Substituent Effects on the NMR Chemical Shifts of Aromatic Side Chain Protons. I. The Effects of meta-Substituents

The Hammett type treatment of the chemical shift of substituted aromatic side chain protons has not always been successful. The failure might be ascribed to the neglect of magnetic longrange effects. When the corrections were made both for the ring current diminution due to the contribution of polar resonance structure of the introduced substituent and for the substituent magnetic anisotropy effect, an excellent equation was obtained to relate, the chemical shifts of meta-substituted aromatic side chain protons to the Hammett’s constants.