The Effect of Solvent on Tautomerization of 4-bromo Substituted 1HPyrazoles: Density Functional Theory Study

Density functional theory was used to study the tautomerization of 4-bromo substituted 1Hpyrazoles in different solvents. Mechanism and transition state structures of five tautomeric reactions were detected using quadratic synchronous transit with B3LYP method. The effect of solvent was considered with PCM method. We have found that the tautomerization is done through the transferring of hydrogen atoms between two nitrogen atoms in all tautomeric reactions. Also, it was found that the tautomeric reaction rate is dependent on solvent and reach to constant value for solvents with dielectric constant of greater than 8.93. Moreover, we found that the effect of solvent on equilibrium constant is dependent on considered molecules.