5-Butylbenzotriazole
[CAS# 3663-24-9]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate
• Name: 5-Butylbenzotriazole
• Synonyms: 5-n-Butylbenzotriazole
• Molecular Formula: C₁₀H₁₃N₃
• Molecular Weight: 175.23
• CAS Registry Number: 3663-24-9
• SMILES: CCCCC1=CC2=NNN=C2C=C1

Properties

• Solubility: Very slightly soluble (0.96 g/L) (25 °C), Calc.^*
• Density: 1.136±0.06 g/cm³ (20 °C 760 Torr), Calc.^*
• Melting point: 75 °C (ligroine )^**
• Boiling point: 370.3±11.0 °C 760 mmHg (Calc.)^*
• Flash point: 174.1±12.2 °C (Calc.)^*
• Index of refraction: 1.611 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H315-H319-H335
• Safety Statements: P261-P305+P351+P338

Discovery and Applications

5-Butylbenzotriazole is an organic compound belonging to the class of substituted benzotriazoles, with the molecular formula C₁₀H₁₂N₃. It consists of a benzotriazole ring system in which a butyl group is attached at the 5-position of the aromatic ring. This modification enhances its hydrophobic character compared to the parent benzotriazole, while retaining the strong coordinating ability of the triazole moiety.

The history of 5-butylbenzotriazole is tied to the broader development of benzotriazoles, which were first studied in the early 20th century for their unique heteroaromatic stability and corrosion-inhibiting properties. As industrial needs grew for materials capable of resisting oxidation and degradation, substituted benzotriazoles, including the butyl derivative, were developed to improve solubility and surface affinity in protective coatings and lubricants.

The most prominent application of 5-butylbenzotriazole is as a corrosion inhibitor. It strongly adsorbs onto metal surfaces such as copper, brass, and their alloys, forming a protective molecular film that prevents oxidation and tarnishing. The introduction of the butyl group increases hydrophobic interactions, enhancing the durability of this protective layer in aqueous and harsh environments. For this reason, it is used in metalworking fluids, cooling systems, and industrial lubricants.

In addition to corrosion protection, 5-butylbenzotriazole finds application in polymer stabilization. When incorporated into plastics, coatings, and resins, it can act as a light stabilizer and antioxidant, preventing degradation caused by ultraviolet radiation and heat. This has made it valuable in coatings for automotive, aerospace, and marine industries where long-term durability is required.

The compound also has utility in specialty formulations such as antifreeze and hydraulic fluids, where it prevents corrosion of metallic components while maintaining chemical stability under operational conditions. Its chemical robustness and compatibility with various solvents and additives make it a versatile additive.

Synthesis of 5-butylbenzotriazole generally involves diazotization of butyl-substituted anilines followed by cyclization to form the benzotriazole ring system. Industrial methods focus on ensuring high purity and reproducibility, as small impurities can significantly affect performance in sensitive applications like electronics or coatings.

Overall, 5-butylbenzotriazole is an important member of the benzotriazole family, valued for its enhanced surface activity and corrosion resistance. Its discovery and application highlight the significance of structural modification in tailoring heteroaromatic compounds for industrial protection and stabilization roles.

References

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