Excess Enthalpies for (Carbon Tetrachloride+, Chloroform+, and Dichloromethane+ Methyl Methylthiomethyl Sulfoxide) at 298. 15 K

Abstract

The molar excess enthalpies HE of the title mixtures have been determined by using twin-microcalorimeter of heat-conduction type which requires only 10 cm³ of each component liquid for a series of runs over the whole range of mole fraction.
The H^E for (carbon tetrachloride+CH₃SOCH₂SCH₃) is endothermic as shown in Fig.1, having a maximum of 286 J·mol^-1 at mole fraction x₂=0.28, of CH₃SOCH₂SCH₃. This maximum value is comparable to the one reported for (carbon tetrachloride+DMSO), For (chloroform+CH₃SOCH₂SCH₃) and (dichloromethane+CH₃SOCH₂SCH₃), both H^E's are exothermic. The minimum values of H^E is -2.38 kJ·mol^-1 at x₂=0.38 for the former mixture and is -895 x₂ at x₂=0.45 for the latter.
For (chloroform +CH₃SOCH₂SCH₃), an equilibrium constant K₁ expressed in terms of mole fractions and standard enthalpy ΔH₁° of formation of 1: 1 associated complex, CH₃·(CH₃SCH₂)SO…H-CCl₃, have been evaluated to be K₁=2.2 and ΔH₁°=-8.7 kJ·mol^-1, by assuming an ideal mixture of monomeric molecules and their associated complexes. Enthalpic stabilization by hydrogenbonding between chloroform and CH₃SOCH₂SCH₃ molecules is smaller than that between chloroform and DMSO molecules by about 20 per cen.