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Few Compounds (few + compound)
Selected AbstractsGroup contribution prediction of surface charge density profiles for COSMO-RS(Ol)AICHE JOURNAL, Issue 12 2007Tiancheng Mu Abstract A new method for predicting the surface charge density distribution (, profile) and cavity volume of molecules based on group contributions was developed. The original , profiles used for the regression were obtained using Gaussian 03 B3LYP/6-311G(d,p). In total 1363 , profiles were used for the regression of group parameters. Group definitions are identical to those used previously for boiling point estimation. Original and estimated , profiles were used to predict activity coefficients at infinite dilution and VLE data of binary systems using the COSMO-RS(Ol) model. The results were compared with the experimental data stored in the Dortmund Data Bank. In many cases the results were of comparable accuracy. However, for a few compounds, poor results were obtained, in particular for conjugated components like nitrobenzenes. The method offers a fast and reliable generation of , profiles to be used with COSMO-RS(Ol) within its range of applicability. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Electrospray ionization and atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry of antioxidants applied in lubricants,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2009Alexander Kassler The aim of this study was to investigate the utility of ion trap mass spectrometry (ITMS) in combination with the two desorption/ionization methods, electrospray (ESI) and atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI), for the detection of antioxidants which are applied in lubricants. These experiments should form the base for future investigations of antioxidants in tribologically formed thin layers on the surface of frictional systems. Seventeen different antioxidants were selected out of the group of hindered phenolic and aromatic aminic compounds. Practically all antioxidants could be characterized by positive ion ESI- and AP-MALDI-ITMS, forming various types/species of molecular ions (e.g. [M]+., [M+H]+, [M+Na]+ or [M,2H+H]+). A few compounds could be analyzed by negative ion ESI-MS, too, but none by negative ion AP-MALDI-MS. The influence of target materials in AP-MALDI-MS (gold- and titanium nitride (TiN)-covered stainless steel, micro-diamond-covered hard metal, hand-polished and sand-blasted stainless steel targets) with respect to the molecular ion intensity and type of molecular ion of two selected antioxidants was evaluated. The surface properties are of particular interest because in friction tests different materials with different surface characteristics are used. However, the MS results indicate that optimal target surfaces have to be found for individual antioxidants in AP-MALDI-MS but in general smooth surfaces were superior to rough surfaces. Finally the gold-covered stainless steel MALDI target provided the best mass spectra and was selected for all the antioxidants investigated. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effect of chemically bonded stationary phases and mobile phase composition on , -blockers retention in RP-HPLCBIOMEDICAL CHROMATOGRAPHY, Issue 3 2009Boguslaw Buszewski Abstract The effects of stationary and mobile phase on retention of 18 , -adrenolytic drugs (, -blockers) have been studied. Four ,deactivated surface' stationary phases (polar-embedded or end-capped) were examined. Special attention was drawn to the cholesterolic (SG-CHOL) and alkylamide (SG-AP) stationary phases, and their application for analysis of the compounds. The retention of analyzed substances was also examined in terms of mobile phase composition. Sixteen different configurations of mobile phases were prepared, all based on methanol and acetonitrile with ammonium acetate and ammonium formate. The difference in retention between ammonium formate and acetate water solutions, and peak shape changes related to the addition of triethylamine (TEA), were investigated. Principal component analysis was used to find the similarities between stationary phases. Polar-embedded phases synthesized on the same sorbent possess very similar properties. All phases based on silica gel compared with the monolithic column also showed similarities in retention of , -blockers. The addition of TEA to the mobile phase did not influence strongly the retention, and analysis of asymmetry factors showed only a little peak broadening for a few compounds on the monolithic column. Copyright © 2008 John Wiley & Sons, Ltd. [source] ,1 - and ,2 -Adrenoreceptor Antagonist Profiles of 1- and 2-[, -(4-Arylpiperazin-1-yl)alkyl]-1,2,3-benzotriazolesCHEMISTRY & BIODIVERSITY, Issue 10 2005Alessandro Boido A series of pharmacologically interesting 1- and 2-[, -(4-arylpiperazin-1-yl)alkyl]-1,2,3-benzotriazoles, compounds 1,27, were synthesized (Scheme) and subjected to various biological studies to identify structure,activity relationships (SAR). The new compounds were found to exhibit good non-selective binding affinity towards the ,1 -adrenoreceptor (Table,1). In several cases, high functional antagonism was observed towards the ,1A -, ,1B -, and ,1D -adrenoreceptor subtypes (Table,2). The selectivity for these three subtypes was comparable with or superior to that displayed by the standard drug prazosin. The most-common selectivity rank order was ,1D>,1B>,1A, followed by ,1B>,1D>,1A. In functional experiments, antagonism towards the ,2 -adrenoreceptor was generally low; however, a few compounds were endowed with significant antagonist properties (pA2 values of up to 7.87). [source] Enthalpy change on mixing a couple of S - and R -enantiomers of some chiral compounds at 298.15 KCHIRALITY, Issue 8 2006Takayoshi Kimura Abstract Enthalpy change on the mixing of R - and S -enantiomers of chiral liquid compounds such as dimethyl malate (1), methyl 3-hydroxylbutanoate (2), 2-butanol (3), ethyl 4-chloro-3-hydroxylbutanoate (4), 1,3,3-trimethylbicycle-[2.2.1]heptan-2-one (5), 3,7-dimethyl-6-octenal (6), and 8-bromo-2,6-dimethyl-2-octene (7) is measured over the entire range of mole fractions at 298.15 K, albeit very small values. The mixing of chiral liquids of R - 1 + S - 1, R - 2 + S - 2, R - 3 + S - 3, R - 6 + S - 6, and R - 7 + S - 7 produces enthalpic destabilization over the entire range of mole fractions, while that of R - 4 + S - 4 and R - 5 + S - 5 shows enthalpic stabilization over entire compositions. Enthalpy change on mixing at an equimolar concentration and the intermolecular interaction obtained by the molecular mechanics calculations show a linear correlation, except for a few compounds measured. Chirality, 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||