In organic chemistry, compounds composed of carbon and hydrogen are divided into two classes: aromatic compounds, which contain benzene rings or similar rings of atoms, and aliphatic compounds (: [ˌæləˈfætɪk]; G. aleiphar, fat, oil), which don't contain aromatic rings. Aliphatic compounds can be cyclic, like cyclohexane, or acyclic, like hexane. They also can be saturated, like hexane, or unsaturated, like hexene. In aliphatic compounds, carbon atoms can be joined t… (More on Aliphatic)