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. In contrast to early-twentieth century textbooks, numerous studies conducted since ca. 1990 identified H₂C O₃ as a real molecule with a distinct Raman spectrum and with a first-order life-time of ca. 20 ms at 37 °C. Solid anhydrous carbonic acid has also been isolated.

The interconversion of carbon dioxide and carbonic acid is related to the breathing process of all aerobic organisms and to the acidification of natural waters.