GB1203108A - Production of cyclohexadiene dicarboxylic acids - Google Patents

Abstract

1,203,108. Cyclohexadiene dicarboxylic acids. BADISCHE ANILIN- & SODA-FABRIK A.G. 10 Jan., 1968 [11 Jan., 1967], No. 1413/68. Heading C2C. [Also in Division C7] 3,5 - Cyclohexadiene - 1,2 - dicarboxylic acid and 2,5-cyclohexadiene-1,4-dicarboxylic acid are produced by electrochemical hydrogenation of o-phthalic acid and terephthalic acid respectively in dilute aqueous sulphuric acid at a temperature up to 80‹ C. and at a current density of 1-40 amps per sq. decimetre at the cathode, there being added to the catholyte an ether, amide and/or nitrile which is miscible with water, is inert under the reaction conditions and is liquid at room temperature. The organic solvents which may be used are saturated cyclic ethers, e.g. dioxane, or tetrahydrofuran; monoethers or diethers of ethylene glycol or 1,2- propylene glycol; alkyl radicals of ether groups such as ethylene glycol monomethyl ether.; N- monoalkyl substituted and N,N-dialkyl substituted amides of aliphatic monocarboxylic acids such as methyl formamide, N-methylacetamide, N-ethylacetamide, dimethyl formamide, diethyformamide or N,N-dimethylacetamide and other N,N-dialkylacetamides, N,N-dimethylpropionamide; N-alkyl substituted laotams such as N-methylpyrrolidone, N-ethylpyrrolidone or N-methylpiperidone; formamide; or nitriles such as acetonitrile. As anolyte an aqueous solution of sulphuric acid may be used. The anodes used may be formed of lead, lead dioxide, platinum, graphite, silicon carbide or magnetic materials, and the cathodes used may be of lead, amalgamated lead, cadmium, tin, thallium, bismuth or alloys of at least two of the metals lead, mercury, silver, cadmium, tin, thallium and bismuth. The cell used may be formed of glass, metal or plastics. The diapragm separating analyte and catholyte may comprise an ion exchange membrane, plastics fabric or ceramic materials, e.g. porous clay. One form of cell comprises a double-walled glass tube which is cooled with water, a cylindrical lead cathode in contact with the inner wall of the glass tube, a cylindrical clay diaphragm positioned within the cathode and separating cathode from anode, and an anode comprising a lead tube cooled by water.