Raman spectroscopic studies of different forms of cholesterol and its derivatives in the crystalline state.

A Raman spectroscopic study has been carried out on a number of cholesterols and cholesterol derivatives in the crystalline state, in order to obtaine some empirical correlations between the Raman spectra and structure of each cholesterol form. Although the Raman spectra of the various cholesterols are highly complex it was found that three regions of the spectrum yield considerable information about the crystalline chain packing in each form. They are: (1) the low frequency region below 300 cm-1, giving information on the inter-and intramolecular vibrations in the cholesteryl moiety; (2) the methylene rocking/deformation region between 1400 and 1500 cm-1 giving information on chain packing in the crystalline state, and (3) the C-H stretching region between 2700 and 3100 cm-1 which appears to indicate that there is a correlation between branching in the side chains of the cholesterols, polarity of the substituent groups in the various derivatives studied and relative chain order in the packing arrangements in the crystalline state. A study of two branched chain aerosol derivatives, bis(di2-octyl) sodium sulphosuccinate and its isomer bis(di-2-ethylhexyl) sodium sulphosuccinate, indicate that branched chain amphiphiles are good Raman spectroscopic models for the cholesterols, similar to previous Raman spectroscopic studies which have found straight chain amphiphiles to be good models for more complex phospholipids.