Acetic acid

Acetic acid, or ethanoic acid, is a carboxylic acid. It is the main compound of vinegar, other than water. The chemical formula is CH₃COOH (also written as CH₃CO₂H, HC₂H₃O₂, or C₂H₄O₂).

Acetic acid

Skeletal formula of acetic acid Spacefill model of acetic acid
Skeletal formula of acetic acid with all explicit hydrogens added Ball and stick model of acetic acid
Names
Preferred IUPAC name Acetic acid[1]
Systematic IUPAC name Ethanoic acid
Other names Vinegar (when dilute); Hydrogen acetate; Methanecarboxylic acid[2][3]
Identifiers
CAS Number	64-19-7 Y
3D model (JSmol)	Interactive image
3DMet	B00009
Abbreviations	AcOH
Beilstein Reference	506007
ChEBI	CHEBI:15366 Y
ChEMBL	ChEMBL539 Y
ChemSpider	171 Y
DrugBank	DB03166 Y
ECHA InfoCard	100.000.528
EC Number	200-580-7
E number	E260 (preservatives)
Gmelin Reference	1380
IUPHAR/BPS	1058
KEGG	D00010 N
MeSH	Acetic+acid
PubChem CID	176
RTECS number	AF1225000
UNII	Q40Q9N063P Y
UN number	2789
CompTox Dashboard (EPA)	DTXSID5024394
SMILES CC(O)=O
Properties
Chemical formula	C2H4O2
Molar mass	60.05 g·mol−1
Appearance	Colourless liquid
Odor	Pungent/Vinegar-like
Density	1.049 g cm−3 (liquid); 1.27 g cm cm−3 (solid)
Melting point	16 to 17 °C; 61 to 62 °F; 289 to 290 K
Boiling point	118 to 119 °C; 244 to 246 °F; 391 to 392 K
Solubility in water	Miscible
log P	-0.28[4]
Acidity (pKa)	4.756 (H2O)[5] 12.6 (DMSO)[6]
Basicity (pKb)	9.24 (basicity of acetate ion)
Conjugate base	Acetate
Magnetic susceptibility (χ)	-31.54·10−6 cm3/mol
Refractive index (nD)	1.371
Viscosity	1.22 mPa s
Dipole moment	1.74 D
Thermochemistry
Std enthalpy of formation ΔfHo298	-483.88—483.16 kJ mol−1
Std enthalpy of combustion ΔcHo298	-875.50—874.82 kJ mol−1
Standard molar entropy So298	158.0 J K−1 mol−1
Specific heat capacity, C	123.1 J K−1 mol−1
Pharmacology
ATC code	G01AD02 (WHO) S02AA10 (WHO)
Hazards
NFPA 704	2 3 0
Explosive limits	4–16%
U.S. Permissible exposure limit (PEL)	TWA 10 ppm (25 mg/m3)[7]
Related compounds
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Vinegar contains acetic acid. Aceto balsamico, vinegar from red and from white wine.

It tastes and smells sour; it has no color. Its melting point is 16.5 °C (61.6 °F) and its boiling point is 118.1 °C (244.5 °F). It has a pH of 2.4.

Acetic acid is commonly used as a food additive. It has the E numbers E 260 (acetic acid).

Potassium acetate (E 261), sodium acetate (E 262), and calcium acetate (E 2639) are salts of acetic acid; they are commonly used to preserve food, usually vegetables. In sourdough, ethanol fermentation is used.