alkyne ăl´kīn [key], any of a group of aliphatic hydrocarbons whose molecules contain one or more carbon-carbon triple bonds (see chemical bond). Alkynes with one triple bond have the general formula CnH2n−2. In the International Union of Pure and Applied Chemistry (IUPAC) system of chemical nomenclature, the name of an alkyne is derived from the name of the corresponding alkane by replacing the -ane alkane suffix with -yne and, if necessary, adding a prefix to indicate the location of the triple bond in the molecule. The IUPAC name of the simplest alkyne, HC≡CH, is thus ethyne, which is derived from ethane. Ethyne is more commonly known as acetylene; it is an extremely important starting material in commercial chemical synthesis. The next simplest alkyne is propyne, CH3C≡CH. There are two butynes, 1-butyne and 2-butyne, which are structural isomers that differ in the location of the triple bond in their molecule. The alkynes are sometimes referred to as the acetylene series, the higher members of the series being named as derivatives of acetylene, e.g., propyne as methylacetylene, 1-butyne as ethylacetylene, and 2-butyne as dimethylacetylene. The usefulness of the alkynes in chemical synthesis is due both to the reactions of the triple bond itself and to the relative acidity of a hydrogen atom bonded to a triply bonded carbon.
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