The infra-red absorption bands associated with the COOH and COOD groups in dimeric carboxylic acid—II: The region from 3700 to 1500 cm −1

Abstract

The infra-red spectra of a number of dimeric carboxylic acids and their deutero (COOD) analogues have been investigated in the region of 3700 to 1500 cm −1. The substances were studied in the vapour, liquid, and crystalline solid states, and in solution in carbon tetrachloride. In some cases observations were made over a range of temperature which extended down to that of liquid air. Particular attention was paid to the main broad νOH (νOD) absorption regions centred at 3000 cm −1 (2300 cm −1) and also to the weaker satellite bands to lower frequencies centred near 2650 cm −1 (2100 cm −1). The structure of the satellite bands, the presence of intensity submaxima on the main νOH (νOD) banda, and the general differences in appearance of the νOH and νOD absorption regions have been shown to be reasonably explicable in terms of combination, mostly summation, frequencies involving lower-frequency fundamentals of the COOH (COOD) groups. The summation bands are probably enhanced in intensity by Fermi resonance with the fundamentals responsible for the main νOH (νOD) absorption regions.