Nitrous acid

Nitrous acid
Names
	IUPAC name Nitrous acid
Identifiers
CAS Number	7782-77-6 ;
3D model (JSmol)	Interactive image;
3DMet	B00022;
ChEBI	CHEBI:25567 ;
ChEMBL	ChEMBL1161681 ;
ChemSpider	22936 ;
ECHA InfoCard	100.029.057
EC Number	231-963-7;
Gmelin Reference	983
KEGG	C00088 ;
MeSH	Nitrous+acid
PubChem CID	24529;
UNII	T2I5UM75DN ;
CompTox Dashboard (EPA)	DTXSID7064813 ;
	InChI InChI=1S/HNO2/c2-1-3/h(H,2,3) Key: IOVCWXUNBOPUCH-UHFFFAOYSA-N ;
	SMILES O=NO;
Properties
Chemical formula	HNO2
Molar mass	47.013 g/mol
Appearance	Pale blue solution
Density	Approx. 1 g/ml
Melting point	Only known in solution or as gas
Acidity (pKa)	3.15
Conjugate base	Nitrite
Hazards
NFPA 704 (fire diamond)	4 0 2 OX
Flash point	Non-flammable
Related compounds
Other anions	Nitric acid
Other cations	Sodium nitrite; Potassium nitrite; Ammonium nitrite
Related compounds	Dinitrogen trioxide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Nitrous acid (molecular formula H N O
₂) is a weak and monoprotic acid known only in solution, in the gas phase, and in the form of nitrite (NO⁻
₂) salts.^[3] It was discovered by Carl Wilhelm Scheele, who called it "phlogisticated acid of niter". Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagents in azo coupling reactions to give azo dyes.

^ "Nitrous Acid".
^ Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2^nd ed.). Oxford: Pergamon (published 1984). Entry 156. ISBN 0-08-029214-3. LCCN 82-16524.
^ Cite error: The named reference G&E was invoked but never defined (see the help page).

Names

IUPAC name Nitrous acid^[1]
Identifiers
CAS Number	7782-77-6^Y
3D model (JSmol)	Interactive image
3DMet	B00022
ChEBI	CHEBI:25567^Y
ChEMBL	ChEMBL1161681^Y
ChemSpider	22936^Y
ECHA InfoCard	100.029.057
EC Number	231-963-7
Gmelin Reference	983
KEGG	C00088^N
MeSH	Nitrous+acid
PubChem CID	24529
UNII	T2I5UM75DN^Y
CompTox Dashboard (EPA)	DTXSID7064813
InChI InChI=1S/HNO2/c2-1-3/h(H,2,3)^Y Key: IOVCWXUNBOPUCH-UHFFFAOYSA-N^Y
SMILES O=NO
Properties
Chemical formula	HNO₂
Molar mass	47.013 g/mol
Appearance	Pale blue solution
Density	Approx. 1 g/ml
Melting point	Only known in solution or as gas
Acidity (pK_a)	3.15^[2]
Conjugate base	Nitrite
Hazards
NFPA 704 (fire diamond)	4 0 2 OX
Flash point	Non-flammable
Related compounds
Other anions	Nitric acid
Other cations	Sodium nitrite Potassium nitrite Ammonium nitrite
Related compounds	Dinitrogen trioxide
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