Ortho acids are the most hydroxylated acid in a set of oxoacids, such as orthophosphoric acid. In general, when an element can form several oxoacids, these are called ortho-, meta- or pyroacids, with the ortho acid being the most hydrated of the three.[1]
Some of these compounds are unstable, such as orthocarbonic acid, which is one of a set of ortho acid derivatives of carboxylic acids that have the general structure of RC(OH)3.[2]