As a part of a continuing research program on the relationship between vibrational properties and molecular structure of-phenones(aceto- (1,2), and benzo- (3)) developed in this Laboratory, the results of i.r. measurements and assignments for a number of m-halogen benzophenones are presented here. The presence of rotational isomers has been deduced in the molecules examined and the observed features arising from their existence have been elucidated in the interpretation of the infrared spectra.