Study On The Catalytic Oxidation Performance Of Quinones

Quinones are ubiquitous in nature, which play an important role in transfer of electron and hydrogen atom in biochemical dehydrogenation redox process. Therefore, study of the catalytic performance of quinones is very necessary from the views of academic and application. This thesis is dedicated to develop a new organocatalyst system for hydrocarbon oxidation using molecular oxygen as oxidant under mild conditions through the study of the catalytic properties of quinones.Firstly, the catalytic property of quinones was investigated in the oxidation of hydrocarbons using quinones combined with N-hydroxyphthalimide (NHPI) as catalyst.72.2% conversion with 92.3% selectivity for acetophenone was obtained in ethylbenzene oxygenation catalyzed by NHPI and 2,3-dichloro-5,6-dicyano-benzoquinone (DDQ) under 0.3 MPa of molecular oxygen at 80℃for 10 h. UV/Vis spectroscopy of the catalytic system indicated that there was interaction between quinones and NHPI, and DDQ accelerated the generation of free radical phthalimido-N-oxyl (PINO) by abstracting a hydrogen atom from NHPI. In addition, the catalytic system DDQ/NHPI also exhibited excellent catalytic activity in the selective oxidation of alkene and the alkyl of aromatic hydrocarbon.The study on the steric effects of substituents of quinones showed that sterically-hindered substituents reduced the chance of elimination of radicals by C=C double bonds in the quinone ring, which is related to the catalytic performance of quinones. On the other hand, too many substituents hindered the contact between the reaction center of quinone (C=O) and the reactant, which led to the decrease of the catalytic activity.In addition, the oxidation of aldehyde to carboxylic acid and of ascorbate to dehydroascorbic acid catalyzed by quinone also was researched. Quinone showed high efficiency in these oxidation reactions.