of dihydrogen and on the distribution of the coprocessed products. Accomplishments are described.

  1. Sodium concrete reaction: structural considerations

    SciTech Connect

    Freskakis, G.N.

    1984-09-01

    An overview of the sodium concrete reaction phenomenon, with emphasis on structural considerations, is presented. Available test results for limestone, basalt, and magnetite concrete with various test article configurations are reviewed. Generally, tests indicate reaction is self limiting before all sodium is used. Uncertainties, however, concerning the mechanism for penetration of sodium into concrete have resulted in different theories about a reaction model. Structural behavior may be significant in the progression of the reaction due to thermal-structural-chemical interactions involving tensile cracking, compressive crushing, or general deterioration of concrete and the exposure of fresh concrete surfaces to react with sodium. Structural behavior of test articles and potential factors that could enhance the progression of the reaction are discussed.

  2. Large scale total synthesis of apoptolidinone and progress towards the total synthesis of ammocidin

    E-print Network

    Liu, Qingsong

    2009-05-15

    apoptolidinone 1.26 by an intra-molecular Horner-Wadsworth-Emmons approach featuring a Suzuki coupling, cross metathesis and two diastereoselective aldol reactions is discussed. 15 mg apoptolidinone is prepared via our previously developed intramolecular Suzuking...

  3. Integrated Microreactors for Reaction Automation: New Approaches to Reaction Development

    NASA Astrophysics Data System (ADS)

    McMullen, Jonathan P.; Jensen, Klavs F.

    2010-07-01

    Applications of microsystems (microreactors) in continuous-flow chemistry have expanded rapidly over the past two decades, with numerous reports of higher conversions and yields compared to conventional batch benchtop equipment. Synthesis applications are enhanced by chemical information gained from integrating microreactor components with sensors, actuators, and automated fluid handling. Moreover, miniaturized systems allow experiments on well-defined samples at conditions not easily accessed by conventional means, such as reactions at high pressure and temperatures. The wealth of synthesis information that could potentially be acquired through use of microreactors integrated with physical sensors and analytical chemistry techniques for online reaction monitoring has not yet been well explored. The increased efficiency resulting from use of continuous-flow microreactor platforms to automate reaction screening and optimization encourages a shift from current batchwise chemical reaction development to this new approach. We review advances in this new area and provide application examples of online monitoring and automation.

  4. Theoretical StudyTheoretical Study ofof ReactionReaction

    E-print Network

    of boron nitride films was developed. The gas-phase mechanism includes 35 species and 1012 reactions considerable interest in recent years, in the growth of boron nitride thin films Ã? Like carbon, boron nitride

  5. 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

  6. 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

  7. 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.

  8. Nuclear Reactions & Scaling Arguments 11 October 2011

    E-print Network

    Militzer, Burkhard

    Nuclear Reactions & Scaling Arguments 11 October 2011 Goals · Review nuclear reaction rates · Practice using scaling arguments Nuclear Reactions 1. Consider the simple reaction A k1 ---- B k2 ---- C rate for something like p + p D scales like n2 p. Think in microscopic terms. #12;nuclear 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. 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.

  11. Reaction detection in liquid chromatography

    SciTech Connect

    Krull, I.S.

    1986-01-01

    High-performance liquid chromatography (HPLC) has developed to such a degree that analytical chemists are now ''specialists'' in various subcategories of HPLC, including on-line sample concentration, valve switching, boxcar chromatography, multi-columns, multiple detection, selective detection, post-column reaction detectors, among others. This volume summarizes and describes reactions and reaction detectors in HPLC. To date, HPLC has lacked a truly general and highly sensitive detector. Many general or selective detectors have appeared in the literature -- some more useful and practical than others -- but none has met the need for specific and sensitive detection approached in LC. Post-column chemical, photochemical, or enzymatic reactions offer promising theoretical and applied detection venues for HPLC. This reference reviews the extensive literature on the subject and familiarizes readers with where this area of science and technology stands today.

  12. 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.

  13. 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.

  14. Direct reactions with radioactive beams

    NASA Astrophysics Data System (ADS)

    Bonaccorso, Angela

    2014-07-01

    Since the first measurements in the 80's of total reaction cross sections from radioactive beams up to the most recent and advanced exclusive experiments for dripline unbound nuclei, our understanding of exotic nuclei has greatly evolved. This has been possible through a joint effort in the description of the reaction mechanisms and of the underlying nuclear structure. Most exotic nuclei are weakly bound due to the excess of either neutrons or protons and they breakup easily in peripheral reactions. We will discuss in this paper the mechanism responsible for nuclear and Coulomb breakup. Some open problems will be discussed in detail, such as kinematical effects on core parallel momentum distributions and the possibility and consequences that such cores be themselves weakly bound. A general framework for the reaction theory will be used, based on a time dependent perturbation theory approach. Its eikonal limit will be also mentioned.

  15. Experimental Study of Serpentinization Reactions

    NASA Technical Reports Server (NTRS)

    Cohen, B. A.; Brearley, A. J.; Ganguly, J.; Liermann, H.-P.; Keil, K.

    2004-01-01

    Current carbonaceous chondrite parent-body thermal models [1-3] produce scenarios that are inconsistent with constraints on aqueous alteration conditions based on meteorite mineralogical evidence, such as phase stability relationships within the meteorite matrix minerals [4] and isotope equilibration arguments [5, 6]. This discrepancy arises principally because of the thermal runaway effect produced by silicate hydration reactions (here loosely called serpentinization, as the principal products are serpentine minerals), which are so exothermic as to produce more than enough heat to melt more ice and provide a self-sustaining chain reaction. One possible way to dissipate the heat of reaction is to use a very small parent body [e.g., 2] or possibly a rubble pile model. Another possibility is to release this heat more slowly, which depends on the alteration reaction path and kinetics.

  16. Adalimumab induced pulmonary sarcoid reaction

    PubMed Central

    Bhargava, S.; Perlman, D.M.; Allen, T.L.; Ritter, J.H.; Bhargava, M.

    2013-01-01

    Sarcoidosis is a multisystem granulomatous inflammatory disease of unknown etiology. There is evidence that Tumor Necrosis Factor alpha (TNF-?) antagonists are useful in the treatment of advanced or refractory disease. However, sarcoidosis-like reaction has been reported with TNF-? blockade in other inflammatory conditions. Here we report a case of sarcoid-like reaction in a patient with psoriatic arthritis shortly after initiation of adalimumab therapy. Stopping adalimumab and systemic anti-inflammatory therapy with corticosteroids resulted in resolution of pulmonary symptoms and chest radiographic findings. Though TNF-? plays a critical role in pathogenesis of sarcoidosis, the development of sarcoid reaction with TNF-? blockade is paradoxical and the mechanism of this response remains unknown. TNF-? induced sarcoid-reaction could involve multiple organs. Its development with one agent does not preclude therapy with other TNF-? blockers.

  17. Positive reaction to allergen (image)

    MedlinePLUS

    ... a sensitivity to a specific substance, called an allergen, that is contacted through the skin, inhaled into ... swallowed or injected. The body's reaction to an allergen can be mild, such as a localized rash, ...

  18. Reaction-driven viscous fingering

    NASA Astrophysics Data System (ADS)

    de Wit, A.; Riolfo, L. A.; Iwata, S.; Maes, R.; Trevelyan, P. M. J.; Nagatsu, Y.

    2011-11-01

    An experimental demonstration of reaction-driven viscous fingering developing when a more viscous solution of a reactant A displaces a less viscous miscible solution of another reactant B is presented. In the absence of reaction, such a displacement of one fluid by another more mobile one is classically stable. However, a simple A+B ->C reaction can destabilize this interface if the product C is either more or less viscous than both reactant solutions. Using the pH dependence of the viscosity of some polymer solutions, we provide experimental evidence of both scenarios. We demonstrate quantitatively that reactive viscous fingering results from the build-up in time of non-monotonic viscosity profiles with patterns behind or ahead of the reaction zone respectively depending on whether the product is more or less viscous than the reactants. The experimental findings are backed up by numerical simulations.

  19. 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 ...

  20. 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

  1. Thermodynamics of Random Reaction Networks

    PubMed Central

    Fischer, Jakob; Kleidon, Axel; Dittrich, Peter

    2015-01-01

    Reaction networks are useful for analyzing reaction systems occurring in chemistry, systems biology, or Earth system science. Despite the importance of thermodynamic disequilibrium for many of those systems, the general thermodynamic properties of reaction networks are poorly understood. To circumvent the problem of sparse thermodynamic data, we generate artificial reaction networks and investigate their non-equilibrium steady state for various boundary fluxes. We generate linear and nonlinear networks using four different complex network models (Erd?s-Rényi, Barabási-Albert, Watts-Strogatz, Pan-Sinha) and compare their topological properties with real reaction networks. For similar boundary conditions the steady state flow through the linear networks is about one order of magnitude higher than the flow through comparable nonlinear networks. In all networks, the flow decreases with the distance between the inflow and outflow boundary species, with Watts-Strogatz networks showing a significantly smaller slope compared to the three other network types. The distribution of entropy production of the individual reactions inside the network follows a power law in the intermediate region with an exponent of circa ?1.5 for linear and ?1.66 for nonlinear networks. An elevated entropy production rate is found in reactions associated with weakly connected species. This effect is stronger in nonlinear networks than in the linear ones. Increasing the flow through the nonlinear networks also increases the number of cycles and leads to a narrower distribution of chemical potentials. We conclude that the relation between distribution of dissipation, network topology and strength of disequilibrium is nontrivial and can be studied systematically by artificial reaction networks. PMID:25723751

  2. 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

  3. Cutaneous adverse reactions to lenalidomide.

    PubMed

    Imbesi, S; Allegra, A; Calapai, G; Musolino, C; Gangemi, S

    2015-01-01

    Lenalidomide is an immunomodulatory drug (IMiD) used principally in the treatment of multiple myeloma (MM), myelodysplastic syndromes (MS) and amyloidosis. Adverse reactions related to lenalidomide include myelosuppression (mainly neutropenia but also thrombocytopenia), gastrointestinal problems, skin eruption, atrial fibrillation and asthenia, decreased peripheral blood stem cell yield during stem cell collection, venous thromboembolism, and secondary malignances. In this review we focused our attention on the cutaneous adverse reactions to lenalidomide. PMID:24998775

  4. Vibrational excitation induces double reaction.

    PubMed

    Huang, Kai; Leung, Lydie; Lim, Tingbin; Ning, Zhanyu; Polanyi, John C

    2014-12-23

    Electron-induced reaction at metal surfaces is currently the subject of extensive study. Here, we broaden the range of experimentation to a comparison of vibrational excitation with electronic excitation, for reaction of the same molecule at the same clean metal surface. In a previous study of electron-induced reaction by scanning tunneling microscopy (STM), we examined the dynamics of the concurrent breaking of the two C-I bonds of ortho-diiodobenzene physisorbed on Cu(110). The energy of the incident electron was near the electronic excitation threshold of E0=1.0 eV required to induce this single-electron process. STM has been employed in the present work to study the reaction dynamics at the substantially lower incident electron energies of 0.3 eV, well below the electronic excitation threshold. The observed increase in reaction rate with current was found to be fourth-order, indicative of multistep reagent vibrational excitation, in contrast to the first-order rate dependence found earlier for electronic excitation. The change in mode of excitation was accompanied by altered reaction dynamics, evidenced by a different pattern of binding of the chemisorbed products to the copper surface. We have modeled these altered reaction dynamics by exciting normal modes of vibration that distort the C-I bonds of the physisorbed reagent. Using the same ab initio ground potential-energy surface as in the prior work on electronic excitation, but with only vibrational excitation of the physisorbed reagent in the asymmetric stretch mode of C-I bonds, we obtained the observed alteration in reaction dynamics. PMID:25489788

  5. 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

  6. Expert system for predicting reaction conditions: the Michael reaction case.

    PubMed

    Marcou, G; Aires de Sousa, J; Latino, D A R S; de Luca, A; Horvath, D; Rietsch, V; Varnek, A

    2015-02-23

    A generic chemical transformation may often be achieved under various synthetic conditions. However, for any specific reagents, only one or a few among the reported synthetic protocols may be successful. For example, Michael ?-addition reactions may proceed under different choices of solvent (e.g., hydrophobic, aprotic polar, protic) and catalyst (e.g., Brønsted acid, Lewis acid, Lewis base, etc.). Chemoinformatics methods could be efficiently used to establish a relationship between the reagent structures and the required reaction conditions, which would allow synthetic chemists to waste less time and resources in trying out various protocols in search for the appropriate one. In order to address this problem, a number of 2-classes classification models have been built on a set of 198 Michael reactions retrieved from literature. Trained models discriminate between processes that are compatible and respectively processes not feasible under a specific reaction condition option (feasible or not with a Lewis acid catalyst, feasible or not in hydrophobic solvent, etc.). Eight distinct models were built to decide the compatibility of a Michael addition process with each considered reaction condition option, while a ninth model was aimed to predict whether the assumed Michael addition is feasible at all. Different machine-learning methods (Support Vector Machine, Naive Bayes, and Random Forest) in combination with different types of descriptors (ISIDA fragments issued from Condensed Graphs of Reactions, MOLMAP, Electronic Effect Descriptors, and Chemistry Development Kit computed descriptors) have been used. Models have good predictive performance in 3-fold cross-validation done three times: balanced accuracy varies from 0.7 to 1. Developed models are available for the users at http://infochim.u-strasbg.fr/webserv/VSEngine.html . Eventually, these were challenged to predict feasibility conditions for ?50 novel Michael reactions from the eNovalys database (originally from patent literature). PMID:25588070

  7. Polarization phenomena in collinear reactions

    SciTech Connect

    Moravcsik, M.J.; Arash, F.

    1985-06-01

    It is shown for a collinear reaction containing four particles with arbitrary spins which amplitudes remain nonzero and how they are related to the observables. In terms of primary observables all submatrices relating products of amplitudes to observables either vanish or turn into one-by-one submatrices, except the 8/sub i/ types which may turn into three-by-three submatrices, but these latter submatrices are mostly avoidable when determining amplitudes. In terms of the secondary observables the 1/sub M/ and 2/sub i/ submatrices are slightly larger. Specifically, it is shown that in collinear reactions all observables in which only one particle is polarized (no matter how) vanish. Since reactions at very high energies are expected to be predominantly very close to being collinear, the smallness of such observables in such reactions can be expected on general grounds but polarization effects involving observables with more than one polarized particle can very well be very large. An iterative approximation method for the polarization analysis of reactions at very high energies is suggested. The results of this paper are also applicable to all models in which helicity conservation holds, since they are, for all t values, formally identical with collinear reactions.

  8. Kinetics of actinide complexation reactions

    SciTech Connect

    Nash, K.L.; Sullivan, J.C.

    1997-09-01

    Though the literature records extensive compilations of the thermodynamics of actinide complexation reactions, the kinetics of complex formation and dissociation reactions of actinide ions in aqueous solutions have not been extensively investigated. In light of the central role played by such reactions in actinide process and environmental chemistry, this situation is somewhat surprising. The authors report herein a summary of what is known about actinide complexation kinetics. The systems include actinide ions in the four principal oxidation states (III, IV, V, and VI) and complex formation and dissociation rates with both simple and complex ligands. Most of the work reported was conducted in acidic media, but a few address reactions in neutral and alkaline solutions. Complex formation reactions tend in general to be rapid, accessible only to rapid-scan and equilibrium perturbation techniques. Complex dissociation reactions exhibit a wider range of rates and are generally more accessible using standard analytical methods. Literature results are described and correlated with the known properties of the individual ions.

  9. Reaction Theory Advances For FRIB

    NASA Astrophysics Data System (ADS)

    Thompson, Ian

    2012-10-01

    Much interest in rare isotopes centers on how they interact with neutrons, in particular concerning their neutron capture rates in many slow and fast processes. Since neutrons do not make a target, we must use indirect methods, and use reaction theory to bridge the gap. Many of these indirect methods are transfer reactions, in which the rare isotope has a neutron or two added or subtracted. Most common is the (d,p) reaction to add one neutron, just as in a capture reaction. The deuteron is itself weakly bound, however, so I will review recent work on few-body methods to describe deuterons incident on heavy nuclei. When bound neutron states are measured, we can predict direct capture rates for neutrons. Continuum states for the neutron may also be produced in (d,p) reactions. If individual resonances can be distinguished, new theory can describe the transfer cross section in terms of R-matrix parameters for the neutron state. If, however, we have a high level density, then we must use energy averaging, giving a complex optical potential for the neutron. I review the theory of partial fusion needed in this case to describe the competition between breakup and compound-nucleus production. Neutron pickup reactions such as (^3He,?) and (p,t) are also useful to probe hole states, and do not have competition with direct breakup.

  10. Reactions of stabilized Criegee Intermediates

    NASA Astrophysics Data System (ADS)

    Vereecken, Luc; Harder, Hartwig; Novelli, Anna

    2014-05-01

    Carbonyl oxides (Criegee intermediates) were proposed as key intermediates in the gas phase ozonolysis of alkenes in 1975 by Rudolf Criegee. Despite the importance of ozonolysis in atmospheric chemistry, direct observation of these intermediates remained elusive, with only indirect experimental evidence for their role in the oxidation of hydrocarbons, e.g. through scavenging experiments. Direct experimental observation of stabilized CI has only been achieved since 2008. Since then, a concerted effort using experimental and theoretical means is in motion to characterize the chemistry and kinetics of these reactive intermediates. We present the results of theoretical investigations of the chemistry of Criegee intermediates with a series of coreactants which may be of importance in the atmosphere, in experimental setups, or both. This includes the CI+CI cross-reaction, which proceeds with a rate coefficient near the collision limit and can be important in experimental conditions. The CI + alkene reactions show strong dependence of the rate coefficient depending on the coreactants, but is generally found to be rather slow. The CI + ozone reaction is sufficiently fast to occur both in experiment and the free troposphere, and acts as a sink for CI. The reaction of CI with hydroperoxides, ROOH, is complex, and leads both to the formation of oligomers, as to the formation of reactive etheroxides, with a moderately fast rate coefficient. The importance of these reactions is placed in the context of the reaction conditions in different atmospheric environments ranging from unpolluted to highly polluted.

  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. Reaction rates for mesoscopic reaction-diffusion kinetics

    NASA Astrophysics Data System (ADS)

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-01

    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 scale-dependent 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 Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on 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. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.

  13. 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)

  14. Directly Imaging Fast Reaction Fronts

    SciTech Connect

    Kim, J S; LaGrange, T B; Reed, B W; Campbell, G H; Browning, N D

    2007-02-21

    Direct observation of fast intermetallic phase formation in Reactive Multilayer Foils (RMLFs) has been achieved. Snap-shots of the reaction appear to show development of mass-thickness contrast of the unmixed Al and Ni layers and an intermetallic phase. Electron imaging of these RMLF reaction fronts have never been attained in the past. The reaction front travels at {approx}10 meters per second as the nanoscale layers mix in an exothermic chain reaction, thus making traditional in situ electron microscopy {approx}10{sup 5} times too slow to produce such an image. The DTEM capability to produce several million electrons within nanoseconds for single-pulse imaging made this experiment possible. Additionally, the sample drive laser ensures reliable experiment initiation and repeatability. In no other way could such a high velocity event be captured at this magnification. RMLF reaction fronts continue to be analyzed via diffraction for complete phase evolution with respect to time. High quality diffraction patterns enable quantitative phase information to be obtained for future comparison to simulation.

  15. 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.

  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. 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

  18. Combustion kinetics and reaction pathways

    SciTech Connect

    Klemm, R.B.; Sutherland, J.W. [Brookhaven National Laboratory, Upton, NY (United States)

    1993-12-01

    This project is focused on the fundamental chemistry of combustion. The overall objectives are to determine rate constants for elementary reactions and to elucidate the pathways of multichannel reactions. A multitechnique approach that features three independent experiments provides unique capabilities in performing reliable kinetic measurements over an exceptionally wide range in temperature, 300 to 2500 K. Recent kinetic work has focused on experimental studies and theoretical calculations of the methane dissociation system (CH{sub 4} + Ar {yields} CH{sub 3} + H + Ar and H + CH{sub 4} {yields} CH{sub 3} + H{sub 2}). Additionally, a discharge flow-photoionization mass spectrometer (DF-PIMS) experiment is used to determine branching fractions for multichannel reactions and to measure ionization thresholds of free radicals. Thus, these photoionization experiments generate data that are relevant to both reaction pathways studies (reaction dynamics) and fundamental thermochemical research. Two distinct advantages of performing PIMS with high intensity, tunable vacuum ultraviolet light at the National Synchrotron Light Source are high detection sensitivity and exceptional selectivity in monitoring radical species.

  19. Programmable reaction-diffusion fronts

    E-print Network

    Zadorin, Anton S; Galas, Jean-Christophe; Estevez-Torres, André

    2014-01-01

    Morphogenesis is central to biology but remains largely unexplored in chemistry. Reaction-diffusion (RD) mechanisms are, however, essential to understand how shape emerges in the living world. While numerical methods confirm the incredible potential of RD mechanisms to generate patterns, their experimental implementation, despite great efforts, has yet to surpass the paradigm of stationary Turing patterns achieved 25 years ago. The principal reason for our difficulty to synthesize arbitrary concentration patterns from scratch is the lack of fully programmable reaction-diffusion systems. To solve this problem we introduce here a DNA-based system where kinetics and diffusion can be individually tuned. We demonstrate the capability to precisely control reaction-diffusion properties with an autocatalytic network that propagates in a one-dimensional reactor with uniform velocity, typically 100 {\\mu}m min-1. The diffusion coefficient of the propagating species can be reduced up to a factor 2.7 using a species-speci...

  20. Enantioselective catalysis of photochemical reactions.

    PubMed

    Brimioulle, Richard; Lenhart, Dominik; Maturi, Mark M; Bach, Thorsten

    2015-03-23

    The nature of the excited state renders the development of chiral catalysts for enantioselective photochemical reactions a considerable challenge. The absorption of a 400?nm photon corresponds to an energy uptake of approximately 300?kJ?mol(-1) . Given the large distance to the ground state, innovative concepts are required to open reaction pathways that selectively lead to a single enantiomer of the desired product. This Review outlines the two major concepts of homogenously catalyzed enantioselective processes. The first part deals with chiral photocatalysts, which intervene in the photochemical key step and induce an asymmetric induction in this step. In the second part, reactions are presented in which the photochemical excitation is mediated by an achiral photocatalyst and the transfer of chirality is ensured by a second chiral catalyst (dual catalysis). PMID:25728854

  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 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.

  3. Reactions of Stabilized Criegee intermediates

    NASA Astrophysics Data System (ADS)

    Vereecken, Luc; Harder, Hartwig; Novelli, Anna

    2013-04-01

    Carbonyl oxides (Criegee intermediates) were proposed as key intermediates in the gas phase ozonolysis of alkenes in 1975 by Rudolf Criegee. Despite the importance of ozonolysis in atmopsheric chemistry, direct observation of these intermediates remained elusive, with only indirect experimental evidence for their role in the oxidation of hydrocarbons, e.g. through scavenging experiments. Only recently did Taatjes et al (2008) directly observe thermally stabilized Criegee intermediates (SCI), while work by Welz et al (2012) and others have finally started to elucidate the reaction kinetics and products of SCI with a subset of coreactants. Given the dearth of direct experimental data, theoretical analysis of the chemistry of SCI remains a prime source of information; in general, the predictions are in agreement with the scarce experimental data. We present a set of modern theoretical studies on the chemistry of SCI, with emphasis on high-level quantum chemical calculations and theoretical kinetic analysis as a function of the substitutions in the SCI. A broad range of co-reactants is examined, as well as the unimolecular re-arrangement of SCI. In the atmosphere, the fate of SCI was long assumed to be solely its reaction with H2O, or unimolecular decomposition. However, recent re-analysis (Vereecken et al. 2012) of the available data shows that this view may need to be adjusted, with other fast bimolecular reactions playing a role in the atmosphere, with a strong dependence of the rates on the substituents in the SCI. Based on the new experimental and theoretical data, we re-evaluate the possible sinks of SCI in the atmosphere, putting forward a set of reactions that might have an impact in atmospheric or experimental reaction conditions. The reaction of SCI with SO2 receives particular attention, as it is proposed in the literature to be of importance in the atmospheric formation of H2SO4 as an aerosol precursor.

  4. 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

  5. [Professionals' reactions to patient's suicide].

    PubMed

    Kaufmann Didisheim, Nadine; Camus, Didier; Gulfi, Alida; Castelli Dransart, Angela

    2007-09-19

    Physicians, nurses and social workers have a high risk of being confronted with the suicide of a patient during their career. After such an event they may react with sadness, anger or feelings of helplessness. Acute stress reactions are also observed, with irritability, disordered sleep and intrusive thoughts. Some professionals may fear to take care of suicidal patients. Reactions are particularly intense when there was a strong therapeutic relationship. Clinicians should recognize their need for support and look for help, particularly from colleagues. Such an experience may also help them to accept their limits and to become more vigilant and more sensitive to signs of suicidal risk. PMID:17939528

  6. 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.

  7. Adverse Drug Reactions in Dental Practice

    PubMed Central

    Becker, Daniel E.

    2014-01-01

    Adverse reactions may occur with any of the medications prescribed or administered in dental practice. Most of these reactions are somewhat predictable based on the pharmacodynamic properties of the drug. Others, such as allergic and pseudoallergic reactions, are less common and unrelated to normal drug action. This article will review the most common adverse reactions that are unrelated to drug allergy. PMID:24697823

  8. 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…

  9. 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.

  10. THERMONUCLEAR REACTIONS. FUTURE ENERGY SOURCES

    Microsoft Academic Search

    Hoyaux

    1962-01-01

    The five most promising approaches to the containment and stabilization ; of thermonuclear reactions are described. They are the plasma pinch, the ; stellarator, magnetic mirror machines, cuspidate geometry, and the Astron. The ; auxiliary problems connected with these approaches are indicated. In conclusion, ; the probable role of thermonuclear energy in future energy programs is assessed. ; (J.S.R.);

  11. 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.

  12. Common Reactions to Stress Emotional

    E-print Network

    Weston, Ken

    · Take breaks from social media and news #12;Things to consider... · This may take time, take the time#12;Common Reactions to Stress · Physical · Mental · Emotional · Behavioral #12;Physical · Fatigue Health Services · www.uhs.fsu.edu · (850) 644-4567 #12;Resources · Career Center · www

  13. Adverse drug reactions in dermatology.

    PubMed

    Ferner, R E

    2015-03-01

    Adverse drug reactions (ADRs) - that is, unintended and harmful responses to medicines - are important to dermatologists because many present with cutaneous signs and because dermatological treatments can cause serious ADRs. The detection of ADRs to new drugs is often delayed because they have a long latency or are rare or unexpected. This means that ADRs to newer agents emerge only slowly after marketing. ADRs are part of the differential diagnosis of unusual rashes. A good drug history that includes details of drug dose, time-course of the reaction and factors that may make the patient more susceptible, will help. For example, Stevens-Johnson syndrome with abacavir is much commoner in patients with HLA-B*5701, and has a characteristic time course. Newer agents have brought newer reactions; for example, acneiform rashes associated with epidermal growth factor receptor inhibitors such as erlotinib. Older systemic agents used to treat skin disease, including corticosteroids and methotrexate, cause important ADRs. The adverse effects of newer biological agents used in dermatology are becoming clearer; for example, hypersensitivity reactions or loss of efficacy from antibody formation and progressive multifocal leucoencephalopathy due to reactivation of latent JC (John Cunningham) virus infections during efalizumab treatment. Unusual or serious harm from medicines, including ADRs, medication errors and overdose, should be reported. The UK Yellow Card scheme is online, and patients can report their own ADRs. PMID:25622648

  14. Vertical two chamber reaction furnace

    Microsoft Academic Search

    Blaugher

    1999-01-01

    A vertical two chamber reaction furnace is disclosed. 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

  15. Vertical two chamber reaction furnace

    Microsoft Academic Search

    Blaugher; Richard D

    1999-01-01

    A vertical two chamber reaction furnace. 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.

  16. Alief in Action (and Reaction)

    Microsoft Academic Search

    TAMAR SZABÓ GENDLER

    2008-01-01

    I introduce and argue for the importance of a cognitive state that I call alief. An alief is, to a reasonable approximation, an innate or habitual propensity to respond to an apparent stimulus in a particular way. Recognizing the role that alief plays in our cognitive repertoire provides a framework for understanding reactions that are governed by non- conscious or

  17. Industry's Reactions to the Indochinese.

    ERIC Educational Resources Information Center

    Latkiewicz, John

    Eighty Utah companies currently hiring Indochinese refugees and 73 identified simply as "general employers" took part in a study of employers' reactions to Indochinese refugees as job applicants and as employees. The study used questionnaires and oral interviews directed at personnel managers and supervisors and some language proficiency tests of…

  18. Change in Temperature: Endothermic Reaction

    NSDL National Science Digital Library

    2012-04-08

    Learners investigate signs of a chemical reaction when they mix vinegar and baking soda. In addition to a gas being produced, learners also notice the temperature decreases. Learners can quantify the experiment by using a thermometer to measure the temperature change.

  19. The Debenzhydrylation and Transbenzhydrylation Reactions

    NASA Astrophysics Data System (ADS)

    Buckus, P.

    1983-12-01

    The review describes various reactions involving the cleavage of benzhydrylated compounds and their rearrangements and also the use of the benzhydryl group as a protective group. The lability of the bonds between the benzhydryl group and oxygen, sulphur, nitrogen, carbon, and other atoms is demonstrated. The bibliography includes 484 references.

  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. 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).

  2. 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).

  3. 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

  4. Assembly intermediates in polyketide biosynthesis: enantioselective syntheses of beta-hydroxycarbonyl compounds.

    PubMed

    Le Sann, Christine; Munoz, Dulce M; Saunders, Natalie; Simpson, Thomas J; Smith, David I; Soulas, Florilène; Watts, Paul; Willis, Christine L

    2005-05-01

    A versatile approach for the enantioselective synthesis of functionalised beta-hydroxy N-acetylcysteamine thiol esters has been developed which allows the facile incorporation of isotopic labels. It has been shown that a remarkable reversal of selectivity occurs in the titanium mediated aldol reaction of acyloxazolidinone using either (S)- or (R)-tert-butyldimethylsilyloxybutanal. The aldol products are valuable intermediates in the synthesis of 4-hydroxy-6-substituted delta-lactones. PMID:15858656

  5. Microfabricated electrochemiluminescence cell for chemical reaction detection

    DOEpatents

    Northrup, M. Allen (Berkeley, CA); Hsueh, Yun-Tai (Davis, CA); Smith, Rosemary L. (Davis, CA)

    2003-01-01

    A detector cell for a silicon-based or non-silicon-based sleeve type chemical reaction chamber that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The detector cell is an electrochemiluminescence cell constructed of layers of silicon with a cover layer of glass, with spaced electrodes located intermediate various layers forming the cell. The cell includes a cavity formed therein and fluid inlets for directing reaction fluid therein. The reaction chamber and detector cell may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The ECL cell may also be used in synthesis instruments, particularly those for DNA amplification and synthesis.

  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. Prebiotic condensation reactions using cyanamide

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  8. 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

  9. Magnetic nanocomposites by reaction milling

    SciTech Connect

    Pardavi-Horvath, M. [George Washington Univ., Washington, DC (United States). Institute of Magnetics Research] [George Washington Univ., Washington, DC (United States). Institute of Magnetics Research; Takacs, L. [Univ. of Maryland Baltimore County, Baltimore, MD (United States). Dept. of Physics] [Univ. of Maryland Baltimore County, Baltimore, MD (United States). Dept. of Physics

    1995-12-01

    Systems of small magnetic particles embedded in a nonmagnetic matrix were prepared by high energy ball milling. Besides carefully chosen milling conditions, in situ chemical reactions were used to control the properties of the product. Nanocomposites of iron particles in metal oxides (Al{sub 2}O{sub 3} and ZnO), and magnetite particles in copper metal were prepared by reaction milling. The samples were characterized by X-ray diffraction and magnetic methods. A few hours of ball milling resulted in the completion of most chemical changes. Iron nanoparticles were formed with lattice strains of about 0.005; coercivities up to 400 Oe were achieved. The magnetization of the iron particles is 25--40% less than that expected for bulk iron.

  10. Multicomponent reactions in nucleoside chemistry

    PubMed Central

    Buchowicz, W?odzimierz

    2014-01-01

    Summary This review covers sixty original publications dealing with the application of multicomponent reactions (MCRs) in the synthesis of novel nucleoside analogs. The reported approaches were employed for modifications of the parent nucleoside core or for de novo construction of a nucleoside scaffold from non-nucleoside substrates. The cited references are grouped according to the usually recognized types of the MCRs. Biochemical properties of the novel nucleoside analogs are also presented (if provided by the authors). PMID:25161730

  11. Radiation recall reaction causing cardiotoxicity.

    PubMed

    Masri, Sofia Carolina; Misselt, Andrew James; Dudek, Arkadiusz; Konety, Suma H

    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

  12. 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

  13. Redox Reactions in Polymeric Systems

    NASA Astrophysics Data System (ADS)

    Black, James R., II

    2011-12-01

    Reduction-Oxidization (redox) reactions performed in polymeric environments resulted in the reversible formation of stable silver nanoparticle and two reductive radicals. The reversible formation of stable silver nanoparticles in polyvinyl alcohol (PVA) and polyacrylic acid (PAA) crosslinked polymer films containing silver ions was achieved by electrochemical methods for potential applications in electrochromic devices. Cyclic voltammetry and galvanostatic methods were used to reversibly generate silver particles while the particle formation and decay optical absorption spectra were used to evaluate reversibility, relative particle size and minimum cycle speeds. Mechanisms for the formation and decay of particles are discussed with electron microscopy data determining actual size of generated silver particles. Light activated polymeric radicals produced from sulfonated polyether ether ketone (SPEEK) with PVA or SPEEK with sodium formate solutions were generated using 350 nm photons. The mechanism of radical generation is discussed for potential application for dehalogenating a well known environmental hazard carbon tetrachloride (CCl4). The reaction of the generated radicals with CCl4 was followed by ion selective electrode specific for chlorine allowing for the attainment of kinetic data and reaction mechanisms. The degradation of CCl4 was observed in both SPEEK/PVA and SPEEK/formate solutions but the kinetic data revealed SPEEK/formate to be more efficient. The success of SPEEK radicals in dechlorinating CCl4 lead to the investigation of polymeric blends, films and solution of SPEEK and polyamines for the generation of SPEEK radicals with a higher redox potential. SPEEK/polyamine radicals were generated by exposing polymer blends to 350 nm photons. Optical and electron spin resonance (ESR) spectra confirmed the generation of the anionic radical with a higher reducing potential. Kinetic data was obtained for selected system by following the formation and decay of the optical and ESR signatures. The reactions leading to the generation of highly reductive radicals is discussed.

  14. Management of cutaneous drug reactions

    Microsoft Academic Search

    K. S. Babu; Geeta Belgi

    2002-01-01

    Drugs are potent chemicals that often have effects in the body beyond the desired action. These effects may range from mild\\u000a and expected side effects to dramatic and lifethreatening anaphylaxis. Adverse drug reactions account for between 2% and 6%\\u000a of hospital admissions and may prevent administration of otherwise effective therapeutic agents. Cutaneous and mucocutaneous\\u000a eruptions are the most common adverse

  15. Chemical Reactions Among Indoor Pollutants

    Microsoft Academic Search

    Glenn Morrison

    \\u000a Chemistry takes place all around us, regulating the intensity and nature of our exposure to pollutants in water, air and soil.\\u000a In indoor environments, chemistry can significantly alter the composition of the air we breathe. Transformations reduce our\\u000a exposure to reactants and increase our exposure to products. If this reaction takes place on or in a surface, the relative\\u000a exposure

  16. 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.

  17. Transfer reactions with heavy elements

    SciTech Connect

    Hoffman, D.C.

    1986-04-01

    Transfer reactions for several transuranium elements are studied. (/sup 248/Cm, /sup 249/Bk, /sup 249/CF, /sup 254/Es), /sup 16,18/O, /sup 20,22/Ne, and /sup 40,48/Ca projectiles are used. The production of neutron-rich heavy actinides is enhanced by the use of neutron-rich projectiles /sup 18/O and /sup 22/Ne. The maxima of the isotopic distributions occur at only 2 to 3 mass numbers larger for /sup 48/Ca than for /sup 40/Ca reactions with /sup 248/Cm. The cross sections decrease rapidly with the number of nucleons transferred. The use of neutron-rich targets favors the production of neutron-rich isotopes. ''Cold'' heavy targets are produced. Comparisons with simple calculations of the product excitation energies assuming binary transfers indicate that the maxima of the isotopic distributions occur at the lightest product isotope for which the energy exceeds the reaction barrier. The cross sections for transfer of the same nucleon clusters appear to be comparable for a wide variety of systems. 23 refs., 4 figs., 4 tabs.

  18. Microfabricated sleeve devices for chemical reactions

    DOEpatents

    Northrup, M. Allen (Berkeley, CA)

    2003-01-01

    A silicon-based sleeve type chemical reaction chamber that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The reaction chamber combines a critical ratio of silicon and non-silicon based materials to provide the thermal properties desired. For example, the chamber may combine a critical ratio of silicon and silicon nitride to the volume of material to be heated (e.g., a liquid) in order to provide uniform heating, yet low power requirements. The reaction chamber will also allow the introduction of a secondary tube (e.g., plastic) into the reaction sleeve that contains the reaction mixture thereby alleviating any potential materials incompatibility issues. The reaction chamber may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The reaction chamber may also be used in synthesis instruments, particularly those for DNA amplification and synthesis.

  19. 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

  20. [Adverse reaction to not iodinated contrast].

    PubMed

    Palma-Gómez, Samuel; González-Díaz, Sandra Nora; Arias-Cruz, Alfredo; Macías-Weinmann, Alejandra; Amaro-Vivian, Laura Elizabeth; Pérez-Vanzzini, Rafael; Gutiérrez-Mujica, José Julio; Yong-Rodríguez, Adrián

    2014-01-01

    Adverse reactions to drugs are relatively frequent in clinical practice, and some of them can be life threatening. Reactions to contrast material (CM) represent an important percentage of these adverse reactions. It has been found that 70% of reactions to contrast material happen within the first five minutes of their administration. Despite the fact that hypersensitivity reactions are traditionally classified as non-allergic, in recent years investigators have reported positive skin prick tests in patients with immediate and late reactions to contrast material. This paper reports the case of a female patient with non-Hodgkin lymphoma that has presented on two distinct occasions adverse reactions to contrast material. We discuss on the type of reaction, severity, suggested prophylaxis, prognosis and recommendations, keeping in mind the underlying disease and the need to have further image studies performed. PMID:25473874

  1. A Clock Reaction Based on Molybdenum Blue

    E-print Network

    Neuenschwander, Ulrich

    Clock reactions are rare kinetic phenomena, so far limited mostly to systems with ionic oxoacids and oxoanions in water. We report a new clock reaction in cyclohexanol that forms molybdenum blue from a noncharged, yellow ...

  2. Reactions of organocyclosiloxanes with tetrabutyl orthotitanate

    Microsoft Academic Search

    K. A. Andrianov; Sh. V. Pichkhadze; V. V. Komarova; Ts. N. Vardosanidze

    1962-01-01

    1.A study was made of the reaction of tetrabutyl orthotitanate with octamethylcyclotetrasiloxane, with tetramethyltetravinylcyclotetrasiloxane, and with octaethylcyclotetrasiloxane; this resulted in the formation of organosilicon esters.2.A mechanism is proposed for the reaction of tetrabutyl orthotitanate with various organocyclosiloxanes.

  3. Paradoxical reaction in HIV negative tuberculous meningitis.

    PubMed

    Garg, Ravindra Kumar; Malhotra, Hardeep Singh; Kumar, Neeraj

    2014-05-15

    This review focusses on paradoxical reactions occurring during the treatment of tuberculous meningitis (TBM) in human immunodeficiency virus-negative cases. A paradoxical reaction is defined as the worsening of a pre-existing lesion or the appearance of new lesion in a patient whose clinical symptoms initially improved with anti-tuberculosis treatment. A number of different paradoxical reactions have been reported in patients with TBM including expansion of existing cerebral tuberculomas, and appearance of new tuberculomas, hydrocephalus, and optochiasmatic and spinal arachnoiditis. While the exact mechanism of paradoxical reactions is uncertain, an exaggerated immune reaction against Mycobacterium tuberculosis-associated antigens is currently the most accepted theory for tuberculous paradoxical reaction. Corticosteroids are considered to have a beneficial effect in the management of paradoxical reactions. Immuno-modulatory drugs, including tumor necrosis factor-? antagonists, thalidomide and interferon-? have been used in isolated cases with more severe forms of paradoxical reactions. PMID:24680563

  4. Diamine ligands in copper-catalyzed reactions

    E-print Network

    Surry, David S.

    The utility of copper-mediated cross-coupling reactions has been significantly increased by the development of mild reaction conditions and the ability to employ catalytic amounts of copper. The use of diamine-based ligands ...

  5. Investigating Factors Influencing Rates of Chemical Reactions

    NSDL National Science Digital Library

    Paula Derickson

    This activity is a lab investigation in which students observe the rate of generation of hydrogen gas from a reaction, and then modify the procedure to compare another variable affecting the rate of this reaction.

  6. Reactions at supercritical conditions: Applications and fundamentals

    SciTech Connect

    Savage, P.E.; Gopalan, S.; Mizan, T.I.; Martino, C.J.; Brock, E.E. [Univ. of Michigan, Ann Arbor, MI (United States). Chemical Engineering Dept.] [Univ. of Michigan, Ann Arbor, MI (United States). Chemical Engineering Dept.

    1995-07-01

    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 for reactions involved in fuels processing, biomass conversion, biocatalysis, homogeneous and heterogeneous catalysis, environmental control, polymerization, materials synthesis, and chemical synthesis. Moreover, supercritical fluids can be used profitably in fundamental chemical investigations of intermolecular interactions and their influence on chemical processes. Work on chemical reactions in and with supercritical fluids is reviewed. The authors discuss both fundamental studies and applications of reactions at supercritical conditions, with focus on work published after 1985. 425 refs.

  7. If I Had - An Allergic Reaction

    MedlinePLUS Videos and Cool Tools

    ... Wood is also the author of the book, "Food Allergies For Dummies." We asked Dr. Wood for ... two-phased reaction, and about a third of food reactions follows this two-phase pattern. You should ...

  8. 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.

  9. 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.

  10. 5, 51675182, 2005 Gas-phase reaction

    E-print Network

    Paris-Sud XI, Université de

    the reactions of NaCl in sea salt particles 5168 #12;ACPD 5, 5167­5182, 2005 Gas-phase reaction of atomicACPD 5, 5167­5182, 2005 Gas-phase reaction of atomic chlorine with aldehydes D. Rodr´iguez et al and Physics Discussions Kinetic study of the gas-phase reaction of atomic chlorine with a series of aldehydes

  11. Study of the reaction ?- p??'?' n

    NASA Astrophysics Data System (ADS)

    Beladidze, G. M.; Berdnikov, E. B.; Bityukov, S. I.; Borisov, G. V.; Gouz, Yu. P.; Dzhelyadin, R. I.; Ivanyushenkov, Yu. M.; Karyukhin, A. N.; Kachaev, I. A.; Klyuchnikov, G. A.; Konstantinov, V. F.; Kostrikov, M. E.; Kostyukhin, V. V.; Kriushin, A. A.; Khokhlov, Yu. A.; Lapin, V. V.; Lomtadze, T. A.; Matveyev, V. D.; Makarov, G. P.; Obraztsov, V. F.; Ostankov, A. P.; Ryabchikov, D. I.; Semenov, V. K.; Starchenko, E. A.; Isaev, A. N.; Tskhadadze, E. G.; Vishnevsky, N. K.; Vlasov, E. V.; Zaitsev, A. M.; Zimin, S. A.

    1993-03-01

    The reaction ?- p??'?' n has been studied at p ?=37 GeV/c. Total of 14 events of this reaction have been selected. It has been shown that in the effective mass spectrum of the ?'?' system the events are concentrated mainly near the reaction threshold, which might be caused by the decay X(1910)??'?'. The reaction cross-section has been evaluated: ?(?- p??'?' n)=110±40 nb.

  12. Chemical reaction networks: Colour by number.

    PubMed

    Scalise, Dominic; Schulman, Rebecca

    2013-12-01

    Using chemical reactions and diffusion to control pattern formation requires the careful design of reaction networks and a balance of kinetics that is difficult to achieve. Now, it has been shown that DNA-based reaction networks provide a robust method for transforming patterns. PMID:24256857

  13. Emotional and Behavioral Reaction to Intrusive Thoughts

    ERIC Educational Resources Information Center

    Berry, Lisa-Marie; May, Jon; Andrade, Jackie; Kavanagh, David

    2010-01-01

    A self-report measure of the emotional and behavioral reactions to intrusive thoughts was developed. The article presents data that confirm the stability, reliability, and validity of the new seven-item measure. Emotional and behavioral reactions to intrusions emerged as separate factors on the Emotional and Behavioral Reactions to Intrusions…

  14. The Catalytic Asymmetric Intramolecular Stetter Reaction

    PubMed Central

    de Alaniz, Javier Read; Rovis, Tomislav

    2010-01-01

    This account chronicles our efforts at the development of a catalytic asymmetric Stetter reaction using chiral triazolium salts as small molecule organic catalysts. Advances in the mechanistically related azolium-catalyzed asymmetric benzoin reaction are discussed, particularly as they apply to catalyst design. A chronological treatise of reaction discovery, catalyst optimization and reactivity extension follows. PMID:20585467

  15. Negative Temperature Coefficient in Chemical Reactions

    Microsoft Academic Search

    I A Leenson; Gleb B Sergeev

    1984-01-01

    A systematic analysis of reactions whose rate decreases with increase of temperature is presented. The possibility of a negative temperature coefficient in the elementary reactions is examined from the standpoint of the transition state theory and of collision theory. The mechanisms of complex reactions in which the temperature dependence of the rate is anomalous are discussed, and possible reasons for

  16. A New Method for Initiating Nuclear Reactions

    Microsoft Academic Search

    Edmund Storms

    Energy from present sources has proven to have serious limitations. Fortunately for the future of mankind, several new but controversial sources of energy have been discovered. This talk will describe a method to initiate nuclear reactions within solid materials, so-called Chemically Assisted Nuclear Reactions (CANR) when the environment is the focus or Low Energy Nuclear Reactions (LENR) if the process

  17. The Spinning World of Spacecraft Reaction Wheels

    NSDL National Science Digital Library

    This is a activity about how reaction wheels affect spacecraft orientation (attitude). Learners will observe Newton's Third Law (action-reaction) in the changes caused by a reaction wheel acting upon a spacecraft suspended from a support wire and in the ensuing interfering forces from the wire support. The experiment includes an option for demonstration and for learner investigation. Notes about gyroscopes are included.

  18. '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...

  19. 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.

  20. Reaction Order Ambiguity in Integrated Rate Plots

    ERIC Educational Resources Information Center

    Lee, Joe

    2008-01-01

    Integrated rate plots are frequently used in reaction kinetics to determine orders of reactions. It is often emphasised, when using this methodology in practice, that it is necessary to monitor the reaction to a substantial fraction of completion for these plots to yield unambiguous orders. The present article gives a theoretical and statistical…

  1. Reaction rates in accreting neutron stars

    Microsoft Academic Search

    Mary Beard; Michael Wiescher

    2002-01-01

    Temperature conditions in the deep layers of neutron star crusts can be affected by the occurence of pycnonuclear reaction processes. To simulate the fate of accreted matter in neutron star binary systems, we have calculated pycnonuclear reactions for the ashes of rp-process nucleosynthesis at extreme density conditions. Building on the work of Salpeter and Van Horn, nuclear reactions between very

  2. An Iodine Fluorescence Quenching Clock Reaction

    ERIC Educational Resources Information Center

    Weinberg, Richard B.; Muyskens, Mark

    2007-01-01

    Clock reactions based upon competing oxidation and reduction reactions of iodine and starch as the most popular type of chemistry example is presented to illustrate the redox phenomena, reaction kinetics, and principles of chemical titration. The examination of the photophysical principles underlying the iodine fluorescence quenching clock…

  3. 2, 109145, 2002 Uptake and reaction

    E-print Network

    Boyer, Edmond

    .028 respectively, were obtained. The uptake and reaction of HOBr on dry20 salt surfaces was also investigatedACPD 2, 109­145, 2002 Uptake and reaction of HOBr J. W. Adams et al. Title Page Abstract European Geophysical Society 2002 Atmospheric Chemistry and Physics Discussions Uptake and reaction of HOBr

  4. 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

  5. Relay cross metathesis reactions of vinylphosphonates

    PubMed Central

    Malla, Raj K; Ridenour, Jeremy N

    2014-01-01

    Summary 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. 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 ...

  7. Reactions : AcidBaseRxns (20 Variations)

    NSDL National Science Digital Library

    In order to answer the following questions, write the net ionic equation for the reaction between equal volumes of 0.10 M solutions of the following acid and base: KOH(aq) + HBr(aq) What are the reaction products? Does the reaction yield an acidic, basic, or neutral aqueous solution?

  8. Ultracold Chemistry and its Reaction Kinetics

    E-print Network

    Florian Richter; Daniel Becker; Cédric Bény; Torben A. Schulze; Silke Ospelkaus; Tobias J. Osborne

    2015-01-08

    We study the reaction kinetics of chemical processes occurring in the ultracold regime and systematically investigate their dynamics. Quantum entanglement is found to play a key role in driving an ultracold reaction towards a dynamical equilibrium. In case of multiple concurrent reactions Hamiltonian chaos dominates the phase space dynamics in the mean field approximation.

  9. Asymmetric Addition of Alkylzinc Reagents to Cyclic r, -Unsaturated Ketones and a Tandem Enantioselective Addition/Diastereoselective

    E-print Network

    Walsh, Patrick J.

    derivatives with high enantioselectivity. In contrast to related addition reactions with aldehyde substrates of an investigation into the efficient and highly enantioselective 1,2-addition reactions of cyclic R, -unsaturated enantioselectivity, but with diminished yields due to aldol/ dehydration side reactions. Reactions of 2-phenyl

  10. Shame reactions after suicide attempt.

    PubMed

    Wiklander, Maria; Samuelsson, Mats; Asberg, Marie

    2003-09-01

    Shame reactions were spontaneously described by 13 of 18 patients interviewed in a qualitative study investigating experiences of care following a suicide attempt. The shame data from the interview study were extracted, analysed separately, and are reported in this article. The shame reactions often occurred in conjunction with the suicide attempt. Feelings of shame were accompanied by impulses to hide or flee, i.e., fear of seeking help or impulses to leave the hospital. The attempted suicide patients often experienced the initial encounter at the hospital as difficult. Having attempted suicide and survived was often perceived as yet another failure, in addition to the problems leading to the attempt. The attempted suicide patients were sensitive to the attitudes and behaviours of the personnel. Experiencing the personnel as kind, respectful, and nonjudgemental seemed to contribute to a relief from shame for some patients. Some respondents expressed that a tolerant and flexible atmosphere in the psychiatric ward, with low demands on the attempted suicide patient, helped them accept treatment and made them feel less ashamed for not living up to the expectations of everyday life. On the other hand, feeling too exposed to others or experiencing negative attitudes from the personnel seemed to contribute to an exacerbation of shame for some patients. Being aware of possible shame reactions after a suicide attempt might help caring personnel to understand and interact with attempted suicide patients in a way that could make it easier for these patients to accept and benefit from psychiatric care after a suicide attempt. PMID:12919465

  11. Blood product transfusions and reactions.

    PubMed

    Osterman, Jessica L; Arora, Sanjay

    2014-08-01

    Blood product transfusions are an essential component of the practice of emergency medicine. From acute traumatic hemorrhage to chronic blood loss necessitating transfusion for symptomatic anemia, familiarity with individual blood products and their indications for transfusion is an essential tool for every emergency physician (EP). Although the focus of this article is primarily on the transfusion of red blood cells, many of the concepts are applicable to the transfusion of all blood products. EPs must be fully familiar with both the individual blood components and the potential reactions and complications of these transfusions. PMID:25060259

  12. 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

  13. Highly enantioselective organocatalytic Biginelli reaction.

    PubMed

    Chen, Xiao-Hua; Xu, Xiao-Ying; Liu, Hua; Cun, Lin-Feng; Gong, Liu-Zhu

    2006-11-22

    A series of binol- and H8-binol-based phosphoric acids have for the first time been evaluated for their ability to catalyze Biginelli reactions of aldehydes, thiourea or urea, and beta-keto esters. A new chiral phosphoric acid, derived from 3,3'-diphenyl-H8-binol, exhibited superior catalytic activity and enantioselectivity compared to its structural analogues, affording high enantioselectivities ranging from 85 to 97% ee with a wide scope of substrates. A metal-free preparation of optically active monastrol was achieved on the basis of the current process. PMID:17105279

  14. Nazarov-like cyclization reactions.

    PubMed

    Di Grandi, Martin J

    2014-08-01

    The Nazarov cyclization, a well-known method for the formation of cyclopentenones, mechanistically involves the 4? electrocyclization of a 1,4-pentadienyl cation, generated from cross-conjugated divinyl ketones. Recently, advances related to this cyclization, such as the incorporation of heteroatoms as well as the use of cyclopropanes as double bond equivalents have extended the scope of the original reaction. The modifications discussed in this review, which covers the years 2009-2013, have allowed the realization of both heteroatom- and homo-Nazarov cyclizations. PMID:24947937

  15. Cutaneous adverse reactions of amiodarone.

    PubMed

    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. 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.

  17. Photochemical reactions of microcrystalline thymidine.

    PubMed

    Jian, Yajun; Ames, David M; Ouyang, Hao; Li, Lei

    2015-02-20

    Nucleoside/nucleotide/oligonucleotide photoreactions usually result in a number of products simultaneously due to a wide range of conformers existing at a given time. Such a complicated reaction pattern makes it difficult for one to focus on a single DNA photoproduct and elucidate the requirements for its formation. A rare example of thymidine photoreaction in microcrystals is reported, where 5-thyminyl-5,6-dihydrothymine, e.g., the spore photoproduct (SP), is produced as the dominant species in ?85% yield. This unprecedented high yield clears the major obstacle for future SP photochemistry studies in detail. PMID:25668312

  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. Kinetic studies of elementary chemical reactions

    SciTech Connect

    Durant, J.L. Jr. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    This program concerning kinetic studies of elementary chemical reactions is presently focussed on understanding reactions of NH{sub x} species. To reach this goal, the author is pursuing experimental studies of reaction rate coefficients and product branching fractions as well as using electronic structure calculations to calculate transition state properties and reaction rate calculations to relate these properties to predicted kinetic behavior. The synergy existing between the experimental and theoretical studies allow one to gain a deeper insight into more complex elementary reactions.

  1. 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

  2. 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 nanopores Martin Lísala E. Hála Laboratory of Thermodynamics, Institute of Chemical Process Fundamentals

  3. Instabilities in propagating reaction-diffusion fronts of the iodate-arsenous acid reaction

    E-print Network

    Showalter, Kenneth

    of the iodate-arsenous acid reaction are predicted by an empirical rate-law model. The planar front loses of premixed flames, where the heat of reaction plays the role of the activator and a stoichio- metricallyInstabilities in propagating reaction-diffusion fronts of the iodate-arsenous acid reaction Dezso

  4. 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.

  5. 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.

  6. Nuclear reactions from lattice QCD

    DOE PAGESBeta

    Briceno, Raul A. [JLAB; 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 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.

  7. 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.

  8. Surface catalyzed mercury transformation reactions

    NASA Astrophysics Data System (ADS)

    Varanasi, Patanjali

    Mercury is a known pollutant that has detrimental effect on human health and environment. The anthropogenic emissions of mercury account for 10 to 30% of worldwide mercury emissions. There is a need to control/reduce anthropogenic mercury emissions. Many mercury control technologies are available but their effectiveness is dependent on the chemical form of mercury, because different chemical forms of mercury have different physical and chemical properties. Mercury leaves the boiler in its elemental form but goes through various transformations in the post-combustion zone. There is a need to understand how fly ash and flue gas composition affect speciation, partitioning, and reactions of mercury under the full range of post-combustion zone conditions. This knowledge can then be used to predict the chemical transformation of mercury (elemental, oxidized or particulate) in the post combustion zone and thus help with the control of mercury emissions from coal-burning power plants. To accomplish this goal present study was conducted using five coal fly ashes. These ashes were characterized and their catalytic activity was compared under selected reaction conditions in a fixed bed reactor. Based on the results from these fly ash experiments, three key components (carbon, iron oxide and calcium oxide) were chosen. These three components were then used to prepare model fly ashes. Silica/alumina was used as a base for these model fly ashes. One, two or three component model fly ashes were then prepared to investigate mercury transformation reactions. The third set of experiments was performed with five different oxidation catalysts to further understand the mercury oxidation process. Based on the results of these three studies the key components were predicted for different fly ash compositions under variety of flue gas conditions. A fixed bed reactor system was used to conduct this study. In all the experiments, the inlet concentration of Hg0(g) was maintained at 35 mug/m 3 using a diffusion tube as the source of Hg0(g). All experiments were conducted using 4% O2 in nitrogen mix as a reaction gas, and other reactants (HCl, H2O and SO2, NO 2, Br2) were added as required. The fixed bed reactor was operated over a temperature range of 200 to 400°C. In each experiment, the reactor effluent was analyzed using the modified Ontario-Hydro method. After each experiment, fly ash particles were also analyzed for mercury. The results show that the ability of fly ash to adsorb and/or oxidize mercury is primarily dependent on its carbon, iron and calcium content. There can be either one or more than one key component at a particular temperature and flue gas condition. Surface area played a secondary role in effecting the mercury transformations when compared to the concentration of the key component in the fly ash. Amount carbon and surface area played a key important role in the adsorption of mercury. Increased concentration of gases in the flue gas other than oxygen and nitrogen caused decreased the amount of mercury adsorbed on carbon surface. Mercury adsorption by iron oxide primarily depended on the crystalline structure of iron oxide. alpha-iron oxide had no effect on mercury adsorption or oxidation under most of the flue gas conditions, but gamma-iron oxide adsorbed mercury under most of the flue gas conditions. Bromine is a very good oxidizing agent for mercury. But in the presence of calcium oxide containing fly ashes, all the oxidized mercury would be reduced to elemental form. Among the catalysts, it was observed that presence of free lattice chlorine in the catalyst was very important for the oxidation of mercury. But instead of using the catalyst alone, using it along with carbon may better serve the purpose by providing the adsorption surface for mercury and also some extra surface area for the reaction to occur (especially for fly ashes with low surface area).

  9. The Ozone-Iodine-Chlorate Clock Reaction

    PubMed Central

    Sant'Anna, Rafaela T. P.; Monteiro, Emily V.; Pereira, Juliano R. T.; Faria, Roberto B.

    2013-01-01

    This work presents a new clock reaction based on ozone, iodine, and chlorate that differs from the known chlorate-iodine clock reaction because it does not require UV light. The induction period for this new clock reaction depends inversely on the initial concentrations of ozone, chlorate, and perchloric acid but is independent of the initial iodine concentration. The proposed mechanism considers the reaction of ozone and iodide to form HOI, which is a key species for producing non-linear autocatalytic behavior. The novelty of this system lies in the presence of ozone, whose participation has never been observed in complex systems such as clock or oscillating reactions. Thus, the autocatalysis demonstrated in this new clock reaction should open the possibility for a new family of oscillating reactions. PMID:24386257

  10. 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.

  11. 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).

  12. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1990-01-01

    The objective was to obtain accurate potential energy surfaces (PES's) for a number of reactions which are important in the H/N/O combustion process. The interest in this is centered around the design of the SCRAM jet engine for the National Aerospace Plane (NASP), which was envisioned as an air-breathing hydrogen-burning vehicle capable of reaching velocities as large as Mach 25. Preliminary studies indicated that the supersonic flow in the combustor region of the scram jet engine required accurate reaction rate data for reactions in the H/N/O system, some of which was not readily available from experiment. The most important class of combustion reactions from the standpoint of the NASP project are radical recombinaton reactions, since these reactions result in most of the heat release in the combustion process. Theoretical characterizations of the potential energy surfaces for these reactions are presented and discussed.

  13. Reactions of butadiyne. 1: The reaction with hydrogen atoms

    NASA Technical Reports Server (NTRS)

    Schwanebeck, W.; Warnatz, J.

    1984-01-01

    The reaction of hydrogen (H) atoms with butadiene (C4H2) was studied at room temperature in a pressure range between w mbar and 10 mbar. The primary step was an addition of H to C4H2 which is in its high pressure range at p 1 mbar. Under these conditions the following addition of a second H atom lies in the transition region between low and high pressure range. Vibrationally excited C4H4 can be deactivated to form buten-(1)-yne-(3)(C4H4) or decomposes into two C2H2 molecules. The rate constant at room temperature for primary step is given. The second order rate constant for the consumption of buten-(1)-yne-(3) is an H atom excess at room temperature is given.

  14. Nonequilibrium velocity distribution and reaction rate in ion-molecule reactions

    Microsoft Academic Search

    Katsuhisa Koura

    1981-01-01

    The nonequilibrium velocity distribution and reaction rate in fast ion-molecule reactions with non-Langevin reaction cross sections are studied using the Monte Carlo simulation in steady-state systems where ions are diluted in heat-bath reactant molecules and ion sources compensate the loss of ions due to the reaction. The non-Langevin reaction cross sections are taken as the power and exponential dependences on

  15. Metal implants and surface reactions.

    PubMed

    Steinemann, S G

    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 oxide-hydrates 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 behaviour of metals is variable; gold, stainless steel and most other metals react as described while few others like titanium and tantalum do not. The absence of a foreign body effect of a chemical kind is, without doubt, favorable in terms of tissue susceptibility to infection in the presence of titanium. PMID:9039349

  16. Back reaction is for real

    NASA Astrophysics Data System (ADS)

    Abramo, L. R.; Woodard, R. P.

    2002-03-01

    We demonstrate the existence of a secular back reaction on inflation using a simple scalar model. The model consists of a massless, minimally coupled scalar with a quartic self-interaction which is a spectator to ?-driven inflation. To avoid problems with coincident propagators, and to make the scalars interact more like gravitons, we impose a covariant normal ordering prescription which has the effect of removing tadpole graphs. This version of the theory exhibits a secular slowing at three loop order due to interactions between virtual infrared scalars which are ripped apart by the inflating background. The effect is quantified using an invariant observable and all orders bounds are given. We also argue that, although stochastic effects can have either sign, the slowing mechanism is superimposed upon them.

  17. Classical Gravitational Back-Reaction

    E-print Network

    N. C. Tsamis; R. P. Woodard

    2014-05-24

    The quantum gravitational back-reaction on inflation is based on the self-gravitation of infrared gravitons which are ripped out of the vacuum during inflation. The only quantum part of this process is the creation of gravitons; after they have emerged from the vacuum their behaviour is essentially classical. To test the thesis that a sufficiently dense ensemble of classical gravitons can hold the universe together in pure gravity with a positive cosmological constant, we compute the initial value and first time derivative of an invariant measure of the expansion rate for arbitrary classical initial value data. Our result is that the self-gravitation from the kinetic energy of an initial ensemble of gravitons can indeed slow expansion enough to hold the universe together.

  18. Adverse reactions of ferric carboxymaltose.

    PubMed

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

    2014-10-01

    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. Back reaction in a cylinder

    SciTech Connect

    Eisenberg, J.M. (School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 69978 Tel Aviv (Israel) TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada))

    1995-02-15

    A system is studied in which initially a strong classical electric field exists within an infinitely long cylinder and no charges are present. Subsequently, within the cylinder, pairs of charged particles tunnel out from the vacuum and the current produced through their acceleration by the field acts back on the field, setting up plasma oscillations. This yields a rough model of phenomena that may occur in the preequilibrium formation phase of a quark-gluon plasma. In an infinite volume, this back reaction has been studied in a field-theory description, and it has been found that the results of a full calculation of this sort are well represented in a much simpler transport formalism. It is the purpose here to explore that comparison for a situation involving a cylindrical volume of given radius.

  20. 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.

  1. 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.

  2. 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.

  3. A clock reaction based on molybdenum blue.

    PubMed

    Neuenschwander, Ulrich; Negron, Arnaldo; Jensen, Klavs F

    2013-05-30

    Clock reactions are rare kinetic phenomena, so far limited mostly to systems with ionic oxoacids and oxoanions in water. We report a new clock reaction in cyclohexanol that forms molybdenum blue from a noncharged, yellow molybdenum complex as precursor, in the presence of hydrogen peroxide. Interestingly, the concomitant color change is reversible, enabling multiple clock cycles to be executed consecutively. The kinetics of the clock reaction were experimentally characterized, and by adding insights from quantum chemical calculations, a plausible reaction mechanism was postulated. Key elementary reaction steps comprise sigmatropic rearrangements with five-membered or bicyclo[3.1.0] transition states. Importantly, numerical kinetic modeling demonstrated the mechanism's ability to reproduce the experimental findings. It also revealed that clock behavior is intimately connected to the sudden exhaustion of hydrogen peroxide. Due to the stoichiometric coproduction of ketone, the reaction bears potential for application in alcohol oxidation catalysis. PMID:23634968

  4. Studying Reaction Intermediates Formed at Graphenic Surfaces

    NASA Astrophysics Data System (ADS)

    Sarkar, Depanjan; Sen Gupta, Soujit; Narayanan, Rahul; Pradeep, Thalappil

    2014-03-01

    We report in-situ production and detection of intermediates at graphenic surfaces, especially during alcohol oxidation. Alcohol oxidation to acid occurs on graphene oxide-coated paper surface, driven by an electrical potential, in a paper spray mass spectrometry experiment. As paper spray ionization is a fast process and the time scale matches with the reaction time scale, we were able to detect the intermediate, acetal. This is the first observation of acetal formed in surface oxidation. The process is not limited to alcohols and the reaction has been extended to aldehydes, amines, phosphenes, sugars, etc., where reaction products were detected instantaneously. By combining surface reactions with ambient ionization and mass spectrometry, we show that new insights into chemical reactions become feasible. We suggest that several other chemical transformations may be studied this way. This work opens up a new pathway for different industrially and energetically important reactions using different metal catalysts and modified substrate.

  5. Disulfiram-like reaction with ornidazole.

    PubMed

    Sharma, V; Sharma, A; Kumar, V; Aggarwal, S

    2009-01-01

    Many drugs are implicated in causation of disulfiram-like reaction. The disulfiram-like reaction can vary in severity and can occasionally be fatal. The reaction is believed to result from inhibition of metabolism of acetaldehyde to acetate by inhibition of aldehyde dehydrogenase. The increase in serum acetaldehyde results in unpleasant clinical manifestations. Metronidazole is known to cause disulfiram-like reaction. Although no previous report has implicated ornidazole in causation of disulfiram-like reaction, caution has been advised with the use of all imidazoles. We report the case of a 48-year-old male, who was taking ornidazole and developed features of disulfiram-like reaction after taking alcohol. The patient was managed with supportive measures and improved. The report highlights the need for clinicians to advise patients to restrict intake of alcohol if they are being prescribed imidazole derivatives. PMID:20083883

  6. 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.

  7. Autocatalytic reactions of phase distributed active particles.

    PubMed

    Santoboni, Giovanni; Nishikawa, Takashi; Toroczkai, Zoltan; Grebogi, Celso

    2002-06-01

    We investigate the effect of asynchronism of autocatalytic reactions taking place in open hydrodynamical flows, by assigning a phase to each particle in the system to differentiate the timing of the reaction, while the reaction rate (periodicity) is kept unchanged. The chaotic saddle in the flow dynamics acts as a catalyst and enhances the reaction in the same fashion as in the case of a synchronous reaction that was studied previously, proving that the same type of nonlinear reaction kinetics is valid in the phase-distributed situation. More importantly, we show that, in a certain range of a parameter, the phenomenon of phase selection can occur, when a group of particles with a particular phase is favored over the others, thus occupying a larger fraction of the available space, or eventually leading to the extinction of the unfavored phases. We discuss the biological relevance of this latter phenomenon. (c) 2002 American Institute of Physics. PMID:12779571

  8. Graft-versus-host reactions in dermatology

    Microsoft Academic Search

    Martin Lewis Johnson; Evan Ragland Farmer

    1998-01-01

    Graft-versus-host reactions frequently produce cutaneous and systemic complications in patients receiving bone marrow transplants. Characteristic skin involvement typically heralds graft-versus-host reactions and significantly contributes to the morbidity associated with marrow transplants. Familiarity with these reactions and their treatment is important to dermatologists involved in the care of marrow transplant recipients. (J Am Acad Dermatol 1998;38:369-92.) Learning objective: At the conclusion

  9. Diamine Ligands in Copper-Catalyzed Reactions

    PubMed Central

    Surry, David S.

    2012-01-01

    The utility of copper-mediated cross-coupling reactions has been significantly increased by the development of mild reaction conditions and the ability to employ catalytic amounts of copper. The use of diamine-based ligands has been important in these advances and in this review we discuss these systems, including the choice of reaction conditions and applications in the synthesis of pharmaceuticals, natural products and designed materials. PMID:22384310

  10. Nuclear reaction rates and the primordial nucleosynthesis

    Microsoft Academic Search

    Abhishek Mishra; D. N. Basu

    2011-01-01

    The theoretical predictions of the primordial abundances of elements in the big-bang nucleosynthesis (BBN) are dominated by uncertainties in the input nuclear reaction rates. We investigate the effect of modifying these reaction rates on light element abundance yields in BBN by replacing the thirty-five reaction rates out of the existing eighty-eight. We have studied these yields as functions of evolution

  11. 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

  12. 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 .

  13. Reaction dependence of nuclear decay linewidths

    Microsoft Academic Search

    D. Overway; J. Jänecke; F. D. Becchetti; C. E. Thorn; G. Kekelis

    1981-01-01

    Various light- and heavy-ion reactions, 20 < E < 100 MeV, have been used to study the reaction dependence of alpha-decay widths for 8Be*(2 + , 2.9 MeV) and 16O*(1-, 9.6 MeV). Although slight differences (< 20 %) are found for the observed line shapes (Gamma), the resonance widths inferred (GammaR) are self-consistent and indicate little if any reaction dependence

  14. Advances in tandem reactions with organozinc reagents.

    PubMed

    Kim, Ju Hyun; Ko, Young Ok; Bouffard, Jean; Lee, Sang-Gi

    2015-04-10

    The design and implementation of tandem reactions provides organic chemists with numerous challenges, in particular that of undesired cross-reactivity between substrates. Among organometallics, the use of organozinc reagents in tandem reactions provides several advantages as a result of their broad functional group tolerance and compatibility with transition metals. This review highlights prominent examples of recent advances in tandem reactions with organozinc reagents that illustrate their potential in organic synthesis. PMID:25708795

  15. Stability of sharp reaction fronts in porous rocks and implications for non-sharp reaction zones

    NASA Astrophysics Data System (ADS)

    Wangen, Magnus

    2014-05-01

    The flow of reactive fluids in the subsurface, like for instance acids, may create reaction fronts. A sharp reaction front is an idealization of the narrow zone where the reaction takes place. Narrow reaction zones are studied with a one-component reaction transport model, where a first order reaction changes the porosity. The porosity field is coupled to the permeability field, where an increasing porosity leads to an increasing permeability. Therefore, the reaction has a feed-back on the flow field. We have derived 1D approximate solutions for the change in concentration and porosity across the reaction zone. These solutions are used to derive a condition for reaction fronts to be narrow. The condition gives a minimum reaction rate necessary for 90% of the reaction to be restricted to the given area. Sharp fronts are idealizations of narrow fronts that are more amendable for analytical treatment. A condition has recently been derived for the stability of sharp reaction fronts in homogeneous porous medium using linear stability analysis. The condition gives that a perturbation of a flat reaction front of any wave-length becomes unstable if the permeability behind the front increases. The front instability grows faster for short wave lengths than for long wave lengths. Similarly, the perturbations of the front will die out if the permeability behind the front decreases, and short wave length perturbations will die out faster than long wave length perturbations. It is a condition that applies for both 2D and 3D porous media. Numerical experiments are shown that demonstrate the front stability criterion, when the fronts are narrow, but not sharp. The sharp front approximation turns out to be useful for the interpretation of reactions that are not sufficiently fast to give narrow reaction zones, when the reaction alters the porosity- and the permeability fields. Dissolution is an important example of reactions that increase the porosity and therefore the permeability. Numerical modelling shows that the flow field becomes directed towards tip of the reaction zone, because of the increased permeability towards the tip. This becomes the place where the Darcy flux is largest and where the reaction runs fastest. The largest Darcy flux at the tip implies a larger supply of reactive fluid at the tip than for the other parts of the reaction zone. Dissolution reactions are therefore unstable reactions, and they may be difficult to predict even though the data for the reaction kinetics is accurate. The same argumentation leads to that precipitation reaction propagate in a stable manner, since the precipitated minerals direct the flow away towards areas that have received less precipitation.

  16. Accelerated glass reaction under PCT conditions

    SciTech Connect

    Ebert, W.L.; Bates, J.K.; Buck, E.C.; Bradley, C.R.

    1992-01-01

    Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.

  17. Accelerated glass reaction under PCT conditions

    SciTech Connect

    Ebert, W.L.; Bates, J.K.; Buck, E.C.; Bradley, C.R.

    1992-12-31

    Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.

  18. Direct reactions in/for astrophysics

    E-print Network

    C. A. Bertulani

    2006-07-13

    Precise nuclear reaction rates are needed for a detailed description of the production of elements in primordial nucleosynthesis and during the hydrostatic burning of stars to constrain the astrophysical models. The relevant reactions are extremely difficult to measure directly in the laboratory at the small astrophysical energies. In recent years direct reactions methods have been developed and applied to extract low-energy astrophysical S factors. The application of these methods requires a combination of experimental and theoretical efforts. This contribution focuses on the underlying reaction theories that have to be well understood in order to assess the precision and limitations of the various approaches.

  19. Atmospheric pressure microwave assisted heterogeneous catalytic reactions.

    PubMed

    Chemat-Djenni, Zoubida; Hamada, Boudjema; Chemat, Farid

    2007-01-01

    The purpose of the study was to investigate microwave selective heating phenomena and their impact on heterogeneous chemical reactions. We also present a tool which will help microwave chemists to answer to such questions as "My reaction yields 90% after 7 days at reflux; is it possible to obtain the same yield after a few minutes under microwaves?" and to have an approximation of their reactions when conducted under microwaves with different heterogeneous procedures. This model predicting reaction kinetics and yields under microwave heating is based on the Arrhenius equation, in agreement with experimental data and procedures. PMID:17909495

  20. Precautions and Adverse Reactions during Blood Transfusion

    MedlinePLUS

    ... leukocyte reduction), allergic reactions are less common. Fluid overload: Transfusion recipients can receive more fluid than their ... Special Blood Donation Procedures Next: Overview of Iron Overload

  1. Automatic analysis of computation in biochemical reactions.

    PubMed

    Egri-Nagy, Attila; Nehaniv, Chrystopher L; Rhodes, John L; Schilstra, Maria J

    2008-01-01

    We propose a modeling and analysis method for biochemical reactions based on finite state automata. This is a completely different approach compared to traditional modeling of reactions by differential equations. Our method aims to explore the algebraic structure behind chemical reactions using automatically generated coordinate systems. In this paper we briefly summarize the underlying mathematical theory (the algebraic hierarchical decomposition theory of finite state automata) and describe how such automata can be derived from the description of chemical reaction networks. We also outline techniques for the flexible manipulation of existing models. As a real-world example we use the Krebs citric acid cycle. PMID:18606208

  2. Delayed dermatologic hypersensitivity reaction secondary to ipilimumab.

    PubMed

    Ludlow, Steven P; Kay, Noriko

    2015-05-01

    The treatment of melanoma has long favored the use of immunologic agents. Ipilimumab is a monoclonal antibody used to enhance the immune response. This therapy is associated with a variety of adverse reactions including skin reactions. Although dermatologic toxicities associated with the use of ipilimumab are common, delayed hypersensitivity reactions related to the drug have yet to be identified. This report is believed to be the first case of a delayed, severe dermatologic drug-related reaction secondary to ipilimumab. This case highlights the potential for severe toxicity for long periods after administration of ipilimumab. PMID:25839442

  3. Multicomponent reactions for the synthesis of heterocycles.

    PubMed

    Jiang, Bo; Rajale, Trideep; Wever, Walter; Tu, Shu-Jiang; Li, Guigen

    2010-11-01

    Multicomponent domino reactions (MDRs) serve as a rapid and efficient tool for the synthesis of versatile heterocycles, particularly those containing structural diversity and complexity, by a one-pot operation. These reactions can dramatically reduce the generation of chemical wastes, costs of starting materials, and the use of energy and manpower. Moreover, the reaction period can be substantially shortened. This Review covers recent advances on multicomponent domino reactions for the construction of five-, six-, and seven-membered heterocyclic skeletons and their multicyclic derivatives. PMID:20922748

  4. Process for operating equilibrium controlled reactions

    DOEpatents

    Nataraj, Shankar (Allentown, PA); Carvill, Brian Thomas (Orefield, PA); Hufton, Jeffrey Raymond (Fogelsville, PA); Mayorga, Steven Gerard (Allentown, PA); Gaffney, Thomas Richard (Allentown, PA); Brzozowski, Jeffrey Richard (Bethlehem, PA)

    2001-01-01

    A cyclic process for operating an equilibrium controlled reaction in a plurality of reactors containing an admixture of an adsorbent and a reaction catalyst suitable for performing the desired reaction which is operated in a predetermined timed sequence wherein the heating and cooling requirements in a moving reaction mass transfer zone within each reactor are provided by indirect heat exchange with a fluid capable of phase change at temperatures maintained in each reactor during sorpreaction, depressurization, purging and pressurization steps during each process cycle.

  5. Thermodynamics in the limit of irreversible reactions

    NASA Astrophysics Data System (ADS)

    Gorban, A. N.; Mirkes, E. M.; Yablonsky, G. S.

    2013-03-01

    For many complex real physicochemical systems, the detailed mechanism includes both reversible and irreversible reactions. Such systems are typical in homogeneous combustion and heterogeneous catalytic oxidation. Most complex enzyme reactions include irreversible steps. Classical thermodynamics has no limit for irreversible reactions, whereas kinetic equations may have such a limit. We represent systems with irreversible reactions as the limits of fully reversible systems when some of the equilibrium concentrations tend to zero. The structure of the limit reaction system crucially depends on the relative rates of this tendency to zero. We study the dynamics of the limit system and describe its limit behavior as t??. If the reversible systems obey the principle of detailed balance then the limit system with some irreversible reactions must satisfy the extended principle of detailed balance. It is formulated and proven in the form of two conditions: (i) the reversible part satisfies the principle of detailed balance and (ii) the convex hull of the stoichiometric vectors of the irreversible reactions does not intersect the linear span of the stoichiometric vectors of the reversible reactions. These conditions imply the existence of the global Lyapunov functionals and allow an algebraic description of the limit behavior. Thermodynamic theory of the irreversible limit of reversible reactions is illustrated by the analysis of hydrogen combustion.

  6. 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.

  7. 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.

  8. Dynamics of activationless reactions in solution

    SciTech Connect

    Bagchi, B. (Indian Institute of Science, Bangalore (India)); Fleming, G.R. (Univ. of Chicago, IL (USA))

    1990-01-11

    Recent picosecond and subpicosecond laser spectroscopy experiments have revealed several chemically and biologically important reactions in solution in which the reaction potential surface does not present a barrier to the motion along the reaction coordinate. The dynamics of these reactions display diverse and interesting behavior. They include the dependence of relaxation rate on the solvent viscosity, the solvent polarity, the temperature, and the wavelength of the exciting light. In this article we review the recent developments in the theoretical description of activationless processes in solution and compare them with the available experimental results.

  9. Non-Markovian polymer reaction kinetics.

    PubMed

    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. PMID:22717443

  10. 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.

  11. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D. (Evergreen, CO)

    1999-03-16

    A vertical two chamber reaction furnace. 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.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. 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.

  12. Anaphylactic reaction to lupine flour.

    PubMed

    Brennecke, Sabine; Becker, Wolf-Meinhard; Lepp, Ute; Jappe, Uta

    2007-09-01

    Roasted lupine seeds have been used as snack food in Mediterranean countries for years. Since the 1990s, lupine flour has been used as a substitute for or additive to other flours in countries of the European Union; usually the amount is so low that no declaration is required. Since 1994, a number of cases of immediate-type allergy to lupine flour-containing products have been published. A 52-year-old woman developed facial and mucosal edema, followed by dizziness and shortness of breath a few minutes after ingestion of a nut croissant containing lupine flour; she required emergency care. Allergy diagnostic tests revealed a total IgE of 116 kU/l, a highly elevated concentration of IgE specific for lupine seed (42.9 kU/l) and birch pollen IgE of 2.57 kU/l. Skin prick test with native lupine flour was strongly positive. Allergy against lupine seeds may develop de novo or via cross-reactivity to legumes, particularly peanuts, the latter being detectable in up to 88% of cases, founded on a strong sequence similarity between lupine and peanut allergens. In our patient, no cross-reactivity could be detected via immunoblotting, indicating a rare monovalent sensitization to lupine flour. Treatment consists of avoidance of lupine flour-containing products. Patients with proven peanut allergy should also avoid lupine flour because of the major risk of cross-reaction. PMID:17760898

  13. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1999-03-16

    A vertical two chamber reaction furnace is disclosed. 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 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.

  14. Monitoring for adverse drug reactions

    PubMed Central

    Coleman, J J; Ferner, R E; Evans, S J W

    2006-01-01

    Monitoring describes the prospective supervision, observation, and testing of an ongoing process. The result of monitoring provides reassurance that the goal has been or will be achieved, or suggests changes that will allow it to be achieved. In therapeutics, most thought has been given to Therapeutic Drug Monitoring, that is, monitoring of drug concentrations to achieve benefit or avoid harm, or both. Patients and their clinicians can also monitor the progress of a disease, and adjust treatment accordingly, for example, to achieve optimum glycaemic control. Very little consideration has been given to the development of effective schemes for monitoring for the occurrence of adverse effects, such as biochemical or haematological disturbance. Significant harm may go undetected in controlled clinical trials. Even where harm is detected, published details of trials are usually insufficient to allow a practical monitoring scheme to be introduced. The result is that information available to prescribers, such as the Summary of Product Characteristics, frequently provides advice that is incomplete or impossible to follow. We discuss here the elements of logical schemes for monitoring for adverse drug reactions, and the possible contributions that computerized decision support can make. We should require evidence that if a monitoring scheme is proposed, it can be put into practice, will prove effective, and is affordable. PMID:16542197

  15. Reaction products of chlorine dioxide.

    PubMed Central

    Stevens, A A

    1982-01-01

    Inspection of the available literature reveals that a detailed investigation of the aqueous organic chemistry of chlorine dioxide and systematic identification of products formed during water disinfection has not been considered. This must be done before an informed assessment can be made of the relative safety of using chlorine dioxide as a disinfectant alternative to chlorine. Although trihalomethanes are generally not formed by the action of chlorine dioxide, the products of chlorine dioxide treatment of organic materials are oxidized species, some of which also contain chlorine. The relative amounts of species types may depend on the amount of chlorine dioxide residual maintained and the concentration and nature of the organic material present in the source water. The trend toward lower concentrations of chlorinated by-products with increasing ClO2 concentration, which was observed with phenols, has not been observed with natural humic materials as measured by the organic halogen parameter. Organic halogen concentrations have been shown to increase with increasing chlorine dioxide dose, but are much lower than those observed when chlorine is applied. Aldehydes have been detected as apparent by-products of chlorine dioxide oxidation reactions in a surface water that is a drinking water source. Some other nonchlorinated products of chlorine dioxide treatment may be quinones and epoxides. The extent of formation of these moieties within the macromolecular humic structure is also still unknown. PMID:7151750

  16. Modeling Enzymatic Reactions in Proteins.

    NASA Astrophysics Data System (ADS)

    Friesner, Richard

    2007-03-01

    We will discuss application of our density functional (DFT)-based QM/MM methodology to modeling a variety of protein active sites, including methane monooxygenase, myoglobin, and cytochrome P450. In addition to the calculation of intermediates, transition states, and rate constants, we will discuss modeling of reactions requiring protein conformational changes. Our methodology reliably achieves small errors as a result of imposition of the QM/MM boundary. However, the accuracy of DFT methods can vary significantly with the type of system under study. We will discuss a novel approach to the reduction of errors in gradient corrected and hybrid DFT functionals, using empirical localized orbital corrections (DFT-LOC), which addresses this problem effectively. For example, the mean unsigned error in atomization energies for the G3 data set using the B3LYP-LOC model is 0.8 kcal/mole, as compared with 4.8 kcal/mole for B3LYP and 1.0 kcal/mole for G3 theory.

  17. Pyrotechnic reaction residue particle analysis.

    PubMed

    Kosanke, Kenneth L; Dujay, Richard C; Kosanke, Bonnie J

    2006-03-01

    Pyrotechnic reaction residue particle (PRRP) production, sampling and analysis are all very similar to that for primer gunshot residue. In both cases, the preferred method of analysis uses scanning electron microscopy to locate suspect particles and then uses energy dispersive x-ray spectroscopy to characterize the particle's constituent chemical elements. There are relatively few times when standard micro-analytical chemistry performed on pyrotechnic residues may not provide sufficient information for forensic investigators. However, on those occasions, PRRP analysis provides a greatly improved ability to discriminate between materials of pyrotechnic origin and other unrelated substances also present. The greater specificity of PRRP analysis is the result of its analyzing a large number of individual micron-sized particles, rather than producing only a single integrated result such as produced using standard micro-analytical chemistry. For example, PRRP analyses are used to demonstrate its ability to successfully (1) discriminate between pyrotechnic residues and unrelated background contamination, (2) identify that two different pyrotechnic compositions had previously been exploded within the same device, and (3) establish the chronology of an incident involving two separate and closely occurring explosions. PMID:16566762

  18. Sonochemical reactions with mesoporous alumina.

    PubMed

    Chave, Tony; Nikitenko, Sergei I; Granier, Dominique; Zemb, Thomas

    2009-04-01

    Herein, we report the sonochemical reactions with MSU-X mesoporous alumina (m-Al(2)O(3)) in aqueous solutions. Sonication (f=20 kHz, I=30 Wcm(-2), W(aq)=0.67 WmL(-1), T=36-38 degrees C, Ar) causes significant acceleration of m-Al(2)O(3) dissolution in the pH range of 4-11. Moreover, power ultrasound has a dramatic effect on the textural properties and phase composition of m-Al(2)O(3). Short-time sonication at pH = 4 leads to the formation of nanorods and nanofibers of boehmite, AlO(OH). Prolonged ultrasonic treatment causes high aspect morphology transformation to aggregated nanosheets in weakly acid solutions or plated nanocrystals in alkaline solutions. Sonochemical products in alkaline medium are composed principally from boehmite and small amounts of bayerite, Al(OH)(3). Silent hydrolysis of m-Al(2)O(3) yields boehmite at pH = 4 and bayerite at pH = 11. The effect of ultrasound on the textural properties of mesoporous alumina as well as on the transformation of nanosized bayerite to boehmite can be consistently attributed to the transient strong heating of the liquid shell surrounding the cavitation bubble which caused the chemical processes similar to those occurred during hydrothermal treatment. PMID:19211292

  19. Alchemical derivatives of reaction energetics

    NASA Astrophysics Data System (ADS)

    Sheppard, Daniel; Henkelman, Graeme; von Lilienfeld, O. Anatole

    2010-08-01

    Based on molecular grand canonical ensemble density functional theory, we present a theoretical description of how reaction barriers and enthalpies change as atoms in the system are subjected to alchemical transformations, from one element into another. The change in the energy barrier for the umbrella inversion of ammonia is calculated along an alchemical path in which the molecule is transformed into water, and the change in the enthalpy of protonation for methane is calculated as the molecule is transformed into a neon atom via ammonia, water, and hydrogen fluoride. Alchemical derivatives are calculated analytically from the electrostatic potential in the unperturbed system, and compared to numerical derivatives calculated with finite difference interpolation of the pseudopotentials for the atoms being transformed. Good agreement is found between the analytical and numerical derivatives. Alchemical derivatives are also shown to be predictive for integer changes in atomic numbers for oxygen binding to a 79 atom palladium nanoparticle, illustrating their potential use in gradient-based optimization algorithms for the rational design of catalysts.

  20. Secondary Organic Aerosol Formation by Heterogeneous

    E-print Network

    Goddard III, William A.

    Secondary Organic Aerosol Formation by Heterogeneous Reactions of Aldehydes and Ketones: A Quantum), for various short-chain aldehydes and ketones. We show that quantum mechanical gas- phase Gibbs free energies constants (reported as log K) of aerosol-phase chemical reactions, including hydration reactions and aldol

  1. Total synthesis of (-)-mucocin.

    PubMed

    Crimmins, Michael T; Zhang, Yan; Diaz, Frank A

    2006-05-25

    [reaction: see text] An enantioselective total synthesis of (-)-mucocin has been completed. A combination of asymmetric glycolate aldol additions and ring closing metathesis reactions were exploited to construct the C18-C34 and C7-C17 fragments. A selective cross-metathesis reaction was employed as the key step to couple two complex fragments. PMID:16706528

  2. One-Pot Enantioselective Syntheses of Iminosugar Derivatives Using Organocatalytic

    E-print Network

    Barbas III, Carlos F.

    -catalyzed intermolecular aldol reaction7 and other related reactions,8 enantioselective syntheses of a number of compoundOne-Pot Enantioselective Syntheses of Iminosugar Derivatives Using Organocatalytic anti-Michael-anti-Aza-Henry Reactions Ritsuo Imashiro, Hisatoshi Uehara, and Carlos F. Barbas III* The Skaggs Institute for Chemical

  3. Magnetite-supported sulfonic acid: a retrievable nanocatalyst for the Ritter reaction and multicomponent reactions

    EPA Science Inventory

    Magnetite-sulfonic acid (NanocatFe-OSO3H), prepared by wet-impregnation method, serves as a magnetically retrievable sustainable catalyst for the Ritter reaction which can be used in several reaction cycles without any loss of activity....

  4. Trajectory studies of the reaction F - +HCl --> HF+Cl - . I. Reaction rate constant

    Microsoft Academic Search

    Jianmei Wei; Qin Meng; Timothy Su

    1995-01-01

    Abinitio calculations at the MP4\\/6–31G** level in conjunction with experimental data were used to derive an analytical potential energy function for the reaction F?+HCl?HF+Cl?. A Monte Carlo-classical trajectory method was used to estimate the thermal energy reaction rate constants at various temperatures. The results showed that the reaction efficiency decreases sharply as temperature increases. At room temperature, the calculated reaction

  5. Nonequilibrium velocity distributions and reaction rates in fast highly exothermic reactions

    Microsoft Academic Search

    Katsuhisa Koura

    1973-01-01

    The nonequilibrium velocity distributions and reaction rates in fast highly exothermic reactions with a low activation energy &egr;*f?k T0 ?slant 5, a high steric factor P ?slant 0.1, and a large heat of reaction Q*?k T0 ? O (10), are investigated by solving the semiclassical Boltzmann equation with a Monte Carlo method. The explicit time-dependent velocity distribution functions and reaction

  6. Complicated Grief Reactions in Children and Adolescents

    Microsoft Academic Search

    Kathleen Nader; Alison Salloum

    2011-01-01

    An understanding of complicated grief in youth is incomplete, because the full range of observed, theorized, and studied symptoms and reactions has not yet been examined in different age groups. Until recently, scales to assess complicated grief in youth were based on adult constructs of complicated grief and did not include many of the symptoms and reactions proposed for posttrauma

  7. Modelling Reaction Times John A. Bullinaria

    E-print Network

    Bullinaria, John

    error scores in standard back­propagation networks should also be correlated with response timesModelling Reaction Times John A. Bullinaria Department of Psychology, University of Edinburgh 7 George Square, Edinburgh EH8 9JZ, UK Abstract We discuss the simulation of reaction times

  8. Modelling Reaction Times John A. Bullinaria

    E-print Network

    Bullinaria, John

    error scores in standard back-propagation networks should also be correlated with response timesModelling Reaction Times John A. Bullinaria Department of Psychology, University of Edinburgh 7 George Square, Edinburgh EH8 9JZ, UK Abstract We discuss the simulation of reaction times

  9. Basic Chemical Principles 1: Reaction Kinetics

    E-print Network

    Schofield, Jeremy

    of reactants ! mobility (masses) and density { Di#11;usion-controlled reactions: prefactor A is the most that Oxygen atom and molecule O 2 are ground state triplets. #15; Important fact: Quantum mechanics tell us: Spin forbidden #15; Consequence: Reactions with ground state Oxygen are slow #15; Molecules can

  10. The Science of Low Energy Nuclear Reactions

    Microsoft Academic Search

    Edmund Storms

    2007-01-01

    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,

  11. Detecting radiation reaction at moderate laser intensities

    NASA Astrophysics Data System (ADS)

    Heinzl, Thomas; Harvey, Chris; Ilderton, Anton; Marklund, Mattias; Bulanov, Stepan S.; Rykovanov, Sergey; Schroeder, Carl B.; Esarey, Eric; Leemans, Wim P.

    2015-02-01

    We propose a new method of detecting radiation reaction effects in the motion of particles subjected to laser pulses of moderate intensity and long duration. The effect becomes sizable for particles that gain almost no energy through the interaction with the laser pulse. Hence, there are regions of parameter space in which radiation reaction is actually the dominant influence on charged particle motion.

  12. Resonances and the thermonuclear reaction rate

    E-print Network

    M. S. Hussein; M. Ueda; A. J. Sargeant; M. P. Pato

    2003-07-21

    We present an approximate analytic expression for thermonuclear reaction rate of charged particles when the cross section contains a single narrow or wide resonance described by a Breit-Wigner shape. The resulting expression is uniformly valid as the effective energy and resonance energy coalesce. We use our expressions to calculate the reaction rate for $^{12}$C(p,$\\gamma$)$^{13}$N.

  13. Factors Affecting Reaction Kinetics of Glucose Oxidase

    Microsoft Academic Search

    Kristin A. Johnson

    2002-01-01

    Basic principles of enzyme kinetics are demonstrated using the enzyme glucose oxidase. The glucose oxidase enzymatic reaction is coupled to horseradish peroxidase, which in turn catalyzes the oxidation of a dye to a bright blue-green color. The appearance of the blue-green dye is used to monitor the course of the reaction and is quite visible in a classroom setting. A

  14. Form coke reaction processes in carbon dioxide

    Microsoft Academic Search

    L. Douglas Smoot; Steven R. Eatough; Amber B. Miller

    2007-01-01

    Uncertainty in metallurgical coke supplies has prompted development of form coke from low quality coals and fines. Reaction rates have been measured and mechanisms identified that control carbonaceous briquette reaction rate in CO2. Three briquette formulations were prepared, characterized and coked in an inert atmosphere at high temperature. A given weight of each formulation was then reacted in a packed

  15. 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...

  16. 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…

  17. Entropy Generation in a Chemical Reaction

    ERIC Educational Resources Information Center

    Miranda, E. N.

    2010-01-01

    Entropy generation in a chemical reaction is analysed 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…

  18. 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

  19. 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.

  20. Organic Reaction Mechanisms at A-Level.

    ERIC Educational Resources Information Center

    Norman, R. O. C.; Waddington, D. J.

    1979-01-01

    Advocates teaching of organic reaction mechanisms through the methods which are used in elucidating them. This also provides a useful way of illustrating the theories and methods of physical chemistry. Describes an approach to teaching three reaction mechanisms: substitution in alkanes; addition to alkenes; and ester hydrolysis. (Author/GA)