The determination of inductive effects by 13C nuclear magnetic resonance spectrometry

Abstract

A series of meta- and para-XCH₂-substituted methyl cinnamates has been prepared and the ¹³C n.m.r. chemical shifts of the α- and β-side-chain carbons have been determined in ethanol. In the majority of cases the magnitudes of the substituent-induced chemical shifts are directly proportional to the inductive substituent constants of the group X. C–H Hyperconjugation appears to play a significant role in the relay of inductive effects from the substituent to the more distant ethenyl carbon in the para-series, but in the other three cases relay appears to be mainly via a direct field effect.