Search results for "Pentane"
showing 10 items of 174 documents
Isobaric vapor–liquid equilibrium for binary and ternary mixtures of 2-methyl-2-propanol+methyl 1,1-dimethylpropyl ether+2,2,4-trimethylpentane
2000
Abstract New consistent vapor–liquid equilibrium (VLE) data for the binary system methyl 1,1-dimethylpropyl ether (TAME)+2,2,4-trimethylpentane (isooctane) and the ternary system 2-methyl-2-propanol (TBA)+methyl 1,1-dimethylpropyl ether (TAME)+2,2,4-trimethylpentane (isooctane) are reported at 101.3 kPa. In the binary system, the results indicate a positive deviation from ideality and no azeotrope is present. The ternary system presents a saddle point azeotrope that can be predicted from binary data. The activity coefficients and boiling points of the solutions were correlated with their composition by Wilson, UNIQUAC and NRTL equations.
Ligand structures of synthetic deoxa-pyranosylamines with raucaffricine and strictosidine glucosidases provide structural insights into their binding…
2014
Insight into the structure and inhibition mechanism of O-β-d-glucosidases by deoxa-pyranosylamine type inhibitors is provided by X-ray analysis of complexes between raucaffricine and strictosidine glucosidases and N-(cyclohexylmethyl)-, N-(cyclohexyl)- and N-(bromobenzyl)-β-d-gluco-1,5-deoxa-pyranosylamine. All inhibitors anchored exclusively in the catalytic active site by competition with appropriate enzyme substrates. Thus facilitated prospective elucidation of the binding networks with residues located at <3.9 A distance will enable the development of potent inhibitors suitable for the production of valuable alkaloid glucosides, raucaffricine and strictosidine, by means of synthesis in …
Retention behaviour of volatile compounds in normal-phase high-performance liquid chromatography on a diol column
1993
Abstract Retention data on a diol column for over 300 compounds of the chemical classes usually contained in aroma extracts of plants and foodstuffs are reported. A concept that largely corrects for minor fluctuations of the mobile phase composition and of the flow-rate was used to measure capacity factors. The mobile phase was composed of pentane and diethyl ether. The high volatility of these two solvents makes the method perfectly adaptable to the prefractionation of aroma extracts and the semi-preparative isolation of compounds. Non-polar compounds such as hydrocarbons are not retained on diol. Polar compounds can be readily eluted, with the exception of strong acids and bases.
Synthesis of 3-Oxa-guaianolides from Santonin
2000
Abstract This article reports on the transformation of santonin into two C10-epimeric 3-oxa-guaianolides which are 8-deoxyderivatives of several natural 3-oxaguaianolides isolated from Achillea species. The synthesis involved the photochemical rearrangement of the eudesmane skeleton into a guaiane skeleton and the transformation of the cyclopentane ring into a furan moiety with the concomitant loss of C3. Comparison of the NMR data of the synthetic products with those of the natural products confirms the β orientation of the hydroxyl group at C10 in the products isolated from Achillea.
Densities, refractive indices, and derived excess properties of tert-butyl alcohol, methyl tert-butyl ether and 2-methylpentane binary and ternary sy…
2000
Abstract This paper reports experimental densities and refractive indices of the binary systems tert-butyl alcohol (TBA)+methyl tert-butyl ether (MTBE), TBA+2-methylpentane, and MTBE+2-methylpentane, and the ternary system TBA+MTBE+2-methylpentane, over the entire range of composition at 303.15 K. Excess molar volumes and changes of refractive indices were evaluated from the experimental data obtained. These derived properties were fitted to variable-degree polynomials. The experimental values of physical properties were compared with the values estimated by different methods of prediction.
Selective "one-pot" synthesis of functionalized cyclopentenones.
2012
Double addition (1,2-1,4) of vinyl magnesium bromide to squaric acid derivatives allows the preparation of polyoxygenated cyclopentenones (8) in a "one-pot" procedure. The reaction occurs through the intermediate formation of octatetraenes (6). Protonation of this latter intermediate at -78 °C with TFE occurs selectively at the vinyl CH(2) closer to the metallic centers. DFT studies of the cyclization step justify the observed diastereoselectivity.
Synthesis of Highly Functionalized Cyclopentanes as Precursors of Hydroxylated Azidocarbonucleosides
2009
Regio- and stereoisomers of functionalized azido amino alcohols with a cyclopentane skeleton were synthesized in enantiomerically pure forms. Enzymatic ring cleavage of racemic 2-azabicyclo[2.2.1]hept-5-en-3-one gave the corresponding amino acid and one enantiomer of the lactam stereospecifically. These were protected by esterification and carbamoylation, and then epoxidized. The resulting oxiranes underwent cleavage by sodium azide with complementary stereoselectivities. The regioisomeric products were easily separated by crystallization or column chromatography.
Coarse-graining dipolar interactions in simple fluids and polymer solutions: Monte Carlo studies of the phase behavior
2009
In this paper we investigate the phase diagram of pure dipolar substances and their mixtures with short alkanes, using grand canonical Monte Carlo simulations of simplified coarse-grained models. Recently, an efficient coarse-grained model for simple quadrupolar molecules, based on a Lennard-Jones (LJ) interaction plus a spherically averaged quadrupolar potential, has been shown to be successful in predicting single-component and mixture phase diagrams. Motivated by these results, we investigate the phase diagrams of simple dipolar molecules (and their mixtures with alkanes) using a spherically averaged potential. First, we test the model on pure components. A generalized (state-dependent) …
N‐Heterocyclic Carbene Catalyzed Quadruple Domino Reactions: Asymmetric Synthesis of Cyclopenta[ c ]chromenones
2018
An N-heterocyclic carbene catalyzed domino sequence via α,β-unsaturated acyl azolium intermediates has been developed. This strategy provides a convenient enantioselective route to functionalized tricyclic coumarin derivatives and cyclopentanes. DFT studies and control experiments were performed to gain better insight into the reaction mechanism.
First donor stabilized-phosphenium rhodium complexes
2008
Abstract The coordination properties of a donor stabilized-phosphenium adduct have been examined in rhodium chemistry. The preparation as well as the characterization of the first examples of donor stabilized-phosphenium rhodium(I) complexes is reported in this paper. Indeed, mono- and di-cationic rhodium complexes were obtained in quantitative yield by the direct addition of this imidazolium P(III)-ligand to [RhCl(1,5-COD)] 2 in CH 2 Cl 2 solution with a 1:1 P/Rh ratio under argon and 2:1 P/Rh ratio under CO atmosphere, respectively. Crystal structure of the bis-cationic donor stabilized-phosphenium rhodium(I) complex has been obtained from an acetone/pentane mixture. Its molecular structu…