Glyoxal

Glyoxal

Names
IUPAC name Ethanedial
Other names Ethane-1,2-dial Ethanedione Ketoethanal Oxalaldehyde Oxaldehyde
Identifiers
Jmol-3D images	Image
SMILES C(=O)C=O
Properties
Chemical formula	C2H2O2 CHOCHO
Molar mass	58.036 g/mol
Appearance	Colorless to yellow solid, yellow liquid giving off greenish vapors (pure) Colorless liquid (solution)
Odor	Mild odor
Density	1.14 g/cm3 (liquid) (20 °C) 1.27 g/cm3 (40% aq. solution) (20 °C)
Melting point	15 °C (59 °F; 288 K)
Boiling point	51 °C (124 °F; 324 K)
Solubility in water	Miscible
Solubility	Reacts with amines Miscible with alcohols, ethers, ketones
Vapor pressure	18 mmHg (20 °C)
Hazards
Safety data sheet	Sigma-Aldrich (40% aq. sol.)
Flash point	−4 °C (25 °F; 269 K)
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	3,300 mg/kg (rat, oral)
Related compounds
Related compounds	Acetaldehyde Ethylene glycol Oxalic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Glyoxal is an organic compound with the chemical formula CHOCHO or C₂H₂O₂. It is the simplest dialdehyde (a compound with two aldehyde groups).

Properties

Chemical

Pure glyoxal is said to burn in air/oxygen with a purple flame.

C₂H₂O₂ + 3/2 O₂ → 2 CO₂ + H₂O

Pure glyoxal is not commonly encountered because it forms hydrates, which oligomerize. For many purposes, these hydrated oligomers behave equivalently to glyoxal.

Glyoxal is oxidized by dilute nitric acid to glyoxyl acid, while conc. nitric acid will oxidize it to oxalic acid.

Physical

Glyoxal is a volatile liquid that freezes just slightly below room temperature. The compound is interesting, because unlike other small weight CHO compounds, it is not colorless. The liquid and solid forms are yellow, while the vapors of this compound are green.

Availability

Glyoxal is sold as 40% solution by chemical suppliers.

Preparation

Glyoxal can be prepared by careful oxidation of ethanol with nitric acid.

Another lab route involves oxidation of acetaldehyde with selenous acid. Yield is given to be 70%. If selenium dioxide is used, the yield varies between 60-84%, and selenous acid/selenium dioxide is preferred over nitric acid, as it is more selective.

Commercial glyoxal is prepared either by the gas-phase oxidation of ethylene glycol in the presence of a silver or copper catalyst (the Laporte process) or by the liquid-phase oxidation of acetaldehyde with nitric acid. Cooper oxide can be used as catalyst at 300 °C.

Decarboxylation of dihydroxy-tartaric acid salts in the presence of sodium bisulfite has been shown to yield glyoxal.

Ozonolysis of benzene has been shown to produce glyoxal.

Anhydrous glyoxal is prepared by heating solid glyoxal hydrate(s) with phosphorus pentoxide and condensing the vapors in a cold trap.

Another route to anhydrous glyoxal involves adding dichloroethane to oleum at 58-60 °C, in the presence of mercury(II) chloride as catalyst. Glyoxal sulfate is produced, which is neutralized with calcium carbonate to yield glyoxal.

Projects

• Colored compound
• Preparation of imidazoles and other similar heterocyclic compounds
• Synthesis of HNIW
• Synthesis of glycoluril and tetranitroglycoluril (TNGU)
• Solubilizer and cross-linking agent in polymer chemistry
• Fixative for histology
• Wrinkle-resistant chemical treatments of clothing

Handling

Safety

Glyoxal is volatile, flammable, irritant and like most simple aldehydes, suspected carcinogen. Wear proper protection when working with this compound.

Storage

Should be kept at constant temperature. In solution may precipitate on storage, and can be redissolved by heating at 50-60 °C.

Disposal

Glyoxal can be neutralized by precipitating it with a base. Can also be mixed with acetone or ethanol and burned.

References

Relevant Sciencemadness threads

• Glyoxal Synthesis
• Glyoxal + hydrazine
• 2 Questions about Glyoxal
• incomplete glyoxal amide reaction