The effect of solvent interaction with the hydroxy group of saturated monohydroxy alcohols from measurement of hydroxy stretching vibrations

Abstract

The nature of the interaction of solvent molecules with the hydroxy group of saturated monohydroxy alcohols in specific rotamer conformations has been examined. For non-polar and nucleophilic-type solvents, the interaction centres at the OH proton, causing a decrease in the OH stretching frequency. Shielding of the hydroxy hydrogen by β-alkyl groups reduces the magnitude of the shift. In chloroform solution, evidence is given for an association of the solvent molecules with the oxygen lone-pair sites in conjunction with an association with the OH proton. The interaction of chloroform with the lone-pair sites causes an apparent increase in the OH stretching frequency which is counterbalanced by the decrease caused by association with the OH proton. Shielding of either the lone-pair sites or the OH proton by β-alkyl groups influences the accessibility of the solvent and consequently influences the OH stretching frequency.