METHOD FOR PREPARING 1-(4'-TOLYL)-3-METHYL-5-PYRAZOLONE Russian patent published in 2004 - IPC

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for preparing 1-(4'-tolyl)-3-methyl-5-pyrazolone used in manufacturing dyes and pigments. 1-(4'-Tolyl)-3-methyl-5-pyrazolone is prepared by diazotization of p-toluidine and the following reducing p-tolyldiazonium chloride with sulfite-bisulfite mixture prepared from sodium (ammonium) bisulfite and ammonia water at pH = 5.8-7.0 and the mole ratio bisulfite to p-tolyldiazonium = 2.49:1, hydrolysis of p-tolyl sulfonate to yield reaction solution of p-tolyl hydrazine hydrochloride, its diluting to the concentration 43-45 g/l and condensation of the latter with acetoacetic acid amide at pH = 1.9-2.5 and in the mole ratio p-tolyl hydrazine to acetoacetic acid amide = (1:1):(1:1.1) in the presence of sulfamic acid taken in the amount 0.0029-0.0035 mole per 1 mole of the parent p-toluidine. Invention provides elevating yield of the end product and improving its quality. The yield of the end product is 92-93% as measured for p-toluidine, its melting point is 134.4^oC and mass part of the basic substance is 99.5-99.7%.

EFFECT: improved preparing method, enhanced yield and improved quality.

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