IGCSEScienceEdexcelScience (Double Award)ChemistryRevision Notes4. Organic ChemistryAlkanesHalogens & Alkanes

Halogens & Alkanes (Edexcel IGCSE Science (Double Award))

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Stewart Hird

Written by: Stewart Hird

Reviewed by: Lucy Kirkham

Edexcel Science (Double Award): ChemistryEdexcel ChemistryEdexcel Chemistry (Modular): Unit 1

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Halogens & alkanes

  • In a substitution reaction, one atom is swapped with another atom

  • Alkanes undergo a substitution reaction with halogens in the presence of ultraviolet radiation

The reaction between methane and bromine in the presence of ultraviolet radiation

Substitution-Alkanes-&-Halogens, IGCSE & GCSE Chemistry revision notes

In the presence of ultraviolet (UV) radiation, methane reacts with bromine in a substitution reaction

  •  The equation for the reaction is

methane + bromine → bromomethane + hydrogen bromide

CH4 + Br2 → CH3Br + HBr

  • Chlorine will also react with alkanes under the same conditions to form chloromethane

methane + chlorine → chloromethane + hydrogen chloride

CH4 + Cl2 → CH3Cl + HCl

  • The products belong to a family called halogenoalkanes or haloalkanes

  • Halogenoalkanes have many uses a solvents, refrigerants, propellants and pharmaceuticals

Examiner Tips and Tricks

CFC stands for chlorofluorocarbon, an important class of halogenoalkanes, previously used in fridges and air conditioners, but gradually being phased out because of the damage they cause to the ozone layer.

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    Author
    Reviewer
    Stewart Hird

    Author: Stewart Hird

    Expertise: Chemistry Lead

    Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

    Lucy Kirkham

    Author: Lucy Kirkham

    Expertise: Head of STEM

    Lucy has been a passionate Maths teacher for over 12 years, teaching maths across the UK and abroad helping to engage, interest and develop confidence in the subject at all levels.Working as a Head of Department and then Director of Maths, Lucy has advised schools and academy trusts in both Scotland and the East Midlands, where her role was to support and coach teachers to improve Maths teaching for all.