Study On Synthesis And Thermodynamic Of4-nitrobenzene Arsonic Acid

Paranitroaniline and different diazotization agent were used as raw materials in the synthesis of4-nitrobenzene arsonic acid. The factors which influence the yield of4nitrobenzene arsonic acid were studied and optimized. The tubular reactor was adopted to replace the traditional tank reactor. The computational simulation on thermodynamic of4-Nitrophenylarsonic acid synthesis was studied by using the B3LYP method of density functional theory. The computational studies on thermodynamics of4-Nitrophenylarsonic acid synthesis can provide the theoretical guidance to the reaction process condition control.4-Nitrophenylarsonic acid was prepared by diazotization with paranitroaniline, hydrochloric acid and sodium nitrite as raw materials. The reaction temperature, pH and ratio of the material flow were mainly studied and the by-products were analyzed.The purity and chemical structure of the products were identified by HPLC and IR. The result showed that the optimum reaction conditions were as following, the ratio of hydrochloric acid and paranitroaniline was3, the arsine transition temperature was40℃, the diazotization temperature was0-5℃, the arsine transition pH was10.0and0.05-0.1mol excessive sodium nitrite was preferred. The yield of the product is68.0%4-Nitrophenylarsonic acid was prepared by diazotization with paranitroaniline, concentrated sulfuric acid and sodium nitrite as raw materials. The reaction temperature, pH and stirring speed were mainly studied.The purity and chemical structure of the products were identified by HPLC and IR. The result showed that the optimum reaction conditions were as following, the stirring speed was500r/min, the ratio of nitroso sulfuric acid and paranitroaniline was1.05, the diazotization temperature was30℃, the arsine transition temperature was50℃,the arsine transition pH was10.0.The yield of the product is51.0%The tubular reactor was adopted in the synthesis of4-Nitrophenylarsonic acid in which4-Nitrophenylarsonic acid was prepared by diazotization with paranitroaniline, hydrochloric acid and sodium nitrite as raw materials. The reaction temperature, pH and ratio of the material flow were mainly studied.The purity and chemical structure of the products were identified by HPLC and IR. The result showed that with the replacement of the traditional batch reactor by the tubular one, the side reactions of the target product with the unconverted intermediate diazonium are depressed effectively, the yield and selectivity of the reaction is enhanced. Through process optimization, the optimal pH is8.0-9.0, the optimal temperature is50℃and0.05-0.1mol excessive sodium arsenate is preferred. The residence time is40s. The yield of the product is77.8%; the purity is more than98.6%. The structures of the reactants and products of synthesis of4-Nitrophenylarsonic acid were studied by using the B3LYP method of density functional theory. Then the structures were optimized by computational analysis. The changes in reaction enthalpy, Gibbs free energy and equilibrium constant for the primary and side reaction were calculated and analyzed with the basic thermodynamic data obtained from vibration frequency analysis. The simulation results show that the primary reaction process is exothermic and irreversible, the enthalpy change is-15.0kJ/mol, the Gibbs free energy change is39.7kJ/mol. The side reaction process is endothermic and irreversible, the enthalpy change is1O.OkJ/mol, and the Gibbs free energy change is45.2kJ/mol.