Cyclopropane is the cycloalkane with the molecular formula (CH2)3, consisting of three methylene groups (CH2) linked to each other to form a triangular ring. Because of its strained ring structure, it is more reactive and explosive than other saturated hydrocarbons. It was discovered by A. Freund in 1881; the same year he proposed the correct structure and synthesized it by treating 1,3-dibromopropane with sodium. For a while, cyclopropane was used as an anesthetic, but this use has been discontinued because the gas is dangerous to manufacture and handle.