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Oromí-Farrús Mireia - - 2008
Haloesterification of diverse diols with various carboxylic acids was achieved using potassium halides (KX) as the only halide source in ionic liquids. The best yield was obtained in [BMIM][PF(6)] when 1,2-octanediol, palmitic acid and KBr were used. This yield was 85% and the regioisomer with the bromine in primary position ...
Deshmane Vishwanath G - - 2009
Esterification is one of the most preferred synthesis routes for organic esters which are most frequently used as plasticizers, solvents and perfumery and flavour chemicals. The present work deals with acid catalyzed synthesis of isopropyl esters from palm fatty acid distillate (PFAD) in the presence of ultrasonic irradiations operating at ...
Suzuki Daisuke - - 2008
Self-oscillation for the microgel particles ( approximately 200 nm in diameter) was studied by changing initial substrate concentrations (i.e., malonic acid, sodium bromate, and nitric acid) of the Belousov-Zhabotinsky (BZ) reaction that is used for chemical energy for the self-oscillation. The cross-linked microgels are composed of N-isopropylacrylamide and ruthenium tris(2,2'-bipyridine), ...
Navalon Sergio - - 2009
Chlorine dioxide is a hypochlorite alternative disinfectant agent. In this context, we have determined the products formed in the reaction of ClO(2) with selected amino acids as model compounds that can be present in natural waters. The reaction of tryptophane, histidine and tyrosine (10 ppm each) with ClO(2) were studied ...
Fernández-Alonso Alejandra - - 2008
We have investigated the effects of solvent composition, acidity and temperature on the dediazoniation of 4-bromobenzenediazonium (4BrBD) ions in MeOH-H(2)O mixtures by employing a combination of spectrometric and chromatographic techniques. The kinetic behaviour is quite complex; in the absence of MeOH, dediazoniations follow first-order kinetics with a half-life t(1/2) approximately ...
Verma M L - - 2008
A purified alkaline thermo-tolerant bacterial lipase from Bacillus cereus MTCC 8372 was immobilized on a Poly (MAc-co-DMA-cl-MBAm) hydrogel. The hydrogel showed approximately 94% binding capacity for lipase. The immobilized lipase (2.36 IU) was used to achieve esterification ofmyristic acid and isopropanol in n-heptane at 65 degrees C under continuous shaking. ...
Motokura Ken - - 2008
This article illustrates the modification of oxide surfaces with organic amine functional groups to create acid-base bifunctional catalysts, summarizing our previous reports and also presenting new data. Immobilization of organic amines as bases on inorganic solid-acid surfaces afforded highly active acid-base bifunctional catalysts, which enabled various organic transformations including C--C ...
Matsushita Yasuyuki - - 2009
Sulfuric acid lignin (SAL), which is formed as a by-product during the production of bioethanol from woody biomass, was solubilized and functionalized by hydrothermal reaction. SAL could be easily dissolved in an alkaline medium, especially sodium hydroxide solution, by this reaction. The soluble part of the reaction products (S-HSAL) could ...
Wada Akimori - - 2008
Various 5-substituted retinoic acids were prepared by a palladium-catalyzed cross coupling reactions of vinyl nonaflates and E- or Z-3-tributylstannyl-2-beten-1-ol as a key reaction. These coupling products were then converted to the corresponding all-E- and 9Z-retinoic acid analogs via Horner-Emmons reaction and subsequent basic hydrolysis, and their biological activities were evaluated. ...
Rica Tamás - - 2008
We have studied the density fingering of an acid-catalyzed autocatalytic reaction in the presence of carboxylate containing polyelectrolyte. The decrease in viscosity as a result of the change in the ionic character of the polymer due to the pH-change during the reaction is the major driving force for the spatiotemporal ...
Ma Yan - - 2008
The gas-phase ozonolysis of beta-pinene was studied in static chamber experiments, using gas chromatography coupled to mass spectrometric and flame ionisation detection to separate and detect products. A range of multifunctional organic acids-including pinic acid, norpinic acid, pinalic-3-acid, pinalic-4-acid, norpinalic acid and OH-pinalic acid-were identified in the condensed phase after ...
Chambreau Steven D - - 2008
A class of room-temperature ionic liquids (RTILs) that exhibit hypergolic activity toward fuming nitric acid is reported. Fast ignition of dicyanamide ionic liquids when mixed with nitric acid is contrasted with the reactivity of the ionic liquid azides, which show high reactivity with nitric acid, but do not ignite. The ...
Hudson Reggie L - - 2008
Solid CH(3)CN and solid H(2)O + CH(3)CN were ion irradiated near 10 K to initiate chemical reactions thought to occur in extraterrestrial ices. The infrared spectra of these samples after irradiation revealed the synthesis of new molecules. After the irradiated ices were warmed to remove volatiles, the resulting residual material ...
Dunlop Alex - - 2008
The direct manipulation by atomic force microscopy (AFM) of individual macrocycles within a rotaxane offers a potential route to a new sequencing tool for complex macromolecules such as polysaccharides, glycoproteins and nucleic acids. In this paper we demonstrate for the first time that a sliding contact made between a macrocycle, ...
Si Lin - - 2008
Mercury is an environmental contaminant of global concern. The reduction of oxidized mercury species (Hg(II)) by organic acids to elemental mercury (Hg0) is significant for understanding the cycling of mercury between the atmosphere and aqueous systems. This study focused on the reduction of Hg(II) by small, semivolatile dicarboxylic acids (C2-C4). ...
Weitkamp Emily A - - 2008
Multiphase oxidation of trace organic constituents inside of complex atmospheric particles is not well understood. In this study, organic aerosol formed from flash-vaporized residual grease from meat cooking was exposed to atmospherically relevant ozone concentrations in a smog chamber for 4-6 h. Changes in particle composition were measured to determine ...
Mohandass Chellandi - - 2008
Recycled blue colored paper was treated with laccase under various combinations of physical and chemical parameters including enzyme concentration, temperature, oxygen, and reaction time. Laccase treatment of recycled dyed pulp increased acid group content, tear index, tensile index, and color removal in a dose-dependent manner. Lengthening the treatment time from ...
Seeliger Florian - - 2008
Kinetics of the reactions of four benzenesulfonyl-stabilized carbanions (1a-d)- with reference electrophiles (quinone methides 2 and diarylcarbenium ions 3) have been determined in dimethyl sulfoxide solution at 20 degrees C in order to derive the reactivity parameters N and s according to the linear free-energy relationship logk(20 degrees C) = ...
Chen Jing - - 2008
Resting cells of Bacillus subtilis ZJB-063 were used for the direct transformation of MOPAN (p-methoxyphenylacetonitrile) to MOPAA (p-methoxyphenylacetic acid), which is an important pharmaceutical intermediate. The B. subtilis ZJB-063 culture conditions for the production of nitrilase and the reaction conditions for this nitrilase-mediated conversion were optimized. The maximum production of ...
Chen Hsin-Tsung - - 2008
The mechanisms and kinetics of unimolecular decomposition of succinic acid and its anhydride have been studied at the G2M(CC2) and microcanonical RRKM levels of theory. It was shown that the ZsgsZ conformer of succinic acid, with the Z-acid form and the gauche conformation around the central C-C bond, is its ...
Morishita Takami - - 2008
Arynes were found to couple with aminosilanes and carbonyl compounds in the presence of benzoic acid to provide 2-aminobenzhydrols. Sulfonylimines could also be applied to the reaction, enabling amino and aminomethyl moieties to be incorporated into contiguous positions of aromatic skeletons. Only a small amount of the three-component coupling product ...
Li Nan - - 2008
This study presents an experimental investigation of nonlinear dynamics in the photomediated bromate-1,4-benzoquinone-1,4-hydroquinone reaction, in which the copresence of hydroquinone and benzoquinone results in chemical oscillations taking place shortly after mixing all reagents together, which is in great contrast to the case of a few hours of induction time seen ...
Minerath Emily C - - 2008
Sulfate esters have recently been identified in the secondary organic aerosol (SOA) formed in the photooxidation of biogenic hydrocarbons both in laboratory and under ambient atmospheric conditions. In the present study, the kinetics feasibility of direct reactions between alcohols and sulfuric acid to form sulfate esters in aerosol particles is ...
Sentandreu Enrique - - 2008
This work evaluates the reduction kinetics of the antiradical probe 2,2-diphenyl-1-picrylhydrazyl (DPPH (*)) in methanol and acetonitrile by the antiradical activity of protocatechuic acid (3,4-dihydroxybenzoic acid, 1) and protocatechuic acid methyl ester ( 2). The reduction kinetics of DPPH (*) in both solvents by the antiradical activity of the p-catechol ...
Vanag Vladimir K - - 2008
We discuss the design of reaction-diffusion systems that display a variety of spatiotemporal patterns. We also consider how these patterns may be controlled by external perturbation, typically using photochemistry or temperature. Systems treated include the Belousov-Zhabotinsky (BZ) reaction, the chlorite-iodide-malonic acid and chlorine dioxide-malonic acid-iodine reactions, and the BZ-AOT system, ...
Shimizu Mikio - - 2008
Conversion of glucose to pyruvate via reactions homologous to the non-phosphorylated Entner-Doudoroff (non-P ED) pathway could be achieved in the presence of two amino acid catalysts, cysteine and histidine: cystine oxidizes glucose to gluconic acid by the reaction homologous to glucose dehydrogenase and histidine changes gluconic acid to 2-keto-3-deoxy gluconic ...
Limacher Anita - - 2008
The formation of furan and 2-methylfuran was studied in model systems based on sugars and selected amino acids. Both compounds were preferably formed under roasting conditions in closed systems yielding up to 330 micromol of furan and 260 micromol of 2-methylfuran per mol of precursor. The amounts obtained under pressure ...
Bray Christopher D - - 2008
Deprotonation of o-hydroxybenzyl acetate with (i)PrMgCl provides a method of generating an o-quinone methide under mild, anionic conditions, such that highly sensitive exo-enol ethers can be employed as 2pi partners in hetero-Diels-Alder reactions. This process results in mono-benzannelated spiroketals such as those found in the natural products berkelic acid, the ...
Keerthi Kripa - - 2008
Sulfenic acids (RSOH) are among the most common sulfur-centered reactive intermediates generated in biological systems. Given the biological occurrence of sulfenic acids, it is important to explore the reactivity of these intermediates under physiological conditions. The Morin rearrangement is a synthetic process developed for the conversion of penicillin derivatives into ...
Hallmann Christian - - 2008
The conversion efficiency of alkanoic, alkenoic, branched, alicyclic, aromatic, keto-substituted, and dioic carboxylic acids to their corresponding butyl esters was compared under different reaction conditions (time, temperature, catalyst). We show that boron trifluoride is generally a more efficient catalyst than sulphuric acid. However, optimum derivatisation conditions vary strongly for different ...
Kesselring David - - 2008
A strategy for site-selectively generating reactive N-acyliminium ion intermediates on a microelectrode array has been developed. The route capitalizes on the use of an electroauxiliary for building a methoxylated amino acid substrate, and then the electrochemical generation and solution phase confinement of acid in order to form the N-acyliminium ion. ...
Nakamura Satoshi - - 2008
We present superacid-catalyzed intramolecular cyclization reactions of arylcyanopropionates to give cyclized five- and six-membered beta-enamino esters in moderate to high yields. Known intramolecular ring-closing reactions of protonated nitrile to aromatic carbon atom are limited to the 6-membered case. Interestingly, a significant synergistic increase of reactivity of the cyano functionality was ...
Ohno Yoko - - 2008
Malic enzyme [L-malate: NAD(P)(+) oxidoreductase (EC 1.1.1.39)] catalyzes the oxidative decarboxylation of L-malic acid to produce pyruvic acid using the oxidized form of NAD(P) (NAD(P)(+)). We used a reverse reaction of the malic enzyme of Pseudomonas diminuta IFO 13182 for HCO(3)(-) fixation into pyruvic acid to produce L-malic acid with ...
Nassiri Mahmoud - - 2008
Multicomponent reactions involving azines (phenanthridine or isoquinoline) and dimethyl acetylenedicarboxylate were undertaken in the presence of heterocyclic NH compounds (indole, 2-methyl indole, 3-methyl indole, carbazole and 3,6-dibromocarbazole) or 1,3-dicarbonyl compounds such as N,N'-dimethylbarbituric acid, 1,3-diethyl-2-thiobarbituric acid, acetylacetone, 1,3-diphenyl-1,3-propandione and cyclopentan-1,3-dione to generate enaminoesters in good yields.
Lu Li-li - - 2008
High temperature liquid water (HTLW) has drawn increasing attention as an environmentally benign medium for organic chemical reactions, especially acid-/base-catalyzed reactions. Non-catalyzed hydrolyses of gallotannin and tara tannin in HTLW for the simultaneous preparation of gallic acid (GA) and pyrogallol (PY) are under investigation in our laboratory. In this study, ...
Okazaki Seiji - - 2008
D-Amino acid amidase (DAA) from Ochrobactrum anthropi SV3 catalyzes D-stereospecific hydrolysis of amino acid amides. DAA has attracted attention as a catalyst for the stereospecific production of D-amino acids, although the mechanism that drives the reaction has not been clear. Previously, the structure of DAA was classified into two types, ...
Wang Xiaoqiong - - 2008
A simple, rapid ligand exchange route to prepare highly fluorescent, stable and water-soluble CdSe quantum dots (QDs) is reported by using p-sulfonatocalix(n)arene (SFCA(n), n = 4 or 6) instead of original trioctylphosphine oxide (TOPO) ligands. The ligands were found to have a profound effect on the luminescence response of QDs ...
Massah Ahmad Reza - - 2008
Silica sulfuric acid catalyzes efficiently the reaction of sulfonamides with both carboxylic acid anhydrides and chlorides under solvent-free and heterogeneous conditions. All the reactions were done at room temperature and the N-acylsulfonamides were obtained with high yields and purity via an easy work-up procedure. This method is attractive and is ...
Nematollahi D - - 2008
Electrochemical oxidation of catechols has been studied in the presence of Meldrum's acid derivatives as nucleophiles in aqueous solution, by means of cyclic voltammetry and controlled-potential coulometry. Catechols in the Michael addition reaction react with Meldrum's acids to form adducts that can undergo electrooxidation. Such products were obtained in good ...
Martínez-Ruiz Antonio - - 2008
This paper reports a study of the enzymatic esterification of oleic acid and ethanol. The reaction was catalyzed by lipases produced by solid-state fermentation with Rhizopus sp. Olive oil and perlite were used as an inducer and inert support, respectively. Synthesis of ethyl oleate was carried out in a 10-mL ...
Garbe Leif Alexander - - 2008
The reaction pathways of amino acids and reducing sugars are now fully understood. The focus in the last few years, however, has turned to the reaction of peptides and proteins with reducing sugars. We have investigated the reaction of gamma-aminobutanoic acid, the heptapeptide Nalpha-Acetyl-Lys-Lys-beta-Ala-Lys-beta-Ala-Lys-Gly, and the model protein beta-casein in ...
Hidalgo Francisco J - - 2008
Amino acid degradation plays an important role in the formation of both flavors and toxic compounds during food processing. These reactions are produced, to a significant extent, as a consequence of the Maillard reaction among amino acids and carbohydrates. However, recent studies have shown that lipids also take part in ...
Morawicki R O - - 2008
1-Octen-3-ol and 10-oxo-trans-8-decenoic acid are metabolites of the breakdown of linoleic acid (LA) by mushroom enzymes. These compounds can be produced in a bioreactor using a crude mushroom homogenate and the exogenous addition of LA and oxygen. The factors' duration of blending, mushroom-buffer ratio, effect of a surfactant, whole against ...
Tseng Yao-Hung - - 2008
We demonstrate that glutaric acid can be used to prepare nanorods of hydroxyapatite under hydrothermal condition at 100 degrees C with a Ca(2+):glutaric acid molar ratio of 1:4. Frequency-switched Lee-Goldburg irradiation is employed to obtain high-resolution (31)P{(1)H} correlation spectra of the reaction mixture at two different reaction periods, from which ...
Lemma Kelemu - - 2008
The kinetics and mechanism of the hydrolysis of cysteine sulfenyl thiocyanate (CySSCN) to give cysteine thiosulfinate ester (CyS(=O)SCy) have been investigated between pH 0 and 4. The reaction is reversible. The hydrolysis of CySSCN is second-order in [CySSCN] and inverse first-order in [H+] and [SCN-]. The following mechanism is proposed ...
Narai-Kanayama Asako - - 2008
Papain polymerizes L-glutamic acid diethyl ester (Glu-di-OEt) regioselectively, resulting in the formation of poly (gamma-ethyl alpha-L-glutamic acid) with various degrees of polymerization of less than 13. Reaction temperatures below 20 degrees C were appropriate for the reaction in terms of suppression of non-enzymatic degradation of Glu-di-OEt and an increase in ...
Wiitala Keith W - - 2008
Penam acids 6-8 [i.e., (2S,5R,6R)-, (2S,5S,6R)-, and (2S,5R,6S)-isomers of 6-(1,3-dihydro-1,3-dioxo-2H-isoindol-2-yl)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid] were prepared by deesterification of the corresponding methyl esters 2-4. The same methodology applied to ester 1 did not lead to the (2S,5S,6S)-isomer 5 but rather a 72% yield of the thiazoline derivative 9. High-resolution mass spectrometry analysis of ...
Xu Hui - - 2008
Mandelic acid was synthesized from benzaldehyde with chloroform in a 81% yield at 60 degrees C for 2 h by using triethylbenzylammonium chloride (TEBA) and poly(ethylene glycol)-800 (PEG-800) as a complex phase transfer catalyst under ultrasonic irradiation. The main advantages of this present method are that the reaction time is ...
Adams An - - 2008
Alkylpyrazines are a very important class of Maillard flavor compounds, but their mechanism of formation is complex and consists of different pathways. The model reaction of 20 different amino acids with 1,3-dihydroxyacetone, as a precursor of 2-oxopropanal, was studied by means of SPME-GC-MS to investigate the involvement of the amino ...
Lamoolphak Wiwat - - 2008
Non-catalytic hydrothermal decomposition of sericin and fibroin from silk waste into useful protein and amino acids was examined in a closed batch reactor at various temperatures, reaction times, and silk to water ratios to examine their effects on protein and amino acid yields. For the decomposition of sericin, the highest ...
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