NUCLEAR MAGNETIC RESONANCE STUDIES: PART II. SOLVENT EFFECTS IN THE N.M.R. SPECTRA OF AROMATIC ALDEHYDES

Abstract

The chemical shifts for the aromatic and formyl protons of a series of substituted benzaldehydes have been obtained in a number of solvents. Relative to the shifts observed in chloroform, pronounced effects are observed in acetone and benzene solutions. In general, the shielding of these nuclei is decreased in acetone and increased in benzene, while in benzene the magnitude of the solvent shift for a given proton depends markedly on the nature of the substituent group. These results can be rationalized in terms of a specific solute-solvent interaction in which the site of association is governed by the electron distribution in the solute molecule. The nature of the solvent interactions in this and related systems is discussed.