Glyoxal

Glyoxal

Glyoxal
Skeletal formula of glyoxal
Space-filling model of glyox
Names
IUPAC name
ethanedial
Other names
ethane-1,2-dione
Identifiers
 Y
ChEBI  Y
ChemSpider  Y
Jmol-3D images Image
KEGG  Y
PubChem
UNII  Y
Properties
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
1.044 J/k/g
Hazards
NFPA 704
1
2
1
Flash point −4 °C (25 °F; 269 K)
285 °C (545 °F; 558 K)
Related compounds
Related aldehydes
acetaldehyde
glycolaldehyde
propanedial
methylglyoxal
Related compounds
glyoxylic acid
glycolic acid
oxalic acid
pyruvic acid
diacetyl
acetylacetone
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
 Y  (: Y/N?)

Glyoxal is an 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]

Contents

  • Production 1
  • Applications 2
  • Speciation in solution 3
  • Other occurrences 4
  • See also 5
  • References 6
  • External links 7

Production

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]

Applications

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 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 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

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.

Other occurrences

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

Glyoxal has been observed as a trace-gas in the atmosphere, e.g. as an oxidation product of hydrocarbons.[7] Tropospheric concentrations of 0-200 pptv have been reported, in polluted regions up to 1 ppbv.[8]

See also

References

  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".  
  3. ^ Harries, C.; Temme, F. (1907). "Über monomolekulares und trimolekulares Glyoxal".  
  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.  
  5. ^ Snyder, H. R.; Handrick, R. G.; Brooks, L. A. (1942). "Imidazole".  
  6. ^ Whipple, E. B. (1970). "Structure of Glyoxal in Water".  
  7. ^ M. Vrekoussis, F. Wittrock, A. Richter, J. P. Burrows: Temporal and spatial variability of glyoxal as observed from space. In: Atmos. Chem. Phys. 2009, 9, S. 4485–4504 (Abstract).
  8. ^ Volkamer, Rainer, et al. "A missing sink for gas‐phase glyoxal in Mexico City: Formation of secondary organic aerosol." Geophysical Research Letters 34.19 (2007).

External links

  • Glyoxal Industrial Applications