Study of radiation chemical reactions of oxidising and reducing radicals with furazan derivatives

Citation
Ms. Alam et al., Study of radiation chemical reactions of oxidising and reducing radicals with furazan derivatives, J PHOTOCH A, 143(2-3), 2001, pp. 181-189
Citations number
39
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY
ISSN journal
10106030 → ACNP
Volume
143
Issue
2-3
Year of publication
2001
Pages
181 - 189
Database
ISI
SICI code
1010-6030(20011010)143:2-3<181:SORCRO>2.0.ZU;2-T
Abstract
Reactions of (OH)-O-.,O.-,N-3(.) and SO4.- and e(aq)(-) radicals with furaz an and its dimethyl and diamino derivatives were studied by radiation chemi cal methods, The (OH)-O-. radical reaction is selective with the rates foll owing the order furazan < 3,4-dimethylfurazan (3,4-DMF) < 3,4-diaminofuraza n (3,4-DAF), the k values being < 10(7), 3.5 x 10(8), 3.9 x 10(9) dm(3) mol (-1) s(-1), respectively. The transient absorption spectra measured in the (OH)-O-<bullet> radical reaction with 3,4-DMF and 3,4-DAF exhibited maxima at 270 and 290 nm, respectively, which are assigned to the benzylic and ani lino type radicals. The same intermediates are also formed in the O.- react ion by H abstraction, All three derivatives showed lack of reactivity with N-3(.) radical and was only 3,4-diaminofurazan found reactive with SO4.- (k = 3.6 x 10(9) dm(3) mol(-1) s(-1)). The rates of e(aq)(-) with all the thr ee derivatives are diffusion controlled k = (0.8-1.9) x 10(10) dm(3) mol(-1 ) s(-1) and its reaction mechanism involves very fast protonation of the in itially formed radical anions by water (k greater than or equal to 10(7) s( -1)) followed by tautomerisation of the N-atom protonated C-centred radical to the C-atom protonated N-centred radical. The transformation is catalyse d by OH- and the rates for the spontaneous transformation in neutral soluti on are 5.4 x 10(4) and 1.5 x 10(5) s(-1) with furazan and 3,4-diaminofuraza n, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.