A study of some biphenylamines: Part I. The electronic spectra in acidic solvents of some biphenylamines

The K‐bands in the ultraviolet absorption spectra of meta and para substituted biphenylamines, dissolved in acidic media, appear to be essentially identical with each other and with that of their parent compound, biphenyl. Apparently the electronic interaction of the two aromatic rings is not markedly disturbed by the mere presence of positively charged ammonium groups, provided the molecules are able to assume a planar structure. As can be expected, however, appreciable hypsochromic shifts of the K‐bands become manifest when one or more of these groups are located at the ortho positions. Moreover, a buttressing effect is observed in the case where ammonium groups are present simultaneously in adjoining meta positions. A discussion of results takes into account both steric and electrostatic factors operating between the groups involved.