Preparation Of 2,3,5-Trimethylquinone From One-Step Oxidation Of 1,2,4-trimethylbenzene

Direct oxidation of 1,2,4-trimethybenzene(TMB)to 2,3,5-trimethylquinone(TMBQ)was studied in this paper.This reaction contains two processes.Firstly,the TMB is oxidized to trimethy trimethyphenol(TMP),which is the reaction of inserting oxygen into unactivated aromatic ring.Then,the TMP is oxidized to the target product(TMBQ),which is the reaction of “one step oxidation of TMP to TMBQ”.The two requirements for the active oxygen that act as a key role in the catalytic oxidation of TMB were proposed after summarizing the advances of direct oxidation of benzene to phenol and one-step oxidation of TMP(2,3,5-TMP and 2,3,6-TMP)to TMBQ.The active oxygen species should be electrophilic but not radical and small enough to insert the oxygen into the right correct position(3-and 6-position)especially the 3-position.The requirements were used as the guide to find the suitable catalysts and reaction systems that have the activity of oxidizing TMB to TMBQ.Several kinds of reaction systems(catalysts)which probably have the activity of direct oxidation of TMB were proposed.That contains heteropolyacid,metalloporphyrin catalysts,non-hem metal catalysts,? alumina-hydrogen peroxide system,bicarbonate-hydrogen peroxide system,carboxylic acid-hydrogen peroxide system.The feasibility of theses systems were tested by experiments and the carboxylic acid-hydrogen peroxide system gave a good performance in the process of TMB oxidation.Formic acid,acetic acid,trifluoroacetic acid and acetic anhydride which could generate peroxy-carboxylic acid in situ were studied respectively as the reaction solvent and the formic acid-hydrogen peroxide system was confirmed having the best performance.The effects of sulfuric acid and sodium formate addition are investigated,the overoxidation of TMB was discussed and the main reason for low selectivity was revealed.The oxidation of TMB can be controlled and improved through adjusting the reaction temperature,molar ratio of oxidant to substrate,and reactant concentration.The TMBQ yield of 28% was achieved at reaction temperature 37 ?.The selectivity of 72% was obtained with reaction temperature of 27 ?.In this system the 2,3,5-trimethhydroquione was also obtained.The reaction mechanisms are proposed and discussed based on the GC-FID and GC-MS results.