Relations between Electronic Absorption Spectra and Spatial Configurations of Conjugated Systems. II. o-Alkyl-and o,o′-Dialkylbiphenyls

The method described in the preceding part of this series has been applied with allowance for the electronic bathochromic effect of the substituents to o-alkyl- and o,o′-dialkylbiphenyls, and the relation between the ultraviolet absorption spectra and the most probable spatial configurations of these compounds has been clarified, resulting in the conclusion that the interplanar angle in o-methylbiphenyl as well as its analogues is about 60°C and that o,o′-dimethylbiphenyl as well as its analogues has the cis-configuration in which the interplanar angle is about 70°C. On the basis of the result, the interpretation by Braude and Forbes of the spectra of o-methyl- and o,o′-dimethylbiphenyl has been criticized. In addition, the inferred spatial configurations of these biphenyl derivatives have been correlated with some physical and chemical properties of these and some related compounds.