Chemical Reaction of Electron Donor–Acceptor System: A New Mechanism for the Tricyanovinylation Reaction of Some Aromatic Amines with Tetracyanoethylene

Abstract

Abstract The tricyanovinylation reactions of several aromatic amines with tetracyanoethylene (TCNE) were investigated kinetically by observing the change of the absorbance of the charge-transfer (CT) band in 1,2-dichloroethane. The pseudo first order rate coefficient of the decay of the CT-complex (kobsd) was found to obey the relation, kobsd=kKDn⁄(1+KD) (K: association constant of CT-complex; D: initial concentration of donor molecule), where n=1 in N,N-diethylaniline (DEA)–TCNE and N,N-di-n-butylaniline (DBA)–TCNE systems and n=2 in N-methyl-N-ethylaniline (MEA)–TCNE system. Since the currently accepted mechanism for the tricyanovinylation reaction cannot explain the case of n=1, we have proposed a new reaction mechanism which can explain all the kinetic data reported hitherto. Two characteristic points are involved in the new mechanism, i.e., one is the unimolecular reaction of the CT-complex or the bimolecular reaction between reactants to form the σ-complex, and the other the decomposition of the σ-complex back to the component molecules. The reactions of MEA, DEA, and DBA with TCNE were discussed based on the new mechanism.