Polarisability anisotropies of C—H, C—C, C—Cl and C—Br bonds

Abstract

Electric birefringence data have been analysed to determine molecular polarisability anisotropies for a number of halogenated alkanes in cyclohexane solution. Using carbon–halogen bond anisotropies ±γ^CX from Raman intensity studies, a computational ‘best-fit’ procedure is applied to obtain weighted least-squares estimates of C—H and C—C bond anisotropies and concomitant bond tensor elements. It is shown that use of the +γ^CX options enables a reasonable, if imperfect, scheme of additive bond anisotropies to be devised for the molecular series studied. The procedure allows a resolution of the sign ambiguity for the ±γ^CX bond anisotropies. The results from solution-state measurements indicate that the C(sp³)—H bond is near isotropically polarisable.