Magnetic Constants of Benzene, Naphthalene and Anthracene Molecules

Abstract

IN a recent communication1, I have shown how, by a correlation of the principal susceptibilities of a diamagnetic crystal, with those of the constituent molecules, it is possible to determine the orientations of the molecules in the crystal. Conversely, where the orientations are already known from X-ray measurements, we can calculate the molecular magnetic constants from those of the crystal. The principal susceptibilities of naphthalene and anthracene molecules, calculated in this manner, are given in the following table. Two of the magnetic axes of the molecules line in the plane of the benzene rings, one along the line joining the centres of the rings and the other perpendicular to this line. The third axis is normal to the plane of the rings. The susceptibilities along these axes, per gram molecule, are denoted by K1, K2 and K3 respectively. The values for the benzene molecule, which are also included in the table, have been calculated (in the absence of magnetic data for the crystal) from measurements on magnetic double refraction and on light scattering in the liquid state ; the calculation is possible since the molecule may be assumed to have an axis of symmetry.2