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Benzoin (/ˈbɛnz.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.

Benzoin
Benzoin.svg
Benzoin-3D-balls.png
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)
ChEBI
ChemSpider
ECHA InfoCard 100.003.938
KEGG
UNII
Properties
C14H12O2
Molar mass 212.25 g·mol−1
Appearance off-white crystals
Density 1.31 g/cm3
Melting point 132 to 137 °C (270 to 279 °F; 405 to 410 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
R-phrases (outdated) R36/38 [1]
NFPA 704
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 codeNFPA 704 four-colored diamond
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.

Contents

HistoryEdit

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.[2] The catalytic synthesis by the benzoin condensation was improved by Nikolay Zinin during his time with Liebig.[3][4]

UsesEdit

The main uses of benzoin are as a precursor to benzil, which is a photoinitiator.[5] The conversion proceeds by organic oxidation using copper(II),[6] nitric acid, or oxone. In one study, this reaction is carried out with atmospheric oxygen and basic alumina in dichloromethane.[7]

Hikers and Athletes use benzoin tincture to accelerate the formation of calluses in the feet, which will prevent the painful blisters.

PreparationEdit

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

ReferencesEdit

  1. ^ "Benzoin" (PDF). FischerSci. FischerSci. 
  2. ^ Wöhler, Liebig; Liebig (1832). "Untersuchungen über das Radikal der Benzoesäure". Annalen der Pharmacie. 3 (3): 249–282. doi:10.1002/jlac.18320030302. 
  3. ^ N. Zinin (1839). "Beiträge zur Kenntniss einiger Verbindungen aus der Benzoylreihe". Annalen der Pharmacie. 31 (3): 329–332. doi:10.1002/jlac.18390310312. 
  4. ^ N. Zinin (1840). "Ueber einige Zersetzungsprodukte des Bittermandelöls". Annalen der Pharmacie. 34 (2): 186–192. doi:10.1002/jlac.18400340205. 
  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. ^ Clarke, H. T.; Dreger.E. E. (1941). "Benzil". Org. Synth. ; Coll. Vol., 1, p. 87 
  7. ^ 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. 
  8. ^ Clarke, H. T.; Dreger.E. E. (1941). "Benzil". Org. Synth. ; Coll. Vol., 1, p. 87 

External linksEdit

  • Benzoin synthesis, Organic Syntheses, Coll. Vol. 1, p. 94 (1941); Vol. 1, p. 33 (1921)