Glyoxal is an
organic compoundAn organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic...
with the formula OCHCHO. This yellow colored liquid is the smallest
dialdehydeA dialdehyde is an organic compound with two aldehyde groups. An example is pentanedial .- Nomenclature :Dialdehydes have the ending -dial or sometimes -dialdehyde. Short aliphatic dialdehydes are sometimes named after the diacid from which they can de derived. An example is butanedial, which is...
(two
aldehydeAn aldehyde is an organic compound containing a terminal carbonyl group. This functional group, which consists of a carbon atom bonded to a hydrogen atom and double-bonded to an oxygen atom , is called the aldehyde group...
groups).
Commercial glyoxal is prepared either by the gas phase oxidation of
ethylene glycolEthylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet tasting liquid....
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.
Glyoxal is an
organic compoundAn organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic...
with the formula OCHCHO. This yellow colored liquid is the smallest
dialdehydeA dialdehyde is an organic compound with two aldehyde groups. An example is pentanedial .- Nomenclature :Dialdehydes have the ending -dial or sometimes -dialdehyde. Short aliphatic dialdehydes are sometimes named after the diacid from which they can de derived. An example is butanedial, which is...
(two
aldehydeAn aldehyde is an organic compound containing a terminal carbonyl group. This functional group, which consists of a carbon atom bonded to a hydrogen atom and double-bonded to an oxygen atom , is called the aldehyde group...
groups).
Production
Commercial glyoxal is prepared either by the gas phase oxidation of
ethylene glycolEthylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet tasting liquid....
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
acetaldehydeAcetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is a flammable liquid. Acetaldehyde occurs naturally in ripe fruit, coffee, and bread, and is produced by plants as part of their normal metabolism...
with selenious acid.
The preparation of anhydrous glyoxal entails heating solid glyoxal hydrate(s) with
phosphorus pentoxidePhosphorus pentoxide is a chemical compound with formula P
2O
5. This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant.-Structure:...
and condensing the vapors in a
cold trapIn vacuum applications, a cold trap is a device that condenses all vapors except the permanent gases into a liquid or solid. The most common objective is to prevent vapors from contaminating a vacuum pump. Cold traps also refer to the application of cooled surfaces or baffles to prevent oil...
.
Applications
paper coatings and textiles use large amounts of glyoxal as a crosslinker for
starchStarch or amylum is a polysaccharide carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds.Starch is produced by all green plants as an energy store and is a major food source for humans....
-based formulations and as a starting material with ureas for wrinkle-resistant chemical treatments. It is used as a
solubilizerSolubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution. The solubility of a substance strongly depends on the used solvent as well as on temperature and pressure...
and
cross-linkCross-links are bonds that link one polymer chain to another. They can be covalent bonds or ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers . When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of...
ing agent in
polymer chemistryPolymer chemistry or macromolecular chemistry is a multidisciplinary science that deals with the chemical synthesis and chemical properties of polymers or macromolecules. According to IUPAC recommendations , macromolecules refer to the individual molecular chains and are the domain of chemistry...
:
- proteins (leather tanning process)
- collagen
- cellulose derivatives (textiles)
- hydrocolloids
- starch (paper coatings)
It is a valuable building block in
organic synthesisOrganic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
, especially in the synthesis of heterocycles such as
imidazoleImidazole is an organic compound with the formula C3H4N2. This aromatic heterocyclic is classified as an alkaloid. Imidazole refers to the parent compound whereas imidazoles are a class of heterocycles with similar ring structure but varying substituents...
s. 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.
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, i.e., 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.
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