Trimetaphosphate ion

Fig. 4.13 The phosphorylation of glycerinic acid by the trimetaphosphate ion to give 3- or 2-phosphoglycerinic add. After Kolb and Orgel (1996)...

The P3093 ion (known as the trimetaphosphate ion) and (S03)3, a trimer of S03, also have this structure. The trimetaphosphate ion can be considered as the anion of the acid H3P309 (trimetaphos-phoric acid), a trimeric form of HP03 (metaphosphoric acid). Note that this acid is formally related to H5P3O10, tripolyphosphoric acid, by the reaction... 

Salts of the amidotriphosphate anion are obtained by the action of concentrated ammonia on the trimetaphosphate ion. With acids, the latter is regenerated with the elimination of ammonia (7.271). If ammonium trimetaphosphate is used, ammonium amidotriphosphate can be crystallised out. The monoamido tetraphosphate anion can be obtained in a similar way from ammonium tetrametaphosphate. 

Although reasonably stable at room temperature under neutral conditions, tri- and tetrametaphosphate ions readily hydrolyze in strongly acidic or basic solution via polyphosphate intermediates. The hydrolysis is first-order under constant pH. Small cycHc phosphates, in particular trimetaphosphate, undergo hydrolysis via nucleophilic attack by hydroxide ion to yield tripolyphosphate. The ring strain also makes these stmctures susceptible to nucleophilic ring opening by other nucleophiles. 

It has been seen that this resin has also some important advantages over the other resins in the literature like high total ion exchange capacity, easy synthesis, lower cost, simple regeneration. Furthermore, very good sepai ations were obtained using a concentration gradient of elution. In these elutions, very low concentrations of sodium trimetaphosphate were used. As a result, the resin synthesized can be used as an adsorbent for the effective removal of Pb, Cd, Co, Cu, Fe, Ni, Zn and Cr from aqueous solutions. 

Various polyphosphates are effective sequestering agents under appropriate conditions. The best known of these is sodium hexametaphosphate (10.14), the cyclic hexamer of sodium orthophosphate. Further examples are the cyclic trimer sodium trimetaphosphate (10.15), as well as the dimeric pyrophosphate (10.16), the trimeric tripolyphosphate (10.17) and other linear polyphosphates (10.18). All of these polyanions function by withdrawing the troublesome metal cation into an innocuous and water-soluble complex anion by a process of ion exchange as shown in Scheme 10.7 for sodium hexametaphosphate. Hence these compounds are sometimes referred to as ion-exchange agents. 

As in the hydrolysis of polyphosphates (Sections IV,B, and IV,E,1), hydrolysis of the trimetaphosphate anion is eatalytically accelerated by added cations. Their effect is attributed, as in the ease of the polyphosphates, to the formation of complex ions of the type CafPsOs)- or Ba(P309)- and Na PsOs)3 (130, I44, 146). 

The tetrametaphosphate anion is transformed into the amidotetraphos-phate, (P4O12NH2)5 , by concentrated ammonia solution just as the anion ring of trimetaphosphate is cleaved by ammonia to amidotriphosphate. Acidification of the solution results in partial reconversion to the tetrametaphosphate anion, but there is also partial hydrolysis to NH4+ and tetraphosphate ions as well as to amidomonophosphate and triphosphate ions, with simultaneous formation of trimetaphosphate (800). A complete structure determination has been made for ammonium tetrametaphosphate (1) from which the cyclic structure of the anion is evident (245). The diacid salt Na2H2(P40i2) (108) (see Section V,A) is also undoubtedly a tetrametaphosphate (150) (for structural data, see Section IV,E,3). 

Measurements of the electrical conductivity and solubility of difficultly soluble salts in sodium tetrametaphosphate solutions 62, 151, 196, 197) and potentiometric titrations lead to the assumption of the existence of complexes of the type of Na+(P40i2)3 Ba"1-1", Sr, Ca++, Mg++, Mn++, Ni++, Cu++(PiO]2) - La(P40i2) Cu(P40i2)26- and Ni(P40i2)26. No comparable dissociation constants for these have so far been given, though in any case they will be smaller than for the corresponding ion pairs of the trimetaphosphate anion 145). 

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-... 

Perhaps the formation of trimetaphosphate and small quantities of tetrametaphosphate from dissolved polyphosphates, which can amount to 70% in presence of Mg++ ions, is an indication of the form in which the anion chains are present in the solution. In any case this formation of trimetaphosphates is not, contrary to what was proposed initially (293, 326), an argument for the assumption that trimetaphosphate rings constitute a structural unit in the polyphosphates. Thus in solutions of Maddrell s salt, the anions of which are known to be linear chains from crystal structure determination (78) (see Section IV,E,2), up to 50% yields of trimeta-... 

Various smaller molecules and ions can also inhibit the growth of crystals of calcium phosphate such as phosphocitrate, proteoglycans and trimetaphosphate. Other compounds act as accelerators. 

In the 1960s, Schwartz described the phosphorylation of adenosine with trimetaphosphate to yield 2 - and 3 -AMP. The strong alkaline conditions used for this transformation were not likely to occur on the primitive Earth [137]. Similarly, all natural ribonucleosides were phosphory-lated to corresponding 2 - and 3 -nucleotide monophosphates with sodium trimetaphosphate at high pH and temperature [138,139]. When the reaction was performed under similar experimental conditions at lower pH, 2/,3/-cyclic phosphate nucleotides were recovered as the major products [140]. Magnesium ion catalyzes this transformation in neutral water solution [141]. 

Recently, Zhao has described the phosphorylation of adenosine 42 with trimetaphosphate by a wet-dry cycle process performed at neutral pH. Metal ions were able to catalyze the reaction, Ni(II) being the most active catalyst (30% yield of phosphorylated products, twice the yield produced by magnesium ion). 2/,3/-Cyclic AMP 47 (10%) and 5 -adenosinetriphosphate 5 -ATP 50 (13.0%) were obtained as the main reaction products (Scheme 24) [142]. Different prebiotic syntheses are reported for 5 -ATP [143-149]. 5 -ATP 50 has been for instance synthesized by the phosphorylation of 5 -ADP 51 in aqueous solution containing cyanate and insoluble calcium phosphate (Scheme 25) [150]. Similarly, 5 -ADP was synthesized from 5 -AMP. The yield... 

Y. Yamagata and K. Inomata (1997). Condensation of glycylglycine to oligoglycines with trimetaphosphate in aqueous solution. II catalytic effect of magnesium ion. Origin Life Evol. Biosph., 27, 339-344. 

Some food proteins are rich in phosphoric acid residues. The acid may either form ester bonds with Ser residues, as in caseins and egg proteins, or stabilize the native conformation of protein micelles by electrostatic interactions with negatively charged groups and calcium ions, as in caseins. In soy proteins Ser and Thr residues can be esterihed and Lys amidated with cyclic sodium trimetaphosphate at pH 11.5 and 35°C (Sung et al., 1983) ... 

Cyclic polyphosphates which are salts of anions of general formula [P 03 r. Examples are M3P309, a trimetaphosphate (13-XVII), and M4P4012, a tetrametaphosphate. The eight-membered ring of the P4042 ion is puckered with equal P—O bond lengths.74... 

---