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.