Learning Objectives Describe the general physical and chemical properties of alkynes. Name alkynes given formulas and write formulas for alkynes given names. The simplest alkyne—a hydrocarbon with carbon-to-carbon triple bond—has the molecular formula C 2 H 2 and is known by its common name—acetylene (Figure \(\PageIndex{1}\)). Its structure is H–C≡C–H. Acetylene is used in oxyacetylene torches for cutting and welding metals. The flame from such a torch can be very hot. Most acetylene, however, is converted to chemical intermediates that are used to make vinyl and acrylic plastics, fibers, resins, and a variety of other products. Alkynes are similar to alkenes in both physical and chemical properties. For example, alkynes undergo many of the typical addition reactions of alkenes. The International Union of Pure and Applied Chemistry (IUPAC) names for alkynes parallel those of alkenes, except that the family ending is - yne rather than - ene . The IUPAC name for acetylene is ethyne. The names of other alkynes are illustrated in the following exercises. Key Takeaway Alkynes are hydrocarbons with carbon-to-carbon triple bonds and properties much like those of alkenes.