oxalate compound

Oxalate (systematic IUPAC name: ethanedioate) is an anion with the chemical formula . This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (), and several esters such as dimethyl oxalate (). It is a conjugate base of oxalic acid. At neutral pH in aqueous solution, oxalic acid converts completely to oxalate.

==Relationship to oxalic acid== The dissociation of protons from oxalic acid proceeds in a determined order; as for other polyprotic acids, loss of a single proton results in the monovalent hydrogenoxalate anion . A salt with this anion is sometimes called an acid oxalate, monobasic oxalate, or hydrogen oxalate. The equilibrium constant (Ka) for loss of the first proton is (pKa = 1.27). The loss of the second proton, which yields the oxalate ion, has an equilibrium constant of (pKa = 4.28). These values imply, in solutions with neutral pH, no oxalic acid and only trace amounts of hydrogen oxalate exist. The literature is often unclear on the distinction between , , and , and the collection of species is referred to as oxalic acid.