Benzonitrile:Odor, Hydrogenation reaction, Applications and Synthesis

Benzonitrile, the simplest cyanoaromatic, is a clear liquid with an almond-like odor.

Odor

Like many compounds, benzonitrile is said to smell like almonds. The Secret of Scent: Adventures in Perfume and the Science of Smell by Luca Turin says:

Benzaldehyde, nitrobenzene, benzonitrile, hydrogen cyanide and trans-2-hexenal all smell of bitter almonds, but anyone, even a naive observer, can easily tell them apart by smell after just one showing. Benzaldehyde is the proper bitter-almonds smell (contained in bitter almonds), whereas nitrobenzene smells like a mixture of amaretto and shoe polish, and benzonitrile smells like metallic almonds, and hexenal like cut-grass and almonds."

Hydrogenation reaction

A study performed in a flow reactor on N2 saturated with benzonitrile in the temperature range 550–600°C showed that the main pyrolysis products of this compound are HCN, benzene, monocyanodiphenyls, dicyanodiphenyls, and dicyanobenzenes as well as char. The reaction takes place by a radicalic mechanism, starting with the following initiation reaction[1]:

Applications

Benzonitrile is used as a solvent and intermediate in industries making drugs, perfumes, dyes, rubber, textiles, resins, and specialty lacquers.

Synthesis

Methods for synthesizing it include heating sodium benzenesulfonate with NaCN, adding benzenediazonium chloride to a hot aqueous solution of NaCN and CuSO4, oxidizing toluene in the presence of ammonia,dehydrating benzamide, and treating bromobenzene with CuCN or NaCN.

References

[1]Serban C. Moldoveanu,Chapter 14 - Pyrolysis of Various Derivatives of Carboxylic Acids. Moldoveanu, Pyrolysis of Organic Molecules (Second Edition),Elsevier,2019, Pages 635-696, ISBN 9780444640000, https://doi.org/10.1016/B978-0-444-64000-0.00014-7.