On the sum of chemical reactions

TL;DR

This paper introduces a mathematical operation to combine chemical reactions algebraically, enabling analysis of reaction sequences and their properties, with applications to stochastic reaction networks and network reduction.

Contribution

It defines an associative, non-commutative operation on reaction representations, providing a new algebraic framework for analyzing complex reaction sequences.

Findings

Operation models sequential reactions effectively

Algebraic properties facilitate network analysis

Applications include reachability and reduction of reaction networks

Abstract

It is standard in chemistry to represent a sequence of reactions by a single overall reaction, often called a complex reaction in contrast to an elementary reaction. Photosynthesis $6 \text{CO}_2+6 \text{H}_2\text{O} \to \ \text{C}_6\text{H}_{12}\text{O}_6$ $+\ 6 \text{O}_2$ is an example of such complex reaction. We introduce a mathematical operation that corresponds to summing two chemical reactions. Specifically, we define an associative and non-communicative operation on the product space $\mathbb{N}_0^n\times \mathbb{N}_0^n$ (representing the reactant and the product of a chemical reaction, respectively). The operation models the overall effect of two reactions happening in succession, one after the other. We study the algebraic properties of the operation and apply the results to stochastic reaction networks, in particular to reachability of states, and to reduction of reaction networks.