Electro-oxidation of Catechol in the Presence of L-Histidine at Different pH

The electro-oxidation of Catechol in presence of L-Histidine has been investigated in aqueous solution with various pH values, different electrodes and different concentration of L-Histidine by using cyclic voltammetry, differential pulse voltammetry and controlled potential coulometry. Electrochemically generated o-benzoquinone (Michael acceptor) from oxidation of Catechol reacts with lower concentration of L-Histidine as nucleophiles in the second scan of potential. The products obtained from the reaction are assumed to be 2-((3,4- dioxocyclohexa-1,5-dien-1-yl)amino)-3-(1H-imidazol-4-yl)propanoic acid that undergo electron transfer at more negative potentials than the Catechol. The effect of pH of Catechol in presence of L-Histidine has been studied by varying pH from 5 to 11. The concentration effect of L-Histidine with the fixed concentration of Catechol (2 mM) was measured from 2 mM to 100 mM. The reaction was strongly influenced by the pH as well as concentration of L-Histidine. The reaction is mostly favorable in 30 mM of L-Histidine and 2 mM of Catechol at pH 7. The behavior of the reaction mechanism was of ECE type.