RAMAN-SPECTROSCOPIC STUDY ON KETO-ENOL TAUTOMERS OF 1-PHENYL-3-METHYL-4-BENZOYL-5-PYRAZOLONE

Raman spectral changes of 1-phenyl-3-methyl-4-benzoyl-5-Pyrazolone (PM BP) were measured and its structural changes were studied when the cry stal was heated continuously. The two peaks which appeared at 1599 and 1640 cm(-1) for keto-PMBP were assigned to the intermolecular hydroge n bonded carbonyl (in the pyrazolone ring) and the free carbonyl (in t he benzoyl group) groups, respectively. The keto form of PMBP changed into the enol form when it was melted. The peak at 1640 cm(-1) disappe ared at the same time. The structural change of keto-form PMBP was con firmed by the present continuous heating-Raman spectroscopic method.