Thermochemistry of Molecular Complexes. 2. Enthalpies of Formation and Formation Constants for Molecular Complexes of I2 with Methylbenzenes

Article abstract of DOI:10.1021/jo00266a025

A new technique recently developed in our laboratory has been used to determine the formation constants and enthalpies of formation for the 1:1 molecular complexes that form between I2 and benzene or methyl-substituted benzene derivatives in carbon tetrachloride solution.The results are in good agreement with those found in previous studies.A linear relationship exists between the enthalpy of formation for the molecular complex and the number of methyl groups attached to the benzene ring, with ΔH becoming more negative by approximately 1.1 kJ/mol per methyl group.A linear relationship also exists between ln (K) and the number of methyl groups on the benzene ring.These results are consistent with a simple model where the contributions to the ?-electron density of the benzene ring from the attached methyl groups are, to a first approximation, additive.