Home About us Contact
|
Home About us Contact | ||
|
|
||
Various Alcohols (various + alcohol)
Selected AbstractsReusable Copper-Aluminum Hydrotalcite/rac -BINOL System for Room Temperature Selective Aerobic Oxidation of AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009M. Lakshmi Kantam Abstract An efficient catalyst system consisting of copper-aluminum hydrotalcite/rac- BINOL ligand has been developed for the oxidation of alcohols using air as a green oxidant at room temperature. Various alcohols could be transformed into their corresponding aldehydes or ketones in good to excellent yields using the set of optimal conditions. This composite catalytic system can also be recovered and reused for several cycles without a significant loss of catalytic activity. [source] A visualized analysis of small-angle neutron scattering intensity: concentration fluctuation in alcohol,water mixturesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007T. Sato Small-angle neutron scattering measurements have been performed on tert -butyl alcohol,water mixtures with alcohol concentrations from 0.05 to 0.30 mole fractions at 298, 313 and 328,K. Concentration fluctuations of the mixtures are analysed in terms of fractals. The structure of the concentration fluctuation is visualized by means of a large-scale reverse Monte Carlo technique. Percolation analysis of the visualized structure shows that the concentration fluctuation is characterized by polydisperse mass fractals, as found for 1-propanol,water mixtures. It seems that polydisperse mass fractals are a common structural characteristic in various alcohol,water mixtures. [source] Redox-Active Catalyst Based on Poly(Anilinesulfonic Acid)- Supported Gold Nanoparticles for Aerobic Alcohol Oxidation in WaterADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Daisuke Saio Abstract The hybrid consisting of gold nanoparticles and poly(2-methoxyaniline-5-sulfonic acid), which works as a redox mediator for transferring protons and electrons, catalyzed the oxidation reaction of various alcohols in water under molecular oxygen. [source] Size-Dependent Catalytic Activity of Supported Palladium Nanoparticles for Aerobic Oxidation of AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2008Jing Chen Abstract Silica-alumina (SiO2 -Al2O3)-supported palladium catalysts prepared by adsorption of the tetrachloropalladate anion (PdCl42,) followed by calcination and reduction with either hexanol or hydrogen were studied for the aerobic oxidation of alcohols. The mean size of the Pd particles over the SiO2 -Al2O3 support was found to depend on the Si/Al ratio, and a decrease in the Si/Al ratio resulted in a decrease in the mean size of the Pd nanoparticles. By changing the Si/Al ratio, we obtained supported Pd nanoparticles with mean sizes ranging from 2.2 to 10,nm. The interaction between the Pd precursor and the support was proposed to play a key role in tuning the mean size of the Pd nanoparticles. The Pd/SiO2 -Al2O3 catalyst with an appropriate mean size of Pd particles could catalyze the aerobic oxidation of various alcohols to the corresponding carbonyl compounds, and this catalyst was particularly efficient for the solvent-free conversion of benzyl alcohol. The intrinsic turnover frequency per surface Pd atom depended significantly on the mean size of Pd particles and showed a maximum at a medium mean size (3.6,4.3,nm), revealing that the aerobic oxidation of benzyl alcohol catalyzed by the supported Pd nanoparticles was structure-sensitive. [source] A Mechanistic Study on Alcohol Oxidations with Oxygen Catalysed by TPAP-Doped Ormosils in Supercritical Carbon DioxideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2005Sandro Campestrini Abstract The heterogeneous oxidation of various alcohols with oxygen catalysed by TPAP-doped ormosils in scCO2 at 75,°C and 22.0,MPa has been studied in detail. Sol-gel segregation of TPAP into the inner porosity of an organically modified silica (ormosil) xerogel along with the use of a reaction medium which does not dissolve the catalyst, prevents aggregation of oxidation-inactive ruthenium derivatives without the need of chemical tethering. Thus, at least 140 TONs may be obtained in the oxidation of primary alcohols with the formation of aldehydes as sole reaction products. Investigation of the oxidation mechanism shows that the catalytic process exhibits a first-order dependence on the amount of catalyst, a fractional order on the alcohol concentration and a negative order for oxygen pressures higher than 0.2,bar. Evidence is presented for an associative oxidation mechanism simultaneously involving TPAP, organic substrate and oxygen. [source] Synthesis and some reactions of 4-(ethoxycarbonyl)-1,5-diphenyl-1H -pyrazole-3-carboxylic acidJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2007Ahmet, ener 1,5-Diphenyl-1H -pyrazole-3,4-dicarboxylic acid-4-ethyl ester 2, obtained from the 4-ethoxycarbonyl-5-phenyl-2,3-furandione 1 and N -benzylidene- N,-phenyl hydrazine, was converted via reactions of its acid chloride 3 with various alcohols or N-nucleophiles into the corresponding ester 5 or amide derivatives 6, respectively. In addition, 2 was decarboxylated to give ethyl 1,5-diphenylpyrazole-4-carboxylate 4. Nitrile 7 derivative of 2 was also obtained by dehydration of 6a in a mixture of SOCl2 and DMF. While cyclocondensation reaction of 2 with hydrazine hydrate leads to the formation of pyrazolo[3,4- d]pyridazine-4,7-dione 8, the reaction of 3 with anhydrous hydrazine provided a new bis pyrazole derivative 9. [source] Studies on the reactions of cyclic oxalyl compounds with hydrazines or hydrazones : Synthesis and reactions of 4-benzoyl-1-(3-nitrophenyl)-5-phenyl-1H -pyrazole-3-carboxylic acidJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2002Ahmet, ener The 1H -pyrazole-3-carboxylic acid 2, obtained from the furan-2,3-dione 1 and N -Benzylidene- N'-(3-nitrophenyl) hydrazine, was converted via reactions of its acid chloride 3 with various alcohols or N-nucleo-philes into the corresponding ester or amide derivatives 4 or 5, respectively. Nitrile 6 and anilino-pyrazole acid 7 derivatives of 2 were also obtained by dehydration of 5a in a mixture of SOCl2 with DMF and reduction of 2 with sodium polysulphide, respectively. While cyclocondensation reactions of 2 or 7 with phenyl hydrazine or hydrazine hydrate and 6 with only anhydrous hydrazine lead to derivatives of pyrazolo[3,4- d]-pyridazinone 8 and pyrazolo[3,4- d]pyridazine amine 9, respectivel. The reaction of 2 with 2-hydrazinopyri-dine provided hydrazono-pyrazole acid derivative 10, which was decarboxylated to give hydrazono-pyra-zole derivative 11. Pyrazolo[4,3- d]oxazinone 12 and 2-quinolyl pyrazolo[3,4- d]pyridazine 13 derivatives were also prepared by cyclocondensation reactions of 2 with hydroxylamine hydrochloride and 7 with acetaldehyde, respectively. [source] Profiling human gut bacterial metabolism and its kinetics using [U- 13C]glucose and NMRNMR IN BIOMEDICINE, Issue 1 2010Albert A. de Graaf Abstract This study introduces a stable-isotope metabolic approach employing [U- 13C]glucose that, as a novelty, allows selective profiling of the human intestinal microbial metabolic products of carbohydrate food components, as well as the measurement of the kinetics of their formation pathways, in a single experiment. A well-established, validated in vitro model of human intestinal fermentation was inoculated with standardized gastrointestinal microbiota from volunteers. After culture stabilization, [U- 13C]glucose was added as an isotopically labeled metabolic precursor. System lumen and dialysate samples were taken at regular intervals. Metabolite concentrations and isotopic labeling were determined by NMR, GC, and enzymatic methods. The main microbial metabolites were lactate, acetate, butyrate, formate, ethanol, and glycerol. They together accounted for a 13C recovery rate as high as 91.2%. Using an NMR chemical shift prediction approach, several minor products that showed 13C incorporation were identified as organic acids, amino acids, and various alcohols. Using computer modeling of the 12C contents and 13C labeling kinetics, the metabolic fluxes in the gut microbial pathways for synthesis of lactate, formate, acetate, and butyrate were determined separately for glucose and unlabeled background substrates. This novel approach enables the study of the modulation of human intestinal function by single nutrients, providing a new rational basis for achieving control of the short-chain fatty acids profile by manipulating substrate and microbiota composition in a purposeful manner. Copyright © 2009 John Wiley & Sons, Ltd. [source] A Laser Flash Photolysis Study of Curcumin in Dioxane,Water Mixtures,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2001F. Ortica ABSTRACT Curcumin [bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione] was studied by means of UV,VIS absorption spectroscopy and nanosecond laser flash photolysis in 1,4-dioxane,water mixtures in a series of dioxane,water volume ratios. The transient characteristics were found to be dependent on the amount of water. In pure dioxane the triplet state of the molecule in its enolic form was detected (,max= 720 nm, ,= 3.2 ,s), whereas upon water addition, the diketo form was found to prevail, because of the perturbation of intramolecular H-bonded structure. This led to hydrogen abstraction from dioxane by curcumin triplet state and the formation of the corresponding ketyl radical (,max= 490 nm, ,, 10 ,s). Laser flash photolysis measurements, carried out in solvents of different polarity and proticity (benzene, cyclohexane and various alcohols), allowed the transient assignments to be confirmed, supporting our interpretation. [source] Electrically conductive sensors for liquids based on ternary immiscible polymer blends containing polyanilinePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2004H. Cooper Abstract Electrically conductive blends, containing two immiscible polymers (ethylene vinyl acetate, EVA-19, and copolyamide 6/6.9, CoPA) and polyaniline (PANI), were produced by melt processing. These blends showed a preferred localization of PANI in the CoPA phase, thus enhancing the formation of continuous conducting networks. Electrically conductive PANI-containing filaments produced by a capillary rheometer process at various shear rate levels were studied as sensing materials for a homologous series of alcohols (methanol, ethanol and 1-propanol). All filaments showed a decreasing resistance upon exposure to these solvents. Filaments exposed to methanol, liquid or vapor, exhibited the highest resistance decrease. This behavior was related to the highest polarity of methanol, compared with ethanol and 1-propanol. The filaments' rate of production significantly affects the relative resistance change upon exposure to the various alcohols and their reproducibility. Copyright © 2004 John Wiley & Sons, Ltd. [source] Electrospray ionization mass spectrometric studies of phosphorus oxychloride directed synthesis of homo-oligopeptide ester librariesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2002Ning Zhou With the assistance of phosphorus oxychloride, ,-amino acids were assembled into homo-peptides, which were analyzed by electrospray ionization mass spectrometry (ESI-MS) and multistage electrospray ionization mass spectrometry (ESI-MS/MS). On quenching with water or various alcohols, the reaction mixtures yielded the corresponding peptides or peptide esters, respectively. This paper reports a simple method to synthesize the homo-oligo-peptide-ester conjugated library by phosphorus oxychloride activation. Copyright © 2002 John Wiley & Sons, Ltd. [source] Method for Lipase-Catalyzed Carbonate Synthesis via One- and Two-Step Alkoxycarbonylation ReactionsBIOTECHNOLOGY PROGRESS, Issue 2 2003Sangeetha M. Chandrasekaran Lipase-catalyzed alkoxycarbonylation methods offer potential advantages over the currently practiced industrial scale chemical synthesis of carbonates. We report a method for synthesis of organic carbonates via lipase-catalyzed alkoxycarbonylation between diphenyl carbonate and various alcohols in hexane. This method utilizes precursors that are readily available and does not involve extensive purification of the intermediate. In a two-step process, the two phenyl groups of diphenyl carbonate were substituted by two alcohol nucleophiles. The approach was demonstrated for two-step synthesis of 14 different disubstituted carbonate products. The rates of reaction for the two steps were much slower if the order of nucleophile addition was reversed. Under optimal conditions, complete conversion of diphenyl carbonate occurred within 8,15 h at 50 °C, which is a significant improvement from 50,90 h at 24 °C. A kinetic model for the alkoxycarbonylation reaction was derived based on the Michaelis-Menten equation, which simplified to first-order kinetics at low and equimolar concentration of substrates. [source] Imidazolium Polyoxometalate: An Ionic Liquid Catalyst for Esterification and Oxidative EsterificationCHEMCATCHEM, Issue 9 2010Huan Li Abstract A new family of polyoxometalate-based ionic liquids (POM-IL) is synthesized, characterized, and employed as catalysts in the esterification of various alcohols with acetic acid. The ionic liquid catalyst shows high activity and gives excellent yields of esters. An emulsion forms between the IL catalyst and substrates during the reaction and promotes the catalytic process. After reaction, the emulsion can conveniently be broken by the addition of a weakly polar organic solvent to facilitate the separation of the catalyst. On the basis of the above results, a direct transformation of benzaldehyde to methyl ester under relatively mild conditions is also developed in the absence of any cocatalyst. Finally, the scope of the substrates and recyclability of the catalyst are also investigated. [source] Enantioseparation of novel chiral tetrahedral clusters on an amylose tris-(3,5-dimethylphenylcarbamate) chiral stationary phase by normal phase HPLCCHINESE JOURNAL OF CHEMISTRY, Issue 10 2004Wen-Zhi Li Abstract Amylose tris(3,5-dimethylphenylcamate) (ADMPC) coated on a kind of small particle silica gel was prepared. On this ADMPC chiral stationary phase (CSP), the direct enantiomeric separation of six novel chiral transition metal tetrahedral clusters has firstly been achieved using n -hexane as the mobile phase containing various alcohols as modifiers. The effect of mobile phase modifiers and the structural variation of the solutes on their retention factors (k) and resolutions (Rs) were investigated. The result suggests that not only the structure and concentration of alcohol in mobile phase, but also the structural differences in racemates can have a pronounced effect on enantiomeric separation. ADMPC-CSP is a suitable CSP for the optical resolution of chiral tetrahedral cluster by HPLC. [source] | |||||||||||||