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The solvent-induced shift of the fundamental vibrational mode of the carbonyl group in 2-butanone was measured in 27 solvents using FTIR techniques. Eight model formulations for the reaction field of the solvent in which the dielectric continuum is specified in terms of dielectric constant ( ), optical dielectric constant (n 2 ), and effective dielectric constant ( p ) were applied to the solvent dependence of the carbonyl band. The critical tests for these models included both their statistical fit and their predicted value for the ν j gas for the carbonyl band. Most of the f( ) and f( ,n 2 ) functions including the Kirkwood, McRae, and Block-Walker parameters clearly demonstrate that solvent dipolarity-polarizability is the dominant effect upon ν j(CdO) in 21-23 aprotic solvents. However, a two-term MO perturbation statement in both f( ) and a cross-product function proved to be a better overall model than those using only a single parameter. The poorest fits to the ν j(CdO) data were encountered with continuum statements in terms of the p quantity.

6217dependent on the geometrical profile of the detector. The speeds of sound in (CH,),Si, (CH3),Ge, and (CH,),Sn were determined. The C-H cross sections (Au = 7) were obtained for the three molecules. Accurate determination of the peak positions was enhanced by computer deconvolution of the overtone spectra (Au = 6.7) of the (CH3),M molecules (M = Si, Ge, Sn). Additional bands were assigned to various local mode and normal mode combination bands. The deconvolution also allows for the determination of the overtone bandwidths. The narrow bandwidths observed for the metal-centered compounds may reflect basic changes in molecular properties such as bond lengths and electron density distributions caused by the larger central atom. These changes may affect energy transfer processes by creating a different environment for the excited C-H group. It is possible that the large metal atom limits coupling between different methyl groups in the molecules. Possible energy level resonances in the compounds do not seem to have a strong effect on energy transfer.

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