C13 Splittings in Proton Magnetic Resonance Spectra. III. Formyl Compounds

Electron-coupled spin-spin interaction constants JC–H for a series of formyl compounds are presented and interpreted. It is concluded that JC–H is essentially independent of the polarity of the C–H bond and provides the best experimental measure of the hybridization of the carbon atomic orbital used in the bond. Some of the C–H bonds involve carbon orbitals of surprisingly high s character, especially in view of the available data on the bond lengths. It is suggested that the electrostatic interaction between the C–H proton and the π electron density may play an important part in fixing the lengths of these C–H bonds.