CONFORMATIONAL INVESTIGATIONS OF BENZOPHENONES BY MEANS OF THE KERR-EFFECT AND DIPOLE-MOMENT METHODS

Molar Kerr constants and electric dipole moments are reported for differently substituted benzophenones (such as (4-FC6H4)(2)CO, (4-ClC6H4)(C6H5)CO, (4-MeC(6)H(4))(C6H5)CO, (4-MeOC(6)H(4))(C6H5)CO, (2-ClC6H4)(C6H5)CO, (2-MeC(6)H(4))(C6H5)CO, (4-ClC6H4)(2',4',6'-Me(3)C(6)H(2))CO, (2-ClC6H4)(2',4',6'-Me(3)C(6)H(2))CO, and (C4H3S)(4'-MeOC(6)H(4))CO) as solutes in dioxane solution at 298 K. The data are analysed in terms of the preferred conformations adopted in solution. In most cases these data are consistent with the presence in dioxane of asymmetric (gauche) conformers where both aromatic rings are twisted in the same direction with respect to the C-Ar-C(O)-C-Ar molecular reference plane, although by different torsional angles for each ring. The rings bearing or the substituents adopt orthogonal positions to the reference plane. The (4-FC6H4)(2)CO molecule prefers a helical (both torsional angles equal) rather than a gauche conformation.