Rice-Ramsperger-Kassel-Marcus theories

Assuming that the decay rate k for the activated A is much faster than k2, the rate for production of P can be written in terms of the ki, k.i and k2 constants by making a steady state approximation for A, as shown in eq. (13.5). 

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Klippenstein S J 1992 Variational optimizations in the Rice-Ramsperger-Kassel-Marcus theory calculations for unimolecular dissociations with no reverse barrier J. Chem. Rhys. 96 367-71... 

Marcus is a coauthor of the Rice-Ramsperger-Kassel-Marcus theory of molecular reactions. However, his theoretical work in the 1950s on electron transfer reactions started him on his pathway to eminence. Back then, chemists knew electron-transfer processes were occurring during chemical reactions, but they had no way to predict the speed of a reaction or to develop strategic chemical experiments. In addition, some reactions that were predicted to proceed rapidly instead poked along at a snail s pace. 

RRKM Rice-Ramsperger-Kassel-Marcus [theory]... 

Rice—Ramsperger—Kassel—Marcus Theory (RRKMT) and Quasi-equilibrium Theory (QET)... 

Commonly applied models of reaction kinetics, such as the transition state theory or RRKM (Rice-Ramsperger-Kassel-Marcus) theory, cannot completely describe multistage catalytic cycles or even the simplest reactions in many cases. As a catalytic cycle is a nonlinear dynamic system, statements such as "the reaction is first order with respect to a component A" or "the reaction is zero order with respect to a component B" cannot be universally assumed. 

Optimizations in the Rice-Ramsperger-Kassel-Marcus Theory Calculations For Unimolecular Dissociations With No Reverse Barrier. 

Chemical dynamics simulations of the gas phase 5 2 reactions of methyl halides have been carried out at many different levels of theory and compared with experimental measurements and predictions based on transition state theory and RRKM (Rice-Ramsperger-Kassel-Marcus) theory. Although many 5 2 reactions occur by the traditional pre-reaction complex, transition state, post-reaction complex mechanism, three additional non-statistical mechanisms were detected when the F -CH3-I reaction was analysed at an atomic level (i) a direct rebound mechanism where F attacks the backside of the carbon and CH3-F separates (bounces off) from the iodine ion, (ii) a direct stripping mechanism where F approaches CH3-I from the side and strips away the CH3 group, and (iii) an indirect reaction where the pre-reaction complex activates the C-I bond causing a CH3-I rotation and then the 5 2 reaction. The presence of these processes demonstrate that three non-statistical effects, (i) recrossing of the transition state is important, (ii) the transfer of the translational energy from the reactants into the rotational and vibrational modes of the substrate is inefficient, and (iii) there is... 

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