Search results for "ACETONE"
showing 10 items of 350 documents
Direct synthesis of methyl isobutyl ketone in gas-phase reaction over palladium-loaded hydroxyapatite
2005
Several compositions of palladium-loaded calcium hydroxyapatite Pd(x)/CaHAp were prepared and characterized by XRD, IR, and UV–visible spectroscopy and temperature-programmed reduction (TPR). The acid–base properties of the samples were studied with the use of butan-2-ol conversion and IR spectroscopy coupled with lutidine adsorption/desorption. Calcium hydroxyapatite bears Lewis acid sites of moderate strength and a limited number of Bronsted acid sites, which produce butenes by dehydration. The selectivity of the dehydrogenation reaction (formation of methyl ethyl ketone) is very limited in the absence of oxygen but indicates the existence on the surface of phosphate of basic sites that a…
Novel prolinamide-supported polystyrene as highly stereoselective and recyclable organocatalyst for the aldol reaction
2008
A new prolinamide derivative anchored to a polystyrene support has been straightforwardly prepared and employed as heterogeneous catalyst in the direct asymmetric aldol reaction with good results in terms of yield and stereoselectivity. The optimal reaction conditions were found when a 1:2 (v/v) water/chloroform mixture was used. This mixture was the best compromise between the good swelling properties of chloroform and the formation of a concentrated organic phase due to the presence of water. Noticeably, the enantioselectivities obtained employing acetone as ketone were, to the best of our knowledge, the highest achieved with a supported proline derivative. This catalyst can be easily rec…
Saturated vapour pressure of aroma compounds at various temperatures
2004
Abstract The aim of this study was to determine experimentally the vapour pressures of aroma compounds at various temperatures, especially at negative ones. The aroma compounds were: acetone, 2-butanone, 2-hexanone, 2-octanone, ethyl acetate, ethyl butanoate, ethyl hexanoate, n-hexanal, n-hexanol and γ-hexalactone. The technique used was a static device where vapour pressure was measured at equilibrium. The temperatures of analysis varied from −40 to 25 °C. Volatility of a pure compound depends on characteristics such as length of the aliphatic chain, the functional group and temperature. Among an homologous series, volatility increases when the aliphatic chain decreases and when temperatur…
Photolysis of Adsorbed Phases: Ethanoic Acid-Insulators and Semiconductors Systems. Influence of Acid-Base Properties.
1986
The paper reports the results of experiments in which the photodecomposition of adsorbed ethanoic acid (and in few cases of adsorbed acetone and ethanol) was carried out by using several silica gel samples, whose properties were modified by adding oxidic dopants as γ-Al2O3, which is acidic in character, and MgO, which is mainly basic. Also the related system MgO-Al2O3 was investigated. Few IR spectra on selected pure specimens and on specimens containing adsorbed ethanoic acid were recorded with the aim of following the variation of the surfaces-adsorbate interaction with the variation of the acid-base properties. It was also of interest to compare the photoreactivity of insulators and semi…
Preferential evaporation of precipitants from polymer solutions in mixed solvents
2000
Partial vapor pressures were measured for the volatiles of solutions of polysulfone or polyethersulfone in mixtures of N,N-dimethylformamide (DMF, solvent) and water or acetone (precipitants) by means of headspace gas chromatography. The results demonstrate that the enrichment of water in the gas phase increases exponentially with rising polymer concentration, in contrast to that of acetone which remains constant. The reinforced expulsion of water resulting from the presence of polymers is theoretically conceivable and should be useful in the field of separation techniques.
Evidence of ternary interaction parameters for polymer solutions in mixed solvents from headspace-gas chromatography
2000
Partial vapor pressures of the volatiles have been measured for four solvent/precipitant/polymer systems at different temperatures. The high molecular weight compounds were polysulfone or polyethersulfone and the mixed solvent was either DMF/acetone or DMF/water. Systems containing the very powerful precipitant water exhibit a special phenomenon: Upon the addition of polymer to a mixed solvent of constant composition the partial vapor pressure of water increases by a factor of more than two before it falls to zero as the volume fraction of the polymer approaches unity. This particular situation cannot be modeled using binary interaction parameters only, in contrast to the results obtained w…
Classification of vegetable oils according to their botanical origin using amino acid profiles established by High Performance Liquid Chromatography …
2010
Abstract A preliminary study using amino acid profiles to classify oils according to their botanical origin has been performed. Amino acid profiles were obtained from hydrolysis of proteins present in vegetable oils, and established by High Performance Liquid Chromatography (HPLC) with UV–vis detection. Proteins present in hazelnut, corn, soybean, olive, avocado, peanut and grapeseed oils were precipitated with acetone, and the residue was hydrolysed in acid medium. The amino acids obtained were derivatized with o -phthaldialdehyde and separated by HPLC. Peaks corresponding to 18 amino acids were observed using a C18 column and a gradient of acetonitrile–water in the presence of a 5 mM citr…
Density functional theory study of the 5-pyrrolidin-2-yltetrazole-catalyzed aldol reaction
2005
Abstract The replacement of the carboxylic acid functionality with a tetrazolic acid in the proline-catalyzed asymmetric aldol reaction between acetone and trimethylacetaldehyde has been studied using DFT methods at the B3LYP/6-31G** computational level. For the C–C bond-formation step, four reactive channels corresponding to the syn and anti arrangement of the enamine and the re and si attack modes have been analyzed. The B3LYP/6-31G** results allowed us to explain the stereoselectivity and the increase in reactivity relative to the proline-catalyzed process in DMSO.
ChemInform Abstract: Novel Prolinamide-Supported Polystyrene as Highly Stereoselective and Recyclable Organocatalyst for the Aldol Reaction.
2008
A new prolinamide derivative anchored to a polystyrene support has been straightforwardly prepared and employed as heterogeneous catalyst in the direct asymmetric aldol reaction with good results in terms of yield and stereoselectivity. The optimal reaction conditions were found when a 1:2 (v/v) water/chloroform mixture was used. This mixture was the best compromise between the good swelling properties of chloroform and the formation of a concentrated organic phase due to the presence of water. Noticeably, the enantioselectivities obtained employing acetone as ketone were, to the best of our knowledge, the highest achieved with a supported proline derivative. This catalyst can be easily rec…
Reibungsverhalten und Trägheitsradien von oligomeren Polypropylenglykolen
1971
Die Ergebnisse von Viskositats- und Diffusionsmessungen an oligomeren Propylenglykolen in Aceton und Benzol werden benutzt, um nach den verschiedenen Theorien die viskosimetrischen und Reibungstragheitsradien zu ermitteln. Ein Vergleich mit direkt durch Streuversuche mit der Rontgenkleinwinkelmethode gefundenen Tragheitsradien zeigt die Gultigkeit der klassischen Viskositatstheorien, wahrend die gleichen Theorien bei der Reibung versagen. Aus [f] = 16,4 · R erhalt man jedoch wie bei Hochpolymeren auch fur Oligomere vernunftige Tragheitsradien. Results of viscometric and frictional measurements on oligomeric propylene glycols in acetone and benzene have been used to calculate the values of v…