Enthalpies of transfer of alkane solutes from the vapor state to organic solvents

Abstract

Heats of solution of 5 – 8 C5–C16 alkane liquids have been determined in each of 19 organic solvents covering the Taft–Kamlert π* (dipolarity-polarizability) range −0.08 to 1.00. Enthalpies of alkane transfer from vapor to solvents have been calculated (ΔH(v → S) = ΔHs − ΔHv). The methylene increments in (ΔH(v → S) in the 19 solvents and water (−1.18 to −0.67 kcal/mol) are not well correlated with the Hildebrand solubility parameter δ, but an empirical correlation exists with solvent π* and polarizability:[Formula: see text](n = 20, r = 0.977, see = 0.032). By this criterion the small methylene increment in water appears to be associated with the high dipolarity and low polarizability of water.