In nitrile reduction a
nitrile
In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including met ...
is
reduced to either an
amine or an
aldehyde with a suitable chemical reagent.
Catalytic hydrogenation
The
catalytic hydrogenation of nitriles is often the most economical route available for the production of
primary
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Works
* ...
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
Cobalt borides are inorganic compounds with the general formula CoxBy. The two main cobalt borides are CoB and Co2B. These are refractory materials.
Applications Materials science
Cobalt borides are known to be exceptionally resistant to oxidatio ...
, also can be
regioselective for primary amine production:
: R-C≡N + 2 H
2 → R-CH
2NH
2
A commercial application of this technology includes the production of
hexamethylenediamine from
adiponitrile, a
precursor to
Nylon 66.
Depending on
reaction conditions,
reactive intermediate
In chemistry, a reactive intermediate or an intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these comp ...
imines can also undergo attack by amine products to afford
secondary
Secondary may refer to: Science and nature
* Secondary emission, of particles
** Secondary electrons, electrons generated as ionization products
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and
tertiary amines:
: 2 R-C≡N + 4 H
2 → (R-CH
2)
2NH + NH
3
: 3 R-C≡N + 6 H
2 → (R-CH
2)
3N + 2 NH
3
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
Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivity of ions ...
, temperature, and the pressure of hydrogen.
Stoichiometric reductions
To amines
Reducing agents for the non-catalytic conversion to amines include lithium aluminium hydride
Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula Li Al H4. It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic ...
, lithium borohydride, diborane, or elemental sodium in alcohol
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* Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom
* Alcohol (drug), an intoxicant found in alcoholic drinks
Alcohol may also refer to:
Chemicals
* Ethanol, one of sev ...
solvents.
To aldehydes
Nitriles can also be converted to aldehydes by reduction and hydrolysis. The Stephen aldehyde synthesis
Stephen aldehyde synthesis, a named reaction in chemistry, was invented by Henry Stephen ( OBE/MBE). This reaction involves the preparation of aldehydes (R-CHO) from nitriles (R-CN) using tin(II) chloride (SnCl2), hydrochloric acid (HCl) and que ...
uses Tin(II) chloride and hydrochloric acid to yield an aldehyde via the hydrolysis of a resulting iminium salt. Aldehydes can also form using a hydrogen donor followed by ''in-situ'' hydrolysis of an imine. Useful reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
s for this reaction include formic acid
Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid, and has the chemical formula HCOOH and structure . It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Es ...
with a hydrogenation catalysis or metal hydrides, which are used to add one mol of hydrogen to the nitrile. For example, sodium borohydride reduces nitriles in alcoholic solvents with a CoCl2 catalyst or Raney nickel.
With diisobutylaluminium hydride
The hydride reagent Diisobutylaluminium hydride, 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
Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outco ...
.
See also
* Urushibara cobalt
* Imine
References
{{Reflist
Organic reduction reactions