What is an alkene and how is it formed?

An alkene is a hydrocarbon with a carbon-carbon double bond. It is formed through elimination reactions.

Alkenes are unsaturated hydrocarbons that contain at least one carbon-carbon double bond. The double bond consists of a sigma bond and a pi bond, which is responsible for the reactivity of alkenes. The general formula for alkenes is CnH2n, where n is the number of carbon atoms in the molecule.

Alkenes are formed through elimination reactions, which involve the removal of a leaving group from a molecule to form a double bond. The most common type of elimination reaction is the dehydrohalogenation of alkyl halides, which involves the removal of a hydrogen halide (H-X) from the molecule. This reaction is catalysed by a strong base, such as sodium hydroxide (NaOH), which abstracts the acidic hydrogen from the alkyl halide.

Another way to form alkenes is through dehydration reactions, which involve the removal of a water molecule from an alcohol. This reaction is also catalysed by a strong acid, such as concentrated sulfuric acid (H2SO4), which protonates the alcohol to form a good leaving group.

Alkenes are important intermediates in organic synthesis and are used in the production of a wide range of chemicals, including plastics, solvents, and pharmaceuticals. They are also important in biological systems, where they play a role in the biosynthesis of fatty acids and other natural products.