An electronegativity model for the fundamental infrared intensities of thehalomethanes

A principal component analysis of halomethane polar tenser invariant data s hows that four of the five invariant quantities, the atomic mean dipole mom ent derivative, (p) over tilde (alpha), effective charge, chi (alpha), dete rminant, D-alpha, and minor sum, C-alpha, are linearly related to changes i n substituent electronegativities. The atomic anisotropy, beta (2)(alpha), has a completely different behavior. Based on a linear regression equation involving chi (alpha) and the substituent electronegativity change and the G intensity sum rule an electronegativity model is proposed for estimating the halomethane intensity sums. A single equation involving substituent ele ctronegativities and atomic masses can be used to estimate intensity sums t hat are in good agreement with experimental values. This expression permits an understanding of intensity sum trends for the halomethanes in terms of the electronegativities and atomic masses of the substituent atoms. (C) 200 1 Elsevier Science Ltd All rights reserved.