Electrocatalytic hydrogenation of conjugated enones on nickel boride, nickel, and Raney nickel electrodes

Abstract

Abstract:The selectivity of the electrocatalytic hydrogenation (ECH) of conjugated enones to the corresponding carbonyl compounds has been investigated in aqueous methanol under constant current at nickel boride, fractal nickel, and Raney nickel electrodes made of pressed powders. The influence of various parameters (water percentage, pH, concentration of substrate, and current density) on the selectivity of the carbon-carbon double bond hydrogenation was studied with cyclohex-2-en-I-one at nickel boride electrodes. Under given electrolysis conditions, fractal nickel electrodes were found to give the highest selectivity. The selectivity of the ECH of a variety of conjugated enones at fractal nickel electrodes was determined under electrolysis conditions that gave the best selectivity with cyclohexenone at nickel boride electrodes.Key words: electrocatalytic hydrogenation, a,P-unsaturated ketones, selective hydrogenation, nickel based cathodes.RCsume : Nous avons fait l'ttude de la stlectivite de l'hydrogtnation Clectrocatalytique (HEC) d'tnones conjugutes en cttones saturtes correspondantes dans le methanol-eau 5 courant constant sur des tlectrodes de borure de nickel, nickel fractal et nickel de Raney fabriqutes par pressage de poudres. L'influence de divers paramktres (le pourcentage d'eau, le pH, la concentration du substrat et la densitt du courant) sur la stlectivitt a t t t ttudite avec la cyclohex-2-tn-1-one sur tlectrodes de borure de nickel. Sous des conditions d'Clectrolyse donnCes, la stlectivite s'est averCe la plus Clevte avec les tlectrodes de nickel fractal et celles-ci ont t t t utilistes pour une Ctude de la sClectivitC de I'HEC de diverses cttones conjugCes sous les conditions d'Clectrolyse ayant donnt la meilleure stlectivitt dans le cas de la cyclohextnone.

Electrosynthesis and catalytic activity of polymer-nickel particles composite electrode materials

“…Very similar current efficiency and yields were obtained with these different cathodes, as shown by the comparison of the results summarized in entry 3 (2 nd ECH onto electrode B) and entry 8 (2 nd ECH onto electrode C). Comparison with results reported in the literature for the hydrogenation in aqueous electrolytes of 2-cyclohexenone shows that the catalytic activity of poly1-Ni(0) modified electrodes compare well with that of other nickel-based electrode materials, 33,52,53 in spite of the rather small amount of nickel contained in the polymer films. As a matter of fact, on the basis of the estimation made for nickel concentration into polycarboxylate films coated onto carbon felt (at most 0.22 mg of nickel per mmol of carboxylic acid groups in the films), the amount of nickel metal electrodeposited in poly1 films (2.5 × 10 -5 mol of malonic acid units) could be roughly estimated to a few mg, i.e.…”

“…The results obtained in the course of a series of experiments conducted at different C|poly1-Ni(0) cathodes are summarized in Table 1. Electrocatalytic hydrogenations (ECH) were performed in water-methanol solutions containing 2-cyclohexenone (1 mmol), in the conditions developed by Lessard and co-workers 52 for reductions with Raney nickel-based electrodes (see experimental).…”

Hydrogen evolution reaction at nickel boride electrodes in aqueous and in aqueous methanolic and ethanolic solutions

“…Working electrode compounds is often carried out in methanolic or ethanolic solutions containing NaCl(O.l M) and H3B0, (0.1 M), an acid (8,9). In fact, the organic solvent permits the dissolution of the organic products, NaCl is used as supporting electrolyte, and H3B03 is used as a buffer to prevent rapid increase of the pH during the electrolysis (reaction [5]).…”

“…Nickel boride (Ni'B) was obtained as apowder (average particle size of 0.5 p,m and specific surface area of 9 m2 g-') (7) by reduction of nickel acetate with NaBH4 in aqueous NaOH (9). The electrodes were obtained by pressing the particles atp = 120 NIPa at room temperature.…”

Hidrogenação de compostos orgânicos utilizando método eletroquímico para geração de hidrogênio in situ: hidrogenação eletrocatalítica

“…Mahdavi et al 38 realizaram um estudo da HEC com olefinas conjugadas (2-cicloexen-1-ona, acetilcicloexeno, 3-isopropilideno-6-metil-2-cicloexen-1-ona, etc. ), o qual demonstrou que o eletrodo de níquel fractal apresentou alta seletividade de hidrogenação (99%) com relação a duplas conjugadas em α,β à carbonila, quando comparados aos dados obtidos utilizando-se eletrodos de boreto de ní-quel e níquel de Raney.…”