Molecular complexes. Part XIV. Proton magnetic resonance studies of the interactions of chloroform with benzene and some alkylbenzenes at various temperatures

Abstract

The interactions between chloroform and various alkylbenzenes have been studied by ¹H n.m.r. at several temperatures. The equilibrium quotients, K_x, and thence ΔG⁰, ΔH⁰, and ΔS⁰, and aromatic-induced chemical shifts Δ_c have been deduced. The changes in ΔG⁰, K_x, and Δ_c from reaction to reaction are attributed to three effects, which are identified as an intermolecular electrostatic effect and two steric features of the aromatic compounds, qualitatively referred to as ‘trapping’ and ‘blocking’ effects of the alkyl substituents. The three effects, characterized by x, y, and z respectively, are quantified in equations for ΔG⁰, K_x, and Δ_c and their theoretical significance explained.