is the abundance, expressed as the atom fraction of the isotope distinguished by
the subscript numeral, when the two isotopes
are equilibrated between two different chemical species
(or between specific sites A
in the same or different chemical species). The term is most commonly met in connection
solvent isotope effects
, when the fractionation factor
expresses the ratio:
for the exchangeable hydrogen atoms in the chemical species (or sites) concerned.
The concept is also applicable to transition states.
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1115
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook