METHOD FOR PRODUCTION OF 2,4-DICHLOROPHENOXYACETIC ACID Russian patent published in 1998 - IPC

FIELD: organic chemistry, particularly, production of derivatives of phenoxyacetic acid, namely, production of 2,4-dichlorophenoxyacetic acid which may be used as herbicide for cereals. SUBSTANCE: 2,4-dichlorophenoxyacetic acid is prepared by isolation of sodium salt of 2,4-dichlorophenoxyacetic acid, the process takes place with the help of hydrochloric acid in aqueous medium at temperature being higher than melting point of said acid; thus melt of 2,4-dichlorophenoxyacetic acid in aqueous medium is prepared. Before isolation sodium salt of 2,4-dichlorophenoxyacetic acid is diluted with water till its complete dissolution, the process takes place in reaction medium at melting point of acid. Isolated melt of 2,4-dichlorophenoxyacetic acid is washed against chlorides, the process is carried out in aqueous emulsion of melt of 2,4-dichlorophenoxyacetic acid by circulation of reaction products. Then granulation and crystallization of 2,4-dichlorophenoxyacetic acid takes place by supply of stream of aqueous emulsion of melt of said acid into cooled suspension of granules and crystals of 2,4-dichlorophenoxyacetic acid. These processes are carried out in aqueous-salt medium at temperature being lower than solidification point of melt of 2,4-dichlorophenoxyacetic acid. Granules and crystals are separated of aqueous-salt phase by commonly used procedure. EFFECT: improved efficiency of the method. 1 tbl, 1 dwg