What type of hydrocarbons contain double bonds?

Unsaturated hydrocarbons are characterized by the presence of double bonds (or triple bonds) between carbon atoms. This structural feature allows for additional reactions, such as addition reactions, which distinguish them from saturated hydrocarbons. Saturated hydrocarbons, on the other hand, contain only single bonds and are fully 'saturated' with hydrogen atoms, meaning they cannot react to form additional bonds without breaking existing ones.

While it's true that some cyclic hydrocarbons can also be unsaturated, the key defining characteristic here is the presence of double bonds in the hydrocarbon structure itself, which is true for unsaturated hydrocarbons broadly, encompassing alkenes and alkynes. This highlights their importance in organic chemistry, particularly in the formation of complex organic molecules and in various industrial processes.