Alkén

Alkén, also known as alkene, is a class of unsaturated hydrocarbons characterized by the presence of at least one carbon-carbon double bond. The general formula for alkenes with one double bond is CnH2n, where 'n' represents the number of carbon atoms. Ethene (C2H4) is the simplest alkene, followed by propene (C3H6) and butene (C4H8). The presence of the double bond makes alkenes more reactive than alkanes, which contain only single bonds. This reactivity is primarily due to the pi bond within the double bond, which is weaker than the sigma bond and more accessible for chemical reactions.

Alkenes undergo a variety of addition reactions, where atoms or groups of atoms are added across the double bond. Common examples include hydrogenation, where hydrogen is added to form alkanes, and halogenation, where halogens like bromine or chlorine are added. Hydration, the addition of water, leads to the formation of alcohols. The double bond can also participate in polymerization, a process where small alkene molecules (monomers) join together to form long chains (polymers). Polyethylene, a widely used plastic, is formed from the polymerization of ethene. Alkenes are important intermediates in organic synthesis and are found in various natural products.