Thermodynamics of solution of chloroalkanes in n-heneicosane and in 1-chloroeicosane at 333.15 K using gas-liquid chromatography

Abstract

Thermodynamic properties of solution at infinite dilution in n-C 21H 44 and n-C 20H 41Cl at 333.15 K have been measured for several alkanes and chloroalkanes using g.l.c. The substitution of a chlorine atom for a methyl group in the solvent manifests itself in 16 per cent higher equilibrium vapor pressures for alkane solutes, and 10 to 30 per cent lower values for chloroalkanes, depending on the number of carbon atoms and the number and position of the chlorine atoms in the solute molecules. For the chloroalkanes, both enthalpy and entropy of transfer from n-C 21H 44 to n-C 20H 41Cl are negative, typical values being −0.5 kcal th mol −1 and −1.0 cal th K −1 mol −1. The same properties of transfer from the pure liquid chloroalkanes to both solvents are universally positive; however, α,ω-dichloroalkanes are the only ones studied with significantly higher escaping tendencies from the solvent relative to the pure solute, emphasizing their unusually strong dipole-dipole interaction in the latter. There is evidence that both chlorine atoms in α,ω-dichloroalkanes containing up to 5 carbon atoms interact simultaneously with the single chlorine atom in n-C 20H 41Cl.