Hydrogenoxalate or hydrogen oxalate is an

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

with

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

or , derived from

oxalic acid Oxalic acid is an organic acid with the systematic name ethanedioic acid and formula . It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name comes from the fact that early invest ...

by the loss of a single

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

; or, alternatively, from the

oxalate Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl ...

anion by addition of a proton. The name is also used for any

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

containing this anion. Especially in older literature, hydrogenoxalates may also be referred to as bioxalates, acid oxalates, or monobasic oxalates. Hydrogenoxalate is

amphoteric In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used. One type of amphoteric species are amphipro ...

, in that it can react both as an acid or a base. Well characterized salts include sodium hydrogenoxalate (), potassium hydrogenoxalate (), ammonium hydrogenoxalate (), rubidium hydrogenoxalate () and dimethylammonium hydrogenoxalate (()).

Structure

Most hydrogenoxalate salts are hydrated. For example, potassium hydrogen oxalate crystallizes as 2·. These materials exhibit extended structures resulting from extensive hydrogen bonding and anion-cation interactions. The hydrates dehydrate upon heating: :2· → 2 + Proton transfer in hydrogen oxalates has been studied.

References

{{Authority control Carboxylate anions

Structure

See also

References