SPECTROSCOPIC STUDIES OF THE KETO AND ENOL TAUTOMERS OF 1-PHENYL-3-METHYL-4-BENZOYL-5-PYRAZOLONE

Molecular structures of the two tautomers of a beta-diketone 1-phenyl- 3-methyl-4-benzoyl-5-pyrazolone (PMBP) were studied by MS, UV, TR, and X-ray diffraction methods. The mass spectra show little difference fo r the two forms of PMBP, while there are notable differences in the IR spectra as KBr pellets and in the UV spectra in different solvents fo r the keto- and enol-PMBP. The keto-and enol-PMBP were stabilized resp ectively by intermolecular and intramolecular hydrogen bonds. The two types of hydrogen bonds were characterized by X-ray diffraction. Infra red spectrometric analyses depending on temperature were also performe d to study the thermal properties of PMBP. (C) 1996 Academic Press, In c.