Ab initio analysis of C-H and C-C stretching intensities in Raman spectra of hydrocarbons

Molecular polarizability and changes in the polarizability associated with the stretch of C-C and C-H bonds have been calculated for thirty-four satur ated hydrocarbons, including the series of n-alkanes to C15, as well as sev eral cyclo- and bicycloalkanes, propellanes, prismanes, and hedranes. The a b initio results (HF/D95(d,p)) are compared to experimental Raman trace sca ttering intensities where such information is available. Possible factors g overning trends in the magnitude of the derivatives are considered. For the C-C stretches, chain length and position along the chain are the most impo rtant factors for the n-alkanes, whereas strain appears to be significant f or the ring and caged structures. For the C-H stretches, the most significa nt factors are the same as those found in our earlier work: location, type, and orientation relative to the carbon skeleton.