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 conven ...
with
chemical formula or , derived from
oxalic acid by the loss of a single
proton; or, alternatively, from the
oxalate anion 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 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 amphiprot ...
, in that it can react both as an acid or a base.
Well characterized salts include
sodium hydrogenoxalate
Sodium hydrogenoxalate is salt (ionic compound) of formula , consisting of sodium cations and hydrogenoxalate anions or . The anion can be described as the result of removing one hydrogen ion from oxalic acid , or adding one to the oxalate ani ...
(),
potassium hydrogenoxalate (), ammonium hydrogenoxalate (), rubidium hydrogenoxalate () and dimethylammonium hydrogenoxalate (()).
Structure
Most hydrogenoxalate salts are
hydrated
Drinking is the act of ingesting water or other liquids into the body through the mouth, proboscis, or elsewhere. Humans drink by swallowing, completed by peristalsis in the esophagus. The physiological processes of drinking vary widely among o ...
. 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 +