IGCSEScienceEdexcelScience (Double Award) (Modular)Chemistry Unit 1Revision Notes4. Organic Chemistry: Part 1AlkanesHalogens & Alkanes

Halogens & Alkanes (Edexcel IGCSE Science (Double Award) (Modular)): Revision Note

Exam code: 4XSD1

Stewart Hird

Written by: Stewart Hird

Reviewed by: Philippa Platt

Updated on

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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Stewart Hird

Author: Stewart Hird

Expertise: Chemistry Content Creator

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.

Philippa Platt

Reviewer: Philippa Platt

Expertise: Chemistry Content Creator

Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener