Specification Point 4.22:
Describe the reactions of alkanes with halogens in the presence of ultraviolet radiation, limited to mono-substitution

Reaction of Alkanes with Halogens

Alkanes: A homologous series of hydrocarbon compounds with only single carbon bonds that has the general formula CnH2n+2

Substitution reaction of alkanes with halogens:

In a substitution reaction, one atom is swapped with another atom. Alkanes undergo a substitution reaction with halogens under the presence of ultraviolet radiation.

Example: Under ultraviolet (UV) radiation, methane reacts with bromine

Alkane reactions, Edexcel IGCSE Chemistry

This reaction is a substitution reaction because one of the hydrogen atoms from the methane is replaced by a bromine atom

 Methane   +   Bromine   →   Bromomethane   +   Hydrogen Bromide


    CH4                   Br2                      CH3Br                            HBr

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.