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.
Magnetic field effects on the luminescence of p-phenylenediamine derivatives
Sacher,Grampp
, p. 971 - 974 (1997)
A positive magnetic field effect (MFE) on the luminescence of three different N,N,N′,N′-tetraalkyl-p-phenylenediamines (TAPD) has been detected by field-modulated MARY (MAgnetic Field Effects on Reaction Yields) spectroscopy in a binary solvent mixture of toluene/ dimethylsulfoxide containing more than 20% vol. dimethylsulfoxide and in neat dimethylsulfoxide. The p-phenylenediamine derivatives' luminescence in these solvents could be increased by application of small external magnetic fields in the order of less than 30 mT (1T = 104G) and the B1/2 values could be measured. In a comparative experiment the N,N-dimethylaniline (DMA) fluorescence did not show such a behaviour. In conclusion a reaction scheme involving an electron transfer process between the p-phenylenediamines and the solvent dimethylsulfoxide is suggested. VCH Verlagsgesellschaft mbH, 1997.
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.
ESR and ENDOR investigations on various Wurster's radical cations in solution. Experimental results, theoretical ab initio, and DFT calculations
Grampp, Guenter,Kelterer, Anne-Marie,Landgraf, Stephan,Sacher, Michael,Niethammer, Dominique,Telo, Joao P.,Dias, Rui M. B.,Vieira, Abel J. S. C.
, p. 519 - 536 (2007/10/03)
ESR and ENDOR spectra are reported of several symmetrical substituted N,N,N′,N′-tetraalkyl-p-phenylenediamine radical cations in solution. Different N,N′-alkyl substituted paraphenylenediamines, like the ethyl, n-propyl, and iso-propyl derivative are compared with the parent N,N,N′,N′-tetramethyl-p-phenylenediamine (Wurster's Blue Cation). N,N,N′,N′-Tetrabenzyl-p-phenylenediamine, 1,4-dipyrrolidinylbenzene, and N,N′-bis[4-(dimethylamino)phenyl]piperazine are additionally investigated. Experimental and calculated hyperfine coupling constants are compared. Characteristic UV-VIS data and redox potentials in acetonitrile are reported, together with the syntheses of the compounds. Springer-Verlag 2005.
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.
1- und 2-Elektronenschritte bei der Oxidation substituierter Paraphenylendiamine mit verschiedenen Oxidationsmitteln. II. Reaktionen mit Hexacyanoferrat
Nickel, Ulrich,Jaenicke, Walther
, p. 695 - 701 (2007/10/02)
The oxidation kinetics of several N- and ring-alkylated p-phenylenediamines with hexacyanoferrate(III) (F3) was studied in the pH-range 2,5-9 by means of a multimixing stopped flow technique which is described in detail.The p-phenylene diamine-derivatives (R) are oxidized via reversible one-electron steps to the semiquinone diimine radical S (rate constants k1, k-1) and the quinone diimine T (rate constants k2, k-2). - k1 and k-1 could be measured directly for all compounds, k2 and k-2 for two derivatives. - Only the unprotonated species of R, S, T, F3 are reactive.The reduction is possible by the unprotonated Fe(CN)64- (F2) and by its protonated form F2H.The complexes of F2 with alkali ions are inactive.In this way the respective association constants could be calculated.The kinetics of the reaction was compared with the thermodynamics, represented by potential-pH-diagrams. - The activation parameters of the reaction of p-phenylene diamine-derivatives with F3, F2 and also with iodine were measured.The activation energies of the second step (k2, k-2) are negligible. - Both oxidants attack the alkylated aminogroup of the p-phenylene diamine derivatives.The radical cation is deprotonated before it is oxidized.
