GB395074A - Improvements in the manufacture and production of alphaaminocarboxylic acids, iminodicarboxylic acids and their salts - Google Patents

Abstract

In the manufacture of a -aminocarboxylic acids, iminodicarboxylic acids and salts thereof by condensation of an aliphatic aldehyde with ammonium cyanide and saponification of the resulting a -aminocarboxylic acid nitrile, the condensation is carried out in the presence of a quantity of free ammonia corresponding at least to that present in the combined state in the ammonium cyanide. The nitriles are saponified, preferably directly after their preparation and without previously removing the ammonia, by means of an alkali or alkaline earth metal hydroxide, strong bases such as alkali metal, barium or strontium hydroxides being employed advantageously while heating as rapidly as possible in order to obtain a -aminocarboxylic acids, and weaker bases such as calcium hydroxide to produce p iminodicarboxylic acids. The ammonium cyanide may be dissolved or suspended in any solvents capable of dissolving ammonia, e.g. water, alcohols, ethers, pyridine or mixtures thereof. The condensation should be effected below 50 DEG C., preferably at about -5 DEG to 25 DEG C., and the saponification at about 85-125 DEG C., or at higher temperatures, e.g. up to 150 DEG C. if the reaction is carried out while avoiding evaporation by working in a closed vessel and if desired introducing inert gases to increase the pressure. The salts obtained by the saponification may be converted by known methods into other salts or into the free acids, e.g. the barium salts may be treated with sodium sulphate or sulphuric acid to produce the sodium salt or the acid respectively. In examples: (1) acetaldehyde is treated with ammonium cyanide and ammonia with cooling, producing a -aminopropionitrile, which is saponified with caustic soda to yield the sodium salt of a -aminopropionic acid; (2) a -aminopropionitrile is saponified with barium hydroxide yielding the barium salt of a -aminopropionic acid, which is converted into the sodium salt or the free acid by the action of sodium sulphate or sulphuric acid respectively; (3) a -aminopropionitrile is saponified with calcium hydroxide yielding the calcium salt of iminodipropionic acid, from which the free acid may be liberated by treatment with sulphuric acid; (4) formaldehyde is condensed with ammonium cyanide and ammonia to produce aminoacetonitrile, which is saponified with calcium hydroxide to yield the calcium salt of iminodiacetic acid; (5) aminoacetonitrile is saponified with barium hydroxide, producing the barium salt of aminoacetic acid; (6) a -aminopropionitrile is saponified with potassium hydroxide to produce the potassium salt of a -aminopropionic acid, and (7) with strontium hydroxide to produce the strontium salt, which may be treated with sulphuric acid or a soluble sulphate, e.g. sodium or ammonium sulphate, to produce the free acid or the corresponding salt.