Orthoformic acid

Orthoformic acid is a hypothetical compound with the formula HC(OH)3. In this molecule, the central carbon is bound to one hydrogen and three hydroxyl groups. The compound cannot be isolated in substance as it would decompose into water and formic acid.

While the free acid does not exist, its esters, known as orthoesters, are well known and commercially available. Like acetals, they are stable towards bases but easily hydrolyzed in acidic conditions to the alcohol and an ester of formic acid. Uses are as mild dehydrating agent. Especially well known are trimethyl orthoformate and triethyl orthoformate.