Study On The Synthesis Technology Of (All-rac)-α-tocopherol

Vitamin E is used widely in medicine,cosmetics and food industries because of its excellent biological activity.It can be obtained from natural extraction and chemical synthesis.Natural vitamin E is the mixture of tocopherols and tocotrienols.Synthetic vitamin E is alpha-tocopherol and it takes up approximately 80%global market.Using trimethylhydroquinone and isophytol as raw materials and making metal halide catalyst are the traditional method of synthesizing all-rac-α-tocopherol.First,this paper discussed the effect of reaction condition on the yield of the traditional synthesis process,which was referring to the kinds of catalysts,tapes of solvents,the amount of catalyst,temperature and time.The results showed that this reaction had the best product yield,93.78%,when under nitrogen protection,using Zn Cl₂ and HCl as catalysts,n（Zn Cl₂）:n（TMHQ）=0.6:1,ethyl acetate as solvent,and the mixture was heated at 40 ^oC for 4 hours.Ionic liquids have attracted increasingly attention in organic synthesis owing to their excellent properties.Some researchers succeeded in using ionic liquids to catalyze the synthesis of all-rac-α-tocopherol.As a result,the second part of this paper discussed result of synthesis of vitamin E using ionic liquid as catalyst.Choosing one kind of ionic liquid,form several synthesized new Lewis acid ionic liquids,respectively as catalyst to synthesyze vitamin E under the heating and microwave condition.It turned out that comparing to traditional vitamin E synthesis methods,this method used shorter time and had better yield.In this process,ionic liquid anion played a decisive role instead of cation.It was found that pyridine ionic liquids had better catalyze effects.By comparison,ionic liquid 1-butyl-3-methyl pyridinium bromide was selected to react with zinc chloride making catalyst,which was the main object of study.The influence of catalyst ammount,temperature and reaction time on the yield under microwave irradiation was discussed,and the best reaction condition was found.The catalyst was made with the molar ratio of zinc chloride in the ionic liquid to the TMHQ 1:1,and the 74.61%of products could be obtained when nitrogen protected at 60^oC for 30 minutes.The innovation of this paper was choosing a new pyridine ionic liquid as catalyst to optimize the experiment under microwave heating.Ionic liquid 1-butyl-3-methyl pyridine bromide reacting with zinc chloride results in a catalyst to synthesize vitamine E,eliminating corrosion of equipments and water pollution,avoiding large amount catalyst usage.Meanwhile,microwave reaction saved the reaction time and energy.Another result of this paper was that the usage of the catalyst was n（Zn Cl₂）:n（TMHQ）=0.6:1,and the usage is much less than that in present industrial production.