The Infrared Spectra of Dichloroacetic Acid Derivatives: Characteristic Absorption Frequencies of the -CHCl2 Group

The infrared spectra of seven compounds containing the -CHCl 2 group attached to various carbonyl functionalities have been carefully recorded under a variety of conditions. Group frequency ranges for the CH, CC, and CCl (two) stretching modes and two CH bending modes have been developed. With the exception of the CC stretching mode, these vibrations fall in rather narrow regions of the spectrum. The conformational equilibria present in chlorine-substituted acetic acid derivatives are reflected by their infrared spectra in various ways. The situation with regard to the observed carbonyl stretching frequencies as related to conformational equilibria is reviewed.