Nitrile reduction

Catalytic hydrogenation

The catalytic hydrogenation of nitriles is often the most economical route available for the production of primary amines. Catalysts for the reaction often include group 10 metals such as Raney nickel, palladium black, or platinum dioxide. However, other catalysts, such as cobalt boride, also can be selective for primary amine production:

R-C≡N + 2 H₂ → R-CH₂NH₂

Depending on reaction conditions, intermediate imines can also undergo attack by amine products to afford secondary and tertiary amines:

2 R-C≡N + 4 H₂ → (R-CH₂)₂NH + NH₃3 R-C≡N + 6 H₂ → (R-CH₂)₃N + 2 NH₃

Such reactions proceed via enamine intermediates. The most important reaction condition for selective primary amine production is catalyst choice. Other important factors include solvent choice, solution pH, steric effects, temperature, and the pressure of hydrogen inside the hydrogenation vessel.

Industrial significance

A commercial application of this technology includes the production of hexamethylenediamine from adiponitrile, a precursor to Nylon 66.

Non-catalytic routes to amines

Reducing agents for the non-catalytic conversion to amines include lithium aluminium hydride, lithium borohydride, diborane, or elemental sodium in alcohol solvents.

Non-catalytic routes to aldehydes

Nitriles can also be reduced to aldehydes. For example, one method, called Stephen aldehyde synthesis, uses Tin(II) chloride and hydrochloric acid to yield an aldehyde via the hydrolysis of a resulting iminum salt. Aldehydes can also form using a hydrogen donor followed by in-situ hydrolysis of an imine. Useful reagents for this reaction include formic acid with a hydrogenation catalysis or metal hydrides, such as sodium borohydride.

Electrochemical methods

Nitriles can also be reduced electrochemically.