PULSE-RADIOLYSIS OF BENZIDINE IN AQUEOUS-SOLUTIONS

OH radicals react with benzidine, to give initially adducts, with rate constants of 1.5 x 10(10) and 2.5 x 10(9) dm(3) mol(-1) s(-1) at pHs 7 and 2, respectively, which later give rise to a cation radical (H(2)NR(2)NH(2)(+)) and its protonated form (H(2)NR(2)NH(3)(2+)). At pH 13, O- radicals react with benzidine by H-abstraction with a rate constant of 2.5 x 10(9) dm(3) mol(-1) s(-1) to give anilino type of radical (H(2)NR(2)NH'). Besides the reported bands viz. 455 nm for the cation radical and 380 nm for the 4(4'-aminophenyl)anilino radical, new bands with maxima around 780 and 620 nm were observed for the cation radical and anilino type radical respectively. Similar transient spectra were obtained by the reaction of one electron oxidants also. The cation radical was found to oxidise ascorbate ions with a rate constant of 1 x 10(8) dm(3) mol(-1) s(-1). e(aq)(-) reaction with benzidine (k = 2.1 x 10(9) dm(3) mol(-1) s(-1)) leads to elimination of ammonia and gives a transient species with lambda(max) at 390 nm. H-atoms react by addition (k = 1.3 x 10(9) dm(3) mol(-1) s(-1)) with benzidine to give a species having weak absorption in the UV region with lambda(max) at 360 nm.