This work is a contribution to the molecular understanding of the thermodynamic properties of the chiral compounds. A comprehensive thermochemical study of the liquid enantiopure and racemate pairs of optically active alkyl lactates has been performed. Vapor pressures of DL-(±)-, L-(-)-methyl-, and DL-(±)-, L-(-)-n-butyl esters of lactic acid were measured by the transpiration method.
View Article and Find Full Text PDFImidazolium-based ionic liquids (ILs) with PF6(-) anions are considered as low-cost solvents for separation processes, but they exhibit restricted thermal stabilities. Reliable measurements of vaporization thermodynamics by conventional methods have failed. In this work, we applied a quartz-crystal microbalance method to determine for the first time the absolute vapor pressures for the [Cnmim][PF6] family, with n = 2, 4, 6, 8, and 10, in the temperature range 403-461 K.
View Article and Find Full Text PDFVaporization enthalpy of an ionic liquid (IL) is a key physical property for applications of ILs as thermofluids and also is useful in developing liquid state theories and validating intermolecular potential functions used in molecular modeling of these liquids. Compilation of the data for a homologous series of 1-alkyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide ([C(n)mim][NTf2]) ILs has revealed an embarrassing disarray of literature results. New experimental data, based on the concurring results from quartz crystal microbalance, thermogravimetric analyses, and molecular dynamics simulation have revealed a clear linear dependence of IL vaporization enthalpies on the chain length of the alkyl group on the cation.
View Article and Find Full Text PDFVaporization enthalpies for a series of ionic liquids (ILs) with the common cation 1-ethyl-3-methylimidazolium [C(2)mim] and different counter anions are determined using a quartz crystal microbalance method. Dependences of vaporization enthalpies on physicochemical parameters specific for cation and anion interactions are revealed. A linear relation between enthalpies of vaporization and the intermolecular vibrational frequencies is observed and suggested for calculation of unknown ILs.
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