Peroxymonosulfuric acid

Names
IUPAC names Peroxysulfuric acid Sulfuroperoxoic acid[1]
Systematic IUPAC name (Dioxidanido)hydroxidodioxidosulfur[1][2]
Other names Peroxosulfuric acid[1] Peroxomonosulfuric acid[citation needed] Persulfuric acid[citation needed] Caro's acid
Identifiers
CAS Number	7722-86-3 N
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:29286 Y
ChemSpider	2035480 Y
ECHA InfoCard	100.028.879
EC Number	231-766-6
Gmelin Reference	101039
PubChem CID	2754594
UNII	JC6U8R2UJ9 Y
UN number	1483
CompTox Dashboard (EPA)	DTXSID90884417
InChI InChI=1S/H2O5S/c1-5-6(2,3)4/h1H,(H,2,3,4) Y Key: FHHJDRFHHWUPDG-UHFFFAOYSA-N Y
SMILES OOS(O)(=O)=O [O].[O].OOSO
Properties
Chemical formula	H 2SO 5
Molar mass	114.078 g mol−1
Appearance	White crystals
Density	2.239 g cm−3
Melting point	45 °C
Conjugate base	Peroxomonosulfate
Structure
Coordination geometry	Tetrahedral at S
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	strong oxidizer
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Peroxymonosulfuric acid, H
₂SO
₅, is also known as persulfuric acid, peroxysulfuric acid, or Caro's acid. In this acid, the S(VI) center adopts its characteristic tetrahedral geometry; the connectivity is indicated by the formula HO–O–S(O)₂–OH. It is one of the strongest oxidants known (E⁰ = +2.51 V) and is highly explosive.

H
₂SO
₅ is sometimes confused with H
₂S
₂O
₈, known as peroxydisulfuric acid. The disulfuric acid, which appears to be more widely used as its alkali metal salts, has the structure HO–S(O)₂–O–O–S(O)₂–OH.

History

H
₂SO
₅ was first described in 1898 by the German chemist Heinrich Caro, after whom it is named.^[3]

Synthesis and production

The laboratory scale preparation of Caro's acid involves the combination of chlorosulfuric acid and hydrogen peroxide:^[4]

H₂O₂ + ClSO₂OH ⇌ H₂SO₅ + HCl

Published patents include more than one reaction for preparation of Caro's acid, usually as an intermediate for the production of potassium monopersulfate (PMPS), a bleaching and oxidizing agent. One patent for production of Caro's acid for this purpose gives the following reaction:^[5]

H₂O₂ + H₂SO₄ ⇌ H₂SO₅ + H₂O

This is the reaction that produces the acid transiently in "piranha solution".

Uses in industry

H
₂SO
₅ has been used for a variety of disinfectant and cleaning applications, e.g., swimming pool treatment and denture cleaning. Alkali metal salts of H
₂SO
₅ show promise for the delignification of wood.^[6] It is also used in laboratories as a last resort in removing organic materials since H
₂SO
₅ can fully oxidize any organic materials.^{[citation needed]}

Ammonium, sodium, and potassium salts of H
₂SO
₅ are used in the plastics industry as radical initiators for polymerization. They are also used as etchants, oxidative desizing agents for textile fabrics, and for decolorizing and deodorizing oils.

Potassium peroxymonosulfate, KHSO
₅, is the potassium acid salt of peroxymonosulfuric acid. It is widely used as an oxidizing agent.

Hazards

Pure Caro's acid is highly explosive. Explosions have been reported at Brown University^[7] and Sun Oil. As with all strong oxidizing agents, peroxysulfuric acid should be kept away from organic compounds such as ethers and ketones because of its ability to peroxidize these compounds, creating highly unstable molecules such as acetone peroxide.