Which of the following compounds contains a triple bond?

The compound Propyne contains a triple bond, which is a key characteristic that differentiates it from the other options listed. In organic chemistry, a triple bond consists of one sigma bond and two pi bonds, and is typically represented by three lines between two atoms in a structural formula.

Propyne, with the molecular formula C₃H₄, features a carbon-carbon triple bond between two of its carbon atoms. This configuration contributes to its reactivity and stability properties, making it an alkyne—a class of hydrocarbons characterized by the presence of at least one carbon-carbon triple bond.

In contrast, Ethene (C₂H₄), Butene (C₄H₈), and Hexene (C₆H₁₂) are alkenes, which only contain carbon-carbon double bonds. These compounds do not meet the criteria of containing a triple bond. Thus, the presence of the triple bond in Propyne is what makes it the correct answer in this context.