Propan-1,2-diene is the simplest allene.

3D view of allene.

An allene is a hydrocarbon in which one atom of carbon is connected by double bonds with two other atoms of carbon. Allene also is the common name for the parent compound of this series, propan-1,2-diene. By Magnus Manske File links The following pages link to this file: Allene Categories: GFDL images ... By Magnus Manske File links The following pages link to this file: Allene Categories: GFDL images ... Image File history File links Allene3D.png‎ 3D representation of allene I, the creator of this work, hereby release it into the public domain. ... Image File history File links Allene3D.png‎ 3D representation of allene I, the creator of this work, hereby release it into the public domain. ... Hydrocarbons are refined at oil refineries and processed at chemical plants In chemistry, a hydrocarbon is any chemical compound that consists only of the elements carbon (C) and hydrogen (H). ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... Covalently bonded hydrogen and carbon in a molecule of methane. ...

Such pair of bonds make allenes much more reactive than other alkenes. For example, their reactivity with gaseous chlorine is more like the reactivity of alkynes. The chemical structure of ethylene, the simplest alkene. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Atomic mass 35. ... Alkynes are hydrocarbons that have at least one triple bond between two carbon atoms. ...

In the image at the right, if groups "a" and "b" replace one of the hydrogens on the left and right sides, the molecule will be chiral if "a" is not identical to "b". This is because the two sets of groups are perpendicular to each other, and thus the molecule has no mirror plane. Chirality refers to several phenomena, all having to do with objects that differ from their mirror image. ...

See also

• Compounds with more than two adjacent carbon-carbon double bonds are called cumulenes.
• The allene motif is frequently encountered in carbomers.

A cumulene is an chemical compound with two or more cumulative (consecutive) double bonds, for example 1,2-propadiene. ... A carbomer in organic chemistry is an expanded molecule obtained by insertion of a C2 unit in a given molecule [1]. Carbomers differ from their templates only in size but not in symmetry or energy when each C-C single bond is replaced by at least one alkyne bond and...

Geometry

The central carbon of allene forms two sigma bonds and two pi bonds. The central carbon is sp-hybridised, and the two terminal carbons are sp2-hybridised. The bond angle formed by the three carbons is 180 degrees, indicating linear geometry for the carbons of allene. Electron atomic and molecular orbitals, showing among others the sigma bond of two s-orbitals and a sigma bond of two p-orbitals In chemistry, sigma bonds (σ-bonds) are bonds where there is no nodal plane containing the line segment between the two bonded species. ... Electron atomic and molecular orbitals, showing a Pi-bond at the bottom right of the picture In chemistry, pi bonds (π bonds) are bonds with a single nodal plane containing the line segment between the two atoms. ... four sp³ orbitals three sp² orbitals In chemistry, hybridisation or hybridization (see spelling differences) is the mixing of atomic orbitals belonging to a same electron shell to form new orbitals suitable for the qualitative description of atomic bonding properties. ...

External links

• Stereochemistry study guide
• Synthesis of allenes