Name: oxalic acid
Also known as: oxalic acid; repair acid
English name: Oxalic acid; Ethanedioic acid; Dicarboxylic acid
Molecular formula: H2C2O4
Simple structure: HOOCCOOH;
Molecular Weight: 90.04
Structure: see right
Functional group:-COOH (carboxyl)
Ions in solution components: C2O4 2 - (oxalate ion), H (hydrogen ions), HC2O4-(oxalic acid hydrogen ion)
CAS No. :144-62-7; 6153-56-6 (dihydrate)
Properties: Colorless transparent crystal or powder. The crystal structure of two forms, namely α-(diamond) and β-type (monoclinic crystal form). Odorless, Pickle.
Melting point: α-type: 189.5 ℃, β-type: 182 ℃
Boiling point: [Molecular-dimensional model of] the boiling point of 150 ℃ (sublimation).
Relative density: 1.653 (dihydrate), 1.9 (anhydrous). α-type: 1.900, β-type: 1.895
Refractive index: 1.540
Stability: 189.5 ℃ Decomposition
Dissolved: soluble in ethanol. Soluble in water. Slightly soluble in ether. Not soluble in benzene and chloroform.
Other properties: sublimation of oxalic acid started at 100 ℃, 125 ℃ when the rapid sublimation, 157 ℃ when the large number of sublimation, and began to decompose.
With alkali reaction, can occur esterification, acyl halide, amide reaction. Reduction reaction can occur, heat decarboxylation occurred. Anhydrous oxalic acid are hygroscopic. The formation of oxalic acid with many water-soluble metal complexes.
Acid
Oxalic acid than acetic acid (acetic acid), 10,000 times stronger, is the organic acid in the acid. The level of ionization constant Ka1 = 5.9 × 10 ^ -2, ionization constant Ka2 = 6.4 × 10 ^ -5. Continuity with the acid. Occurrence with alkali and, enable indicator color, to release carbon dioxide and the role of carbonate.
Reduction
Oxalate has a strong reduction, and the oxidant is easily oxidized into carbon dioxide and water [1]. Can make the acidic potassium permanganate (KMnO4) solution, bleaching, and its reduction into two manganese ions. In the quantitative analysis of this reaction was used as a method of determination of concentration of potassium permanganate. Oxalic acid can also wash away the spilled ink on the cloth track.
Instability
In the case of oxalic acid or sulfuric acid 189.5 ℃ will be decomposed into carbon dioxide, carbon monoxide and water.
HOOCCOOH ==== CO2 ↑ CO ↑ H2O
Laboratory can take advantage of this reaction system of carbon monoxide gas.
200 degrees of ammonium hydrogen oxalate decomposed into carbon dioxide, carbon monoxide, ammonia and water
Toxicity
Oxalic acid is poisonous. On the skin, mucous membrane irritation and corrosion, easily through skin and mucous membrane absorption caused by poisoning. Maximum allowable concentration in air 1m g/m3.
Esterification
Adipic acid ester can react with the alcohol. For example the reaction of adipic acid with ethanol diethyl glycol.
Uses:
Bleach reductant rust remover mordant