Carbonic acid

Carbonic acid
Names
	IUPAC name Carbonic acid
	Other names Oxidocarboxylic acid; Hydroxyformic acid; Hydroxymethanoic acid; Carbonylic acid; Hydroxycarboxylic acid; Dihydroxycarbonyl; Carbon dioxide solution; Aerial acid; Metacarbonic acid;
Identifiers
CAS Number	463-79-6 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:28976 ;
ChEMBL	ChEMBL1161632 ;
ChemSpider	747 ;
DrugBank	DB14531;
ECHA InfoCard	100.133.015
EC Number	610-295-3;
Gmelin Reference	25554
KEGG	C01353 ;
PubChem CID	767;
UNII	142M471B3J ;
CompTox Dashboard (EPA)	DTXSID9043801 ;
	InChI InChI=1S/CH2O3/c2-1(3)4/h(H2,2,3,4) Key: BVKZGUZCCUSVTD-UHFFFAOYSA-N ; InChI=1/H2O3/c2-1(3)4/h(H2,2,3,4) Key: BVKZGUZCCUSVTD-UHFFFAOYAU;
	SMILES O=C(O)O;
Properties
Chemical formula	H; 2CO; 3
Appearance	Colorless gas
Melting point	−53 °C (−63 °F; 220 K) (sublimes)
Boiling point	127 °C (261 °F; 400 K) (decomposes)
Solubility in water	Reacts to form carbon dioxide and water
Acidity (pKa)	pKa1 = 3.75 (25 °C; anhydrous); pKa1 = 6.35 (hydrous); pKa2 = 10.33;
Conjugate base	Bicarbonate, carbonate
Hazards
NFPA 704 (fire diamond)	0 0 1
Structure
Crystal structure	monoclinic
Space group	p21/c, No. 14
Point group	-
Lattice constant	a = 5.392 Å, b = 6.661 Å, c = 5.690 Å α = 90°, β = 92.66°, γ = 90° (D; 2CO; 3 at 1.85 GPa, 298 K)
Lattice volume (V)	204.12 Å3
Formula units (Z)	4 formula per cell
	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

Carbonic acid is a chemical compound with the chemical formula H₂C O₃. The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature. The interconversion of carbon dioxide and carbonic acid is related to the breathing cycle of animals and the acidification of natural waters.

In biochemistry and physiology, the name "carbonic acid" is sometimes applied to aqueous solutions of carbon dioxide. These chemical species play an important role in the bicarbonate buffer system, used to maintain acid–base homeostasis.

Names


IUPAC name Carbonic acid
Other names Oxidocarboxylic acid Hydroxyformic acid Hydroxymethanoic acid Carbonylic acid Hydroxycarboxylic acid Dihydroxycarbonyl Carbon dioxide solution Aerial acid Metacarbonic acid
Identifiers
CAS Number	463-79-6^Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:28976^Y
ChEMBL	ChEMBL1161632^Y
ChemSpider	747^Y
DrugBank	DB14531
ECHA InfoCard	100.133.015
EC Number	610-295-3
Gmelin Reference	25554
KEGG	C01353^Y
PubChem CID	767
UNII	142M471B3J^Y
CompTox Dashboard (EPA)	DTXSID9043801
InChI InChI=1S/CH2O3/c2-1(3)4/h(H2,2,3,4)^Y Key: BVKZGUZCCUSVTD-UHFFFAOYSA-N^Y InChI=1/H2O3/c2-1(3)4/h(H2,2,3,4) Key: BVKZGUZCCUSVTD-UHFFFAOYAU
SMILES O=C(O)O
Properties
Chemical formula	H ₂CO ₃
Appearance	Colorless gas
Melting point	−53 °C (−63 °F; 220 K) (sublimes)
Boiling point	127 °C (261 °F; 400 K) (decomposes)
Solubility in water	Reacts to form carbon dioxide and water
Acidity (pK_a)	pK_a1 = 3.75 (25 °C; anhydrous) pK_a1 = 6.35 (hydrous) pK_a2 = 10.33
Conjugate base	Bicarbonate, carbonate
Hazards
NFPA 704 (fire diamond)	0 0 1
Structure
Crystal structure	monoclinic
Space group	p21/c, No. 14
Point group	-
Lattice constant	a = 5.392 Å, b = 6.661 Å, c = 5.690 Å α = 90°, β = 92.66°, γ = 90° (D ₂CO ₃ at 1.85 GPa, 298 K)
Lattice volume (V)	204.12 Å³
Formula units (Z)	4 formula per cell
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is ^YN ?) Infobox references