CHARGE-TRANSFER INTERACTION AND CHEMICAL REACTION .I. REACTION OF ANILINE WITH CHLORANIL

The interaction of aniline with chloranil in mixed solvent of ether-isopropyl alcohol (3:1) was studied by measuring ultraviolet, visible, and infrared absorption spectra at various temperatures ranging from 36°K to room temperature. The (π,π) type outer complex was found to exist stably in an equilibrium with the component molecules at low temperatures below ∼200°K. The equilibrium constant was determined by the aid of the Benesi-Hildebrand equation at several temperatures between 115 and 195°K. The heat of formation and entropy change of the complex were evaluated to be -2.1 (kcal/mol) and -7.2 (cal/deg mol), respectively, from the temperature dependence of the equilibrium constant. With increasing temperature the reaction proceeds yielding 2,5-dichloro-3,6-dianilino-p-benzoquinone as a reaction product. The reaction mechanism through inner (σ) complexes was proposed and discussed.