Triphosphoric acid

Triphosphoric acid, H5P3O10 (3P2O5 5H2O), and the higher polyphosphoric acids have not been individually crystallised, but many well-characterised salts exist. The equilibrium mixture of chain polyphosphoric acids corresponding to a composition H5P3O10 contains only about 18% of this acid, and a solution of the pure species can only be obtained from the sodium salt by cation exchange at O C. 

---

Orthophosphoric acid containing three acid OH groups in the molecule offers many opportunities for the realization of surface-active molecular structures. But phosphoric acid also possesses the ability to form polyacids in an widespread manner. Pyrophophoric acid and triphosphoric acid are substances that have been known for a long time. This presents further possibilities for interesting synthesis. 

The ability of phosphoric acid to form condensed molecules is an additional effect. Examples of this kind of acid are pyrophosphoric acid, H4P207 structure (1), and triphosphoric acid, H5P3O 0 structure (2) ... 

The product, H4 P2 O7, is pyrophosphoric acid. A second condensation leads to triphosphoric acid ... 

Further condensation of phosphate groups leads to the polyphosphoric acids, which contain several phosphate units. The acids themselves are not particularly useful, but salts of some of these acids are used extensively. Triphosphoric acid, also known as tripolyphosphoric acid, H5P3O10, can be considered as a product of the reaction... 

Although Fischer2 stated that D-glucosone is not fermented by yeast it has recently been reported157 to be fermented by yeast extracts fortified with adenosine-5-triphosphoric acid and codehydrogenase I. 

A triokinase, isolated from liver, phosphorylates both D-glycerose and DL-glycerose, at the same rate, in the presence of adenosine-5-triphosphoric acid (ATP), and phosphorylates dihydroxyacetone at approximately half the rate.77-78... 

The most important compound in the series of low molecular weight polyphosphates is the sodium salt of triphosphoric acid, NaBP30io, which... 

This formula also corresponds with the fact that dissociation is strong in three and weak in two of the five H+ ions in triphosphoric acid (250). The correctness of the structural formula is also supported by the quantitative formation of triphosphate from trimetaphosphate on cleaving the anion ring with strong alkali (90, 311). Final proof for the structure of the tri-... 

Free triphosphoric acid has hitherto been obtained only as an aqueous solution prepared by ion exchange from the sodium salt. The dissociation constants are (337) Kt = very high = KF11 A3 = 10 2 3 KA = 10-6-26 if6 = 10-8 90. These values verify the old observation that triphosphoric acid has three strongly dissociated and two weakly dissociated H+ ions and explains why aqueous solutions of alkali triphosphates have an alkaline reaction. 

Problem 13.16 Alkyl esters of di- and triphosphoric acid are important in biochemistry because they are stable m the aqueous medium of living cells and are hydrolyzed by enzymes to supply the energy needed for muscle ontraction and other processes, (a) Give structural formulas for these esters, (b) Write equations for the lydrolysis reactions that are energy-liberating. ... 

---