In organic chemistry, the switching point between the kinetic and thermodynamic control regimes of two competitive, parallel reactions is widely studied. A new definition for this switching point is proposed: the time at which the rates of formation of the competing products are equal. According to this definition, the kinetic control regime is present from the beginning of the reaction, and is valid as long as the rate of formation of the kinetic product is larger than the rate of formation of the thermodynamic product. On the switching point, both rates of formation are equal, so, from this switching point the thermodynamic product has a larger rate of formation, and the thermodynamic control remains until the end of the reaction. A closed form expression is given for the proposed time of the switching point, as a function of the direct and inverse kinetic constants of both competing reactions, as well as the initial concentrations of the starting reagent and the competing products. The concept of competing control regimes is extended also to the case where the reactions start from two competitive reagents which decompose to produce a single product.

在有机化学中，广泛研究了两个竞争性平行反应的动力学和热力学控制方式之间的转换点。提出了这个转换点的新定义：竞争产品的形成速率相等的时间。根据该定义，动力学控制机制从反应开始就存在，并且只要动力学产物的形成速率大于热力学产物的形成速率就有效。在转换点上，两个形成速率相等，因此，从该转换点开始，热力学产物具有较大的形成速率，并且热力学控制一直保持到反应结束。对于开关点的建议时间，给出了一个封闭形式的表达式，它是两个竞争反应的正，反动力学常数以及起始试剂和竞争产物的初始浓度的函数。竞争性控制体系的概念也扩展到反应从两种竞争性试剂开始分解的情况下，这些竞争性试剂分解为一个单一的产物。