Study On The Synthesis And Characterizition Of 3,4-ethylenedioxythiophene

3,4-ethylenedioxythiophene was synthesized from chloroacetic acid via Esterification,Claisen condensation,O-alkylation,Hydrolysis and Decarboxylation. The influences of various process conditions on the reaction were studied in detail by single facor experiments,and the optimum conditions were obtained by orthogonal test. The structures of intermediates and product were then characterized by Elemental Analysis,Infrared Spectrum and Mass Spectrometry.The optimum conditions of synthesis of the intermediate ethyl chloroacetate were as follows:the concentration of catalyst 8%,the mole ratio of chloroacetic acid to ethanol 1:8,the amount of dehydrant benzol 30mL,the reaction time 5h,and the key factor to affect the yield of product was the mole ratio of chloroacetic acid to ethanol.The optimum conditions of synthesis of the intermediate diethyl thiodiglycolate were as follows:the amount of solvent acetone 60mL,the mole ratio of ClCH₂COOC₂H₅ to Na₂S·9H₂O 1:0.7,the reaction time 18h,the feeding time of Na₂S·9H₂O 2.0h,and the key factor to affect the yield of product was the amount of solvent acetone.The optimum conditions of synthesis of the intermediate 2,5-dicarbethoxy-3, 4-dihydroxythiophene were as follows:the amount of sodium 0.7mol,the mole ratio of diethyl thiodiglycolate to diethyl oxalate 1:1.4,the reaction time 3h,the amount of solvent ethanol 120mL,and the key factor to affect the yield of product was the amount of sodium.The optimum conditions of synthesis of the intermediate 2,5-dicarbethoxy-3, 4-ethylenedioxythiophene were as follows:the reaction time 7h,the mole ratio of 2, 5-dicarbethoxy-3,4-dihydroxythiophene to dibromethane 1:1.1,the concentration of catalyst 0.3%,the amount of solvent DMF 80mL,and the key factor to affect the yield of product was the concentration of catalyst.The optimum conditions of synthesis of the intermediate 2,5-dicarboxyl acid-3, 4-ethylenedioxythiophene were as follows:the amount of KOH 0.4mol,the amount of ethanol 40mL,the reaction time 10h,and the key factor to affect the yield of product was the amount of KOH.The optimum conditions of synthesis of 3,4-ethylenedioxythiophene were as follows:the amount of catalyst bronze powder 2.5g,the reaction time 5h,the amount of solvent quinoline 75mL,and the key factor to affect the yield of product was the amount of solvent quinoline.The product yield of this synthesis process can arrive to 28.01%.This synthesis process has the advantages of using more readily available raw materials and being easier to carry out,so it is more suitable for the industrial production.