Propene, also known as propylene or methyl ethylene, 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.
At room temperature and atmospheric pressure, propene is a gas, and as with many other alkenes, it is also colorless 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 Cs).
Propene has the same empirical formula as cyclopropane but their atoms are connected in different ways, making these molecules structural isomers.
Propene is found in nature and is a byproduct of vegetation and fermentation processes. On September 30, 2013 NASA announced that the Cassini orbiter space craft, part of the Cassini-Huygens mission, had discovered small amounts of naturally occurring propene in the atmosphere of Titan (moon) using spectroscopy.