Synthesis of 3,3',4,4'-biphenyltetracarboxylic dianhydride
3,3',4,4'-Biphenyltetracarboxylic dianhydride is a precursor of high-performance material polyimide.This article adopts the method of Grignard reagent coupling to study the synthesis of 3,3',4,4'-biphenyltetracarboxylic dianhydride.Firstly,4-bromo-o-xylene reacted with magnesium metal to pre-pare Grignard reagent.Secondly,under the action of ferric trifluoromethanesulfonate,the Grignard reagent self-coupled to produce 3,3',4,4'-tetramethyl biphenyl,which was oxidized and then dehydrated to ob-tain 3,3',4,4'-biphenyl tetracarboxylic dianhydride.The effects of key factors of the experiments were examined,the optimal reaction conditions of coupling were determined.The reaction mechanism has been analyzed.The results showed that the coupling reaction temperature was 60℃and the reaction time was 8 h,the yield of 3,3',4,4'-tetramethylbiphenyl reached 83%.The yield of 3,3',4,4'-biphenyltetra-carboxylic dianhydride was 78%.Mechanism analysis shows that Grignard reagent undergoes self coupling reaction with iron catalyst and 1,2-dichloroethane to prepare 3,3',4,4'-tetramethylbiphenyl.
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