Raman optical activity of camphor and related molecules

Raman circular intensity differential spectra between 80 and 2 000 cm–1 of (+)-camphor, (+)-3-bromocamphor, (–)-3-bromocamphor-9-sulphonic acid, (+)-3-chlorocamphor, (–)-bornan-2-endo-ol, (–)-bornan-2-exo-ol, and (+)-3-methylcyclohexanone are presented. Several correlations are pointed out, including large conservative couplets at ca. 500 cm–1 that might originate in in-plane and out-of-plane carbonyl deformations. It is demonstrated that the conservative couplets which often dominate Raman optical activity spectra originate in coupling of two vibrational modes of appropriate symmetry through a chiral distortion of the molecular framework.