Synthesis of benzotriazole from o-phenylenediamine
BP406P Medicinal Chemistry I Practical
AIM:
To synthesize and submit benzotriazole from o-phenylene diamine and report its percentage yield.
REFERENCE:
- Practical medicinal chemistry by Dr. Devala Rao, page no:35.
- Comprehensive practical organic chemistry by V.K.Ahluwalia and Renu Aggarval, page no:121.
CHEMICAL REQUIREMENTS:
o-phenylenediamine, glacial acetic acid, sodium nitrite
PRINCIPLE:
The sodium nitrite reacts with glacial acetic acid and liberates nitrous acid. The o-phenylene diamine reacts with nitrous acid and produces a diazonium ion. When the structure and stereochemistry of diazonium ion are stable, intramolecular nitrogen coupling occurs and forms benzotriazole directly.
CALCULATIONS
The molecular weight of o-phenylene diamine = Molecular weight of benzotriazole =
—- g of o-phenylene diamine gives —- g of benzotriazole
1g of o-phenylene diamine =
—- g of o-phenylene diamine =
Theoretical yield =
Practical yield =
Percentage yield =
PROCEDURE:
Time needed: 2 hours and 30 minutes
Synthesis of benzotriazole
- Dissolve o-phenylenediamine
Dissolve 1.3g of o-phenylenediamine in a mixture of 1.5 ml of glacial acetic acid and 5 ml of water in a beaker. Stir until the solid dissolves, warm gently if necessary.
- Cooling of solution
Cool the solution to 15°C
- Addition of sodium nitrite
Add a solution of 2g of sodium nitrite in 2 ml of water. The reaction mixture becomes warm within 2-3 minutes and reaches a temperature of about 85°C and then begins to cool.
- Change of color
Color changes from deep red to pale brown. Continue stirring for 15 minutes till the temperature fall about 35-40°C
- Chill in an ice bath
Thoroughly chill in an ice bath for 30 minutes
- Filter and wash the product
Filter the product and wash it with cold water
Recrystallization:
Dissolve the solid in about 130 ml of boiling water, add decolorizing charcoal, filter, and allow the filtrate to cool to about 50 °C before adding a few crystals of the synthesized product (benzotriazole) which have been retained for seeding. Allow the mixture to attain room temperature slowly (to avoid separation of the material as oil) and then thoroughly chill in ice and collect the benzotriazole which separates as pale straw-colored needles, m.p. 99-100 °C. A second crop may be obtained by concentrating the filtrate. The yield is about 8 g (67%). The benzotriazole crystallizes much more readily from benzene (55 ml) but the material is still slightly coloured. A pure white product can be obtained by sublimation at 90-95 °C at 0.2 mmHg.
USE:
Used in the bulk drug industry as an important intermediate compound.
It is the basic nucleus present in anthelmintic drugs like mebendazole, thiabendazole etc.
REPORT:
Benzotriazole was prepared and submitted. The percentage yield was found to be ———
Frequently Asked Questions (FAQs)
Benzotriazole is a versatile compound commonly used in various industrial applications, including corrosion inhibition, as a stabilizer in the synthesis of dyes and pharmaceuticals, and as an antifreeze agent. Here are some frequently asked questions to help you understand the synthesis of benzotriazole:
Benzotriazole is a heterocyclic compound with the molecular formula C6H5N3. It consists of a triazole ring fused to a benzene ring. It is a colorless solid with various applications due to its unique properties.
One of the common methods for synthesizing benzotriazole is the cyclization of o-phenylenediamine with sodium nitrite in the presence of hydrochloric acid. This reaction forms the benzotriazole ring.
The synthesis involves the diazotization of o-phenylenediamine to form a diazonium salt, which then undergoes a cyclization reaction in the presence of acid to form the benzotriazole ring.
The starting materials typically include o-phenylenediamine and sodium nitrite. Hydrochloric acid is used as a catalyst for the reaction.
The synthesis is typically carried out at low temperatures and under acidic conditions. The reaction mixture is maintained at a specific pH range to facilitate the diazotization and cyclization reactions.
Benzotriazole is used as a corrosion inhibitor for metals, especially in cooling and heating systems. It is also employed as a stabilizer in the synthesis of dyes, pharmaceuticals, and photographic chemicals. Additionally, it finds use as an antifreeze agent in the automotive industry.
Yes, there are alternative methods for benzotriazole synthesis, including the reaction of o-phenylenediamine with nitrous acid and the cyclization of o-aminobenzonitrile.
Benzotriazole is stable, sparingly soluble in water, and has a relatively high melting point. It exhibits good thermal stability and is often used as a stabilizer due to its ability to form protective layers on metal surfaces.
Benzotriazole forms a thin protective layer on metal surfaces, preventing them from coming into contact with corrosive agents. It is commonly used in cooling and heating systems, as well as in aviation and automotive industries to protect metal components.
Yes, benzotriazole can be used as a building block in the synthesis of pharmaceutical compounds. Its unique structure makes it useful in creating molecules with specific properties.
Benzotriazole is generally considered to have low toxicity. However, like any chemical compound, it should be handled with care, and proper safety precautions should be followed during synthesis and use.
Yes, benzotriazole can be synthesized on a larger scale for industrial applications. The synthesis process can be scaled up while adhering to safety and environmental regulations.
Research related to benzotriazole includes the development of more efficient and sustainable synthesis methods, exploring its applications in emerging technologies, and studying its behavior in different environments.
Purity of synthesized benzotriazole is typically ensured through techniques such as chromatography, spectroscopy (such as NMR and IR), and analytical methods to confirm its chemical structure and composition.
Yes, benzotriazole is commercially available from chemical suppliers, making it accessible for various industrial and research purposes.
Understanding the synthesis and applications of benzotriazole is important for industries and research fields that utilize its unique properties for various purposes, ranging from corrosion inhibition to pharmaceutical synthesis and beyond.
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