primary isotope effect

https://doi.org/10.1351/goldbook.P04831
A
kinetic isotope effect
attributable to isotopic substitution of an atom to which a bond is made or broken in the
rate-controlling step
or in a
pre-equilibrium
step of a specified reaction. The corresponding
isotope effect
on the
equilibrium constant
of a reaction in which one or more bonds to isotopic atoms are broken, is called a 'primary
equilibrium isotope effect
'.
See also:
secondary isotope effect
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1130 [Terms] [Paper]