On the relationship between carbon-13 and oxygen-17 carbonyl chemical shifts andn→ π* transition energies

Literature data for δ(13C), δ(17O) and λ n→π* max for carbonyl groups in various compounds are reviewed. In a wide variety of carbonyl compounds there is a linear relation between δ(17O) and gl n→π* max. However, deviations from this general relationship occur for a group of ketones. The explanation is found in differences in electron-donating properties of the substituents at the carbonyl group, which cause changes in the electron density and in the polarity of the carbonyl group. Measurements are reported for the concentration dependence of the three quantities for acetone in water. Here the variations of δ(13C) and δ(17O) can be explained by the changes in carbonyl polarity due to hydrogen bonding. For λ n→π* max the blue shift due to hydrogen bond formation is dominant over the influence of changing carbonyl polarity. The relation between δ(17O) and λ n→π* max is strictly linear; for δ(13C) and λ n→π* max small deviations from linearity occur.