Phosphonic acid nomenclature

Compounds containing a free acid function present a nomenclature problem since they can be regarded as derivatives of phosphonous acids (phosphonites), or of phosphinic acid (primary phos-phinates). The free acids have the phosphinic form whereas the amides are phosphonites (6.203). 

The lUPAC (mostly organic) name is phosphonic acid. This nomenclature is commonly reserved for substituted derivatives, that is, organic group bonded to phosphorus, not simply an ester. For example, (CH3)PO(OH)2 is "methylphosphonic acid", which may of course form "methylphosphonate" esters. 

Names of trivalent and pentavalent acids end in ous and ic , respectively. The overlap of organic and inorganic nomenclature should be noted. Esters of phosphonous and phosphinous acids are named phosphonites, HP (0R)2 and phosphinites H2P (OR), respectively. 

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