Oscillatory Symmetry Breaking in the Soai Reaction

• Published in: The journal of physical chemistry. B 2008-07, Vol.112 (30), p.9196-9200
• Main Authors: Micskei, Károly, Rábai, Gyula, Gál, Emese, Caglioti, Luciano, Pályi, Gyula
• Format: Article
• Language: English
• Subjects: B: Biophysical Chemistry; Kinetics; Models, Chemical; Stereoisomerism
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp803334b

A kinetic model of spontaneous amplification of enantiomeric excess in the autocatalytic addition of diisopropylzinc to prochiral pyrimidine carbaldehydes is extended by a negative feedback process. Simulations based on the extended model result in large-amplitude oscillations both in a continuous-flow stirred tank reactor (CSTR) and in a semibatch configuration under optimized initial conditions. When sustained oscillations are maintained in a CSTR, no enantiomeric product distribution could be observed in the calculated series; the system keeps its initial enantiomeric ratio endlessly. During damped oscillations, or steady-state conditions, however, chiral amplification from a very small initial enantiomeric excess to more than 99% occurs in a semibatch configuration. Calculations indicated spontaneous enantiomeric product enrichment (i.e., accumulation of one of the enantiomers at the cost of the other one) from strictly achiral starting conditions in a semibatch configuration due to the inherent numerical error of the integrator method, which can be regarded as a model of the statistical fluctuation in the numbers of enantiomeric molecules.