Tetra methyl p-phenylenediamine

As for halogens as oxidizing reagents, bromine has proved more useful than its homologs chlorine and iodine. It was employed as early as 1879 on di- and tetra-methyl-p-phenylenediamine [27-29] and early in this century, Wieland used it to generate the aminium salts of triarylamines and tetraarylhydrazines [30, 31]. Since bromine adds readily to unsaturated as well as to some strained ring compounds, it is not expected to be very useful in the context of the radical cations discussed here. 

Other electron-transfer reaction rates which have been measured are those between phenothiazine cation-radical (249) and dimethyl- and tetra-methyl-p-phenylenediamines. Electron transfer takes place at the diffusion-controlled rate equilibrium constants were determined which demonstrated the greater stability of the Wurster s radicals over 249. This... 

The phenomenon of complete electron transfer in solution is best illustrated with the now classic example of the NjNjN jN -tetra-methyl-p-phenylenediamine (TMPD)-chloranil reaction (Kainer and Wherle, 1955 Isenberg and Baird, 1962 Eastman et al., 1962). This pair forms a charge-transfer complex in solvents of low dielectric (e.g. dioxan, benzene, 1,2-dichlorethane) without complete electron transfer, whereas in acetonitrile the detectable, first-formed complex gives way to the separate cation and anion radicals, each of which is detectable by absorption and esr spectroscopy. 

The following chemicals were used as received (from Aldrich unless otherwise noted) 2,6-diaminoanthraquinone, 2,5-dichloro-p-phenylenediamine, 2,6-diamino-5-nitropyrimidine, 2,3,5,6-tetra-methyl phenylenediamine, 2,6-diamino-8-purinol hemisulfate monohydrate, adenine (Chemalog Chemical Dynamics Corp.), 1,9-diamino-nonane, 4,4 -diaminodiphenyl sulfon (Fluka AG), 4,4 -methylene-dianiline, tetraphenyl phosphonium iodide, tetrabutyl ammonium iodide, tetramethyl ammonium bromide, dibenzo-l8-crown-6, 15-crown-5, triphenylantimony dichloride and triethylamine (Eastman Kodak Co.). 

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