2.3.5.6- Tetramethyl-p-phenylenediamine

AMNES - AMINES,AROMATIC - PHENYLENEDIAMINES] (Vol 2) N,N,Ny,Ny-Tetramethyl-p-phenylenediamine (TMPD) [100-22-1]... 

Note The contrast between the colored zones and the layer background can be improved by warming the chromatogram gently [4]. Di-tert-butyl peroxide does not react [3]. N,N,N, N -tetramethyl-p-phenylenediamine (q.v.) can also be used instead of N,N-DPDD for the detection of peroxides [3]. The spray solution for peroxides gradually turns dark red in color but it still retains its ability to react for several weeks [4]. 

The detection limits for peroxides are about 500 ng or with N,N,N, N -tetramethyl-p-phenylenediamine reagent 50 ng substance per chromatogram zone [4]. The detection limits for insecticides are 5 pg per chromatogram zone in the most unfavorable cases [7]. 

Allyl (27, 60, 119-125) and benzyl (26, 27, 60, 121, 125-133) radicals have been studied intensively. Other theoretical studies have concerned pentadienyl (60,124), triphenylmethyl-type radicals (27), odd polyenes and odd a,w-diphenylpolyenes (60), radicals of the benzyl and phenalenyl types (60), cyclohexadienyl and a-hydronaphthyl (134), radical ions of nonalternant hydrocarbons (11, 135), radical anions derived from nitroso- and nitrobenzene, benzonitrile, and four polycyanobenzenes (10), anilino and phenoxyl radicals (130), tetramethyl-p-phenylenediamine radical cation (56), tetracyanoquinodi-methane radical anion (62), perfluoro-2,l,3-benzoselenadiazole radical anion (136), 0-protonated neutral aromatic ketyl radicals (137), benzene cation (138), benzene anion (139-141), paracyclophane radical anion (141), sulfur-containing conjugated radicals (142), nitrogen-containing violenes (143), and p-semi-quinones (17, 144, 145). Some representative results are presented in Figure 12. 

Another type of dimer is that which consists of two radical molecules stacked on each other in a n-n interaction. Such dimers have been observed e.g., with 9-ethylphenazyl radical, tetramethyl-p-phenylenediamine cation radical (167), 7,7,8,8-tetracyanoquinodimethane radical anion (168), methylviologen cation radical (169), and l-alkyl-4-carbomethoxypyridinyl radicals (170). Attempts have been reported (170, 171) to interpret the electronic spectra of dimers of this kind by MO calculations. 

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. 

In a partly biological, partly artificial model (page 397) reduced anthraquinone-2-sulphonate plays the role of NAD+ and tetramethyl-p-phenylenediamine that of plastoquinones. 

Exceeding the limitation of molecular dynamics, the steric requirement of trimethylsilyl groups can cause drastic changes both in structure and of molecular properties of organosilicon compounds. For illustration, the so-called "Wurster s-Blue11 radical ions are selected On one-electron oxidation of tetramethyl-p-phenylenediamine, its dark-blue radical cation, detected as early as 1879 [11a], is gene-... 

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... 

Neutral organic molecules can also be one-electron donors. For example, tetracyano-quinodimethane gives rise to anion-radical on reduction with 10-vinylphenothiazine or N,N,N, N -tetramethyl-p-phenylenediamine. Sometimes, alkoxide or phenoxide anions hnd their applications as one-electron donors. There is a certain dependence between carbanion basicity and their ability to be one-electron donors (Bordwell and Clemens 1981). 

As an example, the reaction of tetrachloromethane with iV,iV,iV, iV -tetramethyl-l,4-phen-ylenediamine (TMPDA) can be discussed. The presence of p-benzoquinone (Q) in the system provokes electron transfer (Sosonkin et al. 1983). Because benzoquinone itself and tetramethyl-p-phenylenediamine interact faintly, the effect is evidently a result of redox catalysis. The following equations reflect such kind of catalysis ... 

In comparison with hydrocarbons, aromatic amines easily transform into cation radicals. Structures of these cation radicals are well documented on the basis of their ESR spectra and MO calculations (see, e.g., Grampp et al. 2005). The stable cation radical of A/,A,A, A -tetramethyl-p-phenylenediamine (the so-called Wuerster s blue) was one of the first ion radicals that was studied by ESR spectroscopy (Weissmann et al. 1953). The use of this cation radical as a spin-containing unit for high-spin molecules has been reported (Ito et al. 1999). Chemical oxidation of N,N -bis [4-(dimethylamino)-phenyl-A/,A -dimethyl-l,3-phenylenediamine with thianthrenium perchlorate in -butyronitrile in the presence of trifluoroacetic acid at 78°C led to the formation of the dication diradical depicted in Scheme 3.58. 

The change from 7V-methyl- (structure a of Scheme 6.29) to Al-isopropyl substitution (structure b) lowers the electron-transfer barrier (Nelsen 1997, p. 171). The p,p -phenylene-linked system (structure c) features fast electron transfer under comparable conditions. The cation-radical from the last bis-hydrazine is instantaneously localized in contrast to the cation-radical from tetramethyl-p-phenylenediamine, which is delocalized (Nelsen et al. 1996, 1997a, 1998b Valverde-Aguilar et al. 2006). 

Nanocolor Peroxid 2 Peroxidase-catalyzed oxidation of iV,iV,iV, iV -tetramethyl-p-phenylenediamine (89) and measurement of the color at 620 nm. Fixed portions of two reagent solutions are added to a sample aliquot. b... 

Glucose (65) kits Commercial kits are based on the enzymatic process shown in equation 16, followed by a chromogenic oxidation process catalyzed by peroxidase, similar to equation 27, involving 4- aminoantipyrine (81) and a phenol or aniUne derivative, leading to a quinoneimine dye. Among the latter aromatic substrates in use are A -ethyl-Al-(2-hydroxy-3-sulfopropyl)-3, 5- dimethoxyaniline (92) , phenol , p-hydroxybenzoic acid and p-hydroxybenzenesidfonate other chromogenic reactions are peroxidase-catalyzed oxidation of iV,iV,iV, iV -tetramethyl-p-phenylenediamine (89) and D-ditoluidine (93) . d... 

Tetramethylammonium ozonide, 736 Tetramethyl-l,2-dioxetane (TMD) chemical titration, 1224 chemiluminescence, 1221, 1234 quantum yield standard, 1224, 1226 N,N, N, A -Tetramethyl-p-phenylenediamine hydrogen peroxide determination, 735, 631, 633... 

V,Af-Dimethylaniline A A,A, AT-Tetramethyl-p-phenylenediamine Cyclic amines 4,4 -Bipyridyl Quinoline Pyridine A-oxide Pyridinium chloride Hydroxides CsOH LiOH NaOH Triton B6 Alkylamines Ammonia Methylamine Ethylamine Propylamine Butylamine Decylamine Dodecylamine Tridecylamine Tetradecylamine Pentadecylamine Hexadecylamine Heptadecylamine Octadecylamine Tributylamine Miscellaneous Ammonium acetate Hydrazine Potassium formate Guanidine... 

The inhibition of hydrocarbon oxidation by aromatic tertiary amines which contain no labile hydrogen, such as N,N-dimethylaniline and N,N,N, N -tetramethyl-p-phenylenediamine, has been assigned to an electron-transfer process. However, this seems rather unlikely as pyridine... 

Stade observed an interesting oxidation with tetrachloro-p-benzoquinone. In methylene chloride an intense red coloration appears, but no signal in the ESR spectrum. Apparently only a charge-transfer complex 61 is formed, without electron transfer. A similar observation has been made in the reaction of N, N, N, N -tetramethyl-p-phenylenediamine with tetrachloro-p-benzoquinone in non-polar solvents Here, as in our case, electron transfer does not take place until a polar solvent such as acetonitrile is added. The ESR spectrum initially shows the doublet of 55 (23,2 Gauss) overlapping with the sharp sin et of tetrachloro-semi-quinone 62 (which has a somewhat smaller g factor). The semiquinone signal slowly disappears until finally only the doublet of 58 remains. The following scheme summarizes the reaction course ... 

The energy of a single photon is obviously insufficient to ionize an organic compound. As early as the nineteen forties (3, 4), however, it -was observed that Wurster blue cation radical is produced by photoirradiation of 3-methylpentane glass containing N,N-tetramethyl p-phenylenediamine (TMPD) at 77° K. The recent detailed study of this system by electric conductivity measurement (5, 6) and electronic spectroscopy (7) provided conclusive evidence that the ionization is brought about via excitation to the triplet state followed by successive photoabsorption at the triplet state. This mechanism is supported by the facts that the life-time of the photochemical intermediate is identical with that of phosphorescence and the formation of Wurster blue, and that phosphorescence is inhibited in the presence of triplet scavengers. 

TMPD = A/,Ai,Ai, Ai -tetramethyl-p-phenylenediamine PTZ = phenothiazine POZ = pbenoxazine TRP = tropylium cmt = c -l,2-dicarbomethoxyethylenedithiolato DDDT = 5,6-dihydro-l,4-dithiin-2,3-dithiolato. 

The kinetics of recombination of the tetramethyl-p-phenylenediamine cation radical TMPD with etr and with the naphthalene anion radical Nh in vitreous squalane was studied in ref. 57. The studies were carried out at temperatures of 77 - 150K in two time ranges 10 4 to 10 1 s and 102 to 10 s. At low temperatures (e.g. at 77 K), for both recombination processes the decay of the luminescence intensity for both time ranges was found to be described by eqn. (7) with m = 1 (see the data for the reaction of TMPDf with et7 in Fig. 13), which is characteristic of the tunneling mechanism of recombination. At higher temperatures, however, the kinetics of the luminescence decay for the reactions with et and Nh" turned out to be different. Thus, for example, at 98 K the kinetics for both reactions is described by eqn. (7) as before. But while for the reaction... 

Fig. 12. Perrin quenching radii, R, [33J vs. variations of the free energy, - AG°, of electron transfer from the excited donor molecule to the acceptor molecule for donor-acceptor pairs in vitreous /nms-l,5-decalindiol. 1, Rubrene + A/ AT-diethylamline (DEA) 2, rubrene + N,N,-Ar,Ar-tetramethyl-p-phenylenediamine (TMPD) 3, rubrene + tetrakis(dimethylaminoethy-lene) 4, tetracene + DEA 5, tetracene + TMPD 6, 9,10-dinaphthylanthracene + DEA 7, 9,10-dinaphthylanthracene + TMPD 8, perylene + DEA 9, perylene + TMPD 10, 9-methylanthracene + TMPD 11, 9,10-diphenylanthracene + TMPD 12, coronene + TMPD 13, benzo[ Ai jperylene + TMPD 14, fluoranthene + DEA 15, acridine + DEA.

In all of the examples considered, Ei/2 of the acceptor was much more negative than that of the donor. However, in liquid phase one-electron transfer from a donor to an acceptor can proceed even with an unfavorable difference in the potentials if the system contains a third component, the so-called mediator. The mediator is a substance capable of accepting an electron from a donor and sending it instantly to an acceptor. Julliard and Chanon (1983), Chanon, Rajzmann, and Chanon (1990), and Saveant (1980, 1993) developed redox catalysis largely for use in electrochemistry. As an example, the reaction of ter-achloromethane with /V,/V,/V ,Af-tetramethyl-p-phenylenediamine (TMPDA) can be discussed. The presence of p-benzoquinone (Q) in the system provokes electron transfer (Sosonkin et al. 1983). Because benzoquinone itself and tetrametyl-p-phenylenediamine interact faintly, the effect is evidently a result of redox catalysis. The following schemes reflect this kind of catalysis ... 

---