# A Note on the Kinetics of Diffusion-mediated Reactions

Source: [A Note on the Kinetics of Diffusion-mediated Reactions](<https://www.sota2.com/research/paper/68fa2dd41e209131ce85cb75>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-24T16:30:28.814Z

Authors: K. Razi Naqvi

Published: 2014-11-09T15:25:04.000Z

## Abstract

The prevalent scheme of a diffusion-mediated bimolecular reaction $A+B\\rightarrow P$ is an adaptation of that proposed by Briggs and Haldane for enzyme action \[{\\em Biochem J.\\/}, 19:338--339, 1925\]. The purpose of this Note is to explain, {\\em by using an argument involving no mathematics\\/}, why the breakup of the encounter complex cannot be described, except in special circumstances, in terms of a first-order process $\\{AB\\}\\rightarrow A+B$. Briefly, such a description neglects the occurrence of re-encounters, which lie at the heart of Noyes's theory of diffusion-mediated reactions. The relation $k=\\alpha k\_{\\mbox{\\scriptsize e}}$ becomes valid only when $\\alpha$ (the reaction probability per encounter) is very much smaller than unity (activation-controlled reactions), or when $\\beta$ (the re-encounter probability) is negligible (as happens in a gas-phase reaction). References to some works (by the author and his collaborators) which propound the correct approach for finding $k$ are also supplied.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/1411.2245>)

[PDF](<https://arxiv.org/pdf/1411.2245.pdf>)