Translational and rotational motion of isolated water molecules in nitromethane studied using 17O NMR

Hydrogen bonding plays an enormous role in determining the solution properties of liquid water. In the present study, the translational diffusion and the reorientational correlation times of isolated water (H-2 O-17) molecules dissolved in nitromethane were studied using O-17 NMR measurements in the temperature range of 260-314 K. It was found that the water diffusion coefficient was considerably faster than in pure water at the same temperature. Further, the activation energy for the translational motion of the water was about 10 kJ mol(-1), which was the same as that of the (solvent) nitromethane. However, the activation energy for the reorientational motion of the water was significantly less at 7.7 kJ mol(-1). In this study we show that the motions of the isolated water molecules behave significantly different than water molecules in pure water due to the absence of hydrogen bonding to nearby water molecules. (C) 2000 American Institute of Physics. [S0021-9606(00)50133-0].