Carbon Dioxide → 5-(2-(Methylthio)ethyl)-2,4-imidazolidinedione
反応式
[NH2:1][CH:2]([C:7]([OH:9])=O)[CH2:3][CH2:4][S:5][CH3:6].[C:10](=[O:12])=O.[NH2:13][C@H](C([O-])=O)CCSC.[K+]>>[CH3:6][S:5][CH2:4][CH2:3][CH:2]1[NH:1][C:10](=[O:12])[NH:13][C:7]1=[O:9]参加物
4
実験手順
To achieve this object, the present invention provides a process for the preparation of D,L-methionine, in which carbon dioxide is fed to an aqueous potassium methioninate solution obtained by hydrolysis of 5-(2-methylmercaptoethyl)hydantoin, in order to precipitate out crude methionine, which is separated off and purified, where, for the purposes of purification, an aqueous solution of the separated-off crude methionine is prepared and subjected to a recrystallization. In the process, the solution from which the recrystallization takes place contains potassium ions and also a crystallization additive, where the crystallization additive is a nonionic or anionic surfactant, or a mixture of different nonionic or anionic surfactants. According to the invention, the recrystallization takes place by introducing a 60 to 110° C.-hot methionine solution into a 35 to 80° C.-warm methionine suspension, the temperature of which is lower than that of the introduced solution, the temperature of the methionine suspension being maintained between 35 and 80° C. during the addition.