Electrooxidation of catechol in the presence of proline at different pH

The electrooxidation characteristics of catechol in the presence of different concentrations of proline in aqueous buffer solutions at different pH levels were examined using cyclic voltammetry, controlled potential coulometry, and differential pulse voltammetry. In the second potential scan, the reaction involving o-benzoquinone and proline occurred at higher proline concentrations. The product of catechol electrooxidation with proline is assumed to be (S)-1-(3,4-dihydroxyphenyl)pyrrolidine-2-carboxylic acid, which undergoes electron transfer at more negative potentials compared to catechol. The influence of the pH of catechol in the presence of proline was assessed by adjusting the pH of the buffer solution from 5 to 11. Both pH and proline concentration significantly affected the reaction, and the optimal conditions for this reaction were observed at a proline concentration of 150 mM and a catechol concentration of 2 mM in a buffer solution of pH 7. The reaction pathway exhibited characteristics of an electron transfer, chemical reaction and electron transfer (ECE) type, followed by a diffusion mechanism.