Endo-exo isomerism

Under endo, exo isomerism is understood in organic chemistry, a special type of isomerism, which occurs only in substituted bridged bicyclic hydrocarbons.

As endo ( endo, Greek, internal ) that is called the isomer in which the substituent is on the opposite side of the shortest bridge. As exo ( exo, Greek, outside) that is called the isomer in which the substituent is on the side of the shortest bridge.

Bicycles that are on the shortest bridge monosubstituted, can not be described with the Endo -exo- definition. The classification of these isomers is effected by the syn-anti notation.

Very easy it is to the endo- exo isomerism explain the basis of the two isomers of 2 -bromo -bicyclo [2.2.1 ] heptane ( 2-bromo- norbornane ):

This bicycle has three bridges: Two each with 2 carbon atoms, and one with a carbon atom. At the second position, the bromine atom can therefore assume two different positions: it can either be on the side of the CH2 - bridge - (and thus " exo " ) or on the opposite side (and thus " endo " ) are.