Pyrophosphoric

Two examples of condensed phosphoricfV) acids are heptaoxo-diphosphoric(V) (pyrophosphoric) and polytrioxophosphoric (meta-phosphoric) acids. 

See also pyrophosphorous acid.) [PHOSPHORUS COMPOUNDS] (Vol 18) Diphosphoric(III,V) acid [14902-77-3]... 

The condensation of cyclohexanol or cyclohexene is generally carried out in the presence of phosphoric acid, pyrophosphoric acid, or HY 2eohtes the aromatization of intermediate cyclohexyUiydroquinone [4197-75-5] (19) is realized in the presence of a dehydrogenation catalyst. 

At equihbrium, the specific composition of a concentrated phosphoric acid is a function of its P2 s content. Phosphoric acid solutions up to a concentration equivalent of about 94% H PO (68% P2O5) contain H PO as the only phosphoric acid species present. At higher concentrations, the orthophosphoric acid undergoes condensation (polymerization by dehydration) to yield a mixture of phosphoric acid species (Table 5), often referred to genericaHy as polyphosphoric or superphosphoric acid, H20/P20 = - 3, or ultraphosphoric acid, H20/P20 = - 1. At the theoretical P2O5 concentration for orthophosphoric acid of 72.4%, the solution is actually a mixture containing 13% pyrophosphoric acid and about 1% free water. Because the pyrophosphoric acid present is the result of an equihbrium state dependent on the P2 5 content of the solution, pure orthophosphoric acid can be obtained because of a shift in equihbrium back to H PO upon crystallization. 

The only clearly defined crystalline compositions are three forms of phosphoric acid and hemihydrate, pyrophosphoric acid, and crystalline P O q. The phosphoric acids obtained in highly concentrated solutions or by mixing phosphoric acid with phosphoms pentoxide are members of a continuous series of amorphous (excluding [Y OO]) condensed phosphoric acid mixtures. Mixtures having more than 86% P2O5 contain some cyclic metaphosphoric... 

Pyrophosphoric (diphosphoric) acid, H4P2O2, is the only condensed phosphoric acid definitely obtainable ia crystalline form. It has a theoretical P2O5 content of 79.8%. However, Hquid polyphosphoric acid of such content shows by analysis only 42.5% the remainder is phosphoric acid and... 

Cocarboxylase tetrahydrate (aneurine pyrophosphoric acid tetrahydrate, thiamine pyrophosphoric acid tetrahydrate) [136-09-4] M 496.4, m 220-222°(sinters at 130-140°), 213-214°, pKes,(1)-2, pKeskd O pKesi(3) 9- Recrystd from aqueous Me2CO. [Wenz et al. Justus Liebigs Ann Chem 618 210 7955 UV Melnick J Biol Chem 131 615 1939 X-ray Carlisle and Cook Acta Cryst (B) 25 1359 1969.] The hydrochloride salt has m 242-244°(dec), 241-243°(dec) or 239-240°(dec) and is... 

First synthesis of aji organo-P comp iund by J. L. Lassaigne who made alkyl phosphites from H P04 + ROH. T. Graham (who later became the Hrst President of the Chemical Society) classiHed phosphates as ortho, pyro or meta, following J. J. Berzelius s preparation of pyrophosphoric acid by heat. 

This section deals with orthopbosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7) and the polyphosphoric acids (H i-2Pfi03n31) Several of these compounds can be isolated pure but their facile interconversion renders this area of phosphorus chemistry far more complex... 

Pyro-phosphorsaure, /. pyrophosphoric acid, -saure, /. pyro acid, -schleimsaure, /. pjto-mucic acid, furoic acid, -schwefelsaure, /. pyrosulfuric acid, disulfuric acid (H2S2O7). 

Most of the chemistry of PA is determined by its acidic nature. It is a strong acid whose ionization constant of 1.6 x 10"1 (Ref 31) makes it comparable in acid strength to pyrophosphoric acid and trichloroacetic acid. PA readily forms salts with bases and esters with alcohols. The salts are known as Picrates. Many of them are expl and will be described in a separate article in this Vol. The esters are phenol ethers, eg, Trinitro-anisolc (see Vol t, A450-L)... 

The reaction product, a viscous brown liquid, is passed to a further reactor, in which the reaction is completed. Here the aging process takes place. This step is necessary to ensure that the formed intermediate pyrophosphoric acid is completely rearranged to LAS (20). During aging the formed anhydrides are also converted to LAS (23) ... 

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) ... 

Note Like sulfuric acid (q.v.) ort/io-phosphoric add is a universal reagent, with which almost all classes of substance can be detected at high temperatures (150-180 °C) by charring e.g. high molecular weight hydrocarbons (mineral oils) [20]. The colors and fluorescences produced at lower temperatures (<120°C) and their intensities are very dependent on the temperature and period of heating. It is not possible to use meta- or pyrophosphoric acid in place of or/Ao-phosphoric add, since, for instance, amanita toxins react well with alcoholic phosphoric add only weakly with aqueous phosphoric add and not at all with meta- or pyrophosphoric acid [17]. 

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

Several of these steroid derivatives underwent elimination of phosphorodichloridate anion, giving hydrocarbon products, rather than ester formation when treated with methanolic pyridine. Pyrophosphoric acid itself has been used to phosphorylate (2-hydroxymethyl)pyridine. ... 

The earliest formulations, as reported by Rollins (1879), Gaylord (1889), Ames (1893), Hinkins Acree (1901) and Fleck (1902), were variously based on syrupy orthophosphoric acid or unstable mixtures of meta-phosphoric acid and sodium metaphosphate in solution. Some used solid pyrophosphoric acid. Many were grossly inferior cements which were hydrolytically unstable. 

The extractant is octyl pyrophosphoric acid (OPPA process). The stripping is by concentrated hydrofluoric acid. Yields UF4. Extracts uranium in tetravalent state. It is, therefore, necessary to use metallic iron as a reducing agent. 

Nucleoside triphosphates are prepared analogously to the diphosphates by the methods a, b, c, and d, representing conversion of a nucleoside phosphoric azolide with inorganic pyrophosphate (Method a), of a nucleoside diphosphoric azolide with inorganic phosphate (Method b), of a phosphoric bisazolide with a nucleoside diphosphate (Method c), and of a diphosphoric bisazolide (bisazolide of pyrophosphoric acid) with a nucleoside phosphate (Method d). 

Figure 5.12.2 The molecular structure of pyrophosphoric acid (H4P2O7).

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