Molecular polarisability. The effect of para-substituents in toluene
Abstract
Dipole moments and molar Kerr constants are reported for the para-substituted toluenes p-XC6H4Me (where X = F, Cl, Br, I, CN, or NO2) in solution in carbon tetrachloride and in benzene. The data are analysed to show that (a) the anisotropic electron polarisabilities of the p-halogenotoluenes can be predicted with reasonable accuracy from additivity of the appropriate component bond and group polarisability parameters, (b) deviations from additivity arise with the –M substituents because of electromeric interactions resulting in an enhanced electron mobility along the molecular 1,4-axis, and (c) stereospecific benzene-solute complex formation occurs in the aromatic solvent.