Alkenes

Basic Structure and Properties

Alkenes are a type of hydrocarbon which contain a carbon–carbon double bond.
This double bond makes alkenes a series of unsaturated hydrocarbons.
The general formula for alkenes is CnH2n, where ‘n’ represents the number of carbon atoms.
Common examples of alkenes include ethene (C2H4), propene (C3H6), and butene (C4H8).

Naming of Alkenes

Alkenes are named based on the number of carbon atoms they contain. For instance, ethene has two carbons, propene has three carbons, and so on.
If a molecule contains more than one double bond, a prefix (di-, tri-, etc.) is added. For example, a molecule with two double bonds is called an alkadiene.

Chemical Reactions

The presence of the double bond makes alkenes more reactive than their alkane counterparts. They undergo addition reactions, where the double bond opens up to allow bonds with other atoms.
Alkenes can easily react with halogens (like bromine and chlorine), hydrogen, water, and hydrogen halides, wherein the double bond breaks and the molecules add across this bond.
The reaction of bromine water with alkenes is a common test for unsaturation, as the bromine water is decolourised.

Uses of Alkenes

Alkenes are primarily used in the petrochemical industry for the production of polymers like plastics and resins.
Ethene, one of the simplest alkenes, can be converted into ethanol, which is used widely in the alcoholic beverages and the biofuel industry.

These key points provide an overview of alkenes, their properties, reactions and uses. Understanding these aspects is crucial in the field of organic chemistry.