Mesoxalic acid
Mesoxalic acid, also called oxomalonic acid or ketomalonic acid, is an organic compound with formula C3H2O5 or HO-(C=O)3-OH.
Mesoxalic acid is both a dicarboxylic acid and a ketonic acid. It readily loses two protons to yield the divalent anion C3O5, called mesoxalate, oxomalonate, or ketomalonate. These terms are also used for salts containing this anion, such as sodium mesoxalate, Na2C3O5); and for esters containing the -C3O5- or -O-(C=O)3-O- moiety, such as diethyl mesoxalate, C2H5)2C3O5. Mesoxalate is one of the oxocarbon anions, which (like carbonate CO3 and oxalate C2O4) consist solely of carbon and oxygen.