Molecular complexes. Part V. Proton nuclear magnetic resonance studies of complexes of benzene with some chloroethylenes and methylene halides at various temperatures

Abstract

The equilibrium quotients, at various temperatures, for complexes of benzene with 1,1,2-trichloroethylene, 1,1-dichloroethylene, cis- and trans-1,2-dichloroethylene, methylene chloride, bromide, and iodide, are deduced from the solute proton-resonance shifts and their dependence on benzene concentration in solute–benzene–cyclohexane systems. Values for ΔG°, ΔH°, and ΔS° for complex formation are determined, and the variation of ΔH° with temperature is used to confirm the assumed nature of the complex equilibria. All the complexes except that involving trans-1,2-dichloroethylene are thereby indicated to have 1 : 1 solute–solvent composition. Structures for the methylene halide–benzene complexes are proposed and the calculated intermolecular interaction energies based on these are shown to be in agreement with the previously demonstrated correlation between the interaction energy and equilibrium quotient.