Substituent effects in infrared spectroscopy. Part 5. Carbonyl stretching frequency in meta- and para-substituted aromatic carbonyl compounds

Abstract

Substituent effects for carbonyl stretching frequencies of m- and p-substituted acetophenones, benzophenones, benzoic acids, and alkyl benzoates are investigated by means of a correlation analysis. The validity of the Hammett, Hammett–Brown, and Exner equations is checked by means of numerous substituents and several limitations of these equations are shown. Coupling between carbonyl groups in dicarbonyl centrosymmetric molecules, dependence of substituent constants on solvent, and dependence of transmission coefficients of substituent effects along the ArCOY series on the Y group are shown.