Benzil

Names
Preferred IUPAC name

Diphenylethanedione

Systematic IUPAC name

1,2-Diphenylethane-1,2-dione

Other names

Diphenylethane-1,2-dione
Benzil
Dibenzoyl
Bibenzoyl
Diphenylglyoxal

Identifiers

CAS Number

* 134-81-6 Y

3D model (JSmol)

* Interactive image
* Interactive image

Beilstein Reference

| 608047
ChEBI |

* CHEBI:51507 Y

ChEMBL |

* ChEMBL189886 Y

ChemSpider |

* 8329 Y

EC Number |

* 205-157-0

PubChem CID

* 8651

RTECS number |

* DD1925000

UNII |

* S85X61172J Y

InChI

* InChI=1S/C14H10O2/c15-13(11-7-3-1-4-8-11)14(16)12-9-5-2-6-10-12/h1-10H Y

Key: WURBFLDFSFBTLW-UHFFFAOYSA-N Y

* InChI=1/C14H10O2/c15-13(11-7-3-1-4-8-11)14(16)12-9-5-2-6-10-12/h1-10H

Key: WURBFLDFSFBTLW-UHFFFAOYAZ

SMILES

* O=C(C(=O)c1ccccc1)c2ccccc2

* c1ccccc1C(=O)C(=O)c2ccccc2

Properties

Chemical formula

| C14H10O2
Molar mass | 210.232 g·mol−1
Appearance  | yellow crystalline powder
Density | 1.23 g/cm3, solid (1.255 g/cm3, x-ray)
Melting point |  94.0 to 96.0 °C; 201.2 to 204.8 °F; 367.1 to 369.2 K
Boiling point |  346.0 to 348.0 °C; 654.8 to 658.4 °F; 619.1 to 621.1 K

Solubility in water

| insoluble
Solubility in ethanol | soluble
Solubility in diethyl ether | soluble
Solubility in benzene | soluble

Magnetic susceptibility (χ)

| -118.6·10−6 cm3/mol
Structure

Crystal structure

| P31,221[1]

Dipole moment

| 3.8 D[2]
Hazards
Main hazards | Irritant
GHS pictograms |
GHS Signal word | Warning

GHS hazard statements

| H315, H319, H335

GHS precautionary statements

| P261, P264, P271, P280, P302+352, P304+340, P305+351+338, P312, P321, P332+313, P337+313, P362, P403+233, P405, P501
NFPA 704 (fire diamond)  |

Lethal dose or concentration (LD, LC):

LD50 (median dose)

| >3 g/kg (mouse, oral)[3]
Related compounds

Related diketones

| diacetyl

Related compounds

| benzophenone
glyoxal
bibenzil

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Y verify (what is YN ?)
Infobox references

Benzil (i.e. Bz2, systematically known as 1,2-diphenylethane-1,2-dione) is the organic compound with the formula (C6H5CO)2, generally abbreviated (PhCO)2. This yellow solid is one of the most common diketones. Its main use is as a photoinitiator in polymer chemistry.[4]

## Contents

* 1 Structure
* 2 Applications
* 2.1 Reactions
* 3 Preparation
* 4 References

## Structure

The compound's most noteworthy structural feature is the long carbon-carbon bond of 1.54 Å, which indicates the absence of pi-bonding between the two carbonyl centers. The PhCO centers are planar, but the pair of benzoyl groups are twisted with respect to the other with a dihedral angle of 117°.[5] In less hindered analogues (glyoxal, biacetyl, oxalic acid derivatives), the (RCO)2 group adopts a planar, anti-conformation.

## Applications

Most benzil can be used as a photoinitiator in the free-radical curing of polymer networks. It absorbs ultraviolet radiation at a wavelength of 260 nm, leading to decomposition with formation of free-radical species and formation of cross-links within the material. However, it is a relatively poor photoinitiator, and is seldom used. It undergoes photobleaching, which allows the curing light to reach deeper layers of the material on longer exposure.[6] Acetal derivatives, such as 2,2-dimethoxy-2-phenylacetophenone, have better properties for this application.[6]

Benzil is a potent inhibitor of human carboxylesterases, enzymes involved in the hydrolysis of carboxylesters and many clinically used drugs.[7]

### Reactions

Benzil is a standard building block in organic synthesis. It condenses with amines to give diketimine ligands. A classic organic reaction of benzil is the benzilic acid rearrangement, in which base catalyses the conversion of benzil to benzilic acid. This reactivity is exploited in the preparation of the drug phenytoin. Benzil also reacts with 1,3-diphenylacetone in an aldol condensation to give tetraphenylcyclopentadienone.

## Preparation

Benzil is prepared from benzoin, for example with copper(II) acetate:[8]

PhC(O)CH(OH)Ph + 2 Cu2+ → PhC(O)C(O)Ph + 2 H+ \+ 2 Cu+

Other suitable oxidizing agents such as nitric acid (HNO3) are used routinely.

Iron(III) chloride (FeCl3) can be used as an inexpensive catalyst for this chemical conversion.[9]

## References

1. ↑ Acta Crystallogr. B43 398 (1987)
2. ↑ Spectrochim. Acta A60 (8-9) 1805 (2004)
3. ↑ "Benzil" (in en). https://pubchem.ncbi.nlm.nih.gov/compound/Benzil#section=Toxicity.
4. ↑ Hardo Siegel, Manfred Eggersdorfer "Ketones" in Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, 2002 by Wiley-VCH, Weinheim. doi:10.1002/14356007.a15_077
5. ↑ Quang. Shen, Kolbjoern. Hagen "Gas-phase molecular structure and conformation of benzil as determined by electron diffraction" J. Phys. Chem., 1987, 91 (6), pp 1357–1360. doi:10.1021/j100290a017.
6. ↑ 6.0 6.1 Green, W. Arthur (2010-04-22). Industrial Photoinitiators: A Technical Guide. p. 31. ISBN 9781439827468. https://books.google.com/books?id=b1jRBQAAQBAJ&dq=benzil+photoinitiator&pg=PA31. Retrieved 2022-05-21.
7. ↑ Wadkins. R. M. et al "Identification and characterization of novel benzil (diphenylethane-1,2-dione) analogues as inhibitors of mammalian carboxylesterases. J. Med. Chem., 2005 48 pp 2906–15.
8. ↑ Depreux, P.; Bethegnies, G.; Marcincal-Lefebvre, A. (1988). "Synthesis of benzil from benzoin with copper(II) acetate". Journal of Chemical Education 65 (6): 553. doi:10.1021/ed065p553. Bibcode: 1988JChEd..65..553D.
9. ↑ Bi, Xiaoxin; Wu, Lintao; Yan, Chaoguo; Jing, Xiaobi; Zhu, Hongxiang (2011). "One-Pot Synthesis Benzils from Aldehydes Via Nhc-Catalyzed Benzoin Dimerization Under Metal-Free Conditions in Water". Journal of the Chilean Chemical Society 56 (2): 663. doi:10.4067/S0717-97072011000200008.

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*[CID]: Compound ID
*[H315]: Causes skin irritation
*[H319]: Causes serious eye irritation
*[H335]: May cause respiratory irritation
*[P261]: Avoid breathing dust/fume/gas/mist/vapours/spray
*[P264]: Wash … thoroughly after handling
*[P271]: Use only outdoors or in a well-ventilated area
*[P280]: Wear protective gloves/protective clothing/eye protection/face protection
*[P302+352]: IF ON SKIN: Wash with soap and water
*[P304+340]: IF INHALED: Remove victim to fresh air and keep at rest in a position comfortable for breathing
*[P305+351+338]: IF IN EYES: Rinse continuously with water for several minutes. Remove contact lenses if present and easy to do – continue rinsing
*[P312]: Call a POISON CENTER or doctor/physician if you feel unwell
*[P321]: Specific treatment (see … on this label)
*[P332+313]: If skin irritation occurs: Get medical advice/attention
*[P337+313]: Get medical advice/attention
*[P362]: Take off contaminated clothing and wash before reuse
*[P403+233]: Store in a well ventilated place. Keep container tightly closed
*[P405]: Store locked up
*[P501]: Dispose of contents/container to …