unsaturated hydrocarbons
Unsaturated hydrocarbons that contain one or more triple bonds are called alkynes . The names of specific alkynes always end in yne and have a prefix for the number of carbon atoms. The structural formula in the Figure below represents the smallest alkyne, named ethyne, which has two carbon atoms and two hydrogen atoms C 2 H 2 . Ethyne is also called acetylene. It is burned in acetylene torches, like the one pictured in the Figure below . The flame of an acetylene torch is so hot that it can melt metal.