A synonym for
pericyclic reaction. 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
transition state. 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 This terminology has largely been superseded by the more detailed one developed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.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1144