Dynamics of hydrophobic hydration of benzene

The dynamics of hydrophobic hydration of benzene was examined by NMR for both the solute and the solvent water. The rotational dynamics of water in the benzene hydration shell was observed to be slower than that in the bulk. This idea, in addition to the data on solitary waters in organic solvents, shows that the rotational dynamics of a water correlates positively with the hydrogen-bond strength of the water with the surrounding environment. The temperature dependence of the rotational motion of the solute benzene was examined to probe the cage structure of water around the benzene. It reveals the competition between the exclusion volume effect of the solute and the attractive and directional effects of solvent structure. The similarity and difference between the rotational and translational mobilities of hydrophobic benzene are also discussed.