No abstract

The absorption spectra of azobenzene and 10 para-substituted derivatives have been determined for the trans, and where sufficiently stable, the cis isomers also. With the aid of an assumption of untested validity estimates are made of the influence of the substituents upon the energies of the individual electronic levels of the trans isomers. The changes in the energy levels are interpreted in terms of the mesomeric and inductive effects of the substituent. The behaviour of the cis forms is complicated by interaction of the benzene rings.