In nitrile reduction a nitrile is reduced to either an

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen Hydrogen is the chemical element wi ...

or an

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

with a suitable chemical reagent.

Catalytic hydrogenation

The

catalytic Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organ ...

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 Palladium black is a coarse, sponge-like form of elemental palladium which offers a large surface area for catalytic activity. It is used in organic synthesis as a catalyst for hydrogenation reactions. The term palladium black is also used co ...

, or

platinum dioxide Adams' catalyst, also known as platinum dioxide, is usually represented as platinum(IV) oxide hydrate, PtO2•H2O. It is a catalyst for hydrogenation and hydrogenolysis in organic synthesis. This dark brown powder is commercially available. The ...

. However, other catalysts, such as cobalt boride, also can be

regioselective In chemistry, regioselectivity is the preference of chemical bonding or breaking in one direction over all other possible directions. It can often apply to which of many possible positions a reagent will affect, such as which proton a strong Base ( ...

for primary amine production: : R-C≡N + 2 H₂ → R-CH₂NH₂ A commercial application of this technology includes the production of

hexamethylenediamine Hexamethylenediamine is the organic compound with the formula H2N(CH2)6NH2. The molecule is a diamine, consisting of a hexamethylene hydrocarbon chain terminated with amine functional groups. The colorless solid (yellowish for some commercial sam ...

from

adiponitrile Adiponitrile is an organic compound with the chemical formula (CH2)4(CN)2. This viscous, colourless dinitrile is an important precursor to the polymer nylon 66. In 2005, about one million tonnes of adiponitrile were produced.M. T. Musser, "Adip ...

, a

precursor Precursor or Precursors may refer to: * Precursor (religion), a forerunner, predecessor ** The Precursor, John the Baptist Science and technology * Precursor (bird), a hypothesized genus of fossil birds that was composed of fossilized parts of u ...

Nylon 66 Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamide or nylon. It, and nylon 6, are the two most common for textile and plastic industries. Nylon 66 is made of two monomers each containing 6 carbon atoms, ...

. Depending on reaction conditions, reactive intermediate

imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bon ...

s can also undergo attack by amine products to afford secondary and

tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

amines: : 2 R-C≡N + 4 H₂ → (R-CH₂)₂NH + NH₃ : 3 R-C≡N + 6 H₂ → (R-CH₂)₃N + 2 NH₃ Such reactions proceed via

enamine An enamine is an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine. Enamines are versatile intermediates. : The word "enamine" is derived from the affix ''en''-, used as the suffix of alkene, and t ...

intermediates. The most important reaction condition for selective primary amine production is catalyst choice. Other important factors include

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

choice, solution pH, steric effects, temperature, and the

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

of hydrogen.

Stoichiometric reductions

To amines

Reducing agents In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are commonly reducing agents include the Earth meta ...

for the non-catalytic conversion to amines include lithium aluminium hydride,

lithium borohydride Lithium borohydride (LiBH4) is a borohydride and known in organic synthesis as a reducing agent for esters. Although less common than the related sodium borohydride, the lithium salt offers some advantages, being a stronger reducing agent and ...

diborane Diborane(6), generally known as diborane, is the chemical compound with the formula B2H6. It is a toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Diborane is a key boron compound with a variety of applications. It has attracte ...

, or elemental

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

in alcohol solvents.

To aldehydes

Nitriles can also be converted to

s by reduction and hydrolysis. The Stephen aldehyde synthesis uses

Tin(II) chloride Tin(II) chloride, also known as stannous chloride, is a white crystalline solid with the formula . It forms a stable dihydrate, but aqueous solutions tend to undergo hydrolysis, particularly if hot. SnCl2 is widely used as a reducing agent (in aci ...

and

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

to yield an aldehyde via the

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolys ...

of a resulting

iminium In organic chemistry, an iminium cation is a polyatomic ion with the general structure . They are common in synthetic chemistry and biology. Structure Iminium cations adopt alkene-like geometries. The central C=N unit is nearly coplanar with al ...

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

hydride In chemistry, a hydride is formally the anion of hydrogen( H−). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride ...

s, which are used to add one mol of hydrogen to the nitrile. For example,

sodium borohydride Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula Na BH4. This white solid, usually encountered as an aqueous basic solution, is a reducing agent that finds applica ...

reduces nitriles in alcoholic solvents with a CoCl₂ catalyst or Raney nickel.

With diisobutylaluminium hydride

The hydride reagent

Diisobutylaluminium hydride Diisobutylaluminium hydride (DIBALH, DIBAL, DIBAL-H or DIBAH) is a reducing agent with the formula (''i''-Bu2AlH)2, where ''i''-Bu represents isobutyl (-CH2CH(CH3)2). This organoaluminium compound is a reagent in organic synthesis. Properties Lik ...

, or DIBAL-H, is commonly used to convert nitriles to the aldehyde. Regarding the proposed mechanism, DIBAL forms a Lewis acid-base adduct with the nitrile by formation of an N-Al bond. The hydride is then transferred to the carbon of the nitrile. Aqueous workup produce the desired aldehyde and ammonia.

Electrochemical methods

Benzyl nitriles can also be reduced electrochemically.

References

{{Reflist Organic reduction reactions