Investigation of the Electromethoxylation Reaction Part 2: Electrochemical Study of 3-Methylcatechol and 2,3-Dihydroxybenzaldehyde in Methanol

Abstract

Electrochemical oxidation of 3-methylcatechol (I) and 2,3-dihydroxybenzaldehyde (II) in methanol at various pH has been studied using cyclic voltammetry and controlled-potential coulometry. The results indicate that the participation of these compounds in methoxylation or side reactions such as dimerization reaction depends on the pH of the solution and the nature of the functional groups in the catechol ring. In the presence of sodium acetate, 3-methylcatechol (I) undergoes methoxylation according to an ECE mechanism to form the methoxyquinone (Ic). Under these conditions 2,3-dihydroxybenzaldehyde (II) participates in a dimerization reaction and in acidic solution, this compound undergoes a methoxylation reaction parallel to the dimerization reaction, to give the related methoxyquinone (IIe).