Benzonitriles

Benzonitriles are a class of aryl nitriles in which a single cyano group (–CN) is attached to a benzene ring. The simplest member is benzonitrile (benzene carbonitrile), with the formula C7H5N and a molecular weight of 103.12 g/mol. The nitrile group imparts polarity to the molecule and gives characteristic infrared absorption near 2220 cm−1.

Structure and properties: The –CN substituent is a strongly electron-withdrawing group and acts as a meta-director in electrophilic aromatic substitution, reducing the ring’s reactivity toward electrophiles. Benzonitriles are typically colorless liquids or solids with relatively high boiling points and limited water solubility, reflecting the balance between the polar nitrile group and the nonpolar aromatic ring.

Production and occurrence: Benzonitriles are produced on a large scale as building blocks in organic synthesis. The major industrial route for benzonitrile is the ammoxidation of toluene over oxide catalysts in the presence of ammonia and oxygen. Alternative routes include the dehydration of benzamide or related benzoic acid derivatives.

Reactions and transformations: The nitrile group enables a range of transformations. Hydrolysis converts benzonitrile to benzoic acid or its amide under acidic or basic conditions. Reduction of the nitrile yields the corresponding primary amine, benzylamine. Nitriles can also participate in various carbon–carbon bond-forming reactions and serve as versatile intermediates in the synthesis of pharmaceuticals, dyes, agrochemicals, and polymers.

Uses: Benzonitriles and substituted benzonitriles are widely used as precursors in organic synthesis. They serve as intermediates for the preparation of dyes, pharmaceuticals, agrochemicals, and specialty polymers, as well as in research contexts exploring nitrile chemistry. Safety considerations include typical nitrile hazards and handling requirements for industrial chemicals.