Molecular motion and solvation of benzene in water, carbon tetrachloride, carbon disulfide and benzene: A combined molecular dynamics simulation and nuclear magnetic resonance study

Benzene, dissolved in several solvents of varying viscosities and as a neat liquid, is investigated using both MD simulation techniques and NMR spectroscopy. Molecular motions-linear translation, angular rotation and reorientational motion-are studied and related to intermolecular interactions and to the microscopic solvation structure obtained from MD simulation. Self-diffusion coefficients are measured by Fourier transform pulse-gradient spin-echo NMR techniques. The reorientational rotational motion of benzene is studied using H-2 NMR T-1 relaxation measurements. The H-2 T-1 measurements also include benzene in solvents: hexane, cyclohexane, chloroform, dodecane and hexadecane. A special emphasis is on the anisotropy of benzene. Attempts are made to interpret the anisotropic behavior in terms of specific solute-solvent interactions and the solvation structure around benzene. Concerning the three solvents-water, carbon tetrachloride and carbon disulfide-a fairly clear and consistent picture emerges from both experimental and theoretical studies. The reorientational motion of benzene is found to be highly anisotropic in water, slightly less anisotropic in carbon tetrachloride, while it is nearly isotropic in carbon disulfide solution. MD simulations show some evidence for hydrogens of water approaching the ring region of benzene. (C) 1998 American Institute of Physics.