Hydrogenation* to treat with hydrogen* also a form of chemical
reduction* is a
chemical reactionhydrogen (H2) and another compound or element* usually in the presence of a catalyst. The process is commonly employed to
reduce or
saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of
hydrogen atoms to a molecule* generally an alkene.
Catalysts are required for the reaction to be usable; non-catalytic hydrogenation takes place only at very high temperatures.
Hydrogen adds to
double and
triple bonds in
hydrocarbons.
[1] between molecular
Because of the importance of hydrogen* many related reactions have been developed for its use. Most hydrogenations use gaseous hydrogen (H2)* but some involve the alternative sources of hydrogen* not H2: these processes are called
transfer hydrogenations. The reverse reaction* removal of hydrogen from a molecule* is called
dehydrogenation. A reaction where bonds are broken while hydrogen is added is called
hydrogenolysis* a reaction that may occur to carbon-carbon and carbon-heteroatom (
O*
N*
X) bonds. Hydrogenation differs from
protonation or
hydride addition: in hydrogenation* the products have the same charge as the reactants.
An illustrative example of a hydrogenation reaction is the addition of hydrogen to
maleic acid to
succinic acid.
[2] Numerous important applications are found in the
petrochemical* pharmaceutical and food industries. Hydrogenation of
unsaturated fats produces
saturated fats and* in some cases*
trans fats.