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

Abstract

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