First‐order stochastic cellular automata simulations of the lindemann mechanism

The Lindemann mechanism explains how apparent unimolecular chemical reactions arise from bimolecular collisions. In this mechanism an ingredient M activates reactants A through collisions, and the resulting activated species A* can either decay to products P or be deactivated back to A, again via collisions with M. A first‐order stochastic cellular automata model described previously [Seybold, Kier, and Cheng, J Chem Inf Comput Sci 1997 , 37 , 386] has been modified to simulate this mechanism. It is demonstrated that this model accurately reflects the salient features of the Lindemann mechanism, including the normal second‐order kinetic behavior at low [M] and apparent first‐order kinetics at high [M]. At low [M] the mechanism is equivalent to a rate‐limited sequential process, whereas at high [M] it becomes a preequilibrium with leakage to products. The model also allows an examination of the validity of the steady‐state approximation normally employed in a deterministic analysis of this mechanism, and it is seen that this approximation is not well justified under reasonable conditions. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 230–237 2004