Simulation of Chemical Reactions with High Barriers

Simulation of Chemical Reactions with High Barriers 

Rosenberg et al. calculated the rate constant for this process, from which the transmission coefficient could be derived. They found that recrossings are quite frequent for this reaction, leading to a transmission coefficient of 0.36 for 

Wilson and Chandler calculated the free energy profile for the boat-chair isomerization at each of the CS2 densities. They found that the barrier to chair— boat isomerization was 11 kcal/mol and the reverse process had a barrier of 5 kcal/mol. In particular, they found that these barrier heights were independent of solvent density and did not differ qualitatively from results for gas phase isomerization. 

Straub et al. described several systems in detail, concentrating on system parameters where a comparison with one or more analytic rate theories Grote-Hynes,9 etc.) could be made, and in addition where tests of connection formulas that bridge these analytic theories could be performed. While we will discuss their detailed comparisons in a later section, we note here that the power of simulation in understanding the range of applicability of analytic theories is evident in the work of Straub et al. As Straub et al. point out, extending these comparisons to experiment requires the consideration of several quantities (potential of mean force, friction on the reaction coordinate, etc.), which may in fact be difficult to estimate from experimental measurements. There is still a need in many types of reactions to connect the parameters of such models to experimental measurements on real systems. 

The first molecular dynamics simulations of bimolecular reactions in solution were those of Wilson, Hynes, and co-workers on an A -I- BC — AB -I- C atom exchange reaction in rare gas solution. - The short-range Lennard-Jones solvent-solute interactions and intrasolvent interactions simplify the interpretation of the reaction dynamics. 

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