Illustrated Glossary of Organic Chemistry

Syn addition: An addition reaction in which all new bonds are formed on the same face of the reactant molecule.

1. BH3 2. HOOH, NaOH

This hydroboration-oxidation reaction is a syn addition because this reaction delivers an H and OH to the same face of the alkene.

+

[4+2]

This Diels-Alder reaction is a syn cycloaddition reaction because the two new carbon-carbon sigma bonds are formed on the same face of the diene or dienophile.


Addition of Br₂ to an alkene is an anti addition because the two new carbon-bromine bonds are formed on opposite faces of the alkene.