GB601817A - Process for making salts of carboxylic acids - Google Patents

Abstract

Salts of carboxylic acids are prepared by heating an alcohol containing a primary alcohol group with an alkali metal hydroxide in the presence of a cadmium catalyst at a temperature sufficiently elevated to cause liberation of hydrogen from the reaction mixture. The salts may be converted to the free acids by treating with mineral acid. It is stated that the invention may be applied to the process of oxidising amino alcohols described in Specification 601,816. The alcohols used contain a hydroxyl group attached to a terminal carbon atom which may be attached to a saturated or unsaturated straight or branched chain aliphatic radical or to a carbocyclic or heterocyclic radical, e.g. methyl, ethyl, propyl alcohols and higher alkanols having up to twenty or more carbon atoms; glycols and polyglycols of the ethylene and propylene glycol series; benzyl, phenyl ethyl and cinnamyl alcohols and amino alcohols having more than one carbon atom. The cadmium catalyst may be cadmium metal or a compound of the metal such as the oxide and fresh portions of catalyst may be added during the reaction. The temperature employed is generally 140 DEG to 300 DEG C. and atmospheric or elevated pressure may be employed. The reaction vessel is preferably formed of or lined with copper or copper alloys or with cadmium or may be of stainless steel. In examples: (1) and (2) glycine is obtained by heating monoethanolamine, potassium hydroxide and cadmium oxide, washing and filtering the crude product, evaporating the filtrate to dryness, extracting with ethyl alcohol followed by filtration of the extract and acidification with acetic acid; (3) tetraethanol ethylene diamine is heated with sodium hydroxide, water and cadmium oxide under hydrogen pressure and the sodium salt of tetracarboxymethyl ethylene diamine produced may be converted to the free acid by means of strong mineral acids such as sulphuric or hydrochloric acids; (4) potassium tetracarboxymethyl ethylene diamine is made by heating tetraethanol ethylene diamine, aqueous potassium hydroxide and cadmium oxide; (5) sodium tetracarboxymethyl propylene diamine is made by heating tetraethanol propylene diamine, aqueous sodium hydroxide and cadmium oxide; (6) pentaethanol diethyllene triamine is heated with aqueous sodium hydroxide and cadmium oxide to produce sodium pentacarboxymethyl diethylene triamine; (7) sodium hexacarboxymethyl triethylene tetramine is obtained by heating hexaethanol triethylene tetramine, aqueous sodium hydroxide and cadmium oxide; (8) n-hexanol, aqueous sodium hydroxide, cadmium oxide and stearic acid are heated and after distilling the product to recover unreacted hexanol the residue is treated with sulphuric acid to obtain caproic acid; (9) butyric acid is obtained by heating n-butanol, aqueous sodium hydroxide and cadmium oxide and acidifying the product as in (8); (10) beta-ethoxy ethyl alcohol, sodium hydroxide, water and cadmium oxide are heated under hydrogen pressure, the unreacted alcohol is removed by distillation and the residue acidified with sulphuric acid to yield ethoxy acetic acid. Other products specified are the alkali salts of carboxylic acids such as glycollic and oxalic acids from ethylene glycol, lactic acid from propylene glycol, dicarboxymethyl amine from diethanolamine, tricarboxymethyl amine from triethanolamine and isopropyl and butyl dicarboxymethyl amines from the corresponding isopropyl and butyl diethanolamines. Comparative results obtained in catalysed and uncatalysed reactions for the preparation of glycine and of salts of tetracarboxy methyl ethylene diamine are tabulated. Tetraethanol ethylene diamine is made by reaction of ethylene diamine and ethylene oxide. Tetraethanol-propylene diamine iss prepared by reacting ethylene oxide with a mixture of propylene diamine, water and ethanol and distilling the reaction mixture under reduced pressure. Penta-ethanol-diethylene-triamine and hexaethanol-triethylene-tetramine are made by reacting ethylene oxide with a mixture of ethanol and diethylene triamine and triethylene-tetramine respectively.