Nitrile
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A nitrile is any organic compound which has a -C≡N functional group. The -C≡N functional group is called a nitrile group. In the -CN group, the carbon atom and the nitrogen atom are triple bonded together. The prefix cyano is used in chemical nomenclature to indicate the presence of a nitrile group in a molecule. A cyanide ion is a negative ion with the formula CN−. The -CN group is sometimes, less properly, referred to as a cyanide group or cyano group and compounds with them are sometimes referred to as cyanides.
Nitriles sometimes release the highly toxic CN− cyanide ion. See the article on cyanide for a discussion of biological effects and toxicity.
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History
Hydrogen cyanide was first synthesized by K.W. Scheele in 1782 and he was killed in an attempt to get the anhydrous compound <ref>The Preparation of Nitriles. David T. Mowry Chem. Rev.; 1948; 42(2) pp 189 - 283; Template:DOI</ref>. J. L. Gay-Lussac was the first to prepare the pure acid in 1811 and Friedrich Wohler and Justus von Liebig were the first to prepare the first nitriles benzoyl cyanide and benzonitrile in 1832. Théophile-Jules Pelouze synthesized propionitrile in 1834.
Synthesis of nitriles
Nitriles can be prepared in organic synthesis by the following methods:
- Nucleophilic aliphatic substitution reactions of alkyl halides with metal cyanides.
- dehydration of primary amides
- dehydration of secondary amides (von Braun amide degradation)
- dehydration of aldoximes with triethylamine/sulfur dioxide, zeolites, or sulfuryl chloride
- One-pot synthesis of aldehyde with hydroxylamine and sodium sulfate.
- In one study <ref>One pot synthesis of nitriles from aldehydes and hydroxylamine hydrochloride using sodium sulphate (anhyd) and sodium bicarbonate in dry media under microwave irradiation Sharwan K, Dewan, Ravinder Singh, and Anil Kumar Arkivoc 2006 (ii) 41-44 Online article</ref> an aromatic or aliphatic aldehyde is reacted with hydroxylamine and anhydrous sodium sulfate in a dry media reaction for a very small amount of time under microwave irradiation through an intermediate aldoxime.
- reaction of metal cyanides with aldehydes in the cyanohydrin reaction
- from aryl carboxylic acids (Letts nitrile synthesis)
Reactions of Nitriles
Nitrile groups in organic compounds can undergo various reactions when subject to certain reactants or conditions. A nitrile group can be hydrolyzed, reduced, or ejected from a molecule as a cyanide ion.
- In hydrolysis the nitrile is reacted with an acid and water at a high temperature, or with a base and water. The acid hydrolysis forms a carboxylic acid, the alkali hydrolysis forms a carboxylate.
- In organic reduction the nitrile is reduced by reacting it with hydrogen with a nickel catalyst; an amine is formed in this reaction.
- A nitrile is an electrophile in a nucleophilic addition reaction with an organozinc compound in the Blaise reaction.
- Other nucleophilic addition reactions with nitriles and alcohols are found in the Pinner reaction.
- In reductive decyanation the nitrile group is replaced by a proton <ref>The reductive decyanation reaction: chemical methods and synthetic applications Jean-Marc Mattalia, Caroline Marchi-Delapierre, Hassan Hazimeh, and Michel Chanon Arkivoc (AL-1755FR) pp 90-118 2006 Article</ref>. An effective decyanation is by a dissolving metal reduction with HMPA and potassium metal in tert-butyl alcohol. α-Amino-nitriles can be decyanated with Lithium aluminium hydride.
- Nitriles self-react in presence of base in the Thorpe reaction in a nucleophilic addition
See also
- For the polymer used to make safety gloves, see Nitrile rubber.
- Thorpe reaction
