Relating to a short-lived reaction
intermediate. It can be defined only in relation to a time scale fixed by the experimental conditions
and the limitations of the technique employed in the detection of the intermediate.
The term is a relative one. Transient species are sometimes also said to be '
metastable'. However, this latter term should be avoided, because it relates a thermodynamic
term to a kinetic property, although most transients are also thermodynamically
unstable with respect to reactants and products.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1174