Propane (/ˈproʊpeɪn/) is a three-carbon chain alkane with the molecular formula C₃H₈. It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum refining, it is often a constituent of liquefied petroleum gas (LPG), which is commonly used as a fuel in domestic and industrial applications and in low-emissions public transportation; other constituents of LPG may include propylene, butane, butylene, butadiene, and isobutylene. Discovered in 1857 by the French chemist Marcellin Berthelot, it became commercially available in the US by 1911. Propane has lower volumetric energy density than gasoline or coal, but has higher gravimetric energy density than them and burns more cleanly.

Propane

Names
Preferred IUPAC name Propane
Systematic IUPAC name Tricarbane (never recommended)
Identifiers
CAS Number	74-98-6 Y
3D model (JSmol)	Interactive image
Beilstein Reference	1730718
ChEBI	CHEBI:32879 Y
ChEMBL	ChEMBL135416 Y
ChemSpider	6094 Y
ECHA InfoCard	100.000.753
EC Number	200-827-9
E number	E944 (glazing agents, ...)
Gmelin Reference	25044
KEGG	D05625 Y
PubChem CID	6334
RTECS number	TX2275000
UNII	T75W9911L6 Y
UN number	1978
CompTox Dashboard (EPA)	DTXSID501019643 DTXSID5026386, DTXSID501019643
InChI InChI=1S/C3H8/c1-3-2/h3H2,1-2H3 Y Key: ATUOYWHBWRKTHZ-UHFFFAOYSA-N Y
SMILES CCC
Properties
Chemical formula	C3H8
Molar mass	44.097 g·mol−1
Appearance	Colorless gas
Odor	Odorless
Density	2.0098 kg/m3 (at 0 °C, 101.3 kPa)
Melting point	−187.7 °C; −305.8 °F; 85.5 K
Boiling point	−42.25 to −42.04 °C; −44.05 to −43.67 °F; 230.90 to 231.11 K
Critical point (T, P)	370 K (97 °C; 206 °F), 4.23 MPa (41.7 atm)
Solubility in water	47 mg⋅L−1 (at 0 °C)
log P	2.236
Vapor pressure	853.16 kPa (at 21.1 °C (70.0 °F))
Henry's law constant (kH)	15 nmol⋅Pa−1⋅kg−1
Conjugate acid	Propanium
Magnetic susceptibility (χ)	−40.5 × 10−6 cm3/mol
Dipole moment	0.083 D
Thermochemistry
Heat capacity (C)	73.60 J⋅K−1⋅mol−1
Std enthalpy of formation (ΔfH⦵298)	−105.2–104.2 kJ⋅mol−1
Std enthalpy of combustion (ΔcH⦵298)	−2.2197–2.2187 MJ⋅mol−1
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H220
Precautionary statements	P210
NFPA 704 (fire diamond)	2 4 0
Flash point	−104 °C (−155 °F; 169 K)
Autoignition temperature	470 °C (878 °F; 743 K)
Explosive limits	2.37–9.5%
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 1,000 ppm (1,800 mg/m3)
REL (Recommended)	TWA 1,000 ppm (1,800 mg/m3)
IDLH (Immediate danger)	2,100 ppm
Related compounds
Related alkanes	ethane butane isobutane
Related compounds	propene allene cyclopropane
Supplementary data page
Propane (data page)
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

Propane gas has become a popular choice for barbecues and portable stoves because its low −42 °C boiling point makes it vaporise inside pressurised liquid containers (it exists in two phases, vapor above liquid). It retains its ability to vaporise even in cold weather, making it better-suited for outdoor use in cold climates than alternatives with higher boiling points like butane. LPG powers buses, forklifts, automobiles, outboard boat motors, and ice resurfacing machines, and is used for heat and cooking in recreational vehicles and campers. Propane is also becoming popular as a replacement refrigerant (R290) for heat pumps as it offers greater efficiency than the current refrigerants: R410A / R32, higher temperature heat output and less damage to the atmosphere for escaped gases—at the expense of high gas flammability.