Controlled Potential Electrolysis Experiments Research Articles

Electrochemical reduction of 4-thienylquinazoline in dimethylformamide

Electrochemical reduction of 4-thienylquinazoline (4-TQ) at the dropping mercury electrode in dimethylformamide solutions containing 0.1 M tetrabutyl ammonium iodide supporting electrolyte gave two well-defined diffusion-controlled waves. The first wave was found to be quasi-reversible and the second irreversible, on the basis of the usual criteria. The controlled potential electrolysis experiments carried out at the limiting regions of the frist and the total waves of 4-TQ yielded the same number of electrons, namely two, in both cases. Mechanisms corresponding to the total wave and the first wave were proposed based on the results obtained.

Electrochemical reduction of 4-thienylquinazoline in dimethylformamide

Electrochemical reduction of 4-thienylquinazoline (4-TQ) at the dropping mercury electrode in dimethylformamide solutions containing 0.1 M tetrabutyl ammonium iodide supporting electrolyte gave two well-defined diffusion-controlled waves. The first wave was found to be quasi-reversible and the second irreversible, on the basis of the usual criteria. The controlled potential electrolysis experiments carried out at the limiting regions of the frist and the total waves of 4-TQ yielded the same number of electrons, namely two, in both cases. Mechanisms corresponding to the total wave and the first wave were proposed based on the results obtained.

On the reaction kinetics of electrogenerated superoxide ion with aryl benzoates

The reactions between electrogenerated superoxide ion O 2 ⨪ and two benzoate esters in N, N-dimethylformamide containing tetrabutylammonium perchlorate have been investigated. By using cyclic voltammetric techniques an e.c.e. type mechanism was found to be operative; this was confirmed by controlled potential electrolysis experiments. Secondorder rate constants for nucleophilic displacement by O 2 ⨪ on p -chlorophenyl benzoate and phenyl benzoate were estimated to be 25.0±5 and 3.0±0.3 M −1 s −1 respectively by fitting potential step reduction data to i k / i d vs. log kt working curves.

On the reaction kinetics of electrogenerated superoxide ion with aryl benzoates

The reactions between electrogenerated superoxide ion O 2 ⨪ and two benzoate esters in N, N-dimethylformamide containing tetrabutylammonium perchlorate have been investigated. By using cyclic voltammetric techniques an e.c.e. type mechanism was found to be operative; this was confirmed by controlled potential electrolysis experiments. Secondorder rate constants for nucleophilic displacement by O 2 ⨪ on p-chlorophenyl benzoate and phenyl benzoate were estimated to be 25.0±5 and 3.0±0.3 M −1 s −1 respectively by fitting potential step reduction data to i k/ i d vs. log kt working curves.

Application of direct digital control of electrode potential to controlled-potential electrolysis experiments

Application of direct digital control of electrode potential to controlled-potential electrolysis experiments

Electrochemical studies on 3,3′-methylenebis-(4-hydroxycoumarin) (dicoumarol) in dimethylformamide

The electrochemical behaviour of 3,3′-methylenebis-(4-hydrocoumarin) (Dicoumarol, H2A) and 4-hydroxycoumarin (HR) has been studied in DMF-0.5 F (Et4N)ClO4 solutions. H2A is reduced in two steps at the dme, the solvated proton originating from the dissociation of H2A is the electro-active species involved in the first stage of reduction. The wave corresponds to the wave of solvated proton from HClO4 in the same base solution [E12 = −1·23 V(sce)]. The second step of H2A reduction corresponds to hydrogen discharge from the undissociated HA−. 4-Hydroxycoumarin behaves like HA−. Coulometric and controlled-potential electrolysis experiments substantiate the mechanism previously described. H2A, a weak acid in hydroxylic solvents, exhibits an enhanced strength in the aprotic solvent DMF; this is consistent with current ideas about anion solvation in DMF.

Polarographic behaviour of ω-diazoacetophenones in aqueous buffer solutions

The polarographic behaviour of ω-diazoacetophenone and 12 meta- and para-substituted ω-diazoacetophenones has been studied in aqueous buffer solutions. The polarograms generally show three waves corresponding to successive reduction of the diazo-ketone to the corresponding ω-aminoacetophenone, acetophenone, and either 2-phenylethanol or 2,3-diphenylbutane-2,3-diol. The reduction scheme may be represented: first wave, XC6H4·CO·CHN2+ 7H++ 6e → XC6H4·CO·CH2·NH2+ NH4+, second wave, XC6H4·CO·CH2·NH2+ 3H++ 2e → XC6H4·CO·CH3+ NH4+, third wave, XC6H4·CO·CH3+ 2H++ 2e → XC6H4·CH(OH)·CH3, or 2XC6H4·CO·CH3+ 2H++ 2e →[graphic omitted] where X is the meta- or para-substituent (including H). For the p-nitro-substituted compound an additional wave is observed, preceding that for the diazo-ketone reduction, and corresponding to reduction of the nitro-group.The polarographic behaviour of p-bromo-ω-diazoacetophenone and preparative controlled potential electrolysis experiments indicate that the six-electron reduction follows the scheme: XC6H4CO·CHN2+ 2H++ 2e → XC6H4CO·CH:N·NH2, XC6H4CO·CH:N·NH2+ 2H++ 2e → XC6H4CO·CH2·NH·NH2, XC6H4CO·CH2·NH·NH2+ 3H++ 2e → XC6H4CO·CH2·NH2+ NH4+