Unsaturated Hydrocarbons
Definition and meaning of Unsaturated Hydrocarbons in chemistry.
Unsaturated hydrocarbons are organic compounds consisting entirely of carbon and hydrogen atoms that contain at least one double or triple carbon-carbon bond.
In more detail
Because of the definitive presence of these multiple bonds, unsaturated hydrocarbons inherently possess fewer hydrogen atoms than the corresponding saturated alkanes with the identical number of carbon atoms. The presence of pi bonds in these molecules makes them highly chemically reactive, allowing them to readily undergo various addition reactions where new chemical substituents are added directly across the multiple bonds without replacing existing atoms. The main structural categories of unsaturated hydrocarbons are alkenes, which contain one or more double bonds, alkynes, which contain triple bonds, and aromatic hydrocarbons, which feature exceptionally stable conjugated ring systems.
Key facts
| Field | Organic Chemistry |
|---|---|
| General Formula | CnH2n for alkenes, CnH2n-2 for alkynes |
| Key Feature | Contains reactive double or triple bonds |
| Typical Reactivity | Highly prone to addition reactions |
Ethene (C2H4) is the simplest possible unsaturated hydrocarbon and contains a single carbon-carbon double bond. This fundamental molecule is widely used in the chemical industry as the primary building block for the large-scale production of polyethylene plastic.
Frequently asked questions
How can you visually test for the clear presence of an unsaturated hydrocarbon?
Adding aqueous bromine water is a classic common test; a typical unsaturated hydrocarbon will rapidly react with the bromine and quickly decolorize the previously colored solution.