Chlorous acid

Chlorous acid
IUPAC name Chlorous acid
Identifiers
CAS number	13898-47-0 Y
PubChem	24453
ChemSpider	22861 Y
KEGG	C01486 Y
ChEBI	CHEBI:29219 Y
Jmol-3D images	Image 1
SMILES O=ClO
InChI InChI=1S/ClHO2/c2-1-3/h(H,2,3) Y Key: QBWCMBCROVPCKQ-UHFFFAOYSA-N Y InChI=1/ClHO2/c2-1-3/h(H,2,3) Key: QBWCMBCROVPCKQ-UHFFFAOYAO
Properties
Molecular formula	HClO2
Molar mass	68.46 g/mol
Acidity (pKa)	1.96
Y acid (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

Chlorous acid is an inorganic compound with the formula HClO₂. It is a weak acid. Chlorine has oxidation state +3 in this acid. The pure substance is unstable, disproportionating to hypochlorous acid (Cl oxidation state +1) and chloric acid (Cl oxidation state +5):

2 HClO₂ → HClO + HClO₃

Although the acid is difficult to obtain in pure substance, the conjugate base, chlorite, derived from this acid are stable. One example is the salt is well known sodium chlorite. This and related salts are sometimes used in the production of chlorine dioxide.

Preparation

HClO₂ can be prepared through reaction of barium chlorite and dilute sulfuric acid:

Ba(ClO₂)₂ + H₂SO₄ → BaSO₄ + 2HClO₂

Stability

Chlorous acid is a powerful oxidizing agent, although its tendency to disproportionation counteracts its oxidizing potential.

Chlorine is the only halogen to form an isolable acid of formula HXO₂.^[1] Fluorine resists oxidation above the 1+ level. Neither bromous acid nor iodous acid have been isolated. A few salts of bromous acid, bromites, are known, but no iodites.^[1]

References

Media related to Chlorous acid at Wikimedia Commons

1. ^ ^{a b} Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5