May 30, 2024

2,3-diphenyl quinoxaline synthesis from o-phenylenediamine

2,3-diphenyl quinoxaline synthesis from o-phenylenediamine


To synthesize and submit 2,3-diphenyl quinoxaline from o-phenylenediamine and report its percentage yield.


  1. Vogels textbook of practical organic chemistry,5th edition, page no:90.
  2. Comprehensive practical organic chemistry by V.K.Ahluwalia and Renu Aggarwal, page no:123.


o-phenylenediamine, benzil, rectified spirit.


Quinoxalines are a type of heterocyclic compounds. They are also known as benzopyrazines.

Generally quinoxaline is formed by the condensation of o-phenylenediamine with diketones. Here 2,3-diphenyl quinoxaline is prepared by treating o-phenylenediamine with benzil


Add a solution of 1.1g of o-phenylenediamine in 8ml rectified spirit to a warm solution of 2.1g of benzil in 8ml rectified spirit. Warm the mixture for 30 minutes in a water bath. Add water dropwise until slight cloudiness persists. Cool the solution and filter the product.


Quinoxaline derivatives are used as antimicrobial agents like levomycin. They are also used in dyes.


2,3-diphenyl quinoxaline was prepared and submitted. The percentage yield was found to be ———

Frequently Asked Questions about Diphenyl Quinoxaline Synthesis

What are the different methods for synthesizing diphenyl quinoxaline?

The most common methods include:
Condensation of o-phenylenediamine with benzil: This classical approach involves reacting orthophenylene diamine and benzil in a suitable solvent like ethanol or acetic acid under reflux conditions. Variations include microwave irradiation or ultrasonic irradiation for faster reaction times.
Cyclization of N-phenyl-o-phenylenediamine: This method involves the intramolecular cyclization of N-phenyl-o-phenylenediamine using various catalysts or reagents like acids, bases, or transition metals.
Dehydrogenation of N,N’-diphenyl-1,2-diaminobenzene: This approach converts the precursor molecule through oxidation using catalysts like palladium or copper.

What are the factors affecting the yield and purity of diphenyl quinoxaline?

Reaction temperature and time: Optimizing these parameters can significantly impact the yield and purity. High temperatures may lead to decomposition, while insufficient time could leave unreacted starting materials.
Solvent selection: Choosing the right solvent can influence the solubility of reagents, reaction rate, and product formation. Polar solvents like ethanol or acetic acid are commonly used.
Catalyst selection: When using catalysts, their type and amount heavily influence the reaction efficiency and product selectivity.
Purification methods: Proper workup and purification techniques are crucial to obtain clean diphenyl quinoxaline free of impurities. Recrystallization or column chromatography are commonly employed.

What are the important safety considerations when synthesizing diphenyl quinoxaline?

Some reagents used, like benzil, may be irritating to the skin and eyes. Wear appropriate personal protective equipment like gloves and safety glasses.
Work in a well-ventilated fume hood as some solvents and reactions may release harmful vapors.
Follow proper waste disposal procedures for spent solvents and reaction residues.