Stephanie Patterson-Elenbaum, John T. Stanley, Debra K. Dillner
Aug 1, 2006
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Journal
Magnetic Resonance in Chemistry
Abstract
13C NMR Substituent chemical shift (SCS) increments have been determined for the carbonyl carbon of a variety of substituted benzaldehydes and acetophenones. The 13C NMR chemical shift of the carbonyl carbon can be predicted for many di‐ and trisubstituted benzaldehydes and acetophenones through simple additivity of the SCS increments. The magnitude and sign of the SCS increments have been explored using Hartree‐Fock 6‐31G* calculations to determine the natural atomic charges of the carbonyl carbon. When a substituent capable of intermolecular hydrogen bonding is present, deviations from additivity on the order of 2 ppm are observed in dilution experiments; deviations of up to 6 ppm can result from intramolecular hydrogen bonding. Copyright © 2006 John Wiley & Sons, Ltd.