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.
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