Studies on ¹³C Magnetic Resonance Spectroscopy. XVIII. Elucidation of the ¹³C Substituent-Induced Chemical Shifts of Monosubstituted Benzenes by Means of a Novel Substituent Entropy Constant σ_s°

Abstract

^<13>C Substituent-induced chemical shifts (SCS) of phenyl ring carbons of monosubstituted benzenes and their homologs are well correlated with linear combinations of entropic and enthalpic descriptors, namely (σ_s°)², σ_S°, σ_i, σ_π. The novel substituent entropy constant σ_S°contributes to SCS_ipso of an electron-donating group of monosubstituted benzenes and α-substituted toluenes. The effects of magnetic anisotropy in SCS could be represented by σ_s°.