See page 969. In nature the 5 and 6 C compounds are the most common. Alkenes and Alkynes Unsaturated hydrocarbons, those that contain either C to C double or triple bonds. More H atoms can be added to these compounds. Alkynes-hydrocarbons which contain ato least one .
Unsaturated compound can add hydrogen and become saturated.
V. Aromatic Hydrocarbons-Derived from the compound called benzene. Has a molecular formula of C 6 H 6 . Doesn't fit the properties of other hydrocarbons. Unsaturated but don't add H 2 readily 2. Structure for benzene proposed by August Kekule in 1865.