Electron-transfer reactions involving simple free radicals

Kinetics of Oxidation of Azide by [Ethylenebis(biguanide)]silver(III) in Aqueous Acidic Media

“…An alternative for the assigned fate of the azidyl radical could be the dimerisation to produce N 6 that ultimately produces N 2 . But, this appears unlikely here as, if it were the actual pathway, then sufficient accumulation of N 3 to cause appreciable reversal of reaction (9) and hence rate retardation (deviation from simple first‐order kinetics) could be anticipated 48b,53. No such retardation could be detected and thus the dimerisation pathway is neglected in the present study.…”

“…The azidyl radical (N 3 ) may decay to N 2 in several ways, like by fragmentation45 to N 2 and N, the process, although spin‐forbidden, is close to thermoneutral46 with a rate constant47,48 around 10 6 s −1 . In yet another possibility, N 3 can combine with N 3 − forming49−51 N 6 − (however, attempts to observe the radical dimer N 6 − using pulse radiolysis met with no success,48b but nanosecond laser flash photolysis50,51 and kinetic evidences16 suggest involvement of N 6 − in some instances) and then rapid reaction of N 6 − with the oxidant species or a rapid direct reaction of two mol of N 3 radical could produce three mol of N 2 (2 N 3 ⇄ 3 N 2 , 2 k = 9·10 9 M −1 ·s −1 ) 28. The absence of EPR evidence for Ag II or N 3 radicals in our study cannot conclusively eliminate the formation of such species as it may only indicate that such species are formed but decayed too rapidly before they can diffuse into the bulk solvent sufficiently quickly to permit detection.…”

Direct Resonance Raman Characterization of a Peroxynitrito Copper Complex Generated from O2 and NO and Mechanistic Insights into Metal‐Mediated Peroxynitrite Decomposition

“…The kinetics of the PN2 transformation into Cu II ÀNO 2 À species 2 is overall first order in Cu ( Figure S17), consistent with unimolecular decay,most likely through cleavage of the O À O bond. Thec oupling of phenoxyl species to give the observed diol can be rationalized by successive hydrogen atom abstractions by LCu II ÀOC and NO 2 C (a strong oxidant [57,58] )t og ive LCu II À OH and HNO 2 before ligand exchange to give LCu II À NO 2 À and H 2 O(Scheme 3). [27,28] Thed etection and characterization (see the Supporting Information) of ah igh yield cupric nitrite (NO 2 À )p roduct from a PN2 thermal transformation is consistent with the formation of cupryl [Cu II (TMG 3 tren)(OC)] + and NO 2 C intermediates following peroxynitrite homolytic OÀObond cleavage;the most common recombination of such radicals to give aCunitrate product does not occur (Scheme 1).…”

Mechanism of the oxidation of hydrazoic acid by tetrachloroaurate(III) ion

“…[Ag(OH) 4 ] - [12], [Cu III (H 2 TeO 6 ) 2 ] 5-and [Ag III (H 2 TeO 6 ) 2 ] 5- [13] in alkaline medium and [(CH 2 ) 2 (C 2 N 5 H 6 ) 2 Ag] 3+ , ethylenebisbiguanidesilver(III) in acidic medium [14] are inner-sphere. A reinvestigation of an earlier study [15] with IrCl 6 2-, IrBr 6 2-and [Fe(bpy) 3 ] 3+ ions made in the presence of N-tert-butyl-aphenylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO), traps for the free radical N 3 • , suggested that the reactions are outer-sphere [16]. The outer-sphere nature of the reactions is supported by the application of the Marcus cross relation [17].…”