CROATICA CHElVIICA ACTA

Information derived from a study of 'isolated' CH stretching frequencies, measured in partially deuterated organic and organemetallic compounds, is reviewed. This includes CH bond lengths . and dissociation energies, and HCH angles in methyl groups, Excellent agreement is found between CH bond length differences predicted from VCH's values and those calculated by ab initio methods. V'sCH data also agree with the results of high overtone, local mode studies in distinguishing differences in CH bond strengths. The former however are based on spectra which are easier to assign to specific bonds. They also enable one to understand the spectra of normal, undeuterated molecules in the CH stretching region, through 'energy factored force field' calculations. Reference is made to situations involvlng free internal rotation of methyl groups, and to studies of other 'isolated' MH bonds (M = N, Si, Ge, Sn).