Cyclic reaction process of synthesis of pyrogallic acid from 2,2,6,6-tetrahalocyclohexanone

Pyrogallic acid(PRLA) was prepared by hydrolytic reaction with sodium hydrogen citrate as hydrolysis agent,2,2,6,6-tetrahalocyclohecanone(TCCH) as raw material. The as-prepared product was analyzed by means of infrared absorption spectrum(FT-IR),nuclear magnetic resonance spectrum(NMR),and high performance liquid chromatograph(HPLC),which confirmed that the main product was pyrogallic acid. The hydrolysis reaction conditions,such as reaction temperature(T),reaction time(t),concentration of 2,2,6,6-tetrahalocyclohecanone(CTCCH) and molar ratio of sodium hydrogen citrate to 2,2,6,6-tetrahalocyclohecanone(r),were studied,based on which the optimum reaction conditions were given as below : T=368K, t=4h, CTCCH=0.4mol/L, r=5. Under the optimal conditions,total yield reached 85%. Recycling of sodium hydrogen citrate in hydrolytic reaction was studied. Makeup water and Na OH aqueous solution had serious effect on the cyclic reaction,and recycling sodium hydrogen citrate twice could significantly cut down the cost of production.