Polar and steric effects of substituents in aromatic nucleophilic substitution. Reactions of 4-, 5-, and 6-substituted 1-chloro-2-nitrobenzenes with sodium thiophenoxide in methanol

Abstract

The kinetics of the reactions of 4-, 5-, and 6-substituted 1-chloro-2-nitrobenzenes with sodium thiophenoxide in methanol have been determined, and the thermodynamic parameters, energy and entropy of activation, calculated.

For the 5-substituted series a plot of log k against σ-values gave a ρ-value + 5·15. The σ_4-Subst values corresponding to this reaction have been estimated by regression. For the 6-substituted-series a plot of log k_6-Subst against σ_4-Subst parameters gave a ρ-value + 3·46 showing that the polar influence of an ortho-substitutent predominates over its steric effects.