Using Gaussian 03, software the thermodynamic functions such as Gibbs free energy, G, Enthalpy, H, and Entropy, S, of Alanine and Valine amino acids were theoretically studied at different solvents. First, the Density Functional Theory (B3LYP) level with 3-21G, 6-31G and 6-31+G basis sets were employed to optimization of isolated Alanine and Valine amino acids in the gas phase. Moreover, Vibrational frequencies were calculated in gas phase on the optimized geometries at the same level of theory to obtain the thermodynamic functions such as Gibbs free energy, G, Enthalpy, H, and Entropy, S,. Then, the calculation about the solvent effects on the thermodynamic functions of Alanine and Valine amino acids were performed for the various solvents (Water, Methanol and Ethanol) by using self consistent Reaction-Field (SCRF=PCM) model at B3LYP/6-31+G. Thermodynamically analysis shows the relative Gibbs free energy changes, G, Enthalpy changes, H, are negative values but the Entropy changes, S, are positive values for Alanine and Valine amino acids. Also, the results shows, with increasing of dielectric constant of solvents the stability of considered amino acids increases. تفاصيل المقالة

The thermodynamic functions such as enthalpy, H°, Gibbs free energy, G°, and entropy, S°, of Arginine and Lysine amino acids were theoretically studied at different polar solvents by using ²Gaussian o3², software. First, the structural optimization of isolated Arginine and Lysine were done in the gas phase by applying the Density Functional Theory (B3LYP) level with 3-21G, 6-31G and 6-311G basis sets. Moreover, vibrational frequencies were calculated in gas phase on the optimized geometries at the same level of theory to obtain enthalpy, H°, Gibbs free energy, G°, and entropy, S°. Then, the calculation about the solvent effects on the thermodynamic functions of Arginine and lysine amino acids were performed for the various polar solvents (Water, Methanol and Ethanol) by using self-consistent Reaction-Field (SCRF=PCM) model at B3LYP/6-311G. Thermodynamically analysis shows the relative enthalpy changes, DH°, Gibbs free energy changes, DG°, are negative values but the entropy changes, DS°, are positive values for Arginine and Lysine molecules. Also, the results shows, with increasing dielectric constant of solvents the stability of considered molecules increases. تفاصيل المقالة

The thermodynamic functions such as enthalpy (H), Gibbs free energy (G) and entropy (S) ofPyrazole was theoretically studied at 5 different temperatures 25, 30, 35, 40 and 45°C by usingGussian o3, software. First, the structural optimization of isolated Pyrazole was done in the gas phaseby appling the Density Functional Theory (B3LYP) level with 3-21G, 6-31G and 6-31+G(d) basissets. Moreover, vibrational frequencies were calculated in gas phase on the optimized geometries atthe same level of theory to obtain enthalpy, Gibbs free energy and entropy at 5 differenttemperatures.Finally the temperature effects on the thermodynamic functions were discussed. تفاصيل المقالة

The physical and chemical properties of Pyrazole and Pyrazoline molecules were theoreticallystudied by Gaussian 03, software with NMR and Molecular orbital calculations at B3LYP/6-31G andB3LYP/6-31+G(d) levels, in gas phase and solution. In this study a comparison effect of threesolvents with different dielectric constants on Pyrazole and Pyrazoline molecules in aspect energyinteraction between solute and solvent, and NMR shielding parameters (ppm) such as,
Iso (
Isotropic),
Aniso (
Anisotropic), anisotropic magnetic shielding tensor, 
, chemical shift, , totalatomic charge and asymmetry parameter, , were performed. These parameters were calculated byusing the GIAO method. The results show solvent-induced shielding variation is more stronglyrelated to the intensity of the solvent reaction field rather than on the change of molecular geometryinduced by the solvent. تفاصيل المقالة

The interaction of Fe2+ ion with Pyrazole was theoretically studied by Gussian 03, software at HF/(LanL2DZ+6-31G) and HF/ (LanL2DZ+6-31G (d)) levels in gas phase and solution. In this study acompartion between optimized structures of Pyrazole molecule in aspect of thermodynamicparameters such as enthalpy (H°), Gibbs free energy (G°) and entropy (S°) in presence of metallic ion(Fe2+), was performed. Thermodynamically analysis indicate that the relative enthalpy (H°) and Gibbsfree energy (G°) are negative values but entropy (S°) is positive value for Pyrazole-Fe2+ complex,suggesting thermodynamic favorability for covalent attachment of Pyrazole into Fe2+ ion. Also, theresults show with increasing dielectric constant of solvent the stability of Pyrazole Fe2+ complexincreases تفاصيل المقالة

Using the Density Functional Theory (DFT) level by means of 3-21G, 6-31G and 6-31+G (d) basissets, the structural optimization of isolated Pyrazole and Pyrazoline was done in the gas phase. Then,the calculation about the solvent effect on the stability energies of Pyrazole and Pyrazoline wasperformed for the ten solvents using PCM model method at B3LYP/6-31+G(d) and then the dielectriceffects of the surrounding and the solvent effects on the stability energies of Pyrazole and Pyrazolinemolecules were discussed. تفاصيل المقالة