Benzoin

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Not to be confused with Benzoin resin.
Benzoin
Benzoin.png
Benzoin-3D-balls.png
Identifiers
CAS number 119-53-9 YesY
PubChem 8400
ChemSpider 8093 YesY
UNII L7J6A1NE81 YesY
KEGG C01408 YesY
ChEBI CHEBI:17682 YesY
ChEMBL CHEMBL190677 YesY
Jmol-3D images Image 1
Image 2
Properties
Molecular formula C14H12O2
Molar mass 212.24 g mol−1
Appearance off-white crystals
Density 1.31 g/cm3
Melting point 132–137 °C
Boiling point 344 °C
Solubility in water Slightly Soluble
Solubility in Chlorine Soluble
Hazards
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 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform 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
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Benzoin (/ˈbɛnz.ɨn/ 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 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[edit]

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[edit]

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]

Preparation[edit]

Benzoin is prepared from benzaldehyde via the benzoin condensation. [7]

References[edit]

  1. ^ Wöhler, Liebig; Liebig (1832). "Untersuchungen über das Radikal der Benzoesäure". Annalen der Pharmacie 3 (3): 249–282. doi:10.1002/jlac.18320030302. 
  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, Org. Synth. ; Coll. Vol. 1: 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. ^ Clarke, H. T.; Dreger.E. E. (1941), Benzil, Org. Synth. ; Coll. Vol. 1: 87 

External links[edit]

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