Propene

"Propylene" redirects here. For the unrelated compound referred to as "propolene", see glucomannan.

Propene
IUPAC name Propene
Identifiers
CAS number	115-07-1 Y
PubChem	8252
ChemSpider	7954 Y
UN number	1077 In Liquefied petroleum gas: 1075
KEGG	C11505 Y
ChEBI	CHEBI:16052 Y
ChEMBL	CHEMBL117213 Y
RTECS number	UC6740000
Jmol-3D images	Image 1
SMILES CC=C
InChI InChI=1S/C3H6/c1-3-2/h3H,1H2,2H3 Y Key: QQONPFPTGQHPMA-UHFFFAOYSA-N Y InChI=1/C3H6/c1-3-2/h3H,1H2,2H3 Key: QQONPFPTGQHPMA-UHFFFAOYAA
Properties
Molecular formula	C3H6
Molar mass	42.08 g mol−1
Appearance	Colorless gas
Density	1.81 kg/m3, gas (1.013 bar, 15 °C) 613.9 kg/m3, liquid
Melting point	− 185.2 °C, 88 K, -301 °F
Boiling point	− 47.6 °C, 226 K, -54 °F
Solubility in water	0.61 g/m3
Viscosity	8.34 µPa·s at 16.7 °C
Structure
Dipole moment	0.366 D (gas)
Hazards
MSDS	External MSDS
R-phrases	12
S-phrases	9-16-33
Main hazards	Highly flammable, Asphyxiant
NFPA 704	4 1 1
Flash point	−108 °C
Related compounds
Related groups	Allyl, Propenyl
Related compounds	Propane, Propyne Propadiene, 1-Propanol 2-Propanol
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Propene, also known as propylene or methylethylene, is an unsaturated organic compound having the chemical formula C₃H₆. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons, and it is also second in natural abundance.

Properties

At room temperature and atmospheric pressure, propene is a gas, and as with many other alkenes, it is also colourless with a weak but unpleasant smell.

Propene has a higher density and boiling point than ethylene due to its greater mass. It has a slightly lower boiling point than propane and is thus more volatile. It lacks strongly polar bonds, yet the molecule has a small dipole moment due to its reduced symmetry (its point group is C_s).

Propene has the same empirical formula as cyclopropane but their atoms are connected in different ways, making these molecules structural isomers.

Production

Propene is produced from fossil fuels—petroleum, natural gas, and, to a much lesser extent, coal. Propene is a byproduct of oil refining and natural gas processing. During oil refining, ethylene, propene, and other compounds are produced as a result of cracking larger hydrocarbon molecules to produce hydrocarbons more in demand. A major source of propene is cracking intended to produce ethylene, but it also results from refinery cracking producing other products. Propene can be separated by fractional distillation from hydrocarbon mixtures obtained from cracking and other refining processes; refinery-grade propene is about 50 to 70%.

Another important petrochemical source of propene is propane dehydrogenation. This route is popular in regions, such as the Middle East, where there is an abundance of propane from oil/gas operations. Less common propene sources are the Fischer-Tropsch process, metathesis of ethylene or an ethylene/butene mixture, and catalytic conversion of methanol.

Propene production has remained static at around 35 million tonnes (Europe and North America only) from 2000 to 2008, but it has been increasing in East Asia, most notably Singapore and China. Total world production of propene is currently about half that of ethylene.

Uses

Propene is the second most important starting product in the petrochemical industry after ethylene. It is the raw material for a wide variety of products. Manufacturers of the plastic polypropylene account for nearly two thirds of all demand. Polypropylene is, for example, needed for the production of films, packaging, caps and closures as well as for other applications. In the year 2008 the worldwide sales of propene reached a value of over 90 billion US dollars.

Propene and benzene are converted to acetone and phenol via the cumene process. Propene is also used to produce isopropanol (propan-2-ol), acrylonitrile, propylene oxide (epoxypropane) and epichlorohydrin.

Reactions

Propene resembles other alkenes in that it undergoes addition reactions relatively easily at room temperature. The relative weakness of its double bond (which is less strong than two single bonds) explains its tendency to react with substances that can achieve this transformation. Alkene reactions include: 1) polymerization, 2) oxidation, 3) halogenation and hydrohalogenation, 4) alkylation, 5) hydration, 6) oligomerization, and 7) hydroformylation.

Environmental safety

Propene is produced naturally by vegetation, particularly certain tree species. It is also a product of combustion, from forest fires and cigarette smoke to motor vehicle and aircraft exhaust. It is an impurity in some heating gases. Observed concentrations have been in the range of 0.1-4.8 parts per billion (ppb) in rural air, 4-10.5 ppb in urban air, and 7-260 ppb in industrial air samples.

In the United States and some European countries a Threshold Limit Value of 500 parts per million (ppm) was established for occupational (8-hour time-weighted average) exposure. It is considered a volatile organic compound (VOC) and emissions are regulated by many governments, but it is not listed by the U.S. Environmental Protection Agency (EPA) as a hazardous air pollutant under the Clean Air Act.

It has a relatively short half-life in the atmosphere, and is not expected to bioaccumulate, based on a calculated bioconcentration factor of 13.18 using a log K_ow value of 1.77.

Propene has low acute toxicity from inhalation. Inhalation of the gas can cause anesthetic effects and at very high concentrations, unconsciousness. However, the asphyxiation limit for humans is about 10 times higher (23%) than the lower flammability level.