Oxoacids of phosphorus and their salts

The oxoacids of P are more numerous than those of any other element, and the number of oxoanions and oxo-salts is probably exceeded only by those of Si. Many are of great importance technologically and their derivatives are vitally involved in many biological processes (p. 528). Fortunately, the structural principles covering this extensive array of compounds are very simple and can be stated as follows  

It follows from these structural principles that each P atom is 5-covalent. However, the oxidation state of P is 5 only when it is directly bound to 4 O atoms the oxidation state is reduced by 1 each time a P-OH is replaced by a P-P bond and by 2 each time a P-OH is replaced by 

The oxoacids of P are dearly very different structurally from those of N (p. 459) and this difference is accentuated when the standard reduction potentials (p. 434) and oxidation-stale diagrams (p. 437) for the two sets of compounds are compared. Some reduction potentials ( /V) in acid solution are in Table 12.8 (p. 513) and these are shown schematically below, together with the corresponding data for alkaline solutions. 

The alternative pre.sentation as an oxidation slate diagram is in Hg. 12.16 which shows the dramatic difference to N (p. 438). 

The fact that the element readily dissolves in aqueous media with disproportionation into PH3 and an oxoacid is immediately clear from the fact that P lies above the line joining PH3 and either H3PO2 (hypophosphorous acid), H3PO3 (phosphorous acid) or H3PO4 (orthophosphoric acid). Phe reaction is even 

7 Heteropolyadds containing P fall outside this classification and are treated, together with the isopolyacids and their salts, on pp. 1010-16. Organic esters such as P(OR)j are also excluded. 

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Oxoacids of phosphorus and their salts Table 12.10 Factors affecting the rate of polyphosphate degradation... 

Many compounds containing the P-N link can be considered formally as derivatives of the oxoacids of phosphorus and their salts (pp. 510 -31) in which there has been isoclccironic replacement of ... 

Nitrogen Oxides 24-16 Some Oxoacids of Nitrogen and Their Salts Phosphorus... 

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