Propionic acid

Propionic acid
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	8.19 g/g (−28.3 °C); 34.97 g/g (−23.9 °C); Miscible (≥ −19.3 °C)
Solubility	Miscible in EtOH, 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 a liquid with a pungent and unpleasant smell somewhat resembling body odor. The anion CH
₃CH
₂CO⁻
₂ as well as the salts and esters of propionic acid are known as propionates or propanoates.

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.