I.1- INTRODUCTION: Conformational analysis is the study of the energy change, a molecule undergoes, as it rotates about one or more single bonds. The conformations of a molecule are those arrangements in space of the atoms which are not superimposeable upon each other. The basic idea behind conformational analysis is that molecules will have certain physical and chemical and thermodynamic properties that are dependent on the preferred conformations. in the modern chemistry, where it can lead to significant improvement in the understanding of more complex system. theoretical calculations were proved to give good results for thermodynamic properties [1-3] The determination of the structural parameters of the preferred conformation and
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The SMD model based on density, solves the Poisson-Boltzmann equation analogously to PCM, but does so using a set of specifically parametrised radii which construct the cavity.[7 ,8]
The COSMO solvation model or (CPCM) :This model uses the scaled conductor boundary condition, which is a fast and robust approximation to the exact dielectric equations and reduces the outlying charge errors as compared to PCM.
Isodensity PCM ( IPCM): Cavity formed using gas-phase static electronic isodensity surface (IPCM) Less arbitrary than spheres on atoms. Cavity changes with electron density and environment. The default density value is 0.0004. occurred only by single point calculations.
Self-Consistent Isodensity model (SCIPCM):in which iterations are folded in SCF issues regarding scaling of charges still remain[9]. Onsager Model: Spherical cavity dipolar reaction field, no constructing of the cavity surface elements, because the Poisson equation is solved analytically. Solute shape is close to spherical and polar (>> 0).[10,11].
The molecular free energy of solvation is computed as the sum of three terms:
Gsol = Ges + Gdr + Gcav
Ges =
The SMD model based on density, solves the Poisson-Boltzmann equation analogously to PCM, but does so using a set of specifically parametrised radii which construct the cavity.[7 ,8]
The COSMO solvation model or (CPCM) :This model uses the scaled conductor boundary condition, which is a fast and robust approximation to the exact dielectric equations and reduces the outlying charge errors as compared to PCM.
Isodensity PCM ( IPCM): Cavity formed using gas-phase static electronic isodensity surface (IPCM) Less arbitrary than spheres on atoms. Cavity changes with electron density and environment. The default density value is 0.0004. occurred only by single point calculations.
Self-Consistent Isodensity model (SCIPCM):in which iterations are folded in SCF issues regarding scaling of charges still remain[9]. Onsager Model: Spherical cavity dipolar reaction field, no constructing of the cavity surface elements, because the Poisson equation is solved analytically. Solute shape is close to spherical and polar (>> 0).[10,11].
The molecular free energy of solvation is computed as the sum of three terms:
Gsol = Ges + Gdr + Gcav
Ges =