primary isotope effect
A @K03405@ attributable to isotopic substitution of an atom to which a bond is made or broken in the @R05139@ or in a @P04810@ step of a specified reaction. The corresponding @I03327-1@ on the @E02177@ of a reaction in which one or more bonds to isotopic atoms are broken, is called a 'primary @I03327-2@'.
See also:
secondary isotope effect
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1130 [Terms] [Paper]