Glyoxal

Glyoxal was first prepared and named by the German-British chemist Heinrich Debus (1824–1915) by reacting ethanol with nitric acid.[3][4]

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.[2]

The first commercial glyoxal source was in Lamotte, France, started in 1960. The single largest commercial source is BASF in Ludwigshafen, Germany, at around 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.

The experimentally determined Henry's law constant of glyoxal is:

${\displaystyle K_{\text{H}}=4.19\times 10^{5}\times \exp \left[{\frac {6.22\times 10^{4}\,{\text{kJ}}\,{\text{mol}}^{-1}}{R}}\times \left({\frac {1}{T}}-{\frac {1}{298\,{\text{K}}}}\right)\right]\,{\text{M}}\,{\text{atm}}^{-1}.}$[7]

Glycation often entails the modification of the guanidine group of arginine residues with glyoxal (R = H), methylglyoxal (R = Me), and 3-deoxyglucosone, which arise from the metabolism of high-carbohydrate diets. Thus modified, these proteins contribute to complications from diabetes.

Advanced glycation end-products (AGEs) are proteins or lipids that become glycated as the result of a high-sugar diet.[8] They are a bio-marker implicated in aging and the development, or worsening, of many degenerative diseases, such as diabetes, atherosclerosis, chronic kidney disease, and Alzheimer's disease.[9]

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 dimethylol ethylene urea, which is used for wrinkle-resistant chemical treatments of clothing, i.e. permanent press.

Glyoxal is used as a solubilizer and cross-linking agent in polymer chemistry.

Glyoxal is a valuable building block in organic synthesis, especially in the synthesis of heterocycles such as imidazoles.[10] 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.

Glyoxal and its derivatives are also used in the chemical probing of RNA structure, as they react with free guanines in RNAs.[11]

Hydrated glyoxal (top) and derived oligomers, called dimers and trimers. The middle and lower species exist as mixtures of isomers.

Glyoxal is supplied typically as a 40% aqueous solution.[2] Like other small aldehydes, glyoxal forms hydrates. Furthermore, the hydrates condense to give a series of oligomers, some of which remain of uncertain structure. For most applications, the exact nature of the species in solution is inconsequential. At least one hydrate of glyoxal is sold commercially, glyoxal trimer dihydrate: [(CHO)₂]₃(H₂O)₂ (CAS 4405-13-4). Other glyoxal equivalents are available, such as the ethylene glycol hemiacetal 1,4-dioxane-trans-2,3-diol (CAS 4845-50-5, m.p. 91–95 °C),

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 above 1 M, dimers predominate. These dimers are probably dioxolanes, with the formula [(HO)CH]₂O₂CHCHO.[12] Dimer and trimers precipitate as solids from cold solutions.

Glyoxal has been observed as a trace gas in the atmosphere, e.g. as an oxidation product of hydrocarbons.[13] Tropospheric concentrations of 0–200 ppt by volume have been reported, in polluted regions up to 1 ppb by volume.[14]

The LD50 (oral, rats) is 3300 mg/kg,[2] when LD50 of common salt is 3000 mg/kg.[15]

• "Glyoxal Industrial Applications". BASF.