How much different are thermochemical properties of enantiomers and their racemates? Thermochemical properties of enantiopure and racemate of methyl- and butyl lactates

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. The liquid phase standard molar enthalpies of formation of these esters were measured by using the high-precision combustion calorimetry. The standard molar enthalpies of vaporization of alkyl lactates at 298.15 K were derived from vapor pressure temperature dependencies. Thermochemical data of these compounds were collected, evaluated, and tested for internal and external consistency. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas phase enthalpies of formation of alkyl lactates. A critical review of the available thermochemical data for the liquid and crystal...