Theoretical study of solvent effect on NMR shielding for Pyrazole and Pyrazoline

The physical and chemical properties of Pyrazole and Pyrazoline molecules were theoretically studied by Gaussian 03, software with NMR and Molecular orbital calculations at B3LYP/6-31G and B3LYP/6-31+G(d) levels, in gas phase and solution. In this study a comparison effect of three solvents with different dielectric constants on Pyrazole and Pyrazoline molecules in aspect energy interaction between solute and solvent, and NMR shielding parameters (ppm) such as, Iso ( Isotropic), Aniso ( Anisotropic), anisotropic magnetic shielding tensor, , chemical shift, , total atomic charge and asymmetry parameter, , were performed. These parameters were calculated by using the GIAO method. The results show solvent-induced shielding variation is more strongly related to the intensity of the solvent reaction field rather than on the change of molecular geometry induced by the solvent.