A FREE-ENERGY PERTURBATION STUDY OF SOLVATION IN HYDRAZINE AND CARBON-TETRACHLORIDE

A free energy perturbation study of solvation in hydrazine and carbon tetrachloride is carried out to examine the process of solvation of different solutes in these two solvents. For this purpose, models of liquid hydrazine and liquid carbon tetrachloride were generated by molecular dynamics simulations. The structure of liquid hydrazine obtained from the molecular dynamics simulation is discussed in detail. Differences in the free energies of solvation of different solutes belonging to different classes of ions and molecules have been determined. The solutes studied include closed shell ions, tetraalkylammonium ions, normal alkanes, and tetraalkylmethane molecules. The calculated differences in free energy of solvation, DELTA-G, between two different solutes in these solvents compare well with the experimental values. Detailed analysis of the solvation behavior in these solvents and their comparison with the behavior of solvation in water suggest that solvation behavior in hydrazine resembles that in water for many solutes, whereas the behavior in carbon tetrachloride is different. The results of this study support the view that the special phenomenon observed in the hydration of apolar solutes is a result of the structural peculiarity of liquid water.