The
linear free-energy relation
applied to the reactions between nucleophiles and certain large and relatively
stable organic cations, e.g. arenediazonium, triarylmethyl and aryltropylium cations in various solvents.
is the
rate constant for reaction of a given
cation with a given nucleophilic system (i.e. given nucleophile in a given solvent).
is the
rate constant for the same
cation with water in water, and
is a parameter which is characteristic of the nucleophilic system and independent of the
cation. A surprising feature of the equation is the absence of a
coefficient of
,
characteristic of the substrate
(
cf. the
in the
Swain–Scott equation), even though values of
vary over 13 log units. The equation thus involves a gigantic breakdown of the
reactivity–selectivity principle. The equation has been extended both in form and in range of application.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1161
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.
doi:10.1351/goldbook.
value in planar chromatography
