Hydrogenoxalate

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Hydrogenoxalate or hydrogen oxalate (IUPAC name: 2-Hydroxy-2-oxoacetate) is an anion with chemical formula HC2O−4 or HO−C(=O)−CO−2, derived from oxalic acid by the loss of a single proton; or, alternatively, from the oxalate anion C2O2−4 by addition of a proton. The name is also used for any salt containing this anion. Especially in older literature, hydrogenoxalates may also be referred to as bioxalates, acid oxalates, or monobasic oxalates. Hydrogenoxalate is amphoteric, in that it can react both as an acid or a base.

Quick facts Names, Identifiers ...
Hydrogenoxalate
Names
IUPAC name
2-Hydroxy-2-oxoacetate[1]
Systematic IUPAC name
2-Hydroxy-2-oxoethanoate
Other names
  • Bioxalate
  • Hydrogen oxalate
  • Hydrogenoxalate
Identifiers
3D model (JSmol)
3601755
ChEBI
ChemSpider
49515
  • InChI=1S/C2H2O4/c3-1(4)2(5)6/h(H,3,4)(H,5,6)/p-1
    Key: MUBZPKHOEPUJKR-UHFFFAOYSA-M
  • C(=O)(C(=O)[O-])O
Properties
HC2O−4
Molar mass 89.026 g·mol−1
Conjugate acid Oxalic acid
Conjugate base Oxalate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Well characterized salts include sodium hydrogenoxalate (NaHC2O4),[2][3] potassium hydrogenoxalate (KHC2O4),[4] ammonium hydrogenoxalate ([NH4]+HC2O−4), rubidium hydrogenoxalate (RbHC2O4)[5] and dimethylammonium hydrogenoxalate ([(CH3)2NH]+HC2O−4).[6]

Structure

Most hydrogenoxalate salts are hydrated. For example, potassium hydrogen oxalate crystallizes as 2KHC2O4·H2O. These materials exhibit extended structures resulting from extensive hydrogen bonding and anion-cation interactions. The hydrates dehydrate upon heating:[4]

2KHC2O4·H2O → 2 KHC2O4 + H2O

Proton transfer in hydrogen oxalates has been studied.[7]

See also

References

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