Phosphinic acid

Structural formula
General
Surname	Phosphinic acid
other names	Hypophosphorous acid (obsolete) Hypophosphorous acid (obsolete) Phosphoric acid
Molecular formula	H 3 PO 2
Brief description	colorless and odorless leaflets
External identifiers / databases
CAS number 6303-21-5 EC number 228-601-5 ECHA InfoCard 100.026.001 PubChem 4124402 ChemSpider 10449263 Wikidata Q409658
properties
Molar mass	66,00 g · mol -1
Physical state	firmly
density	1.49 g cm −3
Melting point	26.5 ° C
boiling point	108 ° C (decomposition)
Vapor pressure	0.43 Pa (25 ° C)
pK s value	2.0 2.23
solubility	soluble in water
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 290-314 P: 262-270-273-280-303 + 361 + 353-305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Phosphinic acid , also known as hypophosphorous acid out of date , is one of the acids of phosphorus and has the empirical formula H ₃ PO ₂ . Their salts are called phosphinates or (outdated) hypophosphites ; With alcohols , phosphinic acid can formally form phosphinic acid esters . The phosphorus in these compounds has the oxidation state + I.

Manufacturing

Phosphinic acid can be produced by disproportionation of white phosphorus (P ₄ ) in an alkaline medium:

${\displaystyle \mathrm {P_{4}+6\ H_{2}O\longrightarrow PH_{3}+3\ H_{3}PO_{2}} }$

It is also possible to display it by decomposing barium hypophosphite with sulfuric acid .

${\displaystyle \mathrm {Ba(H_{2}PO_{2})_{2}\cdot H_{2}O+H_{2}SO_{4}\longrightarrow 2\ H_{3}PO_{2}+BaSO_{4}+H_{2}O} }$

properties

Anhydrous hypophosphorous acid crystallizes in colorless flakes, which dissolve very easily in water. When heated to 130–140 ° C, disproportionation to monophosphine and phosphonic acid occurs .

${\displaystyle \mathrm {3\,H_{3}PO_{2}\rightleftharpoons 2\,H_{3}PO_{3}+PH_{3}} }$

use

In aqueous solution, hypophosphorous acid can be used as a reagent for reducing diazonium groups ( dediazonation ). Elemental nitrogen and phosphorous acid are formed as reaction products .

See also

• phosphoric acid
• Phosphonic acid

literature

• AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 764.

Individual evidence

1. ↑ ^{a b c d e f g} Entry on phosphinic acid in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .
2. ↑ Registration dossier on phosphinic acid (section Vapor pressure ) at the European Chemicals Agency (ECHA), accessed on June 14, 2017.
3. ↑ ^{a b} chem.wisc.edu: pKa Data , Compiled by R. Williams (PDF, 78 kB).
4. ↑ ^{a b} Georg Brauer (Ed.), With the collaboration of Marianne Baudler u a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 539.