Unimolecular reaction

Unimolecular reaction is an elementary reaction involving a single molecule that undergoes a chemical transformation. These reactions typically involve either a rearrangement of the molecule’s internal structure, known as isomerization, or the breakdown of the molecule itself through dissociation. Importantly, a unimolecular reaction hinges on a single reactant molecule playing the central role in the rate-determining step—the slowest step that dictates the overall reaction speed. Therefore, the reaction’s progress is directly influenced by the behaviour and transformation of that initial molecule, making it a key concept in understanding reaction kinetics.