4-Cyano-4'-pentylbiphenyl
[CAS# 40817-08-1]

Identification

• Classification: Chemical reagent >> Organic reagent >> Cyanide/nitrile
• Name: 4-Cyano-4'-pentylbiphenyl
• Synonyms: 4-(4'-Pentylphenyl)benzonitrile; 4'-Pentyl[1,1'-biphenyl]-4-carbonitrile
• Molecular Formula: C₁₈H₁₉N
• Molecular Weight: 249.35
• CAS Registry Number: 40817-08-1
• EC Number: 255-093-2
• SMILES: CCCCCC1=CC=C(C=C1)C2=CC=C(C=C2)C#N

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*, 1.008 g/mL (Expl.)
• Melting point: 22 - 23 °C (Expl.)
• Boiling point: 361.6 °C 760 mmHg (Calc.)^*, 416.8 - 432.9 °C (Expl.)
• Flash point: 193.5±17.3 °C (Calc.)^*
• Index of refraction: 1.569 (Calc.)^*, 1.532 (Expl.)

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

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H312-H315-H317-H319-H332-H335
• Safety Statements: P261-P264-P264+P265-P270-P271-P272-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P317-P319-P321-P330-P332+P317-P333+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H302
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Skin irritation	Skin Irrit.	2	H315
Skin sensitization	Skin Sens.	1	H317

Discovery and Applications

4-Cyano-4'-pentylbiphenyl is an aromatic compound consisting of a biphenyl core substituted with a cyano group at the 4-position of one phenyl ring and a pentyl chain at the 4'-position of the other phenyl ring. Its molecular formula is C₁₇H₁₇N, with a molecular weight of approximately 235.33 g/mol. The rigid biphenyl structure provides planarity and π-conjugation, while the cyano group is strongly electron-withdrawing and the pentyl chain is lipophilic, creating a molecule with both polar and nonpolar characteristics.

The compound is typically synthesized through cross-coupling reactions, such as the Suzuki–Miyaura reaction, between a 4-cyanophenyl halide and a 4-pentylphenyl boronic acid. Palladium catalysts are commonly employed to achieve efficient coupling under mild conditions, providing the desired substitution pattern on the biphenyl framework. Alternative methods include Ullmann-type couplings or other metal-mediated strategies, although Suzuki coupling is preferred for its high regioselectivity and functional group tolerance.

Chemically, the cyano group imparts electron-withdrawing properties, activating the aromatic ring toward nucleophilic substitution at ortho and para positions relative to the cyano group. It can also undergo transformations such as reduction to amines, hydrolysis to carboxylic acids, or conversion to heterocycles under appropriate conditions. The pentyl chain contributes steric bulk and hydrophobic character, influencing solubility, molecular packing, and intermolecular interactions. The biphenyl core is chemically stable and capable of π–π stacking interactions, which is important in applications that rely on ordered molecular alignment.

4-Cyano-4'-pentylbiphenyl is typically a solid at room temperature and shows solubility in organic solvents such as chloroform, toluene, and tetrahydrofuran. Its stability is good under ambient conditions, but care should be taken to avoid strong oxidizing agents that could attack the biphenyl core or the cyano group. The combination of polar and nonpolar substituents influences both the solubility and the thermal properties of the compound, which is particularly relevant for its use in liquid crystal applications.

In practical applications, 4-cyano-4'-pentylbiphenyl is widely used in the field of liquid crystal research as a mesogenic compound. The combination of a rigid biphenyl core, a terminal cyano group, and a flexible alkyl chain promotes nematic phase formation, thermal stability, and controlled molecular orientation. It also serves as a building block for designing liquid crystalline materials with tailored dielectric, optical, and alignment properties. Beyond liquid crystals, the compound can be employed as an intermediate in organic synthesis to construct functionalized biphenyl derivatives for material science and molecular electronics.

Overall, 4-cyano-4'-pentylbiphenyl combines a rigid π-conjugated core, a polar electron-withdrawing group, and a hydrophobic alkyl chain, making it a versatile compound in both synthetic chemistry and material applications. Its structural features enable selective chemical modifications and provide desirable physical and electronic properties for use in advanced molecular and liquid crystalline systems.

References

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DOI: 10.1038/s41524-023-01189-z

2024. Microfluidic flowmeter based on a liquid crystal-filled nested capillary. Communications Engineering, 3.
DOI: 10.1038/s44172-024-00202-7

2024. Liquid Crystal Purity Detection Using Surface Plasmon Resonance Phenomena. Plasmonics.
DOI: 10.1007/s11468-024-02313-5