Benzoin

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Structural formula
Structural formula of benzoin
Simplified structural formula without specifying the stereochemistry
General
Surname Benzoin
other names
  • 2-hydroxy-1,2-diphenylethanone ( IUPAC )
  • α -hydroxy- α -phenylacetophenone
Molecular formula C 14 H 12 O 2
Brief description

white to yellowish solid with an aromatic odor

External identifiers / databases
CAS number
  • 119-53-9 (racemate)
  • 5928-66-5 [( R ) -enantiomer]
  • 5928-67-6 [( S -) enantiomer]
EC number 204-331-3
ECHA InfoCard 100.003.938
PubChem 8400
ChemSpider 8093
DrugBank DB14020
Wikidata Q426819
properties
Molar mass 212.25 g mol −1
Physical state

firmly

density

1.31 g cm −3

Melting point
  • 132-134 ° C (racemates)
  • 135-137 ° C [( R ) - and ( S ) -enantiomer]
boiling point

344 ° C

Vapor pressure

1.3 h Pa (136 ° C)

solubility
  • very bad in water (0.3 g l −1 at 25 ° C)
  • soluble in acetone and warm ethanol
safety instructions
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
Toxicological data
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Benzoin is the simplest aromatic hydroxyketone . It occurs naturally in some plants, e.g. B. in bitter almond oil . Benzoin is a chiral substance that is commercially available in both the racemic and the two enantiomerically pure forms.

history

The word "benzoin" already existed in the 17th century and, like benzoin, probably referred to the resin of Indonesian storax trees . Benzoin was first synthesized in 1832 by Justus von Liebig and Friedrich Wöhler during their studies of bitter almond oil , which consists of benzaldehyde with traces of hydrogen cyanide. The catalytic synthesis in the form of benzoin addition was improved by Nikolai Zinin during his time with Liebig.

Manufacturing

Benzoin can be produced from benzaldehyde by cyanide - catalyzed addition ( benzoin addition ).

Production of Benzoin

The cleaning can be done by sublimation . This reaction works for many aromatic aldehydes and glyoxals . The resulting α-hydroxycarbonyl compounds are called benzoins.

properties

Benzoin is a pure white, otherwise white to yellowish solid with an aromatic odor. Its rotation value is ( R ): −115 ° (c = 1.5 in acetone ) or ( S ): + 115 ° (c = 1.5 in acetone). The flash point is 181 ° C.

Benzoin has a reducing effect as an α-hydroxyketone. Benzil is formed during dehydration .

use

Benzoin is used in powder coatings as a degassing and leveling agent and is used as a starting material for the synthesis of benzil.

Benzoin is also suitable for an interesting chemical experiment. To do this, small amounts of benzoin and benzil are dissolved in ethanol in a closed vessel at room temperature and then sodium hydroxide is added. If the vessel is shaken, the solution immediately takes on a clear yellow color, which turns purple again after a few seconds at rest. The reason for the reaction, which can be repeated any number of times, is the formation of a radical anion which reacts with the oxygen when shaken.

Individual evidence

  1. ↑ a b c d e f g h i j Entry on benzoin in the GESTIS substance database of the IFA , accessed on December 20, 2019 (JavaScript required)
  2. ↑ Data sheet (R) - (-) - Benzoin from Sigma-Aldrich , accessed on June 12, 2010 ( PDF ).
  3. ↑ Data sheet (S) - (+) - Benzoin from Sigma-Aldrich , accessed on June 12, 2010 ( PDF ).
  4. ↑ Benzoin data sheet (PDF) from Merck , accessed on January 11, 2020.
  5. ↑ Entry on benzoin. In: Römpp Online . Georg Thieme Verlag, accessed on April 21, 2014.
  6. ↑ Thomas Gleinser: Anna von Diesbach's Bernese 'Pharmacopoeia' in the Erlacher version of Daniel von Werdts (1658), Part II: Glossary. (Medical dissertation Würzburg), now at Königshausen & Neumann, Würzburg 1989 (= Würzburg medical-historical research , 46), p. 53.
  7. ↑ Wöhler, Liebig: Investigations on the radical of benzoic acid . In: Annals of Pharmacy . 3, No. 3, 1832, pp. 249-282. doi : 10.1002 / jlac.18320030302 .
  8. ^ N. Zinin: Contributions to the knowledge of some compounds from the benzoyl series . In: Annals of Pharmacy . 31, No. 3, 1839, pp. 329-332. doi : 10.1002 / jlac.18390310312 .
  9. ↑ N. Zinin: About some decomposition products of bitter almond oil . In: Annals of Pharmacy . 34, No. 2, 1840, pp. 186-192. doi : 10.1002 / jlac.18400340205 .
  10. ^ R. Adams and CS Marvel: Benzoin In: Organic Syntheses . 1, 1921, p. 33, doi : 10.15227 / orgsyn.001.0033 ; Coll. Vol. 1, 1941, p. 94 ( PDF ).
  11. ↑ Müller, Bodo; Poth, Ulrich: Paint formulation and paint recipe The textbook for training and practice . 4th edition. Vincetz Verlag, Hannover 2007, ISBN 978-3-86630-617-2 , p. 286, 297, 299, 302 .
  12. ↑ Reaction of benzil with benzoin .