Aliphatic compound

Acyclic aliphatic/non-aromatic compound (butane)

Cyclic aliphatic/non-aromatic compound (cyclobutane)

Inorganic chemistry,hydrocarbons(compoundscomposed solely ofcarbonandhydrogen) are divided into two classes:aromatic compoundsandaliphatic compounds(/ˌælɪˈfætɪk/;G.aleiphar,fat, oil). Aliphatic compounds can besaturated(in which all the C-C bonds are single requiring the structure to be completed, or 'saturated', by hydrogen) likehexane,orunsaturated,likehexeneandhexyne.Open-chain compounds,whether straight or branched, and which contain no rings of any type, are always aliphatic.Cyclic compoundscan be aliphatic if they are notaromatic.

Structure

Aliphatic compounds can besaturated,joined by single bonds (alkanes), or unsaturated, with double bonds (alkenes) or triple bonds (alkynes). If other elements (heteroatoms) are bound to thecarbon chain,the most common beingoxygen,nitrogen,sulfur,andchlorine,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 fromaromatic amines.

The least complex aliphatic compound ismethane(CH₄).

Properties

Most aliphatic compounds areflammable,allowing the use ofhydrocarbonsasfuel,such as methane innatural gasfor stoves or heating;butaneintorchesandlighters;various aliphatic (as well as aromatic) hydrocarbons in liquid transportation fuels likepetrol/gasoline,diesel,andjet fuel;and other uses such asethyne(acetylene) inwelding.

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
CH4	Methane		Alkane
C2H2	Acetylene		Alkyne
C2H4	Ethylene		Alkene
C2H6	Ethane		Alkane
C3H4	Propyne		Alkyne
C3H6	Propene		Alkene
C3H8	Propane		Alkane
C4H6	1,2-Butadiene		Diene
C4H6	1-Butyne		Alkyne
C4H8	1-Butene		Alkene
C4H10	Butane		Alkane
C6H10	Cyclohexene		Cycloalkene
C5H12	n-pentane		Alkane
C7H14	Cycloheptane		Cycloalkane
C7H14	Methylcyclohexane		Cyclohexane
C8H8	Cubane		Prismane,Platonic hydrocarbon
C9H20	Nonane		Alkane
C10H12	Dicyclopentadiene		Diene, Cycloalkene
C10H16	Phellandrene		Terpene,Diene, Cycloalkene
C10H16	α-Terpinene		Terpene, Diene, Cycloalkene
C10H16	Limonene		Terpene, Diene, Cycloalkene
C11H24	Undecane		Alkane
C30H50	Squalene		Terpene, Polyene
C2nH4n	Polyethylene		Alkane