Search

Electrochemical behaviour of N-bromosuccinimide (NBS, mp 174 ºC) was investigated in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFP) by cyclic and pulsed voltammetry at platinum electrode. The cyclic voltammetric response was characterized by an irreversible reduction peak at around 0.7 V vs. SCE, and an anodic peak at about 0.1 V on reverse sweep. The possible mechanism for electro-reduction of NBS was outlined. In case of normal pulse voltammetry, a well-defined sigmoid-shaped curve was obtained. An increase in step time resulted in a significant cathodic shift. Differential pulse voltammetric response was consistent with the normal pulse behaviour, and featured a single peak centered at about 0.88 V. Linear variation of summit current with pulse height was observed.

Linear sweep voltammetry of N-bromosuccinimide at glassy carbon electrode in aqueous nitrate solution yielded a single, irreversible reduction wave. The cathodic peak current showed linear variation with concentration of N-bromosuccinimide. The reduction wave was simulated and kinetic parameters evaluated. Pulsed (differential and normal) voltammetric techniques are explored for determination of N-bromosuccinimide

Electrochemical simulation of the cyclic voltammogram of a 2,6- di-methyl-4-(diphenylmethylene)-2,5-cyclohexadien-1-one in DMSO/tetra-n-butylammonium hexafluorophosphate at a mercury cathode was carried out using two shareware simulation programs; CVSIM and ESP 2.4. Two cathodic and two anodic peaks were analyzed. 3,5-Bis(1,1-dimethylethyl)-4-oxo-2,5-cyclohexadienylideneacetonitrile, is an electron acceptor. Simulation of cyclic voltammogram of 3,5-bis(1,1-dimethylethyl)-4- oxo-2,5-cyclohexadienylideneacetonitrile, in acetonitrile at platinum electrode was carried out, and a scheme was suggested to obtain the heterogeneous rate constants for electron transfer. The results of simulations based on two shareware programs were generally consistent with theoretical and experimental work (3). Steady-state voltammetry was used to measure the heterogeneous electron-transfer rates for the reduction of quinones to determine the dependence of ko on molecular size, according to Marcus theory. This dependence was then used to predict the electron- transfer rate constants of related quinones, and the predictions were compared to experimental measurements (4).

Whereas reductive voltammetry of 1-bromopyrrolidin-2,5-dione (N-Bromosuccinimide), or SBr has been extensively studied in non-aqueous systems, relatively few papers have dealt with its electro-reduction in aqueous solutions. This paper describes voltammetry of 1-bromopyrrolidin-2,5-dione at platinum electrode in aqueous nitrate solution. The electrochemical reduction of N-chlorosuccinimide in acetonitrile at a platinum cathode parallels the reductions of N-bromosuccinimide. The overall n-value is 1; the succinimide anion, generated by a two electron reduction of N-chlorosuccinimide, is an intermediate; homogeneous electron transfer from the succinimide anion to N- chlorosuccinimide generates the succinimidyl radical, which is the precursor for the other products formed. The reduction of N-chlorosuccinimide by the succinimide anion, added, as a quaternary ammonium succinimide in a homogenous chemical system is significantly different from the comparable reaction with N-bromosuccinimide. Rate constants for the pertinent reactions were measured, and the reaction mechanism was proposed (2). Electron transfer between N-bromosuccinimide and tetra butyl ammonium succinimidate gave 65% succinimide, and ∼10% polymer), the nature of which was determined by nuclear magnetic resonance. The build up and decay of maleimide were followed by nuclear magnetic resonance. The development of the characteristic base induced yellow-red color of the polymaleimide could be followed kinetically and the effect of additive studied. The reaction resulted in weak chemiluminescence. This supports the hypothesis that the initial step of the reaction is electron transfer, forming a cage radical ion/radical pair. N-Br bond cleavage within the cage forms a pair of succinimide radicals, which react with disproportionation to give succinimide and maleimide. The latter then undergoes predominant radical polymerization. The reaction of N-chlorosuccinimide with tetra butyl ammonium succinimidate also gave polymaleimide (40%) and succinimide (47%) (3, 4).