Nitrileiden

Nitrileiden is a term used in chemistry to describe compounds that contain the nitrile functional group, typically the cyano group -C≡N, attached to a carbon skeleton. In some languages, nitriliden (or nitrile imines) denotes a related but distinct class of reactive species with the general structure R-C=N-N:, which are used as 1,3-dipoles in cycloaddition reactions. The broad group known as nitriles includes simple aliphatic and aromatic nitriles as well as more complex nitrile-containing polymers and natural products.

Structure and properties

The nitrile group is linear and highly polar, which increases the polarity of the molecules bearing it. Nitriles generally have relatively high boiling points for their molecular weight and resist many reactions until activated by heat or catalysts. The -C≡N bond is relatively strong, but nitriles can undergo hydrolysis under acidic or basic conditions to give carboxylic acids (or amides as intermediates), and they can be reduced to primary amines. Nitrile imines, when formed, behave as 1,3-dipoles and participate in cycloaddition chemistry to form heterocycles such as pyrazoles.

Synthesis and reactivity

Nitriles are prepared by various routes, including dehydration of amides, cyanation of carbon nucleophiles, or dehydration of aldoximes and related precursors. Reactivity centers on the nitrile carbon or the nitrogen atom, enabling transformations to amides, carboxylic acids, amines, or other functional groups. Nitrile imines are typically generated in situ from precursors and engaged in 1,3-dipolar cycloadditions with alkenes or alkynes.

Applications and occurrence

Nitriles are widespread in chemical synthesis and industry. Acetonitrile is a common laboratory solvent and HPLC solvent; benzonitrile and acrylonitrile are important building blocks for pharmaceuticals, agrochemicals, and polymers. Polyacrylonitrile, for example, is a key precursor for certain synthetic fibers. Nitrile-containing natural products also occur in nature.

Safety and handling

Nitriles can be toxic or irritating and may pose health and environmental risks. They should be handled with appropriate PPE, proper ventilation, and adherence to regulatory guidelines. Storage and disposal follow standard practices for organic solvents and reactive intermediates.