PRODUCTION OF CARBOXYLIC ACID OR ITS ESTER

PROBLEM TO BE SOLVED: To isolate carboxylic acid or its ester which is useful as an intermediate for medicines or as a starting material for liquid crystal in high purity and high yield by bringing a salt of carboxylic acid into contact with a hydrogen halide to effect salt dissolution in a substantially water-free (anhydrous) organic solvent. SOLUTION: Preferably, in an alcohol solvent or in at least one of organic solvent selected from ethers, halogenated hydrocarbons and hydrocarbons containing an alcohol, (A) a salt of carboxylic acid (a salt of tetrahydrofrancarboxylic acid or tetrahydropyranecarboxylic acid with an alkali metal ion, an alkaline earth metal ion or an organic amine) is brought into contact with (B) a hydrogen halide such as hydrogen chloride, hydrogen bromide or hydrogen iodide to dissolve the salt to give the objective carboxylic acid or its ester. The component A is preferably brought into contact with the component B at 0 deg.C-50 deg.C. The amount of the organic solvent is preferably 0.5-20 times, more preferably 1-10 times the component A in weight.