Raman spectra and frequency calculations for some steroids

Abstract

The Raman spectra of cholestan-3-one, 2α-bromocholestan-3-one (1), 2β-bromocholestan-3-one (5), and 2α-bromo-2β,4,4-trideuteriocholestan-3-one (2) between 150 and 1000 cm^–1 have been recorded. Frequencies have been calculated for 2α-bromo-4,4,5β-trimethylcyclohexanone (3), 2β-bromo-4,4,5β-trimethylcyclohexanone (8), and the corresponding 2,6,6-trideuteriated species (4) and (9). From consideration of the calculated frequencies and the recorded Raman spectra, a strong band observed at 625 cm^–1 has been assigned to an essentially carbon–bromine stretching mode of the axial bromocholestan-3-one. A number of modes between 800 and 200 cm^–1 in the spectrum of the equatorial bromo-compound involve an appreciable potential energy contribution from carbon–bromine stretching, although no vibration is primarily a carbon–bromine stretch. Substantial changes in the natures and frequencies of these modes are exhibited on deuteriation at the 2-axial, 4-axial and 4-equatorial positions (of the steroid).