DECARBOXYLATION OF HALOGENATED AROMATIC CARBOXYLIC ACID

PROBLEM TO BE SOLVED: To carry out decarboxylation of a halogenated aromatic carboxylic acid in simple process without use of catalysts, bases and organic solvents. SOLUTION: This decarboxylation of a halogenated aromatic carboxylic acid to obtain a compound of formula I (X is H, Cl or Br; (n) is 1 or 2), for example, 2,3,5,6-tetrafluorobenzoic acid, comprises heating a halogenated aromatic terephthalic acid of formula II (for example, 2,3,5,6-tetrafluoroterephthalic acid) together with water up to a temperature of 80-180 deg.C or together with water and another acid up to 80 deg.C or higher temperature to decarboxylate the halogenated aromatic terephthalic acid. The quantity of the water used for the decarboxylation is preferably 0.8-6 times and the quantity of the acid is preferably 0.01-5 times as much as the quantity of the compound of formula I by weight.