The carbonyl group frequency. Part V. Alkyl formates

Abstract

The low carbonyl frequency of alkyl formates is not attributable to substituent polar effects. Calculations for a simplified model and comparison with other carbonyl compounds suggest it may arise from vibrational perturbations due to the presence of the hydrogen substituent, notably those due to the low mass and large coupling effects. The main carbonyl band is accompanied by a weaker band at higher frequency; this is assigned to the less stable s-cis isomer.