Propionic acid

Propionic acid
Simplified skeletal formula	Full structural formula
Ball-and-stick model	Space-filling model
Names
	Preferred IUPAC name Propanoic acid
	Other names Carboxyethane; Ethanecarboxylic acid; Ethylformic acid; Metacetonic acid; Methylacetic acid; C3:0 (Lipid numbers)
Identifiers
CAS Number	Propionic acid: 79-09-4 ; Propionate: 72-03-7 ;
3D model (JSmol)	Propionic acid: Interactive image; Propionate: Interactive image;
ChEBI	Propionic acid: CHEBI:30768 ;
ChEMBL	Propionic acid: ChEMBL14021 ;
ChemSpider	Propionic acid: 1005 ; Propionate: 94556;
DrugBank	Propionic acid: DB03766 ;
ECHA InfoCard	100.001.070
EC Number	Propionic acid: 201-176-3;
E number	E280 (preservatives)
IUPHAR/BPS	Propionic acid: 1062;
PubChem CID	Propionic acid: 1032; Propionate: 104745;
RTECS number	Propionic acid: UE5950000;
UNII	Propionic acid: JHU490RVYR ; Propionate: AKW5EM890C ;
CompTox Dashboard (EPA)	Propionic acid: DTXSID201058721 DTXSID8025961, DTXSID201058721 ;
	InChI InChI=1S/C3H6O2/c1-2-3(4)5/h2H2,1H3,(H,4,5) Key: XBDQKXXYIPTUBI-UHFFFAOYSA-N ;
	SMILES Propionic acid: CCC(=O)O; Propionate: CCC(=O)[O-];
Properties
Chemical formula	C3H6O2
Molar mass	74.079 g·mol−1
Appearance	Colorless, oily liquid
Odor	Pungent, rancid, unpleasant
Density	0.98797 g/cm3
Melting point	−20.5 °C (−4.9 °F; 252.7 K)
Boiling point	141.15 °C (286.07 °F; 414.30 K)
Sublimation; conditions	Sublimes at −48 °C; ΔsublHo = 74 kJ/mol
Solubility in water	Miscible
Solubility	Miscible in ethanol, ether, CHCl; 3
log P	0.33
Vapor pressure	0.32 kPa (20 °C); 0.47 kPa (25 °C); 9.62 kPa (100 °C)
Henry's law; constant (kH)	4.45·10−4 L·atm/mol
Acidity (pKa)	4.88
Magnetic susceptibility (χ)	−43.50·10−6 cm3/mol
Refractive index (nD)	1.3843
Viscosity	1.175 cP (15 °C); 1.02 cP (25 °C); 0.668 cP (60 °C); 0.495 cP (90 °C)
Structure
Crystal structure	Monoclinic (−95 °C)
Space group	P21/c
Lattice constant	a = 4.04 Å, b = 9.06 Å, c = 11 Å α = 90°, β = 91.25°, γ = 90°
Dipole moment	0.63 D (22 °C)
Thermochemistry
Heat capacity (C)	152.8 J/mol·K
Std molar; entropy (S⦵298)	191 J/mol·K
Std enthalpy of; formation (ΔfH⦵298)	−510.8 kJ/mol
Std enthalpy of; combustion (ΔcH⦵298)	1527.3 kJ/mol
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Corrosive
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314
Precautionary statements	P280, P305+P351+P338, P310
NFPA 704 (fire diamond)	3 2 0
Flash point	54 °C (129 °F; 327 K)
Autoignition; temperature	512 °C (954 °F; 785 K)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	1370 mg/kg (mouse, oral)
	NIOSH (US health exposure limits):
PEL (Permissible)	none
REL (Recommended)	TWA 10 ppm (30 mg/m3) ST 15 ppm (45 mg/m3)
IDLH (Immediate danger)	N.D.
Related compounds
Related Carboxylic acids	Acetic acid; Lactic acid; 3-Hydroxypropionic acid; Tartronic acid; Acrylic acid; Butyric acid
Related compounds	1-Propanol; Propionaldehyde; Sodium propionate; Propionic anhydride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Propionic acid (/proʊpiˈɒnɪk/, from the Greek words πρῶτος : prōtos, meaning "first", and πίων : píōn, meaning "fat"; also known as propanoic acid) is a naturally occurring carboxylic acid with chemical formula CH
₃CH
₂CO
₂H. It is an oily liquid with a pungent and unpleasant smell. The anion CH
₃CH
₂CO⁻
₂ as well as the salts and esters of propionic acid are known as propionates or propanoates. Propionic acid is the third simplest carboxylic acid, with the first two being formic acid and acetic acid.

About half of the world production of propionic acid is consumed as a preservative for both animal feed and food for human consumption. It is also useful as an intermediate in the production of other chemicals, especially polymers.