Study On Synthesis Process Of Lopoic Acid

α-Lipoic acid is a medical drug. With further research, it was found that a-lipoic acid has a board application prospect.In the thesis, the reaction mechanism of α-lipoic acid ethyl ester synthesized by6,8-dichlorooctanoic acid ethyl ester was studied. α-Lipoic acid ethyl ester and1,2,3-trithiane-4-pentanoic acid ethyl ester were obtained in The reaction among6,8-dichlorooctanoic acid ethyl ester, disodium sulfide and sulfur. In addition, α-lipoic acid ethyl ester can react with sulfur to synthesize1,2,3-trithiane-4-pentanoic acid ethyl ester;1,2,3-trithiane-4-pentanoic acid ethyl ester can react with disodium sulfite to synthesize α-lipoic acid ethyl ester;1,2,3-trithiane-4-pentanoic acid ethyl ester may react with disodium sulfide and6,8-dichlorooctanoic acid ethyl ester to synthesize synthesize α-lipoic acid ethyl ester. It was a guidance to research the process optimization.The reason of a lower yield in the reaction of a-lipoic acid prepared without solvents was founded. The reason was that a-lipoic acid sodium had a surface activity. When the concentration of a-lipoic acid sodium was high, the thermodynamically stable micelle was formed spontaneously. With the diluted hydrochloric acid into the system, a-lipoic acid sodium reacted to a-lipoic acid. a-Lipoic acid sodium in the system can solubilize a-lipoic acid not to crystallize thea-lipoic acid readily,causing the concentration highly to form the polymer to decrease the yield.Optimal conditions for the preparation of a-lipoic acid without solvents were the quality of water was20times to the quality of a-lipoic acid,32%NaOH and a-lipoic acid (molar ratio of1.5:1) was reacted to prepare the alkaline solution. Under the4-8degrees Celsius, the alkaline solution was added into the5%HC1solution to pH1-2.