Hydrogenoxalate

Well characterized salts include sodium hydrogenoxalate (NaHC₂O₄), potassium hydrogenoxalate (KHC₂O₄), ammonium hydrogenoxalate ([NH₄]⁺HC₂O−4), rubidium hydrogenoxalate (RbHC₂O₄) and dimethylammonium hydrogenoxalate ([(CH₃)₂NH]⁺HC₂O−4).

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:

2KHC₂O₄·H₂O → 2 KHC₂O₄ + H₂O

Proton transfer in hydrogen oxalates has been studied.