76614-86-3Relevant academic research and scientific papers
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.
A Frontier Orbital Study of Substituent Effects in the Deamination of N-Substitued Quinone Di-imines
Grampp, Guenter
, p. 2001 - 2004 (2007/10/02)
The substituent effects on the rate constant of the acid and alkaline deamination of quinone di-imines are explained, using the frontier orbital (FO) perturbation theory.The main contributions to the pertubation energy are electrostatic and orbital interactions.The alkaline deamination is both orbital and charge controlled, whereas the acid deamination is only an orbital-controlled reaction.
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.
