Cathodic macroelectrolysis of acetophenone: A careful analysis of product distribution

The electrochemical reduction of acetophenone has been reinvestigated because of uncertainty, not only in the quantitative data given in the literature, but also in the knowledge of well known synthetic routes to both pure diastereometric pinacols and availability of advanced analysis techniques. The reduction of acetophenone has been carried out at a graphite electrode in a cell divided into two compartments by an anion exchange membrane. It has been found that the reaction products with a product yield higher than 1% at 25°C are 1-phenylethanol, meso-pinacol and dl-pinacol. The diastereometric ratio, SDL/Sm, between the selectivities of both forms of pinacol depends strongly on the pH of the solution, but for acidic media SDL/Sm is practically independent of electrode potential, water content of water—organic solvent mixture, nature of alcohol used as organic solvent, and nature of added organic and inorganic compounds. The ratio SDL/Sm reaches a limiting value, viz about 1, at a pH of about 0.5. The selectivity for 1-phenylethanol formation is very low, viz about 1-2%.