On the induction of optical activity in achiral molecules

Abstract

It has been observed experimentally that circular dichroism bands can appear at absorption frequencies of achiral molecules when chiral species (which do not associate with the achiral molecules) are added to the solution. This paper treats those contributions to the induced activity in the achiral species which are the results of van der Waals coupling to the chiral species. Use of perturbation theory leads to the expression of the induced rotatory strength as a series in 1/r, r being used in a general sense as the effective achiral-chiral molecule separation. Averaging over all orientations of each molecule yields non-vanishing terms falling off as 1/r ⁶. The results suggest that the effect may be important even in completely dissociated systems.