Production method of N-Acetyl-cysteine

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N-Acetyl-cysteine ​​is obtained by acetylation of L-cysteine ​​with acetic anhydride
1. Neutralization: L-cysteine ​​hydrochloride without crystal water is dissolved in 0.8 times of distilled water, and then slightly dissolved in a water bath, then poured into a Buchner funnel pre-coated with activated carbon, and the filtrate is taken. Ethanol (95%) was added, and then pyridine was added thereto, and the mixture was cooled in an ice water bath, and placed in a refrigerator overnight to precipitate crystals, which were filtered, washed with CHCl3, and dried. It is quickly dried in a vacuum desiccator to obtain L-cysteine.
2. Acetylation: L-cysteine ​​is put into a reaction tank, glacial acetic acid and chloroform are added, and acetic anhydride is added under vigorous stirring. After the reaction tank interlayer is heated to about 35 ° C, the heating is stopped, and the temperature inside the tank is gradually increased to 82-85 ° C. When the temperature is too high, the cooling is started at about 70 ° C, and the mixture is stirred at about 50 ° C for half an hour, and then the filtrate is filtered. And concentrated under reduced pressure, when more viscous, add appropriate amount of water to concentrate. Repeat this several times, when the concentrate is about 1.8 times cysteine, cool and add a little L-cysteine ​​crystals, inoculate in the refrigerator overnight, crystallize, filter the crystals and dry, wash with ether, N-Acetyl-cysteine ​​crude.
3. Refining: the crude product is dissolved in 0.5-0.6 times of distilled water, decolorized by adding 5% activated carbon, and the filtrate is filtered, placed in a refrigerator overnight, crystallized, crystallized by filtration, dried, washed with diethyl ether and dried in vacuo to obtain N-Acetyl-cysteine ​​boutique.