When a series of structurally related substrates undergo the same general reaction
or when the reaction conditions for a single substrate are changed in a systematic
way, the
enthalpies and
entropies of activation sometimes satisfy the relation:
where the parameter
is independent of temperature. This equation (or some equivalent form) is said to
represent an '
isokinetic relationship'. The temperature
(at which all members of a series obeying the isokinetic relationship react at the
same rate) is termed the '
isokinetic temperature'. Supposed isokinetic relationships as established by direct correlation of
with
are often spurious and the calculated value of
is meaningless, because errors in
lead to compensating errors in
. Satisfactory methods of establishing such relationships have been devised.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1129
Cite as:
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.
