Thermodynamic study of the transfer of pyridines from the gas phase to solution in methanol

Abstract

Enthalpies of solution of eleven pyridines in methanol are combined with vaporization data to obtain enthalpies of transfer of the pyridines from the gas phase to solution in methanol. The data reflect specific solvation effects involving substituent groups and the electronic and steric influence of substituent groups on hydrogen-bonding interactions between methanol molecules and the pyridine nitrogen atom. Free energies of transfer of pyridine, 2-methylpyridine and 2,6-dimethylpyridine from the gas phase to methanol are compared with the effects of 2-methyl and 2,6-dimethyl substitution on the free energy of solvation of the pyridinium ion.