Glyoxal

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Glyoxal
Skeletal formula of glyoxal Space-filling model of glyox
Identifiers
CAS number 107-22-2 YesY
PubChem 7860
ChemSpider 7572 YesY
UNII 50NP6JJ975 YesY
KEGG C14448 YesY
ChEBI CHEBI:34779 YesY
Jmol-3D images Image 1
Properties
Molecular formula C2H2O2
Molar mass 58.04 g/mol
Density 1.27 g/cm3
Melting point 15 °C (59 °F; 288 K)
Boiling point 51 °C (124 °F; 324 K)
Thermochemistry
Specific
heat capacity
C
1.044 J/k/g
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 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point −4 °C (25 °F; 269 K)
Autoignition temperature 285 °C, 558 K, 545 °F
Related compounds
Related aldehydes acetaldehyde
glycolaldehyde
propanedial
methylglyoxal
Related compounds glyoxylic acid
glycolic acid
oxalic acid
pyruvic acid
diacetyl
acetylacetone
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

Glyoxal is an organic compound with the formula OCHCHO. It is a yellow-colored liquid that evaporates to give a green-colored gas. Glyoxal is the smallest dialdehyde (two aldehyde groups). Its structure is more complicated than typically represented because the molecule hydrates and oligomerizes. It is produced industrially as a precursor to many products.[1]

Production[edit]

Commercial glyoxal is prepared either by the gas-phase oxidation of ethylene glycol in the presence of a silver or copper catalyst (Laporte process) or by the liquid-phase oxidation of acetaldehyde with nitric acid.[1] Global nameplate capacity is ~220,000 tons, with production rates less, due to over-capacity mostly in Asia. Most production is done via the gas-phase oxidation route.

The first commercial glyoxal source was in Lamotte, France, started in 1960. The single largest commercial source is BASF in Ludwigshafen, Germany, at ~60,000 tons per year. Other production sites exist also in the US and China. Commercial bulk glyoxal is made and reported as a 40%-strength solution in water.

Glyoxal may be synthesized in the laboratory by oxidation of acetaldehyde with selenious acid.[2] The preparation of anhydrous glyoxal entails heating solid glyoxal hydrate(s) with phosphorus pentoxide and condensing the vapors in a cold trap.[3] The experimentally determined Henry's law constant of glyoxal is: KH = 4.19 × 105 × exp[(62.2 × 103/R) × (1/T − 1/298)].[4][clarification needed]

Applications[edit]

Coated paper and textile finishes use large amounts of glyoxal as a crosslinker for starch-based formulations. It condenses with urea to afford 4,5-dihydroxy-2-imidazolidinone, which further reacts with formaldehyde to give the bis(hydroxymethyl) derivative used for wrinkle-resistant chemical treatments. It[clarification needed] is used as a solubilizer and cross-linking agent in polymer chemistry:

  • proteins (leather tanning process)
  • collagen
  • cellulose derivatives (textiles)
  • hydrocolloids
  • starch (paper coatings)

Glyoxal is a valuable building block in organic synthesis, especially in the synthesis of heterocycles such as imidazoles.[5] A convenient form of the reagent for use in the laboratory is its bis-hemiacetal with ethylene glycol, 1,4-dioxane-2,3-diol. This compound is commercially available.

Glyoxal solutions can also be used as a fixative for histology, that is, a method of preserving cells for examining them under a microscope.

Speciation in solution[edit]

Glyoxal is supplied typically as a 40% aqueous solution. Like other small aldehydes, glyoxal forms hydrates. Furthermore, the hydrates condense to give a series of oligomers, the structures of which remain uncertain. For most applications, the exact nature of the species in solution is inconsequential. At least two hydrates of glyoxal are sold commercially:

  • glyoxal dimer, dihydrate: [(CHO)2]2[H2O]2, 1,4-dioxane-trans-2,3-diol (CAS# 4845-50-5, m.p. 91-95 C),
  • glyoxal trimer, dihydrate: [(CHO)2]3(H2O)2 (CAS# 4405-13-4).

It is estimated that, at concentrations less than 1 M, glyoxal exists predominantly as the monomer or hydrates thereof, i.e., OCHCHO, OCHCH(OH)2, or (HO)2CHCH(OH)2. At concentrations >1 M, dimers predominate. These dimers are probably dioxolanes, with the formula [(HO)CH]2O2CHCHO.[6] Dimer and trimer can precipitate, due to lower solubility, from solution at <40 F[clarify].

Other occurrences[edit]

Glyoxal is an inflammatory compound formed when cooking oils and fats are heated to high temperatures.[citation needed]

See also[edit]

References[edit]

  1. ^ a b Georges Mattioda, Alain Blanc, "Glyoxal" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a12 491
  2. ^ Ronzio, A. R.; Waugh, T. D. (1944), "Glyoxal Bisulfite", Org. Synth. 24: 61 ; Coll. Vol. 3: 438 
  3. ^ Harries, C.; Temme, F. (1907). "Über monomolekulares und trimolekulares Glyoxal". Berichte 40 (1): 165–172. doi:10.1002/cber.19070400124. "Man erhitzt nun das Glyoxal-Phosphorpentoxyd-Gemisch mit freier Flamme und beobachtet bald, dass sich unter Schwarzfärbung des Kolbeninhalte ein flüchtiges grünes Gas bildet, welches sich in der gekühlten Vorlage zu schönen Krystallen von gelber Farbe kondensiert. (One heats the mixture of (crude) glyoxal and P4O10 with an open flame and soon observes that, upon blackening of the contents, a mobile green gas, which condenses in the cooled flask as beautiful yellow crystals)" 
  4. ^ Ip, H. S.; Huang, X. H.; Yu, J. Z. (2009). "Effective Henry's law constants of glyoxal, glyoxylic acid, and glycolic acid". Geophysical Research Letters 36 (1): L01802. doi:10.1029/2008GL036212. 
  5. ^ Snyder, H. R.; Handrick, R. G.; Brooks, L. A. (1942), "Imidazole", Org. Synth. 22: 65 ; Coll. Vol. 3: 471 
  6. ^ Whipple, E. B. (1970). "Structure of Glyoxal in Water". J. Am. Chem. Soc. 92 (24): 7183–7186. doi:10.1021/ja00727a027. 

External links[edit]