Chapter 9. Stochastic Modeling of Asymmetric Autocatalysis in the Soai Reaction

Abstract

For a theoretical chemist, one of the most exciting features of the Soai reaction is the experimentally confirmed occurrence of absolute asymmetric synthesis and the stochastic distribution of enantiomers observed in it. This chapter shows how highly successful models of this rare phenomenon can be built based on the principles of the continuous time discrete state (CDS) approach to stochastic chemical kinetics. First, an updated, particle-based definition of racemic mixtures is discussed, then a minimal model is presented for absolute asymmetric synthesis that is already able to interpret the core features using a minimum number of chemical processes. An 18-step mechanism proposed for the Soai reaction is also discussed in detail and is shown to lead to practically the same enantiomer distribution as the minimal model with second-order autocatalysis does. Finally, it is shown that about 20 initial chiral molecules as an accidental impurity in the initial reaction mixture may already cause the experimentally measured, slight but significant asymmetry in one of the two most analyzed product distributions known in the Soai reaction.