Syn and anti addition

In organic chemistry, syn and anti addition are different ways in which two substituents can be added to a double bond or triple bond. This article will use cycloalkenes as examples.

Syn addition is the addition of two substituents to the same side (or face) of a double bond or triple bond, resulting in a decrease in bond order but an increase in number of substituents. Generally the substrate will be an alkene or alkyne. An example of syn addition would be the oxidation of an alkene to a diol via a suitable oxidizing agent such as Osmium tetroxide OsO₄ or Potassium permanganate KMnO₄.