Studies On The Green Chemistry Of Vitamin E And Its Intermediates

Green chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of poisonous materials. Current and future chemists are being attracted to design products and processes with an increased awareness for environmental pollutions. So far, chemistry and chemical engineering have been regarded as the major contributors to economic progress over the past century, and yet the chemical industry is often taken to task for many serious environmental problems. One of the most attractive concepts for pollution protection is green chemistry: it is better to prevent waste than to treat or clean up waste after it is formed.Vitamin E is the most important antioxidant in the biological system and is widely used as an additive for foodstuffs, pharmaceuticals, cosmetics and animals feeds. It is reported that more than 20,000 tons Vitamin E is produced in our country annually. On the other hand, a lot of wastes are formed.In order to reduce or eliminate the use and generation of poisonous materials during the Vitamin E and its intermediates synthesis and achieve clean production we report here that the simple ammonium ionic liquids have been used as dual catalyst and environmental benign reaction medium for Vitamin E and its intermediates: dialkoxypropanes, 2-alkoxypropenes and pseudoionone preparation, eliminating the need for a volatile organic solvents and poisonous hydrogen chloride catalysts. These simple ammonium ionic liquids are air and water stable, easy to synthesis from amine and acid, and relatively cheap, which makes them suitable for industrial application. The results clearly demonstrate that these ionic liquids can be easily separate and reused without losing their activity. These ionic liquids provide a good alternative for industrial preparation of Vitamin E and its intermediates.The experimental results show that the decompositions of 2,2-Dimethoxypropane (DMP) and 2,2-Diethoxypropane (DEP) have nearly identical rate ratio of 2-methoxypropene (MPP) and 2-ethoxypropene (EPP) in ionic liquids. The yields ratio of MPP/methanol and EPP/ethanol were nearly 1.0. Thefour-center cyclic transition state was found in B3LYP Density Functional Theory of level. Surprisingly, the experimental observations and theoretical rate constants ratio (k_DEP/k_DMP) appeared to differ about ten magnitudes at the experimental temperatures range. Further dynamics study indicated that the significant tunneling effect played an important role in the identical rate constants ratio of the decomposition reactions at low temperatures range. Further dynamics studies in the condensed phase show that the solvent effect and tunneling effect are particularly important and are the main contributors to the identical rate constant ratio which observed in our experiment of the decomposition reactions at low temperatures (below 400K). Due to the introduction of condensed phase, the decomposition reactions that formerly performed at high temperatures range could take place at relatively low temperature. To such kind of decomposition reactions in the condensed phase, the solvent effect and tunneling effect should be taken into account. More accurate solvent model and methods for computing the solvent effect and tunneling effect are underway in our group.All in all, experimental and theoretical study on the preparation of Vitamin E and its intermediates aim to reduce or eliminate the use and generation of poisonous materials. We expect that these methods are applicable to investigate more important phenomena in green chemistry.