Infrared Spectra-Structure Correlations for Monohalogenated Monocarboxylic Acids

Abstract

The ir spectra of 16 monohalogenated monocarboxylic acids have been recorded over the range 4000–200 cm⁻¹. Attempts have been made to find useful spectra structure correlations which would serve to distinguish these acids from their unsubstituted analogs. It is concluded that differentiation of halogenated acids, either from unsubstituted acids or from each other, is not possible on the basis of consistent group frequencies, which forces one to resort to reference spectra for identification of these compounds. The one exception is provided by the alpha chloro-substituted compounds, which can, tentatively, be differentiated from both unsubstituted acids and other halogen-substituted acids. In contrast to previous reports, alpha halogen-substituted acids cannot be differentiated from the others unless the halogen is chlorine.