Molar Cotton-Mouton constants and anisotropy of magnetic susceptibility of benzyl chlorides and benzyl bromides

Based on an analysis of electrical and optical data, they previously established the steric structure of a series of benzyl halides and found that the polarizability ellipsoid of the aromatic nucleus undergoes significant rearrangement of its semiaxes in comparison to the semiaxes in toluene (I). In all of the systems examined the mobility of the electron cloud in the plane of the ring increases and decreases in the perpendicular direction. A conformation is realized in which the benzene ring is close to shielding of the C-H bond. Hyperconjugation of the πarom-σC-Hal* type, particularly manifested in the nuclear quadrupole resonance spectra, is apparently responsible for the observed effects. The effect of similar interactions on the magnetic properties has not been studied either experimentally or theoretically. The anisotropies of magnetic susceptibility of molecules or groups of atoms can be calculated from the known optical polarizabilities using data on the magnetic birefringence constant (the Cotton-Mouton effect) of compounds in the form of vapors or solutions. The molar Cotton-Mouton constants of the title compounds were measured and the magnetic susceptibility ellipsoids (MSE) of the C6H5-C fragment in benzyl halides and (I), whose MSe is known, were comparatively estimated in the present study