Micskei Károly, Rábai Gyula, Gál Emese, Caglioti Luciano, Pályi Gyula
Department of Chemistry, University of Debrecen, H-4010 Debrecen, Hungary.
J Phys Chem B. 2008 Jul 31;112(30):9196-200. doi: 10.1021/jp803334b. Epub 2008 Jul 2.
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.
通过一个负反馈过程扩展了二异丙基锌对手性嘧啶甲醛进行自催化加成反应中对映体过量自发放大的动力学模型。基于扩展模型的模拟结果表明，在连续流动搅拌釜式反应器（CSTR）和半间歇配置中，在优化的初始条件下会出现大幅度振荡。当在CSTR中维持持续振荡时，在计算序列中未观察到对映体产物分布；系统无限期保持其初始对映体比例。然而，在阻尼振荡或稳态条件下，在半间歇配置中会发生从非常小的初始对映体过量到手性放大超过99%的情况。计算表明，由于积分方法固有的数值误差，在半间歇配置中从严格非手性起始条件会出现自发的对映体产物富集（即一种对映体以另一种对映体为代价的积累），这可被视为对映体分子数量统计波动的模型。
