Effect of steric hindrance of ketones in the dielectric relaxation of methanol+ketone systems

The reorientation activation energies of five methanol + ketone systems were determined from the study of the variation of dielectric permittivity with temperature between 303 to 333 K at X band frequency. The results of the activation parameters are interpreted in terms of the rotation of the molecules about the C-O-H hydrogen bond, using a previously reported conformation obtained from semi-empirical and ab initio calculations as the basic conformer. The ketones studied are acetone, 2 butanone, 3 pentanone, cyclohexanone and acetophenone.