Author(s): A.Amar1, H.Meghezzi1*, A. Boucekkine2, A. Saidoun3, Y. Rachedi3and M. Hamdi3
The tautomerism, intramolecular proton transfer and solvent effect of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one have been investigated using B3LYP/6-31G*andB3LYP/6-311+G** level of theory. The solvent effects have been simulated using the self consistent reaction field (SCRF) method within the framework of the polarizable continuum model (PCM). The obtained results showed that among three possible tautomeric forms, the noted CH form is predominant in gas phase and solution while the OH form seems to be the less stable. The calculated equilibrium constants and molar fractions showed that the NH form is more stabilized in solution than CH and OH forms. Results of the global reactivity descriptor give the CH form more electrophilicthan the two considered tautomeric forms in gas phase and in solution. In addition we note that the barrier height of the proton transfer reaction and dipole moments grow with the increase of the solvent polarity.