Benzyl cyanide
[CAS# 140-29-4]

Identification

• Classification: Organic raw materials >> Nitrile compound
• Name: Benzyl cyanide
• Synonyms: Benzeneacetonitrile; Alpha-tolunitrile; Phenyl acetyl nitrile
• Molecular Formula: C₈H₇N
• Molecular Weight: 117.15
• CAS Registry Number: 140-29-4
• EC Number: 205-410-5
• SMILES: C1=CC=C(C=C1)CC#N

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*, 1.015 g/mL (Expl.)
• Melting point: -24 ºC (Expl.)
• Boiling point: 233.5 ºC 760 mmHg (Calc.)^*, 234 ºC (Expl.)
• Flash point: 101.7 ºC (Calc.)^*, 101 ºC (Expl.)
• Solubility: water: insoluble, <0.1 g/100 mL (17 ºC) (Expl.)
• Index of refraction: 1.53 (Calc.)^*, 1.522-1.524 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS06;GHS07 Danger
• Hazard Statements: H301-H302-H311-H330
• Precautionary Statements: P260-P262-P264-P270-P271-P280-P284-P301+P316-P301+P317-P302+P352-P304+P340-P316-P320-P321-P330-P361+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	3	H311
Acute toxicity	Acute Tox.	1	H330
Acute toxicity	Acute Tox.	3	H301
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	2	H330
Carcinogenicity	Carc.	1B	H350
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335

• Transport Information: UN 2470

Discovory and Applicatios

Benzyl cyanide, also known as phenylacetonitrile, is an organic compound with the formula C₆H₅CH₂CN. It is a clear to pale-yellow liquid characterized by a faint almond-like odor, belonging to the nitrile family. Its structure consists of a benzyl group attached to a nitrile functional group, giving it both aromatic and reactive chemical properties that have made it a substance of interest in both industrial and academic chemistry.

The discovery of benzyl cyanide dates back to the 19th century during the rapid expansion of organic chemistry in Europe. Early chemists were investigating derivatives of benzenes and toluenes by applying newly developed reactions involving halogenation and subsequent substitution with nitrogen-containing groups. The synthesis of benzyl cyanide was first reported through reactions involving benzyl halides and metal cyanides, a method that remained a foundation for its preparation. The identification of this compound reflected the growing understanding of nitrile chemistry, a functional group that would later prove crucial in the development of dyes, pharmaceuticals, and agrochemicals. Its discovery was linked to systematic efforts to expand the catalog of aromatic derivatives, and benzyl cyanide quickly found recognition as a useful intermediate for further chemical transformations.

The applications of benzyl cyanide are broad, and its importance lies primarily in its role as a versatile intermediate. One of its earliest uses was in the synthesis of phenylacetic acid, which could be obtained by hydrolyzing the nitrile group. Phenylacetic acid itself became important in fragrance manufacturing, especially in producing compounds with honey-like or floral notes. The fragrance industry later utilized benzyl cyanide directly in formulations for perfumes and flavors, taking advantage of its aromatic qualities. Its relatively high stability and distinct scent made it a valuable raw material for perfumers.

In the pharmaceutical field, benzyl cyanide and its derivatives have played a major role. The nitrile group provides a reactive handle that can be converted into amines, acids, and amides, which are key motifs in medicinal chemistry. Through controlled reactions, benzyl cyanide has been transformed into drug precursors, including intermediates for antihypertensive, antipsychotic, and analgesic agents. For example, its conversion into phenylacetone or substituted phenylacetonitriles allowed the development of synthetic pathways toward therapeutic compounds. This established benzyl cyanide as a cornerstone in fine chemical and pharmaceutical manufacturing.

Beyond fragrances and pharmaceuticals, benzyl cyanide has also been employed in agrochemicals. Derivatives of this compound have been used in the synthesis of herbicides, fungicides, and insecticides, where the aromatic ring and nitrile group contribute to biological activity. Its versatility in organic synthesis further extends to the preparation of heterocycles and polymers. For instance, it can serve as a starting point for the production of indoles and quinolines, both of which are structural motifs in biologically active molecules.

Industrial processes have continually refined the production of benzyl cyanide to meet commercial demand. Large-scale synthesis is typically achieved by the reaction of benzyl chloride with sodium cyanide or by catalytic ammoxidation of toluene derivatives, allowing efficient and economical routes to this valuable intermediate. With improvements in safety and handling of cyanides, its production has become more controlled, enabling consistent supply to fragrance, pharmaceutical, and agrochemical industries.

Today, benzyl cyanide remains an important compound that bridges fundamental organic chemistry with industrial application. Its discovery marked an early step in expanding the family of nitriles, and its enduring relevance comes from its adaptability in synthesis and its value as a precursor to a wide range of functional molecules. The compound exemplifies how a relatively simple structure can have far-reaching significance in multiple branches of applied chemistry.

References

1989. Brain lipid peroxidation and antioxidant protectant mechanisms following acute cyanide intoxication. Toxicology.
DOI: 10.1016/0300-483x(89)90129-7

2005. Solvent-free condensation of phenylacetonitrile and nonanenitrile with 4-methoxybenzaldehyde: optimization and mechanistic studies. Organic & Biomolecular Chemistry.
DOI: 10.1039/b418156e

2012. Biotransformation of Phenylacetonitrile to 2-Hydroxyphenylacetic Acid by Marine Fungi. Marine Biotechnology.
DOI: 10.1007/s10126-012-9464-1

2024. Synthesis of sustainable heterocyclic aryl sulfonamide derivatives: computational studies, molecular docking, and antibacterial assessment. Macromolecular Research.
DOI: 10.1007/s13233-024-00335-w