Aliphatic compound

File:Butan Lewis.svg

Acyclic aliphatic/non-aromatic compound (butane)

File:Cyclobutane2.svg

Cyclic aliphatic/non-aromatic compound (cyclobutane)

In organic chemistry, hydrocarbons (compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (Template:IPAc-en; G. aleiphar, fat, oil). Aliphatic compounds can be saturated (in which all the C-C bonds are single, requiring the structure to be completed, or 'saturated', by hydrogen) like hexane, or unsaturated, like hexene and hexyne. Open-chain compounds, whether straight or branched, and which contain no rings of any type, are always aliphatic. Cyclic compounds can be aliphatic if they are not aromatic.

Structure

Aliphatic compounds can be saturated, joined by single bonds (alkanes), or unsaturated, with double bonds (alkenes) or triple bonds (alkynes). If other elements (heteroatoms) are bound to the carbon chain, the most common being oxygen, nitrogen, sulfur, and chlorine, it is no longer a hydrocarbon, and therefore no longer an aliphatic compound. However, such compounds may still be referred to as aliphatic if the hydrocarbon portion of the molecule is aliphatic, e.g. aliphatic amines, to differentiate them from aromatic amines.

The least complex aliphatic compound is methane (CH₄).

Properties

Most aliphatic compounds are flammable, allowing the use of hydrocarbons as fuel, such as methane in natural gas for stoves or heating; butane in torches and lighters; various aliphatic (as well as aromatic) hydrocarbons in liquid transportation fuels like petrol/gasoline, diesel, and jet fuel; and other uses such as ethyne (acetylene) in welding.

Examples of aliphatic compounds

The most important aliphatic compounds are:

• n-, iso- and cyclo-alkanes (saturated hydrocarbons)
• n-, iso- and cyclo-alkenes and -alkynes (unsaturated hydrocarbons).

Important examples of low-molecular aliphatic compounds can be found in the list below (sorted by the number of carbon-atoms):

Formula	Name	Structural formula	Chemical classification
Template:Chem2	Methane	File:Methane-2D-stereo.svg	Alkane
Template:Chem2	Acetylene	File:Ethyne-2D-flat.png	Alkyne
Template:Chem2	Ethylene	File:Ethene structural.svg	Alkene
Template:Chem2	Ethane	File:Ethan Lewis.svg	Alkane
Template:Chem2	Propadiene	File:Structural formula of propadiene.svg	Diene
Template:Chem2	Propyne	File:Propyne-2D-flat.png	Alkyne
Template:Chem2	Propylene	File:Propene Structural Formula V1.svg	Alkene
Template:Chem2	Propane	File:Propan Lewis.svg	Alkane
Template:Chem2	1,2-Butadiene	File:Buta-1,2-dien.svg	Diene
Template:Chem2	1-Butyne	File:Ethylacetylene.svg	Alkyne
Template:Chem2	1-Butene	File:1-Butene.svg	Alkene
Template:Chem2	Butane	File:Butan Lewis.svg	Alkane
Template:Chem2	Pentane	File:Pentan Skelett.svg	Alkane
Template:Chem2	Cyclohexene	File:Cyclohexen - Cyclohexene.svg	Cycloalkene
Template:Chem2	Cyclohexane	File:Cyclohexane simple.svg	Cycloalkane
Template:Chem2	Hexane	File:Hexan Skelett.svg	Alkane
Template:Chem2	Methylcyclohexane	File:Methylcyclohexane.svg	Cycloalkane
Template:Chem2	Cubane	File:Cuban.svg	Prismane, Platonic hydrocarbon
Template:Chem2	Octane	File:Octan Skelett.svg	Alkane
Template:Chem2	Dicyclopentadiene	File:Di-Cyclopentadiene ENDO & EXO V.2.svg	Diene, Cycloalkene
Template:Chem2	Terpinene	File:Alpha-Terpinene.svgFile:Beta-Terpinene.svg	Terpene, Diene, Cycloalkene
Template:Chem2	Phellandrene	File:Phellandrene alpha.svgFile:Phellandrene beta.svg	Terpene, Diene, Cycloalkene
Template:Chem2	Limonene	File:(R)-Limonen.svgFile:(S)-Limonen.svg	Terpene, Diene, Cycloalkene
Template:Chem2	Decane	File:Decan Skelett.svg	Alkane
Template:Chem2	Squalene	File:Squalene.svg	Terpene, Polyene
Template:Chem2	Polyethylene	File:Polyethylene repeat unit.svg	Alkane