A synonym for
. The number of 'centres
' is the number of atoms not bonded initially, between which single bonds are breaking
or new bonds are formed in the
. This number does not necessarily correspond to the ring size of the transition state
for the pericyclic reaction
. Thus, a Diels–Alder reaction is a 'four-centre reaction
'. This terminology has largely been superseded by the more detailed one developed
for the various pericyclic reactions.
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1144
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