benzophenone

Benzophenone
IUPAC name	1,1-diphenylmethanone
Other names	Diphenylmethanone; phenyl ketone; diphenyl ketone; benzoylbenzene
Identifiers
CAS number	119-61-9 Y
PubChem	3102
SMILES	O=C(c1ccccc1)c2ccccc2
InChI	1/C13H10O/c14-13(11-7-3-1-4-8-11)12-9-5-2-6-10-12/h1-10H
InChI key	RWCCWEUUXYIKHB-UHFFFAOYAX
ChemSpider ID	2991
Properties
Molecular formula	C13H10O
Molar mass	182.217 g/mol
Appearance	White solid
Density	1.11 g/cm3, solid
Melting point	47.9 °C
Boiling point	305.4 °C
Solubility in water	Insoluble
Solubility	Benzene, THF, ethanol, propylene glycol
Hazards
MSDS	External MSDS by JT Baker
Main hazards	Harmful (XN)
NFPA 704	1 3 0
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Benzophenone is the organic compound with the formula (C₆H₅)₂CO, generally abbreviated Ph₂CO. Benzophenone is a widely used building block in organic chemistry, being the parent diarylketone.

Uses

Benzophenone can be used as a photo initiator in UV-curing applications such as inks, imaging, and clear coatings in the printing industry. Benzophenone prevents ultraviolet (UV) light from damaging scents and colors in products such as perfumes and soaps. It can also be added to the plastic packaging as a UV blocker. Its use allows manufacturers to package the product in clear glass or plastic. Without it, opaque or dark packaging would be required.

Synthesis

Benzophenone can be prepared by the reaction of benzene with carbon tetrachloride followed by hydrolysis of the resulting diphenyldichloromethane,^[1] or by Friedel-Crafts acylation of benzene with benzoyl chloride in the presence of a Lewis acid (e.g. aluminium chloride) catalyst. The industrial synthesis relies on the copper-catalyzed oxidation of diphenylmethane with air.^[2]

Organic chemistry

Benzophenone is a common photosensitizer in photochemistry. It crosses from the S₁ state into the triplet state with nearly 100% yield. The resulting diradical will abstract a hydrogen atom from a suitable hydrogen donor to form a ketyl radical.

Benzophenone radical anion

Sodium reduces benzophenone to the deeply colored radical anion, diphenylketyl:

Na + Ph₂CO → Na⁺ + Ph₂CO⁻

This ketyl is used in the purification of hydrocarbon solvents, because it reacts with water and oxygen to give colorless non-volatile products:^[3]

Na + H₂O → NaOH + 0.5H₂

Commercially significant derivatives

Substituted benzophenones such as oxybenzone and dioxybenzone are used in some sunscreens. The use of benzophenone-derivatives which structurally resemble a strong photosensitizer has been strongly criticized.^[4] (see sunscreen controversy)

p,p'-bis(N,N-dimethylamino)benzophenone or Michler's ketone has dimethylamino substituents at each para position.

The high-strength polymers PEEK, polyetherether ketones, are prepared from derivatives of benzophenone.

See also

• Sunscreen for the substituted compounds benzophenone-1 – benzophenone-12

References

Footnotes

• Merck Index, 11th Edition, 1108.

Notations

1. ^ Marvel, C. S.; Sperry, W. M. (1941), "Benzophenone", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0095 ; Coll. Vol. 1: 95 
2. ^ Hardo Siegel, Manfred Eggersdorfer “Ketones” in Ullmann’s Encyclopedia of Industrial Chemistry Wiley-VCH, 2002 by Wiley-VCH, Wienheim. DOI: 10.1002/14356007.a15_077
3. ^ W. L. F. Armarego and C. Chai (2003). Purification of laboratory chemicals. Butterworth-Heinemann. ISBN 0750675713. 
4. ^ Knowland, John; McKenzie, Edward A.; McHugh, Peter J.; Cridland, Nigel A. (1993). "Sunlight-induced mutagenicity of a common sunscreen ingredient". FEBS Letters 324(3): 309–313. doi:10.1016/0014-5793(93)80141-G. 

Gallery

A bottle of benzophenone by Lancaster.	Toluene is refluxed with sodium and benzophenone to produce dry, oxygen-free toluene.	The mixture is still not blue yet indicating that the reaction is not complete.	The intense blue coloration due to the benzophenone ketyl radical shows that the toluene is considered free of air and moisture.
After the toluene has been thoroughly dried by the sodium and benzophenone, it is distilled at atmospheric pressure under a slight positive pressure of nitrogen to prevent contamination by air into the receiving Schlenk flask.