Description
Benzil (134-81-6) also known as 1,2-diphenylethane-1,2-dione is an organic compound with the molecular formula (C6H5CO)2. The compound belongs to the group of organic compounds known as stilbenes which contains a 1,2-diphenylethylene moiety. Benzyl is yellow in color and is one of the most common diketones.
Structure
The most noticeable feature in Benzil’s structure is the long carbon-carbon bond of 1.54 Å, which shows there is no pi-bonding between the two carbonyl centers. Although the par of benzoyl groups are twisted with respect to the other with a dihedral angler of 117o, the PhCO are planar.
Preparation
Benzyl is synthesized from benzoin, for instance with copper (II) acetate.
PhC(O)CH(OH)Ph + 2 Cu2+ → PhC(O)C(O)Ph + 2 H+ + 2 Cu+
Applications
Benzil is utilized as an intermediate in pharmaceuticals and UV curing resin photosensitizer. Benzyl is mostly used in the free-radical curing of polymer networks. Benzyl is decomposed by ultraviolet radiation that generates free-radical species within the material, leading to the formation of cross-links. It is normally employed as a photoinitiator in polymer chemistry. In addition, Benzil is a potent inhibitor of human carboxylesterases, which are enzymes involved in the hydrolysis of many drugs used clinically as well as carboxylesters. It is also used in the synthesis of diketimines by reaction with amines. Benzyl is also used as an intermediate in the famous benil-benzilic acid arrangement. Further, it reacts with 1,3-diphenylacetone to get tetraphenylcyclopentadienone.
Chemical Properties
yellow crystals or powder
Uses
Benzil is used as a pharmaceutical intermediate and uv curing resin photosensitizer. In polymer chemistry, it is used as a photoinitiator. Further, it serves as a potent inhibitor of human carboxylesterases. It is used in the preparation of diketimines by reacting with amines. It is also involved in the famous benil-benzilic acid rearrangement. In addition this, it reacts with 1,3-diphenylacetone to get tetraphenylcyclopentadienone.
Uses
Organic synthesis; insecticide.
Definition
A reaction in which benzil (1,2- diphenylethan-1,2-dione) is treated with hydroxide and then with acid to give benzilic acid (2-hydroxy-2,2-diphenylethanoic acid):
C
6H
5.CO.CO.C
6H
5→
(C
6H
5)
2C(OH).COOH
The reaction, which involves migration of a phenyl group (C
6H
5-) from one carbon atom to another, was the first rearrangement reaction to be described (by Justus von Liebig in 1828).
Definition
ChEBI: An alpha-diketone that is ethane-1,2-dione substituted by phenyl groups at positions 1 and 2 respectively.
Safety Profile
Low toxicity by ingestion. An eyeirritant. Combustible. When heated to decomposition itemits acrid smoke and irritating fumes.
Safety
Potential Acute Health Effects: Very hazardous in case of skin contact (irritant), of eye contact (irritant). Hazardous in case of ingestion, of inhalation.
The substance is toxic to lungs, mucous membranes. Repeated or prolonged exposure to the substance can produce target organs damage. Eye Contact: Check for and remove any contact lenses.
Fine dust dispersed in air may ignite. Dust can form an explosive mixture in air. Thermal decomposition can lead to release of irritating gases and vapors. Keep product and empty container away from heat and sources of ignition.
Solubility in organics
Soluble in ethanol (50 mg/ml), chloroform, ether, and ethyl acetate. Insoluble in water.
Purification Methods
Crystallise benzil from *benzene after washing with alkali. (Crystallisation from EtOH did not free benzil from material reacting with alkali.) [Hine & Howarth J Am Chem Soc 80 2274 1958.] It has also been crystallised from CCl4, diethyl ether or EtOH [Inoue et al. J Chem Soc, Faraday Trans 1 82 523 1986]. [Beilstein 7 IV 2502.]
