Influence of solvents on the -OH and >C=O stretching frequencies of benzoin and methyl mandelate

Abstract

The influence of solvents on the intramolecular hydrogen bond in benzoin and methyl mandelate is studied using infrared spectroscopy. Non-oxygenated solvents could not break the chelation but could shift the OH frequencies to a small extent. Oxygenated solvents like diethyl ether, acetone and dioxan could break the chelation and form intermolecular hydrogen bonds. The relative intensities of the bands of intra and intermolecular hydrogen bonds gave an indication of the donor ability of these solvents, which is linked with their capacity to break the intramolecular hydrogen bonding. Making use of the symmetry numbers of the OH band, the order of the interacting abilities of the oxygenated solvents in breaking the chelation is ascertained and explained.