Phenylglyoxal

Phenylglyoxal

Names
IUPAC name Phenylglyoxal
Other names oxo(phenyl)acetaldehyde 1-phenylethanedione
Identifiers
CAS Number	1075-06-5 (monohydrate) 1074-12-0 (anhydrous)
ChemSpider	13470
Jmol interactive 3D	Image
PubChem	14090
RTECS number	KM5775180
UNII	N45G3015PA
InChI InChI=1S/C8H6O2/c9-6-8(10)7-4-2-1-3-5-7/h1-6H Key: OJUGVDODNPJEEC-UHFFFAOYSA-N InChI=1/C8H6O2/c9-6-8(10)7-4-2-1-3-5-7/h1-6H Key: OJUGVDODNPJEEC-UHFFFAOYAA
SMILES O=C(C=O)c1ccccc1
Properties
Chemical formula	C8H6O2
Molar mass	134.13 g/mol (anhydrous)
Appearance	yellow liquid (anhydrous) white crystals (hydrate)
Density	? g/cm^3
Melting point	76 to 79 °C (169 to 174 °F; 349 to 352 K) (hydrate)
Boiling point	63 to 65 °C (145 to 149 °F; 336 to 338 K) (0.5 mmHg, anhydrous)
Solubility in water	forms the hydrate
Solubility in other solvents	common organic solvents
Hazards
Main hazards	toxic
R-phrases	22-36/37/38
S-phrases	22-26-36
Related compounds
Related aldehydes	3,4-Dihydroxyphenylacetaldehyde Methylglyoxal Phenylacetaldehyde
Related compounds	benzil glyoxal acetophenone
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

Phenylglyoxal is the organic compound with the formula C₆H₅C(O)C(O)H. It contains both an aldehyde and a ketone functional group. It is yellow liquid when anhydrous but readily forms a colorless crystalline hydrate. It has been used as a reagent to modify the amino acid, arginine.^[1]

Properties

Like some other aldehydes, phenylglyoxal polymerizes upon standing, as indicated by solidification of the liquid. Upon heating, this polymer "cracks" to give back the yellow aldehyde. Dissolution of phenylglyoxal in water gives crystals of the hydrate:

C₆H₅C(O)COH + H₂O → C₆H₅C(O)CH(OH)₂

Upon heating, the hydrate loses water and regenerates the anhydrous liquid.

Preparation

Phenylglyoxal was first prepared by thermal decomposition of the sulfite derivative of the oxime:^[2]

C₆H₅C(O)CH(NOSO₂H) + 2 H₂O → C₆H₅C(O)CHO + NH₄HSO₄

More conveniently, it can be prepared from methyl benzoate by reaction with KCH₂S(O)CH₃ to give PhC(O)CH(SCH₃)(OH), which is oxidized with copper(II) acetate.^[3] Alternatively, it can also be prepared by oxidation of acetophenone with selenium dioxide.^[4]

References

1. Kenji Takahashi (1968). "The Reaction of Phenylglyoxal with Arginine Residues in Proteins". J. Biol. Chem. 243 (23): 6171–9. PMID 5723461.
2. H. von Pechmann (1887). "Zur Spaltung der Isonitrosoverbindungen". Chem. Ber. 20 (2): 2904–2906. doi:10.1002/cber.188702002156.
3. Mikol, G. J.; Russell, G. A. (1973). "Phenylglyoxal". Org. Synth.; Coll. Vol. 5, p. 937
4. Riley, H. A.; Gray, A. R. (1943). "Phenylglyoxal". Org. Synth.; Coll. Vol. 2, p. 509