CH STRETCHING FREQUENCES AND BOND STRENGTHS, AND METHYL GROUP GEOMETRY IN CH3CXO COMPOUNDS ( X = H, Me, F, Cl, Br, I, CN, OMe) AND CH3CH2CN

Article abstract of DOI:10.1016/0022-2860(82)80078-1

Infrared spectra in the CH stretching region are reported for CHD2CXO and CH3CXO compounds, where X = F, Cl, Br, I, CN, OMe, and for CHD2CD2CN and CD3CHDCN.In all the carbonyl compounds except the iodide the two out-of-plane CH bonds in the methyl group are significantly weaker than the in-plane one.Differences in CH bond length of up to 0.006 Angstroem are predicted, which are considered to be more reliable than the available microwave data.The separations of ν_asCH3 and νCHD2 frequencies are compatible with a strong angular asymmetry (<*>H_sCH_a <*> H_aCH_a) in the acetyl compounds.The gauche and trans effects of halogen on ν^is_CH are similar, but larger, than those in alkyl halides.In ethyl cyanide, the methyl CH bonds are identical in strength.The α and β substituent effects from the CN group fall into no simple pattern.