Benzonitrile is the chemical compound with the formula C6H5(CN), abbreviated PhCN. This aromatic organic compound is a colorless liquid with a sweet almond odour. It is mainly used as a precursor to the resin benzoguanamine.

Uses

The most important commercial use for benzonitrile is the synthesis of benzoguanamine, which is a derivative of melamine and is used in protective coatings and molding resins.

Reactions

The pyrolysis of benzonitrile under nitrogen at atmospheric pressure has been studied at temperatures of 823–873 K in a flow reactor. The results demonstrate that conversion to hydrogen cyanide occurs directly by a free radical mechanism. The dominant products detected are hydrogen cyanide, monocyanodiphenyl, benzene, dicyanodiphenyl and dicyanobenzene. Reaction orders and activation energies have been determined for product formation. A reaction scheme involving three competing chain reactions in the gas phase with chain carriers H., C6Hurn:x-wiley:03080501:media:FAM810170106:tex2gif-stack-1 and .C6H4CN is proposed to explain the observed kinetics. A mechanism is advanced for the formation of significant quantities of polymer, consistent with infra‐red spectra and elemental analysis.

Production

It is prepared by ammoxidation of toluene, that is its reaction with ammonia and oxygen (or air) at 400 to 450 °C (752 to 842 °F).

In the laboratory it can be prepared by the dehydration of benzamide or by the Rosenmund–von Braun reaction using cuprous cyanide or NaCN/DMSO and bromobenzene.

Health Hazard

Benzonitrile may enter the human body by ingestion, absorption through the skin, or inhalation. The earliest symptoms of cyano compound intoxication may be weakness, headaches, confusion, and occasionally nausea and vomiting. The respiratory rate and depth will usually be increased at the beginning and at later stages become slow and gasping. Blood pressure is usually normal, especially in the mild or moderately severe cases, although the pulse rate is usually more rapid than normal.