THE INFLUENCE OF SURFACTANTS ON THE ELECTROCATALYTIC HYDROGENATION OFORGANIC-COMPOUNDS IN MICELLAR, EMULSIFIED, AND HYDROORGANIC SOLUTIONSAT RANEY-NICKEL ELECTRODES

The electrocatalytic hydrogenation (ECH) of limonene (1) and carvone ( 4) at a Raney nickel cathode was studied both in hydroorganic medium ( methanol-water) and aqueous micellar and emulsified solutions. In meth anol-water, the ECH of 1 stopped at p-menthene (2) and proceeded with low current efficiencies (18-24%). In micellar solutions containing a cationic surfactant (CTAB), the ECH of 1 was more efficient, giving p- menthane (3) as the main product with current efficiencies up to 30%. The pH of the solution (hydroorganic and micellar) had little influenc e. With anionic (SDS) and nonionic (Brij 35) surfactants, some p-menth ane (3) was formed but the conversion rate and current efficiency were much lower. The ECH of carvone (4) was slightly less efficient in met hanol-water than in micellar and emulsified solutions. The saturated a lcohols neocarvomenthol (8), carvomenthol (9), isocarvomenthol (10), a nd neoisocarvomenthol (11) were the main products with current efficie ncies of 75% (hydroorganic medium) to 90% (micellar solutions). The ef fect of surfactant concentration and pH on the efficiency and stereoch emistry of the ECH of carvone (4) was also studied.