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.