Peroxymonosulfuric acid

Peroxymonosulfuric acid
IUPAC name (Dioxidanido)hydroxidodioxidosulfur
Other names Peroxomonosulfuric acidcitation needed Peroxysulfuric acidcitation needed Persulfuric acidcitation needed
Identifiers
CAS number	10361-76-9 N
PubChem	2754594
ChemSpider	2035480 Y
EC number	231-766-6
UN number	1483
ChEBI	CHEBI:29286 Y
Gmelin Reference	101039
Jmol-3D images	Image 1 Image 2
SMILES OOS(O)(=O)=O [O].[O].OOSO
InChI InChI=1S/H2O5S/c1-5-6(2,3)4/h1H,(H,2,3,4) Y Key: FHHJDRFHHWUPDG-UHFFFAOYSA-N Y
Properties
Molecular formula	H2SO5
Molar mass	114.078 g mol-1
Appearance	White crystals
Density	2.239 g cm-3
Structure
Coordination geometry	Tetrahedral at S
Hazards
Main hazards	strong oxidizer
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Peroxymonosulfuric acid, (H₂SO₅), also known as persulfuric acid, peroxysulfuric acid, or Caro's acid, is a liquid at room temperature. 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 (Eº + 1.81 V) and is highly explosive.

H₂SO₅ is sometimes confused with H₂S₂O₈, 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

H₂SO₅ was first described by Heinrich Caro, after whom it is named.

Synthesis and production

The laboratory scale preparation of Caro's acid involve the combination of chlorosulfuric acid and hydrogen peroxide.

H₂O₂ + ClSO₂OH ⇌ H₂SO₅ + HCl

Large scale production of Caro's acid is usually done on site, due to its instability. According to the patent by Martin, Caro's acid is produced by reacting >85% sulfuric acid and >50% hydrogen peroxide ("Piranha solution").

H₂O₂ + H₂SO₄ ⇌ H₂SO₅ + H₂O

Uses in industry

H₂SO₅ has been used for a variety of disinfectant and cleaning applications, e.g., swimming pool treatment and denture cleaning. Alkali metal salts of H₂SO₅ show promise for the delignification of wood.

Ammonium, sodium, and potassium salts of H₂SO₅ are used in the plastics industry as polymerization initiators, etchants, desizing agents, soil conditioner, and for decolorizing and deodorizing oils.

Potassium peroxymonosulfate, KHSO₅, is the potassium acid salt of peroxymonosulfuric acid. It is widely used as an oxidizing agent.

Dangers

Pure Caro's acid is highly explosive. Explosions have been reported at Brown University 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 the compound, creating a highly unstable molecule such as acetone peroxide.