An N.M.R. Investigation of Polarization of Pyridine by +R Substituents and a Proposed New Method for Determination of the Substituent Resonance Parameter (σ_R)

Abstract

The previously established ¹H n.m.r. method of probing bond order¹ has been used to show that electron-donating (+R) substituents at C2 of pyridine cause significant ground-state polarization of the heteroaromatic system. This has led to a new and independent method of estimating the substituent resonance parameter (σ_R ).