Polanyi-Semenov rule

The activation energy of this reaction is usually low. To estimate the activation energy ( ) as the function of the reaction heat Q), one may use a simple approximate equation (so called Polanyi-Semenov rule) [10] ... 

In this equation, ka and kb should remain nearly constant in the presence of hydrogen or deuterium, and thus these terms do not contribute to kinetic isotope effect. Small differences in kc can be estimated from the Evans-Polanyi-Semenov rule. (11)... 

It also follows from these data that the activation energy gradually decreases with increasing reaction heat Q. This regularity was first noted by Ogg and M. Polanyi [352] (see also [129,130]), who established a linear dependence of E on Q. Lateron, Semenov (see [430]) extended this rule, referred to as the Polanyi-Semenov rule, to exchange reactions of other atoms and radicals. 

According to CLTST, the activation energy Ea depends on AE according to empirical Broensted-Polanyi-Semenov (BPS) rule (see, e.g., Glasstone et al. [1941]) ... 

Low Energy Activation in Each Step. In certain cases, the rule is, the better the thermodynamic of the step, the lower the energy activation (Polanyi-Semenov, Bronsted equations, for example). 

This specifically electrochemical law is, as was shown by Frumkin, a direct consequence of an important general kinetic rule formulated by Br0n-sted in the 1920s and later elaborated by Polanyi, Semenov, and other... 

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