Raman optical activity in carbonyl deformations

The contribution of carbonyl deformation co-ordinates to normal modes is discussed in the context of the Raman optical activity of chiral molecules containing a carbonyl group attached to a cyclic system. A comparison of the Raman optical activity spectra of 3-methylcyclohexanone and 3-methyl methylenecyclohexane provides convincing evidence for the dominant role of carbonyl deformations in the generation of the large couplet at about 500 cm−1 in 3-methyl cyclohexanone. The spectra of nopinone, β-pinene and 5-methylcyclohex-2-ene-1-one are also discussed. Finally, a model bond polarizability theory of Raman optical activity in carbonyl deformations is presented