Dipole moments of derivatives of 4-phenylazo-NN-diethylaniline and of 9-phenylazojulolidine (9-phenylazo-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizine)

Abstract

Apparent dipole moments in benzene of a series of para-substituted derivatives of 9-phenylazojulolidine (9-phenylazo-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizine) have been determined together with those of the corresponding series derived from 4-phenylazo-NN-diethylaniline. Vector moments, µ(int), in the direction of the major axis of the molecules have been calculated in order to explain the observed moments. The values of µ(int) for the 9-phenylazojulolidines are all greater than those for the corresponding 4-phenylazo-NN-diethylanilines and, for both series of compounds, increase with increase in the Hammett substituent parameter, σ_p. Evidence is presented that the terminal nitrogen atom is more nearly planar in the 9-phenylazojulolidines than in the 4-phenyl-azo-NN-diethylanilines and also that µ(int) arises by interaction of the para-substituent with the π-electron distribution in the aromatic ring to which it is attached.