Studies On Synthesis Of Chlorinated Pyromellitic Acid

Benzene-1,2,4,5-tetracarboxylic acid (PMA), possessing high symmetry and activity, is a kind of important fine chemical, and has been widely used in chemical synthesis and production. Benzene-1,2,4,5-tetracarboxylic dianhydride (PMDA), whi-ch is named as "universal plastic", is the main monomer of polyimide. Therefore, it is of important significance to study the synthesis method and potential applications of the chlorinated derivatives of PMA.In this thesis, the preparation of chlorinated PMA were researched by chlorinati-on and oxidation with the starting material of durene. Major progresses are as follows:1. We explored the factors of electrophilic substitution of durene (TeMB) with chlorine, including the reaction temperature, time, the rate of chlorine, solvent and catalyst. Experimental results showed that the conversion of TeMB was100%under the conditions of0~-5℃, one bubble/s of chlorine’s rate,1mol%AlCl3and CHCl3as solvent at1.6h. The selectivity and isolated of monochloro product3-chloro-1,2,4,5-tetramethylbenzene (CTeMB) was78.7%and20.2%respectively. Durene was completely conversed under the conditions of0~-5℃, one bubble/s of chlorine’s ra-te, CHCl3as solvent and the catalyst-free after reacting4h. The selectivity of DCTeMB could be up to100%, with the isolated yield94.1%.2. Multifarious methods of the oxidation of DCTeMB, as well as their combined, were explored, including HNO3oxidation in sealing tube, NHPI/MnO2catalytic oxidation, NHPI/cobalt acetate/manganese acetate catalytic oxidation, KMnO4oxida-tion with phase transfer catalyst18-crown-6, etc. It was found that DCTeMB could be oxidized to monomethyl oxidation product2,5-dichloro-3,4,6-trimethylbenzoic acid (DCTMBA) by NHPI catalytic oxidation or acid/alkaline KMnO4oxidation with pha-se transfer catalysis18-crown-6. The yield of DCTMBA was20.9%when NHPI was included in the catalytic oxidation.In summary, this paper explored the chlorinated reaction conditions of TeMB an-d found the optimal conditions for preparing DCTeMB; at well as the various oxid-ation methods of DCTeMB were explored.