METHOD FOR PURIFYING P-HYDROXYBENZALDEHYDE

PURPOSE:To advantageously obtain the titled compound from p-cresol under specific condition, by passing the resultant reaction mixture through steps of diluting the above-mentioned reaction mixture with water/filtrating the diluted mixture, separating a solvent, neutralizing the residual solution, extracting the neutralized solution with a solvent, neutralizing the aqueous layer and extracting the aqueous layer with a solvent successively or in specific order. CONSTITUTION:p-Cresol or a mixture containing the p-cresol oxidized with oxygen or an oxygen-containing gas in the presence of a cobalt compound and base to provide a reaction mixture and the titled compound useful as an intermediate for medicines, agricultural chemicals, perfumes, etc., is then taken therefrom. In the process, the reaction mixture is passed through the following steps of (i) diluting the above- mentioned reaction mixture with water and filtering the mixture, (ii) separating the solvent from the afore-mentioned reaction mixture, (iii) neutralizing the residual solution with an acid to pH 9-11, (iv) extracting the neutralized solution with a solvent, (v) neutralizing the aqueous layer after extraction with the solvent with an acid to pH 3-6 and (vi) directly extracting the above-mentioned neutralized solution with a solvent or separating the solution into layers and extracting the separated aqueous layer with the solvent successively or in the order of (i), (iii), (ii), (iv)-(vi) to industrially and reading afford the aimed compound in high yield and purity.