Zhang et al. have studied the solvation free energy of several organic solvents with both implicit and explicit solvent models. The implicit solvent model was found to be in good agreement with the experimental results, however, it didn't fit well with the explicit solvent model. The detailed investigation reveals that the dielectric constant of a solvent is found as a powerful predictor for polar contribution to the free energy in the implicit model. However, due to the consideration of the Onsager reaction field in case of the implicit model, the numerical value differs in comparison to the explicit model 103 . Further, with the implicit solvent model, the neutral and ionic solute with different dielectric constant and various radii scaling factors were investigated by Klamt et.al . Their study found a good agreement between the calculated and the experimental solvation free energy of the order of 0.5-1.0 kcal/mol (0.02 -0.04 eV).