Microscopic reversibility

The principle of Microscopic reversibility in chemistry states that in a reversible reaction the mechanism in one direction is exactly the reverse of the mechanism in the other direction. A result of microscopic reversibility is that the series of transition states and intermediates of the forward reaction are mirrored in reverse order in the reverse reaction. The principle does not apply to reactions where photochemical excitation is the first step. This law was formulated by R. C. Tolman in 1924 and published in 1938. For macroscopic systems this principle results in detailed balances known in physics.