Triphosphoric acid, preparation

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. 

D-Glucosamine 6-phosphate can be readily acetylated by a AT-acetylase obtained from a preparation of yeast hexokinase. The resulting iV-acetyl-D-glucosamine 6-phosphate is identified by its Morgan-Elson reaction. The acetyl-coenzyme A which appears to be required for this reaction may be generated by acetate, adenosine-5-triphosphoric acid, and coenzyme A (in the presence of an acetate-activating enzyme). 

There are many oxoacids containing phosphorus. Some examples are phosphorous acid, H3PO3 phosphoric acid, H3PO4 hypophosphorous acid, H3PO2 and triphosphoric acid, H5P3O10 (Figure 21.11). Phosphoric acid, also called orthophosphoric acid, is a weak triprotic acid (see p. 619). It is prepared industrially by the reaction of calcium phosphate with sulfuric acid ... 

When phosphoric acid is heated with P2O5 it loses water, forming a phosphoanhy-dride called pyrophosphoric acid. Its name comes frompyr, the Greek word for fire. Thus, pyrophosphoric acid is prepared by fire —that is, by heating. Triphosphoric acid and higher polyphosphoric acids are also formed. 

The hydrochloric acid is removed by the strong tertiary base, methyldibutylamine, which has a soluble hydrochloride. In B.P. s 631,549 and 652,981 it was shown that compound (II) could be prepared by the action of dimethylamine on P0C13 in chloroform containing an excess of methylbutylamine. The further reaction with water is very conveniently carried out in the same system by adding an excess of aqueous sodium hydroxide solution. The chloroform layer contains the tertiary amine and (I). The solvent and amine are stripped off leaving the product. Side reactions take place, and the commercial product also contains some triphosphoric pentadimethylamide (I A) and smaller amounts of other phosphoric amides. The compound (I A) is itself also a valuable systemic insecticide. 

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