Benzoin (organic compound)

Benzoin (/ˈbɛnzoʊ.ɪn/ or /-ɔɪn/) is an organic compound with the formula PhCH(OH)C(O)Ph. It is a hydroxy ketone attached to two phenyl groups. It appears as off-white crystals, with a light camphor-like odor. Benzoin is synthesized from benzaldehyde in the benzoin condensation. It is chiral and it exists as a pair of enantiomers: (R)-benzoin and (S)-benzoin.

Not to be confused with Benzoin (resin).
Benzoin
Names
Preferred IUPAC name
2-Hydroxy-1,2-diphenylethan-1-one
Other names
2-Hydroxy-2-phenylacetophenone
2-Hydroxy-1,2-diphenylethanone
Desyl alcohol
Bitter almond oil camphor
Identifiers
3D model (JSmol)
3DMet
391839
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.938
KEGG
RTECS number
  • DI1590000
UNII
Properties
C14H12O2
Molar mass 212.248 g·mol−1
Appearance Off-white crystals
Density 1.31 g/cm3
Melting point 134 to 138 °C (273 to 280 °F; 407 to 411 K)
Boiling point 344 °C (651 °F; 617 K)
Slightly soluble
Solubility in ethanol Slightly soluble
Solubility in alcohol Soluble
Solubility in ether Slightly soluble
Solubility in chlorine Soluble
Hazards
H412
P273, P501
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
1
0
Lethal dose or concentration (LD, LC):
10.000 mg/kg
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Benzoin is not a constituent of benzoin resin obtained from the benzoin tree (Styrax) or tincture of benzoin. The main component in these natural products is benzoic acid.

History

Benzoin was first reported in 1832 by Justus von Liebig and Friedrich Woehler during their research on oil of bitter almond, which is benzaldehyde with traces of hydrocyanic acid.[1] The catalytic synthesis by the benzoin condensation was improved by Nikolay Zinin during his time with Liebig.[2][3]

Uses

The main uses of benzoin are as a precursor to benzil, which is a photoinitiator.[4] The conversion proceeds by organic oxidation using copper(II),[5] nitric acid, or oxone. In one study, this reaction is carried out with atmospheric oxygen and basic alumina in dichloromethane.[6]

Benzoin can be used in the preparation of several pharmaceutical drugs including oxaprozin, ditazole, and phenytoin.[7]

Preparation

Benzoin is prepared from benzaldehyde via the benzoin condensation.[8]

References
  1. Wöhler, Liebig; Liebig (1832). "Untersuchungen über das Radikal der Benzoesäure". Annalen der Pharmacie. 3 (3): 249–282. doi:10.1002/jlac.18320030302. hdl:2027/hvd.hxdg3f.
  2. N. Zinin (1839). "Beiträge zur Kenntniss einiger Verbindungen aus der Benzoylreihe". Annalen der Pharmacie. 31 (3): 329–332. doi:10.1002/jlac.18390310312.
  3. N. Zinin (1840). "Ueber einige Zersetzungsprodukte des Bittermandelöls". Annalen der Pharmacie. 34 (2): 186–192. doi:10.1002/jlac.18400340205.
  4. 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
  5. Clarke, H. T.; Dreger.E. E. (1941). "Benzil". Organic Syntheses.; Collective Volume, 1, p. 87
  6. Konstantinos Skobridis; Vassiliki Theodorou; Edwin Weber (2006). "A very simple and chemoselective air oxidation of benzoins to benzils using alumina". Arkivoc. 06-1798JP: 102–106.
  7. U.S. Patent 2,242,775
  8. Clarke, H. T.; Dreger.E. E. (1941). "Benzil". Organic Syntheses.; Collective Volume, 1, p. 87
  • Benzoin synthesis, Organic Syntheses, Coll. Vol. 1, p. 94 (1941); Vol. 1, p. 33 (1921)
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