Glyoxal

The simplest di-aldehyde possible is the one obtained by oxidizing ethyl alcohol or acetic aldehyde with nitric acid. 

Ethyl alcohol Acet-aldehyde Glyoxal Di-aldehyde 

The di-aldehyde compound is known as glyoxal. It is obtained as a colorless, amorphous solid readily soluble in water. In all its reactions it possesses the properties of an aldehyde and its constitution and relationship are as represented above. 

The di-ketones are similar to the ketone acids in being classified according to the relative position of the two carbonyl groups. We have, therefore, alpha- beta- gamma-, etc., di-ketones as follows. 

Synonyms ethanedial 1,2-ethanedione bi-formal biformyl oxal oxaldehyde gly-oxylaldehyde 

Glyoxal is used in the production of textiles and glues and in organic synthesis. 

Yellowish liquid, in the solid form—yellow prism becoming white vapors green bp 50.4°C (122.72°F) mp 15°C (59°F) density 1.14 soluble in water (polymerizes), alcohol, and ether. 

Glyoxal is a skin and eye irritant the effect may be mild to severe. Its vapors are irritating to the skin and respiratory tract. An amount of 1.8 mg caused severe irritation in rabbits eyes. Glyoxal exhibited low toxicity in test subjects. Ingestion may cause somnolence and gastrointestinal pain. 

Noncombustible polymerizes on standing or when mixed with water polymerization is exothermic and can become violent if uncontrolled reactions with strong acids, bases, and oxidizers can become violent vapor-air mixture is explosive. 

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Supplement (combined with Volume IV) 1942 195-449 Carbonyl-carboxylic acids Glyoxalic acid, 504. Acetoacotic acid, 630. Hydroxy-carbonyl carboxylic acids Glycuronic acid, 883. 

Glyoxal [108-22-2] Glyoxal Resins Glyoxal resins Glyoxylic acid... 

Uses. Furfuryl alcohol is widely used as a monomer in manufacturing furfuryl alcohol resins, and as a reactive solvent in a variety of synthetic resins and appHcations. Resins derived from furfuryl alcohol are the most important appHcation for furfuryl alcohol in both utihty and volume. The final cross-linked products display outstanding chemical, thermal, and mechanical properties. They are also heat-stable and remarkably resistant to acids, alkaUes, and solvents. Many commercial resins of various compositions and properties have been prepared by polymerization of furfuryl alcohol and other co-reactants such as furfural, formaldehyde, glyoxal, resorcinol, phenoHc compounds and urea. In 1992, domestic furfuryl alcohol consumption was estimated at 47 million pounds (38). 

Acetaldehyde, first used extensively during World War I as a starting material for making acetone [67-64-1] from acetic acid [64-19-7] is currendy an important intermediate in the production of acetic acid, acetic anhydride [108-24-7] ethyl acetate [141-78-6] peracetic acid [79-21 -0] pentaerythritol [115-77-5] chloral [302-17-0], glyoxal [107-22-2], aLkylamines, and pyridines. Commercial processes for acetaldehyde production include the oxidation or dehydrogenation of ethanol, the addition of water to acetylene, the partial oxidation of hydrocarbons, and the direct oxidation of ethylene [74-85-1]. In 1989, it was estimated that 28 companies having more than 98% of the wodd s 2.5 megaton per year plant capacity used the Wacker-Hoechst processes for the direct oxidation of ethylene. 

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

Reaction with Other Aldehydes. Polyacrylamide reacts with glyoxal [107-22-2], C2H2O2, under mild alkaline conditions to yield a polymer with pendant aldehyde fiinctionahty. 

Garbostyrils. Carbostydls such as (14) [33934-60-0] are prepared by the reaction of 2-alkylainino-4-iiitrotoluene with ethyl glyoxalate in the... 

Polyquinoxalines (PQ) have proven to be one of the better heat-resistant polymers with regard to both stabiUty and potential appHcation. The aromatic backbones are derived from the condensation of a tetramine with a bis-glyoxal, reactions first done in 1964 (61,62). In 1967, a soluble, phenylated version of this polymer was produced (63). The chemistry and technology of polyquinoxalines has been reviewed (64). 

Polyquinoxalines are prepared by the solution polymerisation of aromatic bis((9-diamines) such as 3,3, 4,4 -tetraminobiphenyl and aromatic bis(glyoxal hydrates) such as 4,4 -oxybis(phenylglyoxalhydrate) ... 

Carbon—nitrogen double bonds in imines, hydrazones, oximes, nitrones, azines, and substituted diazomethanes can be cleaved, yielding mainly ketones, aldehydes and/or carboxyHc acids. Ozonation of acetylene gives primarily glyoxal. With substituted compounds, carboxyHc acids and dicarbonyl compounds are obtained for instance, stearoHc acid yields mainly azelaic acid, and a smaH amount of 9,10-diketostearic acid. 

Ozonation of Aromatics. Aromatic ring unsaturation is attacked much slower than olefinic double bonds, but behaves as if the double bonds in the classical Kekule stmctures really do exist. Thus, benzene yields three moles of glyoxal, which can be oxidized further to glyoxyUc acid and then to oxahc acid. Substituted aromatics give mixtures of aUphatic acids. Ring substituents such as amino, nitro, and sulfonate are cleaved during ozonation. 

Organic cross-linkers, which include glyoxal (48) and formaldehyde (qv), have also been used. Use of hypohaUte salts (49) and epichlorohydrin (50) promotes gel stabiUty. Phenol—formaldehyde cross-linking systems have been used to produce stable acrylamide copolymer gels at temperatures above 75°C and brine hardness levels above 2000 ppm (51). 

Examples include acetaldehyde, CH CHO paraldehyde, (CH CHO) glyoxal, OCH—CHO and furfural. The reaction is usually kept on the acid side to minimize aldol formation. Furfural resins, however, are prepared with alkaline catalysts because furfural self-condenses under acid conditions to form a gel. 

Glyoxal Resins. Since the late 1960s, glyoxal resins have dorninated the textile-finish market for use as wrinMe-recovery, wash-and-wear, and durable-press agents. These resins are based on l,3-bis(hydroxymethyl)-4,5-dihydroxy-2-imidazohdinone, commonly called... 

A less important glyoxal resin is tetramenthylolglycolutil [5395-50-6] (tetramethylolacetylenediurea) produced by the reaction of 1 mol of glyoxal with 2 mol of urea, and 4 mol of formaldehyde. 

This resin was most popular in Europe, partiy because of its lower requirements of glyoxal. However, because of increased availabiHty and lower glyoxal costs plus certain appHcation weaknesses, it has been generally replaced by DMDHEU. 

A variation involves the reaction of benzylamines with glyoxal hemiacetal (168). Cyclization of the intermediate (35) with sulfuric acid produces the same isoquinoline as that obtained from the Schiff base derived from an aromatic aldehyde and aminoacetal. This method has proved especially useful for the synthesis of 1-substituted isoquinolines. 

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