A method for the preparation of nitriles, alkyl - or aryl esters of aliphatic di - or gestaettigter

摘要

Hydrodimers of aliphatic mono-olefinic nitrites, esters of carboxylic acids, or carboxamides are formed by electrolysis using a cathode of hydrogen over voltage greater than copper, e.g. -1.8 to 2.1 V. relative to a calomel electrode, the concentration of the olefinic compound being at least 10% by weight in an aqueous salt-containing electrolyte, and maintaining the pH value at greater than 7, preferably 8-9. A salt is present as a conductor, preferably an alkali metal sulphonate of a quaternary ammonium compound. A wide range of suitable conducting salts is given and includes mono- or polyalkylamine salts of sulphonic or alkyl sulphonic acids, and the corresponding alkylolamine compounds; sodium tetra alkyl ammonium sulphonates; alkali metal salts of aryl or aralkyl sulphonic acids. The pH value may be conveniently controlled by using a diaphragm cell, the rising pH value in the catholyte being reduced by adding acid, e.g. by leaking into it the acidic anolyte, or by adding an acid, e.g. acetic or phosphoric acid. The process is applied to convert compounds containing less than 20 C atoms, e.g. acrylonitrite to adiponitrite, maleonitrile to butane-1,2,3,4-tetracarbonitrile, methyl acrylate to dimethyl adipate, propyl maleate to tetra propyl butane-1,2,3,4-tetracarboxylate, acrylamide to adipamide; aryl aliphatic derivatives are also exemplified. The hydrodimerization product is a "head-to-head" addition, coupling taking place at the beta-C atom to the functional group. The concentration of a salt in the electrolyte may be 30% by weight and of the alpha-beta mono-olefinic compound up to 50%, where required polar solvents may be added to increase the solvent power, e.g. acetonitrile, dioxane, lower alcohols, dimethyl formamide, or ethylene glycol. The cell used preferably has a porous diaphragm, e.g. an unglazed porcelain cup, the anode being, e.g., carbon, gold, nickel silicide, or lead alloys, or lead deposited on a copper screen. The cathode may be, e.g., mercury, gallium, cadmium, tin, or lead-mercury alloy. The dimer product is then separated by neutralizing, extraction with a solvent, and fractionation.