Abstract: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 methanol-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 influence. With anionic (SDS) and nonionic (Brij 35) surfactants, somep-menthane (3) was formed but the conversion rate and current efficiency were much lower. The ECH of carvone (4) was slightly less efficient in methanol-water than in micellar and emulsified solutions. The saturated alcohols neocarvomenthol (a), carvomenthol (9), isocarvomenthol (lo), and neoisocarvomenthol (11) were the main products with current efficiencies of 75% (hydroorganic medium) to 90% (micellar solutions). The effect of surfactant concentration and pH on the efficiency and stereochemistry of the ECH of carvone (4) was also studied.
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