4 - hydroxy - 2,3,5,6 - tetrafluoro benzoic acid and 2,3,5,6 - production manner null of tetrafluoro

摘要

PURPOSE:To obtain the subject compound at a low cost by heating pentafluorobenzoic acid and an alkaline compound containing an alkaline earth metal compound in an aqueous solvent and, as necessary, heating the product under normal pressure in an aqueous solvent under specific condition to effect the decarbonation of the product. CONSTITUTION:Both of the subject compounds useful as intermediates for pharmaceuticals, agricultural chemicals, liquid crystal materials, etc., can be produced on an industrial scale at a low cost using an inexpensive reaction apparatus such as a reactor made of stainless steel by (a) heating pentafluorobenzoic acid and an alkaline compound containing an alkaline-earth metal compound in an aqueous solvent or (b) heating and decarbonating 4- hydroxy-2,3,5,6-tetrafluorobenzoic acid in an aqueous solvent under normal pressure using 0.1-1 equivalent of an alkaline substance based on 1mol of the compound or (c) separating the water-insoluble components from the reaction mixture of the process (a), adding an acid to the filtrate to partially neutralize the liquid and heating the product under normal pressure to effect decarbonation reaction.