Laage-Hynes mechanism

To be historically fair, other people did observe the existence of jump motions in the rotation of water molecules in the liquid state but detailed analysis of the dynamics of an individual event was not carried out before. Given that perspective, the Laage-Hynes mechanism of water rotation by large-amplitude jumps is indeed a departure from conventional and prevailing wisdom that water rotation is Brownian that is, it occurs differently in water from in other liquids where motion by small steps dominates. Experimental verification of the jump diffusion model came from a beautiful study of the temperature-dependent rate of water rotation. However, both the experiments and the interpretation of results are quite involved. We shall discuss the results as simply as possible. 

As discussed above, the long-time part of the reorientation involves a jump of the 0 -H bond from the direction of the old acceptor (O ) to that of the new aeeeptor (O ) (the Laage-Hynes mechanism). This is a complicated proeess and it fully randomizes the reorientation. It is expected that the timescale of this proeess should depend on the availability of the new aeeeptor and not on the strength of the hydrogen bond formed with the old aeeeptor. This suggests that the long-time part (>100 fs) of the rotational anisotropy need not depend on the frequency of the OD stretch. 

Laage, Burghardt Hynes present and discuss analytic dielectric continuum nonequilibrium solvation treatments of chemical reactions in solution involving conical intersections. Their analysis shows that theories of the rates of mechanisms of the chemical reaction in solution have to incorporate the fact that the solvent can be out of equilibrium with the instantaneous charge distribution of the reacting solutes(s). 

D. Laage and J. T. Hynes, A molecular jump mechanism of water reorientation. Science, 311 (2006), 832-835. 

Laage D, Hynes JT (2006b) A Molecular Jump Mechanism of Water Reorientation. Science 311 832-835... 

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