Oxalaationen

Oxalaationen, or the oxalate anion, is the dianion of oxalic acid with the formula C2O4^2−. It consists of two carboxylate groups connected through a shared carbon framework and is typically represented with resonance between equivalent oxygens. In solution it behaves as a standard bidentate ligand, able to coordinate to metal ions via the two oxygen atoms of adjacent carboxylate groups.

The oxalate anion forms a variety of salts, including calcium oxalate, sodium oxalate, and potassium oxalate. It is a common component of natural and synthetic systems and can participate in chelation chemistry, often forming five- or six-membered rings with metal centers. Oxalate salts have differing solubilities; calcium oxalate, for example, is poorly soluble and can precipitate in biological tissues.

Chemically, oxalic acid is a diprotic acid. Its first and second dissociation steps have pKa values of about 1.27 and 4.27, respectively, so oxalate predominates at neutral pH. In biological systems, oxalate can be produced or metabolized by organisms and may be degraded by oxalate-degrading enzymes in certain microbes. Oxalate can also be oxidized to carbon dioxide and formate in microbial and enzymatic pathways.

Biological and practical relevance includes its role in plant metabolism and its association with kidney stone formation in humans when oxalate combines with calcium. Oxalate salts are used in industrial and analytical contexts as chelating agents and buffering or sequestering agents, and they must be handled with regard for potential health and environmental effects.