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 rotati on and reorientational motion-are studied and related to intermolecula r interactions and to the microscopic solvation structure obtained fro m MD simulation. Self-diffusion coefficients are measured by Fourier t ransform pulse-gradient spin-echo NMR techniques. The reorientational rotational motion of benzene is studied using H-2 NMR T-1 relaxation m easurements. 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 interpr et the anisotropic behavior in terms of specific solute-solvent intera ctions and the solvation structure around benzene. Concerning the thre e solvents-water, carbon tetrachloride and carbon disulfide-a fairly c lear and consistent picture emerges from both experimental and theoret ical studies. The reorientational motion of benzene is found to be hig hly anisotropic in water, slightly less anisotropic in carbon tetrachl oride, while it is nearly isotropic in carbon disulfide solution. MD s imulations show some evidence for hydrogens of water approaching the r ing region of benzene. (C) 1998 American Institute of Physics.