КИСЛОТА фосфорная-пиро

Описание

Pyrophosphoric acid, also known under the name diphosphoric acid, is colorless, odorless, hygroscopic and is soluble in water, diethyl ether and ethyl alcohol. It is produced from phosphoric acid by dehydration. Pyrophosphoric acid slowly hydrolyzes in the presence of water into phosphoric acid.
H4P2O7 +H2O?2H3PO4
Upon heating, phosphoric acid loses water, being converted successively, and to some extent concurrently, into the pyro- and meta-acids:
2H3PO4?H4P2O7 +H2O
nH3PO4?(HPO3)n + [H2O]n

Химические свойства

White to very pale yellow glassy solid

Физические свойства

Colorless needles or liquid; hygroscopic. Crystallizes in two anhydrous forms: a metastable form melting at 54.3°C and a second and more stable form melting at 71.5°C; extremely soluble in cold water, reacting very slowly to form phosphoric acid; decomposing much faster in hot water; very soluble in alcohol and ether.

Использование

Pyrophosphoric Acid has been shown to enhance the rate of pyrophosphate hydrolysis by nonenzymatic catlysis and by inorganic pyrophoshatase. Pyrophosphoric Acid can be used for the preparation of vanadyl pyrophosphato methoxide cluster anion. Pyrophosphoric Acid is used in anion binding of inorganic phosphates due to is ability to form complexes.

Подготовка

According to early investigators, the pyro-acid is formed as low as 100 °C, and the conversion is complete between 255 and 260 °C. Phosphorous oxychloride reacts with phosphoric acid in the following manner:
5H3PO4 + POC13?3H4P2O7 + 3HC1
A mixture of the ortho- and meta-acids may be condensed together to form the pyro-acid by heating on the water bath:
nH3PO4 +[HPO3]n?[H4P2O7]n

Определение

ChEBI: An acyclic phosphorus acid anhydride obtained by condensation of two molecules of phosphoric acid.