Charge-transfer Interaction and Chemical Reaction. IV. Reactions of para-Substituted Derivatives of Aniline with Chloranil

Abstract

Abstract Interactions of chloranil with p-phenyIenediamine, N,N-dimethyl-p-phenyIenediamine, and N,N,N′,N′-tetramethyl-p-phenylenediamine were studied by measuring visible and ultraviolet absorption spectra at various temperatures between 77°K and 300°K. In an ether-isopropyl alcohol (3:1) mixed solvent, the p-phenylenediamine- and N,N-dimethyl-p-phenylenediamine-chloranil systems were led to the substitution reaction through the outer complex and the ionic species as reaction intermediates. In ethyl ether, the p-phenylenediamine- and N,N-dimethyl-p-phenylenediamine-chloranil systems were found to yield the inner complex and the substituted species through the outer complex, respectively. In the N,N,N′,N′-tetramethyl-p-phenylenediamine-chloranil system, the inner complex was found to be formed via a clustering of the outer complexes. The interactions between aromatic amines and chloranil were found to be classified into the following three types: (a) the charge-transfer (outer or inner) complex is formed between an electron donor and an acceptor and no further reaction proceeds; (b) the substitution reaction occurs through the outer and inner complexes; (c) the substitution reaction occurs through the outer complex and ionic species. The difference in the reactivities between mtfta-substituted derivatives of aniline and ortho- and para-substituted ones was explained by taking the π-electron density on the amino group into account.