Transition state theory, also known as TST, is a concept in chemistry that explains the reaction rates of elementary chemical reactions. According to this theory, chemical reactions proceed by a continuous change in the relative positions and potential energies of the constituent atoms and molecules. It assumes a special type of chemical equilibrium (quasi-equilibrium) between reactants and activated transition state complexes. Transition state theory is primarily used to qualitatively understand how chemical reactions take place. This theory was proposed in 1935 by Henry Eyring and further developed by Merrideth G. Evans and Michael Polanyi as a means of accounting for chemical reaction rates
