GB1294790A - A method for the production of solid alkylammonium salts of 2-methyl-4-chlorophenoxyacetic acid - Google Patents

Abstract

1294790 Ammonium salts of MCPA SPOLANA NARODNI PODNIK 19 April 1971 [19 Feb 1970] 23974/71 Heading C2C Compounds of formula (wherein R 1 , R 2 and R 3 are each H, C 1-3 alkyl or C 1-3 hydroxyalkyl, at least one being other than H) are prepared by forming a solution of 2- methyl-4-chlorophenoxyacetic acid (MCPA) in an anhydrous water-immiscible organic slovent in which the desired product is substantially insoluble at ambient temperature (e.g. chlorobenzene), reacting said solution with a compound of formula R 1 R 2 R 3 N, and isolating the precipitated product., Preferably the reaction is effected at 90-100‹ C: whereafter cooling to 0-20‹ C. precipitates the product. The initial organic solution of MCPA may be prepared by reacting a salt (e.g. an alkali metal salt) of MCPA with an acid having a pKa value lower than that of MCPA (e.g. sulphuric acid), the reaction being effected either in an aqueous medium from which the product is subsequently extracted with the organic solvent, or in a mixture of water and the organic solvent with subsequent separation of the organic phase from the aqueous phase. Preferably the reaction is effected at 70-90‹ C. The resultant organic solution is then dried, e.g. by azeotropic distillation.