18996-77-5Relevant articles and documents
Formation and Decay of N,N,N',N'-Tetraethyl-p-Phenylenediamine Radical Cation in Aqueous Solution. A Kinetic Study by Stopped-Flow Technique
Aravindan, Ponnu,Maruthamuthu, Pichai,Dharmalingam, Periyasamy
, p. 109 - 122 (1995)
A kinetic study has been carried out on the oxidation of N,N,N',N'-tetraethyl-p-phenylenediamine (TEPD) by metal ion like Ce4+, oxoanions viz., MnO4- and Cr2O72-; peroxides such as peroxomonosulphate (PMS), peroxodisulphate (PDS), and H2O2; and halogens namely Cl2, Br2, and I2.The fast kinetics of the formation and decay of the radical cation TEPD.+ have been analyzed at 565 nm by the stopped-flow technique under pseudo-first-order conditions.From the kinetic data, it has been inferred that the reactions were found to be of first-order with respect to and but over all it has been of second-order.The observed second-order rate constants in both the formation and decay of TEPD.+ has been correlated with the oxidation potentials of the various oxidants employed in this study.The effect of pH on the oxidation has been investigated in the formation and decay of TEPD.+ as well as reduction studies have also been carried out using dithionite which has been found to regenerate the TEPD from the TEPD.+ and the corresponding rate constant has also been determined.Besides these, this article also explains how the TEPD, which forms TEPD.+ acts as a better electron relay than TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine) which forms TMPD.+, even though both of them undergo one-electron oxidation and are used in the chemical routes to solar energy conversions.The observed rate constants for electron transfer were correlated theoretically using Marcus theory.The observed and calculated rate constants have good correlation.
Pattern of OH Radical Reaction with N6,N6-Dimethyladenosine. Production of Three Isomeric OH Adducts and Their Dehydration and Ring-Opening Reactions
Vieira, A. J. S. C.,Steenken, S.
, p. 7441 - 7448 (1987)
By use of pulse radiolysis with optical and conductance detection, the reactions in aqueous solution of OH radicals with N6,N6-dimethyladenosine (DMAdo) were studied.OH reacts with DMAdo with the rate constant 6.4E9 M-1 s-1 by addition to C-4 (35percent probability), to C-5 (19percent), and to C-8 (30percent) and by H abstraction from the methyl or ribose groups (16percent).The resulting OH adducts A-4-OH and A-5-OH on the one hand and A-8-OH on the other undergo unimolecular transformation reactions characterized by different rates (at 20 deg C) and activation parameters.With A-4-OH and A-5-OH, the transformations involve OH- elimination (dehydration) (k = (4.2-4.9)E5 s-1) to yield the radical cation DMAdo.+; with A-8-OH, opening of the imidazole ring occurs (k = 9.5E4 s-1).DMAdo.+ oxidizes N,N,N',N'-tetramethyl-p-phenylenediamine with k = 2.9E9 M-1 s-1.The OH- elimination reactions of A-4-OH and A-5-OH are inhibited by protonation of the radicals, which occurs at pH 4-5 and probably involves N6 as the proton acceptor.The elimination of OH- is prevented also by OH-.In contrast, the ring-opening reaction that A-8-OH undergoes is enhanced by OH-.A-4-OH, A-5-OH, and A-8-OH and their transformation products differ also with respect to their redox properties.A-4-OH has a low reactivity with O2, whereas A-5-OH and A-8-OH are extremely reactive.
Palladium-catalyzed amination of dihalobenzenes
Beletskaya,Bessmertnykh,Mishechkin,Guilard
, p. 1416 - 1417 (1998)
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Palladium-catalyzed amination of aryl dibromides with secondary amines: Synthetic and mechanistic aspects
Beletskaya, Irina P.,Bessmertnykh, Alla G.,Guilard, Roger
, p. 6393 - 6397 (2007/10/03)
Diaminobenzenes are obtained starting from m- and p-dibromobenzenes and secondary amines in the presence of Pd(dba)2/P(o-tolyl)3 and sodium tert- butoxide in moderate to good yields. Reductive dehalogenation of aryl dibromides is a major side reaction under these conditions. The study of this reaction has shown that the formation of reductive dehalogenation products occurs according to two independent ways. The first one proceeds via the well-known β-hydride elimination from amido-coordinated palladium complexes. The second one involves the formation of hydrido palladium complexes from amino-coordinated derivatives. Although our results do not allow us to propose a detailed mechanistic scheme, they clearly show that the deprotonation step of the catalytic amination cycle has a major effect on the amine/arene ratio.
