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endo–exo isomerism

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Stereoisomerism found in bridged-ring compounds Comparison of endo-norborneol (left) and exo-norborneol

In organic chemistry, endoexo isomerism is a special type of stereoisomerism found in organic compounds with a substituent on a bridged ring system. The prefix endo is reserved for the isomer 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

  1. IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "endo, exo, syn, anti". doi:10.1351/goldbook.E02094
Stereochemistry
Topics
Configuration descriptors
cistrans isomerismcis-, trans-
EZ notation(E)-, (Z)-
Arene substitution patterno-, m-, p- (ortho, meta, para)
Endo-exo isomerismendo, exo
Syn and anti additionsyn, anti
Three identical ligandsfac, mer (facies, meridonal)
In carbon skeletonsn, iso, neo, cyclo
Secondary and tertiarysec-, tert-
Spiro compoundspiro
Catenanecatena
Absolute configurations
CIP (Cahn–Ingold–Prelog) priority rules(R), (S)
Pseudoasymmetric (pseudochiral) centers(r), (s)
Optical rotation(+)-, (−)- or d-, l-
Relative configurationD-, L-
Octahedral propeller twistΛ-, Δ-
Category:Stereochemistry


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