aliphatic compound, any of a large class of organic compounds whose carbon atoms are joined together in straight or branched open chains rather than in rings. The hydrocarbons of the alkane, alkene, and alkyne series are aliphatic compounds, as are fatty acids and many other compounds. Most compounds containing rings are aromatic compounds; compounds that contain a ring but are not aromatic compounds are called alicyclic.

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 (G. aleiphar, fat, oil), which do not contain aromatic rings.

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 such as fatty acids and paraffin hydrocarbons, alkenes (such as ethylene) and alkynes (such as acetylene).

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

Examples

See also

• Aromatic compound
• Carbon-carbon bond

References