Zero-point vibrational effects on optical rotation

We investigate the effects of molecular vibrations on the optical rotation in two chiral molecules, methyloxirane and trans-2,3-dimethylthiirane. It i s shown that the magnitude of zero-point vibrational corrections increases as the electronic contribution to the optical rotation increases. Vibration al effects thus appear to be important for an overall estimate of the molec ular optical rotation, amounting to about 20-30% of the electronic counterp art. We also investigate the special case of chirality introduced in a mole cule through isotopic substitution. In this case, the zero-point vibrationa l effects are the only source of optical activity, and we investigate the m agnitude of these effects through calculations on mono-deuterated oxirane. (C) 2001 Elsevier Science B.V. All rights reserved.