What Is Benzil?
Benzil is an organic compound appearing as a yellow crystalline or crystalline powder, often used in the field of fragrances due to its sweet pea-like odor. Its chemical formula is C6H5COCOC6H5, and it has a molecular weight of 210.23, with a CAS registration number of 134-81-6.
Uses of Benzil
Benzil is utilized as a photosensitizer in photo-curing resins for printing plate making. It’s also used as an intermediate in pharmaceuticals, an initiator of polymerization reactions, and contributes to the improvement of photographic sensitivity.
Properties of Benzil
This aromatic diketone has a melting point of 94-97°C, a boiling point of 346-348°C, and a flash point of 180°C. It is soluble in ethanol and ether but insoluble in water, with a density of 1.23 g/cm3.
Structure of Benzil
Benzil is also known as dibenzoyl, bibenzoyl, or diphenylglyoxal. Its structure consists of two benzene rings connected by a carbonyl group on each side.
Other Information on Benzil
1. Synthesis of Benzil
Benzil can be synthesized from benzaldehyde, which is condensed to benzoin by benzoin condensation, and then oxidized using nitric acid or copper sulfate.
2. Reaction of Benzil
When exposed to a strong base, benzil undergoes a rearrangement to form benzilic acid, known as the benzilic acid rearrangement.
3. Benzilic Acid Rearrangement
This rearrangement reaction, demonstrated by Justus Freiherr von Liebig, involves the 1,2-rearrangement of a phenyl group in benzil when treated with potassium hydroxide, resulting in benzilic acid.
4. Mechanism of Benzilic Acid Rearrangement
The reaction starts with the addition of a hydroxide anion to the carbonyl group, followed by a concerted 1,2-rearrangement and a subsequent proton transfer to yield benzilic acid.
5. Related Compounds of Benzil
Benzilic acid can be produced by heating a mixture of potassium hydroxide and alcohol with benzil. It’s important to note that the benzyl group (C6H5CH2-) is structurally different from benzil, despite the similarity in names.