Carbon-13 chemical shifts of the carbonyl group. VIII. Approximate self-consistent-field perturbation theory

The previously reported SCF perturbation theory of /sup 13/C chemical shifts at the modified INDO level has been extended to oxygen-containing compounds. A promising level of qualitative agreement has been observed between calculated and experimental trends amont alcohols, aldehydes, ketones, carboxylic acids, and their corresponding isoelectronic hydrocarbons. Relationships between computed electron density elements and /sup 13/C shifts are explored, but only limited correlations are found. The modified INDO parameters chosen for oxygen tend to exaggerate the degree of electronic polarizations associated with oxygen in organic compounds. The role of intermolecular interactions, mainly hydrogen bonding, is explored by means of calculations on configurations that model suspected interactions.