Hydrogen bonding. Part 3.—Enthalpies of transfer from 1,1,1-trichloroethane to tetrachloromethane of phenols, N-methylpyrrolidinone (NMP) and phenol–NMP complexes

Abstract

Enthalpies of solution of seven phenols and of NMP have been determined in 1,1,1-trichloroethane and in tetrachloromethane at 298 K. Combination with our previously determined enthalpies of complexation, ΔH°, of the phenols with NMP leads to enthalpies of transfer of the hydrogen-bond complexes ArOH ‥ NMP from 1,1,1-trichloroethane to tetrachloromethane. The substituent-dependent behaviour of values of ΔH° in the two solvents arises exclusively from the effect of the solvents on the reactant phenols and not on the complexes themselves. This finding confirms the suggestion that the ΔH° values in 1,1,1-trichloroethane contain a contribution from association of the phenols with the solvent itself, probably of the dipole–dipole type.