Everything about Glyoxal totally explained
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Glyoxal is an
organic compound with the formula OCHCHO. This yellow-coloured liquid is the smallest
dialdehyde (two
aldehyde groups).
Production
Commercial glyoxal is prepared either by the gas phase oxidation of ethylene glycol in the presence of a silver or copper catalyst or by the liquid phase oxidation of acetaldehyde with nitric acid. 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 and currently owned by Clariant. The single largest commercial source is BASF in
Ludwigshafen, Germany at ~60,000 tons/annum. Only 2 production sites (Geismer, LA and Charlotte, NC) exist in the Americas. Significant recent capacity has been added in China. Commercial bulk glyoxal is made and reported as a 40%-strength solution.
Glyoxal is prepared in the lab by oxidation of
acetaldehyde with
selenious acid.
The preparation of anhydrous glyoxal entails heating solid glyoxal hydrate(s) with
phosphorus pentoxide. A quote from this paper is instructive of the chemistry of that era "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 P
4O
10 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).
Applications
Paper coatings and textiles use large amounts of glyoxal as a crosslinker for starch-based formulations and as a starting material with ureas for wrinkle-resistant chemical treatments. It is used as a
solubilizer and
cross-linking agent in
polymer chemistry.
It is a valuable building block in
organic synthesis, especially in the synthesis of
heterocycles such as
imidazoles.
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)4 (CAS# 4405-13-4).
It is estimated that, at concentrations less than 1 M, glyoxal exists predominantly as the monomer or hydrates thereof, for example, OCHCHO, OCHCH(OH)
2, or (HO)
2CHCH(OH)
2. At concentrations >1 M, dimers predominate. These dimers are probably
dioxalanes, with the formula [(HO)CH]
2O
2CHCHO. 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.
Further Information
Get more info on 'Glyoxal'.
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