Dipole Moment and Dielectric Relaxation of Some Aromatic Ethylenes and Butadienes

Abstract

The dipole moment of 1,1-bis-p-chlorophenylethylene, 1,1-bis-p-bromophenylethylene, 1,1-bis-pmethoxy, -ethoxy, -isopropoxy-phenyl-ethylene, 1,1,4,4-tetrakis-p-methoxy, -ethoxy, isopropoxyphenylbuta- l,3dienes was measured and compared with the calculated value. The mesomeric moment was estimated and found to decrease in the case of the ethylenes with the increase in volume of the substituted group. For the butadienes, the mesomeric moments compensate each other. Investigations of the dielectric relaxation times of the ethylenes showed that the orientation of the -OCH3 group in the 1,1-bis-p-methoxy-phenylethylene is hindered to a large extent. The orientation of the -OC2H5 and -OC3H7 groups in the corresponding molecules are restricted due to steric hindrance