Theoretical Analysis of Optical Rotatory Power of Methylcyclohexanone with Treatment of Conformational Equilibria

Optical rotational strength for the n-π* transition of (R)-3-methylcyclohexanone is calculated by the CNDO/2 and INDO methods and compared with the observed values at 81 and 300 K, taking account of conformational equilibria. The conformer species are chosen so that they have minimal potential energies, the potential energy surface being estimated with a non-bonded interaction approximation. Excited state wave functions are improved by a model potential method. The ratio of the rotational strengths at 81 and 300 K, each of them being calculated as a statistical average of the rotational strengths of four conformers, is in good agreement with the corresponding observed value.