3-Mercaptopropionic acid is an intermediate of pharmaceutical Chlormezanone. Thiopropionic Acid can also be used to prepare cross-linking agents, hardeners, resin additives, antioxidants, catalysts and biochemical reagents. China Thiopropionic Acid can also be used as a PVC heat stabilizer ester tin. Due to the unique properties of β-mercaptopropionic acid, the market prospect is very broad, and it is only produced in the third pharmaceutical factory in Northeast China.It uses the thiourea method, low product content, long reaction time, complicated process, high cost, and three wastes. Big. Therefore, it is of great significance to study the synthesis of 3-mercaptopropionic acid.
3-Thiopropanoic Acid Synthesis
1.1 Synthesis mechanism of Beta-Mercaptopropionic Acid
The synthesis of China 3-Mercaptopropionic Acid CAS 107-96-0 is performed according to the following reactions:
Competitive reactions (2) and (3) between the two products obtained in reaction (1) and the AN added are the key factors affecting the yield of the target product. The occurrence of (2) can be reduced by adding an appropriate amount of sulfur powder, and (3) the generated dithiodipropionic acid can be reduced by zinc powder to break the bonds to generate 3-mercaptopropionic acid.
1.2 Rhenium reaction steps
In a 1000 ml three-necked flask, 261.3 g of a 30% aqueous sodium sulfide solution and 2.7 g of sulfur powder were added. After heating and dissolving, add 53g of acrylonitrile dropwise at 45 ° C for 1.5h, fully react for 2h, acidify with 254ml of concentrated hydrochloric acid, add 81g of water and reflux at 110-112 ° C for 3h, reduce the temperature to 80-90 ° C, add 44g zinc powder, and use hydrochloric acid The pH was adjusted from 1 to 2 to obtain a 3-mercaptopropionic acid aqueous solution.
1.3 Purification of 3-mercaptopropionic acid
The β-mercaptopropionic acid aqueous solution was extracted with ethyl acetate and repeated three times to obtain an organic phase. The organic phase was distilled off at 0.095 MPa to obtain a crude product. The crude product was subjected to vacuum distillation, and a fraction of 100 ° C to 102 ° C was collected at 665 Pa to obtain a colorless transparent liquid. The purity of 3-mercaptopropionic acid was measured by the iodometric method.