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]

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

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

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] In last decades, the frequency of use of effective molarity in scientific literature has shown a marked decrease, because this formalism is being progressively replaced by more important physical quantities.

See also

• Cyclic compound
• Macrocycle
• Intramolecular reaction
• Polymerization

References

1. Kirby, AJ in (1980). Advances in Physical Organic Chemistry. London: Academic Press. pp. 183–278. ISBN 9780120335176.
2. Dougherty, Eric V. Anslyn ; Dennis A. (2006). Modern physical organic chemistry (Dodr. ed.). Sausalito, Calif.: University Science Books. p. 496. ISBN 9781891389313.
3. Hunter, Christopher A.; Anderson, Harry L. (28 September 2009). "What is Cooperativity?". Angewandte Chemie International Edition 48 (41): 7488–7499. doi:10.1002/anie.200902490.
4. Krishnamurthy, Vijay M.; Semetey, Vincent; Bracher, Paul J.; Shen, Nan; Whitesides, George M. (1 February 2007). "Dependence of Effective Molarity on Linker Length for an Intramolecular Protein−Ligand System". Journal of the American Chemical Society 129 (5): 1312–1320. doi:10.1021/ja066780e.