A group additivity rule for integrated band strengths of the C—H chromophore in the infrared

Abstract

Integrated band strengths are reported for the C—H stretching fundamental transition near 3000 cm^–1 in the i.r. vapour-phase spectra of nine saturated fluorohydrocarbon molecules of general formula C_kF_lCl_mH. The nature of the absorption of the C—H chromophore is discussed in terms of conservation of the band strength G when coupling the chromophore states to optically inactive background states and in terms of the local electronic environment of the C—H group. The values of G are found to be well approximated by a three-parameter group additivity rule.