Ultrasonic studies of rotational isomerism in various methylhexanes

Abstract

Ultrasonic attenuations and velocities are reported for 2-methylhexane, 3-methylhexane, 2,2-dimethylhexane, 2,5-dimethylhexane and 2,2,4-trimethylhexane over a temperature range from 296 to 253 K. The dispersion in the attentuation conforms to a single relaxation process, and a study of its temperature dependence was used to obtain activation energies and energy differences for rotational isomerism. Comparison of the activation parameter obtained experimentally with those from predictions based on non-bonded van der Waals interactions between neighbouring groups allows identification of the equilibrium conformations involved in the rotational isomeric process.