76614-86-3Relevant articles and documents
Kinetics and mechanism of the heterogeneous oxidation of N-substituted-p-phenylenediamines over supported zinc oxide
Salem, Ibrahim A.
, p. 249 - 261 (2007/10/03)
The kinetics and mechanism of the oxidation of some N-substituted-p-phenylenediamines over ZnO supported with some transition metal sulfates were investigated at 25°C. The rate of reaction decreased in the following order; N,N,N′,N′-tetramethyl-p-phenylenediamine, TMPPD > N,N-diethyl-p-phenylenediamine, DEPPD > N,N-dimethyl-p-phenylenediamine, DMPPD, due to the positive inductive effect of alkyl groups. For the oxidation of DEPPD, the rate of reaction was observed to have the order: Cu(II) > Fe(III) > Ni(II) > Cr(III) > Mn(II) > Co(II). The initial rate of reaction was decreased with decreasing pH as a result of the protonation of the diamine nitrogen atoms. Also, it follows a first order dependence of the initial concentration of the diamine and attained a maximum at higher concentrations. Moreover, it increased with increasing amount of the oxidant. Greater amounts, however, reduced the rate of reaction as a result of the adsorption of the formed p-semiquinonediimine, S+, by the support. A mechanism is proposed which implies two consecutive electron transfer steps as well as a synproportionation reaction between the diamine and the totally oxidized p-quinonediimine, T.
Activation parameters and mechanism of the deamination of N-substituted quinone monoimines and di-imines
Nickel, Ulrich,Jaenicke, Walther
, p. 1601 - 1605 (2007/10/02)
The deamination rates of six N-substituted quinone monoimines in aqueous solution were measured by a stopped-flow method at temperatures between 278 and 323 K in the pH range between 1 and 9 using u.v. spectra. The observed rate constants are given by k = k′[H2O] + k″[OH-]; k′ and k″ differ by 12 orders of magnitude. The enthalpies of activation of k′ and k″ are nearly equal; the entropies of activation are strongly negative for k′ and strongly positive for k″. The activation parameters of the acid and alkaline deamination of N-substituted quinone di-imines were also measured. With regard to the activation entropies similar results were found as for the quinone monoimines. For all deaminations a common mechanism with a preceding solvation equilibrium is proposed.
