Effective molarity

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]

${\displaystyle EM_{kinetic}={k_{intramolecular} \over k_{intermolecular}}}$

${\displaystyle EM_{thermo}={K_{intramolecular} \over K_{intermolecular}}}$

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.^[4]

See also

• Cyclic compound
• Intramolecular reaction
• Macrocycle
• Polymerization