title: 13C NMR chemical shifts of carbonyl groups in substituted benzaldehydes and acetophenones: substituent chemical shift increments.
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.
authors.affiliation: Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Patterson-Elenbaum
authors.forename: John T
authors.initials: JT
authors.lastname: Stanley
authors.forename: Debra K
authors.initials: DK
authors.lastname: Dillner
authors.forename: Shirley
authors.initials: S
authors.lastname: Lin
authors.forename: Daniel
authors.initials: D
authors.lastname: Traficante