Homologous Series: Alkenes – A Level Chemistry Revision

Homologous Series: Alkenes - A Level Chemistry Revision

Welcome back to Beyond’s Science Blog! This A Level Chemistry blog entry explores the Homologous Series: Alkenes.

Alkenes are unsaturated hydrocarbons. They contain at least one C=C double covalent bond. They are named using the suffix -ene and the position of the double bond is indicated by a number within the compound’s name.

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Functional GroupGeneral Formula
unsaturated hydrocarbons
C = C
(This general formula can also apply to cycloalkanes)

Chemical Properties

Alkenes are more reactive than alkanes.

Alkenes are identified by shaking them with bromine water. Alkenes will decolourise bromine water.

Reactions of alkenes include:

  • Electrophilic Addition
    In these reactions, an electrophile (an electron-pair acceptor) is attracted to the double bond of the alkene due to its high electron density.

  • Addition Polymerisation
    Alkene monomers are joined together to form polymers.

    Addition polymers are unreactive.

    The properties of polymers vary depending on the monomer and the conditions used in the addition polymerisation reaction.

Other Information

  • Addition reactions of unsymmetrical alkenes produce a mixture of major and minor products.
  • Properties of addition polymers can be altered using plasticisers.
  • An example of a common addition polymer is poly(chloroethene), commonly known as PVC.
  • Polyalkenes are non-biodegradable polymers.

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