Preparation of Vitamin E Intermediate from an Inexpensive Substrate by Selective Oxidation of Pseudocumene in HCOOH–H2O2 System

In this paper, 2,3,5-trimethyl-1,4-benzoquinone (TMBQ) was synthesized through the direct oxidation of 1,2,4-trimethylbenzene (pseudocumene, TMB) in the HCOOH–H 2 O 2 system. The influence of three active species was studied, including performic acid (PFA) generated in formic acid, peracetic acid (PAA) generated in acetic acid, and trifluoroperacetic (TFPA) acid generated in trifluoroacetic acid. The effects of sulfuric acid and sodium formate addition were investigated, the over-oxidation of TMB was discussed, and the main reason for the decreasing selectivity was revealed. The oxidation of TMB can be controlled and improved through adjusting the reaction temperature, mole ratio of oxidant to substrate, and reactant concentration. The TMBQ yield of 28% was achieved with a TMB concentration of 0.2 mol/L, H 2 O 2 /TMB mole ratio of 6:1, and reaction temperature 37 °C. The selectivity of 72% was obtained with a TMB concentration of 0.2 mol/L, H 2 O 2 /TMB mole ratio of 5:1, and reaction temperature of 27 °C. The reaction mechanisms were proposed and discussed based on the gas chromatography–flame ionization detection (GC–FID) and gas chromatography–mass spectrometer (GC–MS) results.