Diphosphoric acid

Structural formula
General
Surname	Diphosphoric acid
other names	Pyrophosphoric acid
Molecular formula	H 4 P 2 O 7
Brief description	white to light yellow solid
External identifiers / databases
CAS number 2466-09-3 EC number 219-574-0 ECHA InfoCard 100,017,795 PubChem 1023 ChemSpider 996 DrugBank DB04160 Wikidata Q411092
properties
Molar mass	177.98 g mol −1
Physical state	firmly
Melting point	61 ° C
pK s value	1.52 2.36 6.60 9.25
solubility	very good in water (7090 g l −1 at 23 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 302-314 P: 280-305 + 351 + 338-310
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Diphosphoric acid (also called pyrophosphoric acid ) is an oxo acid of phosphorus and belongs to the inorganic acids . It is derived from phosphoric acid and can be represented as an agglomeration of two phosphoric acid molecules with elimination of water .

${\displaystyle \mathrm {2\ H_{3}PO_{4}\ {\xrightarrow {\triangle }}\ H_{4}P_{2}O_{7}+H_{2}O} }$

Diphosphoric acid is highly hygroscopic and a moderately strong inorganic acid . Diphosphoric acid hydrolyzes exothermically to phosphoric acid with water .

The salts and esters of diphosphoric acid are called diphosphates or pyrophosphates .

Extraction and presentation

Diphosphoric acid is produced according to the above formula by dehydrating phosphoric acid at 200-300 ° C. Pure diphosphoric acid is made from phosphoric acid and phosphorus oxychloride :

${\displaystyle \mathrm {5\ H_{3}PO_{4}+POCl_{3}\longrightarrow 3\ H_{4}P_{2}O_{7}+3\ HCl} }$

See also

• Dimethylallyl pyrophosphate
• Disodium dihydrogen diphosphate
• Adenosine diphosphate

Individual evidence

1. ↑ ^{a b c} sheet diphosphoric from Acros, accessed on 26 February 2010 .
2. ^ ^{A b c d} A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .
3. ↑ ^{a b} Pyrophosphoric acid data sheet from Sigma-Aldrich , accessed on March 28, 2011 ( PDF ).
4. ↑ Entry on diphosphoric acid. In: Römpp Online . Georg Thieme Verlag, accessed on June 16, 2014.
5. ↑ Georg Brauer (Ed.): Handbook of Preparative Inorganic Chemistry. 2nd edition. Volume 1. Academic Press, New York et al. 1963, pp. 546-547.