4 ELECTROCA TALYTIC HYDROGENA TION OF ORGANIC COMPOUNDS JEAN MARC CHAPUZET, ANDRZEJ LASIA, JEAN LESSARD Universite de Sherbrooke, Departement de chimie, 2500 Bid. de r Universite, Sherbrooke (Quebec) CANADA JJ K 2RI 4.1 INTRODUCTION Hydrogenation of organic compounds is a very important reaction from the synthetic point of view. It has been extensively studied in a gas and, to a lesser extent, in a liquid phase [1,2,3,4,5]. Liquid-phase hydrogenation is usually carried out using three methods: (i) catalytic hydrogenation (CH); (ii) direct electroreduction followed by a protonation, the so-called electronation-protonation (EP) reaction; (iii) electro- catalytic hydrogenation (ECH). Catalytic hydrogenation (CH) is usually carried out on large-surface-area catalysts (e.g., Raney-type metals and transition or noble metal blacks), under hydrogen pres- sure (from 1 to 350 atm), and at various temperatures (from ambient to 400°C) [1- 5]. During this process, gaseous hydrogen is adsorbed on the catalyst surface, as demonstrated by Eq. (1), and subsequently reduces organic molecules via reactions (2) to (5): 2M + H2~ 2M-H, M + (Y = Z) ~ M (Y = Z), M(Y = Z) + M-H ~ M (Y - ZH), (1) (2) (3) Electrocatalysis, Edited by Jacek Lipkowski and Philip N. Ross. ISBN 0-471-24673-5 @1998 Wiley- VCH, Inc. 155 -------