A new approach of aromatic solvent-induced shifts (ASIS) in 13C n.m.r. spectroscopy for solving stereochemical problems in some carbonyl compounds

Abstract

A simple method for the estimation of aromatic solvent-induced shifts (ASIS) in ¹³C n.m.r. spectroscopy is reported. The ¹³C ASIS values produced by perdeuteriobenzene (C₆D₆) are obtained for a variety of structurally different compounds containing carbonyl groups. The ¹³C ASIS values observed vary from compound to compound, depending upon conformational variations involving the carbonyl groups. A useful relationship between the magnitude of the ¹³C ASIS values and the geometrical factors estimated on the basis of an assumed model for a 1 : 1 solute–C₆D₆ association is presented as a new approach for the prediction of preferential conformations of cyclohexanones in solution at room temperature.