Hydrochloric Acid → DL-alpha-Tocopherol

Participants

Reaction Conditions

Reaction Steps

13.5 g of trimethyl hydroquinone are dissolved in 100 ml of toluene, and 13.5 g of silica-alumina, 6.0 g of zinc chloride and 0.5 g of concentrated hydrochloric acid (35% hydrochloric acid) are added thereto under nitrogen flow. The reaction system is warmed to 85° C. and then 25.0 g of isophytol are added dropwise over about 20 minutes. After completion of the addition, stirring is continued for about 4 hours at the same temperature and then the reaction system is allowed to cool. Then, 100 ml of toluene are added to the reaction mixture and the insoluble material is filtered off. The filtrate is washed in succession with 3% caustic soda, 1% sodium hydrosulfite, water and saturated aqueous salt solution and dehydrated with anhydrous magnesium sulfate. The solvent is then distilled off under reduced pressure to give 36.2 g of dl-α-tocopherol (yield 99.8%). 25.0 g of dl-α-tocopherol thus obtained are dissolved in 50 ml of acetic anhydride and 12.5 g of sodium acetate and 1.25 g of metallic zinc powder are added thereto. The reaction mixture is acetylated by stirring at 95°-100° C. for about 3.5 hours and then extracted with 200 ml of n-hexane. The extract is washed in succession with 1% caustic soda, water and saturated aqueous salt solution and dried over magnesium sulfate. Thereafter, n-hexane is distilled off under reduced pressure to give 26.2 g of crude dl-α-tocopherol acetate. The crude dl-α-tocopherol acetate thus obtained is subjected to vacuum distillation to give 20.5 g of the main fraction of 165°-175° C./8×10-3 mmHg. The purity of this product is 97.3% and the distillation yield is 78.0%.

Provenance & Evidence