In
organic chemistry, ''endo''–''exo'' isomerism is a special type of
stereoisomerism found in
organic compounds with a
substituent
A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and ''functional group'', as well as ''side ...
on a
bridged ring system. The prefix ''endo'' is reserved for the
isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
Iso ...
with the substituent located closest, or "''syn''", to the longest bridge. The prefix ''exo'' is reserved for the isomer with the substituent located farthest, or "''anti''", to the longest bridge. Here "longest" and "shortest" refer to the number of atoms that comprise the bridge. This type of
molecular geometry is found in
norbornane systems such as
dicyclopentadiene.
The terms ''endo'' and ''exo'' are used in a similar sense in discussions of the
stereoselectivity in Diels–Alder reactions.
References
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{{Navbox stereochemistry
Stereochemistry