The organic compounds, which have a -CN functional group connected through the carbon end, are called nitriles or cyano compounds. They are isomeric to isonitriles which are organic compounds with the functional group -NC. In isonitriles, the organic group is attached through the nitrogen atom and not through the carbon atom. Isonitriles are also called by other names, such as isocyanides or carbylamine. Nitriles are polar compounds with high dielectric constants.
In organic reactions, the nitrile group undergoes various reactions such as hydrolysis, oxidation, alpha-alkylation, cycloaddition, 1,2 or 1,4-addition, reduction, and elimination; and are therefore useful intermediates or reagents in organic synthesis. Nitriles are also used in the Blaise and Pinner reactions, where nitrile acts as an electrophile. Benzonitrile and acetonitrile are useful solvents in organic synthesis. In the area of pharmaceuticals, nitrile compounds are extensively used in a wide variety of drugs (Fleming, F. F.; Yao, L.; Ravikumar, P. C.; Funk, L.; Shook, B. C. Nitrile-Containing Pharmaceuticals: Efficacious Roles of the Nitrile Pharmacophore. J. Med. Chem. 2010, 53, 7902-7917). For example, nitrile compounds are employed as DPP-IV inhibitors and selective serotonin reuptake inhibitors. As aromatase inhibitors, benzonitriles are used for the treatment of estrogen-dependent diseases. Acrylonitrile derivatives are used in the production of several polyacrylonitriles which are acrylic fibres.
Isonitriles have a very short C-N bond distance and are described by two resonance structures, one with a triple bond between the carbon and nitrogen and the other with double bond between carbon and nitrogen. Both the resonance structures are shown in equilibrium for isonitriles. Methyl isocyanides are employed as precursors for the synthesis of heterocycles. Benzyl isocyanide is employed in the synthesis of arylamides. Metal complexes of organonitriles are used as a catalyst for organic transformations such as cyclopropanation of olefins, allylic allylation, hydrosilylation, hydrogenation and polymerization reactions.