Chain compounds include aliphatic compounds and chain compounds containing other elements or groups. Aliphatic hydrocarbons are hydrocarbons with the basic properties of aliphatic compounds. In aliphatic compounds, carbon atoms are arranged in straight chain, branched chain or cyclic, which are respectively called straight chain aliphatic hydrocarbons, branched chain aliphatic hydrocarbons and alicyclic hydrocarbons. Some cyclic hydrocarbons are different in nature from aromatic hydrocarbons, and are very similar to aliphatic hydrocarbons. Such cyclic hydrocarbons are called alicyclic hydrocarbons. In this way, aliphatic hydrocarbons become a general term for all hydrocarbons except aromatic hydrocarbons. Aliphatic hydrocarbons and their derivatives (including halogenated hydrocarbons) and alicyclic hydrocarbons and their derivatives are collectively referred to as aliphatic compounds.