Dipole moments of phenyl,benzo, and benzo[b]thiopheno derivatives of thiophene; 1, 4-dithiin,and thianthrene and their sulfones

The dipole moments of a series of phenyl, benzo-, and benzob]thiopheno-derivatives of thiophene, 1,4-dithiin, and thianthrene have been determined. An increase in the dipole moments of the phenyl derivatives of thiophene with an increase in the number of phenyl groups is connected with the existence of conjugation between the thiophene and benzene rings, a quantitative evaluation of the nature of which is given. It is suggested that the structure of the 1, 4-dithiin ring is close to coplanar.