Vibrational assignment,infrared absorption intensities,gauche dihedral angle and energy difference between rotational isomers of chloroacetone

Infrared absorption intensities of fundamental bands of chloroacetone CH₃COCH₂Cl have been measured in carbon disulphide solution, and intensity data have been analysed to determine the energy difference between the rotational isomers by applying the absolute intensity method. The value determined for the energy difference is in good agreement with that obtained by the temperature variation method. Further, in order to determine the dihedral angle of the gauche isomer, normal frequencies and absolute band intensities have been computed for various rotational angles and compared with observed values. As a result, the gauche dihedral angle has been determined as 150° ± 10°, which is in good agreement with that obtained by previous authors.