In organic chemistry, compounds composed of carbon and hydrogen are divided into two classes: aromatic compounds, which contain benzene rings or similar rings of atoms, and aliphatic compounds (IPA: [ˌæləˈfætɪk]; G. aleiphar, fat, oil), which do not contain aromatic rings.^[1]
Aliphatic compounds can be cyclic, like cyclohexane, or acyclic, like hexane. They also can be saturated, like hexane, or unsaturated, like hexene.

In aliphatic compounds, carbon atoms can be joined together in straight chains, branched chains, or non-aromatic rings (in which case they are called alicyclic). They can be joined by single bonds (alkanes), double bonds (alkenes), or triple bonds (alkynes). Besides hydrogen, other elements can be bound to the carbon chain, the most common being oxygen, nitrogen, sulfur, and chlorine.

The simplest aliphatic compound is methane (CH₄). Aliphatics include alkanes (e.g. paraffin hydrocarbons), alkenes (e.g. ethylene) and alkynes (e.g. acetylene). Fatty acids consist of an unbranched aliphatic tail attached to a carboxyl group.

Most aliphatic compounds are flammable, allowing the use of hydrocarbons as fuel, such as methane in Bunsen burners, and acetylene in welding.

[edit] Examples

Ethane

Isobutane

Acetylene

[edit] See also

• Aromatic compound
• Carbon-carbon bond

[edit] References

1. ^ International Union of Pure and Applied Chemistry (1995). "Aliphatic compounds". Compendium of Chemical Terminology Internet edition.