Phenylenediamines radiolysis

Kemp and coworkers employed the pulse radiolysis technique to study the radiolysis of liquid dimethyl sulfoxide (DMSO) with several amines as solutes [triphenylamine, and N, A, A, N -tetramethyl-p-phenylenediamine (TMPD)]. The radiolysis led to the formation of transient, intense absorptions closely resembling those of the corresponding amine radical cations. Pulse radiolysis studies determine only the product Ge, where G is the radiolytic yield and e is the molar absorption. Michaelis and coworkers measured e for TMPD as 1.19 X 10 m s and from this a G value of 1.7 is obtained for TMPD in DMSO. The insensitivity of the yield to the addition of electron scavenger (N2O) and excited triplet state scavenger (naphthalene) proved that this absorption spectrum belonged to the cation. 

Triphenylamine (TPA), AWW W -tetramethyl-p-phenylenediamine (TMPD) and dimethylaniline (DMA) have been popular substrates for reaction under pulse radiolysis conditions. One of the earlier reports dealt with the formation of the radical cation of TMPD by reaction (k = 3 x 108 M 1 s 1) with the peroxy radical derived from oxidation of methylene chloride (CHCI2O2) by pulse radiolysis26. DMA is also oxidized to its radical cation by the same reagent (k = 2.5 x 107 M 1s 1). Since then it has been... 

Nese C, Schuchmann MN, Steenken S, von Sonntag C (1995) Oxidation vs. fragmentation in radiosensitization. Reactions of a-alkoxyalkyl radicals with 4-nitrobenzonitrile and oxygen. A pulse radiolysis and product study. J Chem Soc Perkin Trans 2 1037-1044 Neta P, Huie RE, Mosseri S, Shastri LV, Mittal JP, Maruthamuthu P, Steenken S (1989) Rate constants for reduction of substituted methyl peroxyl radicals by ascorbate ions and N,N,N, N -tetrameth-yl-p-phenylenediamine. J Phys Chem 93 4099-4104 Neta P, Huie RE, Ross AB (1990) Rate constants for reactions of peroxyl radicals in fluid solutions. J Phys Chem Ref Data 19 413-513... 

Fujita S, Steenken S (1981) Pattern ofOFI radical addition to uracil and methyl-and carboxyl-substituted uracils. Electron transfer ofOFI adducts with N,N, Ar, Ar -tetramethyl-p-phenylenediamine and tetranitromethane. J Am Chem Soc 103 2540-2545 Fujita S, Nagata Y, Dohmaru T (1988) Radicals produced by the reactions of SO4 with uridine and its derivatives. Studies by pulse radiolysis and y-radiolysis. Int J Radiat Biol 54 417-427 Fujita S, Horii FI,Taniguchi R, Lakshmi S, Renganathan R (1996) Pulse radiolytic investigations on the reaction of the 6-yl radicals of the uracils with Cu(ll)-amino acid complexes. Radiat Phys Chem 48 643-649... 

Although reducing conditions are readily achieved in methanol radiolysis, it is also possible to observe one-electron oxidation. For example, pulse radiolysis of N2O-saturated solutions of A,A,7/, A -tetramethyl- -phenylenediamine (TMPD) or 1 results in the formation of TMPD + and I2, respectively. The oxidant was assigned as the methoxy radical CHbO, whose half-life in pure methanol was estimated to be 106 ns [13]. 

Both investigations also reported the pulse radiolysis of solutes dissolved in ionic liquids. Behar et al. studied the effect of the presence of Oj and CCI4 in [bmim][PF6] their results suggested that the latter was a more effective radical scavenger. They also looked at the formation of the radical cations of chlorpromazine (ClPz-+) andN,N,7 r, N -tetramethyl-p-phenylenediamine (TPMD- ) in the same solvent. Finally, the kinetics of oxidation of ClPz in [bmim][PF( ] were studied. The experimentally determined bimolecular rate constant values were corrected for the high viscosity of the ionic liquid by estimation of the values of the diffusion-controlled rate constant, using Equation (5.3),... 

Radiolysis of n-Dodecane Containing a Solution of Tetramethyl-p-Phenylenediamine 255... 

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