Theoretical analysis of molecular polarizabilities and polarizability derivatives in hydrocarbons

Molecular polarizabilities and polarizability derivatives associated with CH and CC bond stretching have been calculated for CH4, C2H2, C2H4, C2H6, C3H6, C3H8, C4H8 (trans and gauche), C5H12 (all-trans) and C6H12. Self-consistent field calculations have been performed with several basis sets, principally the Dunning contractions of the Huzinaga bases with additional polarization functions. The polarizability derivative associated with a CH bond stretch varies significantly with the orientation and position of a bond within a molecule. Results are in agreement with parameters obtained from Raman trace scattering cross sections. A similar orientational dependence appears for the CC bond stretches of alkanes. There is a linear correlation between the molecular volume calculated with the proaim program and the molecular polarizability. Group polarizabilities (CH3 and CH2) are transferable.