Benzophenone

This article is about the basic chemical. For benzophenone-1 – benzophenone-12, see benzophenone-n.
Benzophenone
Names
IUPAC name
Diphenylmethanone
Other names
Phenyl ketone; Diphenyl ketone; Benzoylbenzene; Benzoylphenyl, diphenylmethanone
Identifiers
119-61-9 YesY
ChEBI CHEBI:41308 YesY
ChEMBL ChEMBL90039 YesY
ChemSpider 2991 YesY
DrugBank DB01878 YesY
Jmol 3D model Interactive image
KEGG C06354 YesY
PubChem 3102
UNII 701M4TTV9O YesY
Properties
C13H10O
Molar mass 182.22 g·mol−1
Appearance White solid
Odor Geranium-like[1]
Density 1.11 g/cm3[1]
Melting point 48.5 °C (119.3 °F; 321.6 K)[1]
Boiling point 305.4 °C (581.7 °F; 578.5 K)[1]
Insoluble[1]
Solubility in organic solvents 1 g/ 7.5 mL in ethanol[1]
1 g/ 6 mL in diethyl ether[1]
Hazards
Main hazards Harmful (XN)
Safety data sheet External MSDS by JT Baker
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
1
1
0
Flash point 110 °C (230 °F; 383 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY verify (what is YesYN ?)
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[2] 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.

Benzophenone can also be added to plastic packaging as a UV blocker to prevent photo-degradation of the packaging polymers or its contents. Its use allows manufacturers to package the product in clear glass or plastic (such as a PETE water bottle).[3] Without it, opaque or dark packaging would be required.

In biological applications, benzophenones have been used extensively as photophysical probes to identify and map peptide–protein interactions.[4]

Synthesis

Benzophenone is produced by the copper-catalyzed oxidation of diphenylmethane with air.[5]

A laboratory route involves the reaction of benzene with carbon tetrachloride followed by hydrolysis of the resulting diphenyldichloromethane.[6] It can also be prepared by Friedel-Crafts acylation of benzene with benzoyl chloride in the presence of a Lewis acid (e.g. aluminium chloride) catalyst.

Another route of synthesis is through a palladium(II)/oxometalate catalyst. This converts an alcohol to a ketone with two groups on each side. [7]

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

Main article: Air-free technique
Addition of a solution of benzophenone in THF to a vial containing THF, sodium metal, and a stir bar, yielding the deep blue benzophenone anion radical. Playback speed 4x original recording.

Alkali metals reduce benzophenone to the deeply blue colored radical anion, diphenylketyl:[8]

M + Ph2CO → M+Ph2CO·−

Generally sodium is used as the alkali metal. Although inferior in terms of safety and effectiveness relative to molecular sieves,[9] this ketyl is used in the purification of organic solvents, particularly ethers, because it reacts with water and oxygen to give non-volatile products.[10][11] The ketyl is soluble in the organic solvent being dried, so it accelerates the reaction of the sodium with water and oxygen. In comparison, sodium is insoluble, and its heterogeneous reaction is much slower. When excess alkali metal is present a second reduction may occur, resulting in a color transformation from deep blue to purple:[8]

M + M+Ph2CO·− → (M+)2(Ph2CO)2−

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 (see sunscreen controversy).[12] Its use in sunscreen has been known to cause coral bleaching via algae blooms, as it washes into the ocean from human use.[13]

Michler's ketone has dimethylamino substituents at each para position.

The high-strength polymer PEEK is prepared from derivatives of benzophenone.

Pharmacological activity

Benzophenone derivatives are known to be pharmacologically active. From a molecular chemistry point of view interaction of benzophenone with B-DNA has been demonstrated experimentally.[14] The interaction with DNA and the successive photo-induced energy transfer is at the base of the benzophenone activity as a DNA photosensitizers and may explain part of its therapeutic potentialities.

In 2014, benzophenones were named Contact Allergen of the Year by the American Contact Dermatitis Society.[15]

References

  1. 1 2 3 4 5 6 7 Merck Index, 11th edition, 1108
  2. ↑ Carroll, G.T.; Turro, N.J.; Koberstein, J.T. (2010). "Patterning dewetting in thin polymer films by spatially directed photocrosslinking". Journal of Colloid and Interface Science 351 (2): 556–560. doi:10.1016/j.jcis.2010.07.070.
  3. ↑ Dornath, Paul John (2010). "Analysis of Chemical Leaching from Common Consumer Plastic Bottles Under High Stress Conditions" (PDF). p. 32. Retrieved 26 February 2015.
  4. ↑ Dorman, Gyorgy; Prestwich, Glenn D. (1 May 1994). "Benzophenone Photophores in Biochemistry". Biochemistry 33 (19): 5661–5673. doi:10.1021/bi00185a001.
  5. ↑ 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
  6. ↑ Marvel, C. S.; Sperry, W. M. (1941). "Benzophenone". Org. Synth.; Coll. Vol. 1, p. 95
  7. ↑ Dornan, L.; Muldoon, M. A highly efficient palladium(ii)/polyoxometalate catalyst system for aerobic oxidation of alcohols. Catalysis Science Technology 2015, 5, 1428-1432.
  8. 1 2 Connelly, Neil; Geiger, William (March 28, 1996). "Chemical Redox Agents for Organometallic Chemistry". Chemical Reviews 96 (2): 877–910. doi:10.1021/cr940053x. PMID 11848774. Retrieved May 14, 2014.
  9. ↑ Williams, D. B. G., Lawton, M., "Drying of Organic Solvents: Quantitative Evaluation of the Efficiency of Several Desiccants", The Journal of Organic Chemistry 2010, vol. 75, 8351. doi: 10.1021/jo101589h
  10. ↑ W. L. F. Armarego and C. Chai (2003). Purification of laboratory chemicals. Oxford: Butterworth-Heinemann. ISBN 0-7506-7571-3.
  11. ↑ L. M. Harwood, C. J. Moody and J. M. Percy (1999). Experimental Organic Chemistry: Standard and Microscale. Oxford: Blackwell Science. ISBN 978-0-632-04819-9.
  12. ↑ 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. PMID 8405372.
  13. ↑ Downs, C. A.; Kramarsky-Winter, E.; Segal, R.; Fauth, J.; Knutson, S.; Bronstein, O.; Ciner, F. R.; Jeger, R.; Lichtenfeld, Y.; Woodley, C. M.; Pennington, P.; Cadenas, K.; Kushmaro, A.; Loya, Y. Toxicopathological Effects of the Sunscreen UV Filter, Oxybenzone (Benzophenone-3), on Coral Planulae and Cultured Primary Cells and Its Environmental Contamination in Hawaii and the U.S. Virgin Islands. Arch. Environ. Contam. Toxicol. 2015, Ahead of Print.
  14. ↑ Consuelo Cuquerella, M.; Lhiaubet-Vallet, V.; Cadet, J.; Miranda, M. A. (2012). "Benzophenone Photosensitized DNA Damage". Acc. Chem. Res. 45: 1558–1570. doi:10.1021/ar300054e.
  15. ↑ http://www.skinandallergynews.com/single-view/benzophenones-named-2014-contact-allergen-of-the-year/cb086f7e351cccbcfd9dbf5fa806762b.html

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