Evidence for a single minimum potential for hydrogen bonds of pyridine N-oxide complexes with dichloroacetic acid in dichloromethane

Abstract

FTIR spectra of dichloracetic acid and its eight complexes with substituted pyridine N-oxides and N,N-dimethylaniline in dichloromethane-d 2 are reported. 4- N,N-dimethylaminopyridine N-oxides form two types of complexes with dichloroacetic acid; the acid interacts with NO or Me 2N groups. The shape of the second derivative of absorption in the carbonyl region implies that the hydrogen bonds are described by a strongly asymmetrical quasi-single minimum potential. The situation with regard to the observed carbonyl frequencies as related to conformational equilibria is reviewed.