How does proton transfer help an acid or base catalyze a reaction?

In acid–base catalysis, proton transfer facilitates chemical reactions by altering the substrate to make it reactive or unstable. Rather than acting through a mysterious influence, the catalyst—an acid or base—engages in an actual chemical reaction with the substrate, from which it is later regenerated.1

According to the Brønsted-Lowry concept, this process involves the transfer of protons from an acidic catalyst to the reactant, or from the reactant to a basic catalyst. This transfer can trigger a reaction in two primary ways:2

• Inducing Reactivity: The addition or removal of a proton can cause the substrate to become reactive toward other species present in the system.1
• Promoting Instability: By making the substrate unstable, the proton transfer forces it to decompose or rearrange into a new product.1

In cases of rearrangement, the catalyst is often regenerated when a proton is subsequently added or removed at a different site on the molecule. This mechanism is fundamental to many industrial and natural processes, enabling transformations that might not occur spontaneously.13