METHOD OF PREPARING 2-HYDROXY-4-METHYLTHIOBUTYRIC ACID Russian patent published in 2000 - IPC

FIELD: chemical industry. SUBSTANCE: described is method of preparing 2-hydroxy-4- methylthiobutyric acid by reacting hydrocyanic acid and methylmercaptopropion aldehyde and hydrolyzing the resulting methylmercaptopropion aldehyde cyanohydrin by means of sulfuric acid, subsequently recovering 2-hydroxy-4- methylthiobutyric acid by contacting reaction mixture with substantially water- immiscible organic solvent in extraction liquid/liquid system to form extraction solution containing solvent and 2-hydroxy-4-metylthiobutyric acid recovered from reaction mixture to form extraction solution from which 2-hydroxy-4- methylthiobutyric acid is obtained by evaporation in the form of extract. Methylmercaptopropion cayanohydrin is hydrolyzed as follows. In first stage, methylmercaptopropion aldehyde cyanohydrin is hydrolyzed with 60-85% sulfuric acid at molar ratio methylmercaptopropion aldehyde cyanohydrin to sulfuric acid from 1:0.5 to 1:1.0 at temperatures from 30 to 90 C to obtain substantially 2- hydroxy-4-methylthiobutyric acid amide which is hydrolyzed in second stage by addition of water without further additions of hydrosulfuric acid at temperatures a up to 140 C, and content of salt in reaction mixture prior to extraction in liquid system is adjusted to up to 50 wt % (wt/wt) preferably to 55 wt % (wt/wt) calculated for total amount of inorganic reaction mixture components. EFFECT: simplified process, optionally concentrated product with exceedingly low content of dimers, oligomers and by-products. 17 cl, 5 dwg, 8 ex, 15 tbl