A
secondary isotope effect attributed to the different vibrational amplitudes of
isotopologues. For example, both the mean and mean-square amplitudes of vibrations associated with
C–H
bonds are greater than those of
C–D
bonds. The greater effective bulk of molecules containing the former may be manifested
by a
steric effect on a rate or
equilibrium constant.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1131