PHOSPHONIC ACID DERIVATIVE AND ITS PRODUCTION

PROBLEM TO BE SOLVED: To obtain the subject new compound having two pieces of carboxyl respectively formable of an ester, useful as a monomer for producing a polyester, etc., and also useful as a transparentizing agent for various polymers or resins. SOLUTION: This compound is 2,5-dicarboxyphenyl phosphonic acid expressed by the formula. The compound is obtained as follows: as first, a reaction liquid phase is formed in a reaction zone by supplying 2,5-dialkylphenyl phosphonic acid (preferably 2,5-dimetlylphenyl phosphonic acid), a solvent (preferably acetic acid), a cobalt salt, a manganese salt and/or a cerium salt and bromine or a bromine compound (preferably hydrogen bromide, etc.). Further, an oxidation reaction is performed by supplying oxygen into the reaction liquid phase by bringing an oxygen gas-containing gas into contact with the reaction zone. Preferably, the oxidation reaction is performed at 120-300 deg.C under an oxygen partial pressure of 2-50-atm under stirring. the reaction usually be finished in 1-20hrs.