A Kerr effect and dielectric study of α, ω-dibromoalkanes

Abstract

We report the molar Kerr constants mK and dipole moments squared <μ2≳ of the α, ω-dibromoalkanes Br(CH2)n−1Br (n−1 = 3–20) in cyclohexane. We calculate the average mK and <μ2≳ on the basis of the rotational isometric state theory with nearest-neighbor interactions and the optical valence scheme. The dipole moments at each end of the alkane chain are assumed to be (a) along the C–Br bond only, (b) the sum of a moment along the C–Br bond and an induced moment along the adjoining C–C bond. We obtain good agreement between calculated and experimental mK and <μ2≳ by assuming that the gauche states of the first and last rotatable bonds are φg± = ±80° to ±100° and not ±120°. Better agreement with experimental results is obtained by using assumption (b) for the dipole moment. We calculate the effect of dipole–dipole interactions between the C–Br dipoles on mK and <μ2≳ and find them to be negligible. Finally we use Onsager’s theory of the reaction field to calculate solvent effects on mK and <μ2≳ and find the theory to be inadequate.