A SPECTROSCOPIC STUDY OF HYDROGEN BONDING IN PERFORMIC AND PERACETIC ACIDS

Abstract

The infrared spectra of concentrated performic and peracetic acids were measured in the rock-salt region. The most significant features are theO—H stretching frequency at 3310–3350 cm−1 and the OH bending frequency at 1450 cm−1 which, for both peracids, remain essentially the same in the vapor state as in the liquid or in solution in nonpolar solvents. This is attributed to intramolecular hydrogen bonds resulting in particularly stable five-membered rings,[Formula: see text]Steric conditions in the percarboxylic group are favourable to such ring formation or chelation. From the observed frequency shifts the energy of these hydrogen bonds is estimated to be about 7 kcal. per mole. No evidence for unchelated molecules was found even in very dilute solutions of peracetic acid in nonpolar solvent nor in the vapour at low pressure and moderate temperature. Tentative assignments of the other frequencies in the spectra of the peracids are made by comparison with those of formic and acetic acids.The danger involved in handling these peracids in concentrated form is emphasized.