Reactivity Profile
GLYOXYLIC ACID is a carboxylic acid. Preparative hazard, nitric acid and glyoxal to produce glyoxylic acid has had explosive consequences. Carboxylic acids donate hydrogen ions if a base is present to accept them. They react in this way with all bases, both organic (for example, the amines) and inorganic. Their reactions with bases, called "neutralizations", are accompanied by the evolution of substantial amounts of heat. Neutralization between an acid and a base produces water plus a salt. Carboxylic acids with six or fewer carbon atoms are freely or moderately soluble in water; those with more than six carbons are slightly soluble in water. Soluble carboxylic acid dissociate to an extent in water to yield hydrogen ions. The pH of solutions of carboxylic acids is therefore less than 7.0. Many insoluble carboxylic acids react rapidly with aqueous solutions containing a chemical base and dissolve as the neutralization generates a soluble salt. Carboxylic acids in aqueous solution and liquid or molten carboxylic acids can react with active metals to form gaseous hydrogen and a metal salt. Such reactions occur in principle for solid carboxylic acids as well, but are slow if the solid acid remains dry. Even "insoluble" carboxylic acids may absorb enough water from the air and dissolve sufficiently in GLYOXYLIC ACID (50% OR LESS) to corrode or dissolve iron, steel, and aluminum parts and containers. Carboxylic acids, like other acids, react with cyanide salts to generate gaseous hydrogen cyanide. The reaction is slower for dry, solid carboxylic acids. Insoluble carboxylic acids react with solutions of cyanides to cause the release of gaseous hydrogen cyanide. Flammable and/or toxic gases and heat are generated by the reaction of carboxylic acids with diazo compounds, dithiocarbamates, isocyanates, mercaptans, nitrides, and sulfides. Carboxylic acids, especially in aqueous solution, also react with sulfites, nitrites, thiosulfates (to give H2S and SO3), dithionites (SO2), to generate flammable and/or toxic gases and heat. Their reaction with carbonates and bicarbonates generates a harmless gas (carbon dioxide) but still heat. Like other organic compounds, carboxylic acids can be oxidized by strong oxidizing agents and reduced by strong reducing agents. These reactions generate heat. A wide variety of products is possible. Like other acids, carboxylic acids may initiate polymerization reactions; like other acids, they often catalyze (increase the rate of) chemical reactions.
Synthesis
Add to 3500ml reactor equipped with reflux condenser, stirrer and thermometer300ml (3.55mol) of 50% glyoxal solution, stir and cool, control the temperature to 7±2,Slowly drip 300ml (3.55mol) of 35% hydrogen peroxide solution at the same time within 3 hours,280ml (0.355mol) of 17% ferrous sulfate solution and 120ml (0.75mol) of 15% aqueous ammonia solution, keep at 8±2, react for 3 hours, and let stand overnight, The reaction liquid was filtered to remove the solid by-products, and 350ml of water-carrying toluene was added to the reaction mother liquid.Heat to reflux, remove water, and distill toluene with water-carrying agent to obtain oxidation product.Add 120ml of concentrated sulfuric acid and 700ml of absolute ethanol to the oxidation products.Esterification reaction at 140°C for 3 hours, then distillation under reduced pressure, at 0.02Mpa,The esterification product was collected at 185°C.Add 120ml of 18% sulfuric acid to the esterified product and heat under stirring.The hydrolysis reaction is carried out at 95-98 for 2 hours; the hydrolysis liquid is cooled to room temperature,The precipitated white solid product was filtered, washed 4 times with 120ml of toluene each time, and dried.Obtain 180 g of the target product glyoxylic acid with a purity of 99.5% (HPLC) and a yield of 88%.Melting point is 98.1-98.6.
Environmental Fate
Glyoxylic acid's production and use as a cleaning agent for a variety of industrial applications, as a specialty chemical and biodegradable copolymer feedstock, and as an ingredient in cosmetics may result in its release to the environment through various waste streams. The pKa of glyoxylic acid is 3.3, indicating this compound will exist primarily as an anion in moist soil surfaces and anions are expected to have very high mobility in soils. If released to soil or water, glyoxylic acid is expected to biodegrade. Degradation may also occur in sunlit water through direct photolysis.
