A double bond cannot be placed with one terminus at the bridgehead
of a bridged ring system unless the rings are large enough to accommodate the double
bond without excessive strain
. For example, while bicyclo[2.2.1]hept-1-ene is only capable of existence as a transient
, its higher homologues having a double bond at the bridgehead
position have been isolated: e.g.
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1077
PAC, 1996, 68, 2193
(Basic terminology of stereochemistry (IUPAC Recommendations 1996))
on page 2201
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