limiting carboxylic diacid with gross formula C2H2O4 called for a systematic nomenclature, ethanedioic acid.This compound is also known by other more common name - oxalic acid.For the first time it was received by the German chemist F. Wohler of cyanogen (oxalic acid dinitrile) in 1824.Colourless crystals are dissolved in water to form a colorless solution.Weight molar is 90.04 g / mol.In appearance resembles monoclinic colorless crystals.At 20 ° C in 100 g of water was dissolved 8 g of oxalic acid.It soluble in acetone, ethyl alcohol and sulfuric ether.Density 1.36 g / cm³.It melts at a temperature of 189.5 ° C, sublimates at 125 ° C, decomposes at 100-130 ° C.
all chemical properties characteristic of carboxylic acid, oxalic acid has.Formula her HOOC-COOH.While that relates to carboxylic acids, is considered a strong organic acid (3,000 times stronger than acetic acid): C2O4H2 → C2O4H- + H + (pK = 1.27), and then: C2O4H- → C2O42 - + H + (pK= 4.27).Ethers and salts of this acid called oxalate.Oxalate ion is a reducing C2O42-.When reacting oxalic acid with a solution of potassium permanganate (KMnO4) solution, and the latter is recovered discolored.It is characterized by reversible reaction proceeds slowly and the interaction with alcohols (esterification), which resulted in the formation of esters: HOOC-COOH + 2HOR ↔ 2H2O + ROOC-COOR.
In industry oxalic acid is produced by oxidation of chemical compounds.For example, in the presence of a vanadium catalyst (V2O5) mixture of nitric acid (HNO3) and sulfuric (H2SO4) acids oxidized alcohols, glycols and carbohydrates.Also suitable process for the oxidation of ethylene and acetylene, nitric acid (HNO3) in the presence of palladium salts of Pd (NO3) 2 or PdCl2.Oxalic acid is produced from propylene, a liquid which is oxidized by nitrogen dioxide (NO2).It has a good perspective method of obtaining acid reacts with sodium hydroxide (NaOH) to carbon monoxide (CO) through the intermediate stage of formation of sodium formate: NaOH + CO → HCOONa.Then, formed sodium oxalate and hydrogen is released: HCOONa + NaOH → NaOOC-COONa + H2 ↑.Because sodium oxalate in an acidic environment obtained oxalic acid: NaOOC-COONa + 2H + → HOOC-COOH + 2Na +.
main applications of oxalic acid - a cleaning or bleaching.Oxalic acid is able to effectively remove rust, so many cleaning products contain this chemical compound.About a quarter of oxalic acid produced is used as a mordant for dyeing the leather and textile industries.It is also used as a reagent (GOST 22180-76) in analytical chemistry.Etandioevaya acid dihydrate (HOOC-COOH • H2O) TU 2431-002-77057039-2006 with a mass fraction of the basic substance ≥ 99,3% used in the production processes of organic synthesis, for removal of rust and scale metal for bleaching sections in microscopy.Beekeepers, a solution of oxalic acid in a mass fraction of 3.2% in the sugar syrup to combat parasitic mites.At the conclusion of its marble structure is treated with a surface to seal and make them shine.
oxalic acid and oxalates present in many plants, including black tea, occur in the body of animals.The main harm to humans associated with renal failure, which occurs due to the interaction of oxalic acid with calcium, resulting in the precipitation of solid calcium oxalate (SaS2O4) - the main component of kidney stones.Acid provokes joint pain due to precipitation of such compounds in them.Oxalic acid can be formed in the body by metabolism of ethylene coming from the environment (e.g., means for processing deicing airport runways of airports and airplanes, as well as from other anthropogenic sources).Potential problems with oxalate in human body can be divided into two.The first - an important macro element binds calcium and oxalic acid formed its deficiency in cells of tissues and organs.The second - the formation of kidney stones.The largest number of oxalic acid found in spinach, leaves and stalks of rhubarb, sorrel, beets, parsley, green onions.
