Chemical Kinetics and Mass Action in Coexisting Phases

TL;DR

This paper develops a theoretical framework for understanding chemical reaction kinetics in coexisting phases at equilibrium, highlighting how phase interactions influence reaction rates and providing insights into biological and synthetic systems.

Contribution

It introduces a novel theory linking phase equilibrium with reaction kinetics, emphasizing phase-dependent rate coefficients and diffusive exchanges.

Findings

Reaction rates are coupled with diffusive exchanges between phases.

Differences in reaction rates arise solely from phase-dependent coefficients.

Chemical relaxation follows a flow along the phase equilibrium line.

Abstract

The kinetics of chemical reactions are determined by the law of mass action, which has been successfully applied to homogeneous, dilute mixtures. At non-dilute conditions, interactions among the components can give rise to coexisting phases, which can significantly alter the kinetics of chemical reactions. Here, we derive a theory for chemical reactions in coexisting phases at phase equilibrium. We show that phase equilibrium couples the rates of chemical reactions of components with their diffusive exchanges between the phases. Strikingly, the chemical relaxation kinetics can be represented as a flow along the phase equilibrium line in the phase diagram. A key finding of our theory is that differences in reaction rates between coexisting phases stem solely from phase-dependent reaction rate coefficients. Our theory is key to interpret how concentration levels of reactive components in condensed phases control chemical reaction rates in synthetic and biological systems.