In chemistry, the effective molarity (denoted EM)[1] is defined as the ratio between the first-order rate constant of an intramolecular reaction and the second-order rate constant of the corresponding intermolecular reaction (kinetic effective molarity)[1][2] or the ratio between the equilibrium constant of an intramolecular reaction and the equilibrium constant of the corresponding intermolecular reaction (thermodynamic effective molarity).
[1][3] EM has the dimension of concentration.
High EM values always indicate greater ease of intramolecular processes over the corresponding intermolecular ones.
Effective molarities can be used to get a deeper understanding of the effects of intramolecularity on reaction courses.
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