5-(2-methylsulfanylethyl)imidazolidine-2,4-dione

Conditions: temp:180.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Using pump pressure, a solution of 100 kg of potassium hydrogen carbonate in aqueous solution and 41 kg of 5-(2-methylmercaptoethyl)-hydantoin in 400 l of water is fed hourly into a continuously operating pressurised column 8 made of special steel (compare FIG. 2) operated with steam. The reaction mixture is heated to 180° C. and has an average residence time of about 15 minutes at about 8 bar. Ammonia and carbon dioxide liberated is drawn off at the top of the reactor column by means of a pressure-maintaining valve. The reaction solution is depressurised at the bottom of the pressurised reactor and cooled with the heat exchanger 9. A quantity of 41.9 kg per hour of potassium methioninate in solution is obtained (94.5% of the theoretical). an average residence time of about 15 minutes cooled with the heat exchanger 9

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 13.1 g of 98% sodium hydroxide pellets (0.32 mole) and 17.4 g (0.10 mole) of 5-(beta-methylmercaptoethyl)-hydantoin in 100 ml of water-saturated n-hexanol was heated to boiling over 25 minutes and refluxed with stirring for 26 minutes, after which the reaction mixture was quenched. The cold reaction mixture was stirred with 75 ml water for 1/4 hour, and the aqueous phase was separated. The organic phase (n-hexanol) was washed with four 25 ml portions of water. The combined, filtered, aqueous phases were neutralized to pH of 6 with concentrated hydrochloric acid, stirred at room temperature for the crystallization of methionine, and stored at 5° C. The reaction product was collected, washed with water, and dried to give 3.2 g of methionine, m.p. 268° C. decomposition. The combined mother-liquor and washings were concentrated to about 80 ml during which methionine crystallized. After the mixture had been chilled at 5° C., the reaction product was collected, washed with water, and dried to obtain 3.5 g of methionine, m.p. 268° C. decomposition. was heated refluxed after which the reaction mixture was quenched The cold reaction mixture the aqueous phase was separated The organic phase (n-hexanol) was washed with four 25 ml portions of water filtered stirred at room temperature for the crystallization of methionine stored at 5° C The reaction product was collected washed with water dried

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 13.1 g of 98% sodium hydroxide pellets (0.32 mole) and 17.4 g (0.10 mole) of 5-(beta-methylmercaptoethyl)-hydantoin in 100 ml of water-saturated n-hexanol was heated to boiling over 25 minutes and refluxed with stirring for 26 minutes, after which the reaction mixture was quenched. The cold reaction mixture was stirred with 75 ml water for 1/4 hour, and the aqueous phase was separated. The organic phase (n-hexanol) was washed with four 25 ml portions of water. The combined, filtered, aqueous phases were neutralized to pH of 6 with concentrated hydrochloric acid, stirred at room temperature for the crystallization of methionine, and stored at 5° C. The reaction product was collected, washed with water, and dried to give 3.2 g of methionine, m.p. 268° C. decomposition. The combined mother-liquor and washings were concentrated to about 80 ml during which methionine crystallized. After the mixture had been chilled at 5° C., the reaction product was collected, washed with water, and dried to obtain 3.5 g of methionine, m.p. 268° C. decomposition. was heated refluxed after which the reaction mixture was quenched The cold reaction mixture the aqueous phase was separated The organic phase (n-hexanol) was washed with four 25 ml portions of water filtered stirred at room temperature for the crystallization of methionine stored at 5° C The reaction product was collected washed with water dried

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 1.74 g. of 5-(β-methylthioethyl)hydantoin, 68 mg. of imidazole and 20 ml. of water was heated to 160° C. in a 50 ml. autoclave, and was allowed to react at 160° C. for 6 hours. After the reaction was over, the autoclave was rapidly cooled. The reaction mixture was treated by the same after-treatment as in Example 1 and methionine was obtained in yield of 80%. A mixture of 1.74 g to react at 160° C. for 6 hours was rapidly cooled The reaction mixture was treated by the same after-treatment as in Example 1

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 1.74 g. of 5-(β-methylthioethyl)hydantoin, 68 mg. of imidazole and 20 ml. of water was heated to 160° C. in a 50 ml. autoclave and then allowed to react for 3 hours at 160° C., while being stirred. After the reaction was over, the autoclave was rapidly cooled to room temperature and the residual pressure was released. The autoclave was given a good wash with water to take off the reaction mixture, and then the reaction mixture was subjected to evaporation to dryness by means of a rotary evaporator. The resulting solid was shaken sufficiently with 100 ml. of methyl acetate. The methyl acetate insoluble matter was separated from the methylacetate solution. A portion of of the insoluble matter was recrystallized from water and then subjected to an infrared absorption spectrum and melting point measurements (m.p. 267° C., decomposed). Thus, it was found to be methionine. On the other hand, the methyl acetate soluble matter was found to be unreacted 5-(β-methylthioethyl)hydantoin and a negligible amount of by-products. According to a copper chelatemetric colorimetry of the insoluble matter (the colorimetry was conducted according to the method described in the specification of Japanese Laid-Open Patent Application No. 116008/1974), it was found that 0.75 g. of methionine (yield 50%) was attained. A mixture of 1.74 g to react for 3 hours at 160° C. a good wash with water the reaction mixture was subjected to evaporation to dryness by means of a rotary evaporator The resulting solid was shaken sufficiently with 100 ml The methyl acetate insoluble matter was separated from the methylacetate solution A portion of of the insoluble matter was recrystallized from water subjected to an infrared absorption spectrum

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 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. the present invention provides a process

Conditions: temp:180.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Using pump pressure, a solution of 100 kg of potassium hydrogen carbonate in aqueous solution and 41 kg of 5-(2-methylmercaptoethyl)-hydantoin in 400 l of water is fed hourly into a continuously operating pressurised column 8 made of special steel (compare FIG. 2) operated with steam. The reaction mixture is heated to 180° C. and has an average residence time of about 15 minutes at about 8 bar. Ammonia and carbon dioxide liberated is drawn off at the top of the reactor column by means of a pressure-maintaining valve. The reaction solution is depressurised at the bottom of the pressurised reactor and cooled with the heat exchanger 9. A quantity of 41.9 kg per hour of potassium methioninate in solution is obtained (94.5% of the theoretical). an average residence time of about 15 minutes cooled with the heat exchanger 9

Conditions: temp:180.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Using pump pressure, a solution of 100 kg of potassium hydrogen carbonate in aqueous solution and 41 kg of 5-(2-methylmercaptoethyl)-hydantoin in 400 l of water is fed hourly into a continuously operating pressurised column 8 made of special steel (compare FIG. 2) operated with steam. The reaction mixture is heated to 180° C. and has an average residence time of about 15 minutes at about 8 bar. Ammonia and carbon dioxide liberated is drawn off at the top of the reactor column by means of a pressure-maintaining valve. The reaction solution is depressurised at the bottom of the pressurised reactor and cooled with the heat exchanger 9. A quantity of 41.9 kg per hour of potassium methioninate in solution is obtained (94.5% of the theoretical). an average residence time of about 15 minutes cooled with the heat exchanger 9

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 13.1 g of 98% sodium hydroxide pellets (0.32 mole) and 17.4 g (0.10 mole) of 5-(beta-methylmercaptoethyl)-hydantoin in 100 ml of water-saturated n-hexanol was heated to boiling over 25 minutes and refluxed with stirring for 26 minutes, after which the reaction mixture was quenched. The cold reaction mixture was stirred with 75 ml water for 1/4 hour, and the aqueous phase was separated. The organic phase (n-hexanol) was washed with four 25 ml portions of water. The combined, filtered, aqueous phases were neutralized to pH of 6 with concentrated hydrochloric acid, stirred at room temperature for the crystallization of methionine, and stored at 5° C. The reaction product was collected, washed with water, and dried to give 3.2 g of methionine, m.p. 268° C. decomposition. The combined mother-liquor and washings were concentrated to about 80 ml during which methionine crystallized. After the mixture had been chilled at 5° C., the reaction product was collected, washed with water, and dried to obtain 3.5 g of methionine, m.p. 268° C. decomposition. was heated refluxed after which the reaction mixture was quenched The cold reaction mixture the aqueous phase was separated The organic phase (n-hexanol) was washed with four 25 ml portions of water filtered stirred at room temperature for the crystallization of methionine stored at 5° C The reaction product was collected washed with water dried