EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:4.3.2 Halogens & Alkanes

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:4.3.2 Halogens & Alkanes

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

 

 

Substitution-Alkanes-&-Halogens, IGCSE & GCSE Chemistry revision notesIn the presence of ultraviolet (UV) radiation, methane reacts with bromine in a substitution reaction

 

  •  The equation for the reaction is

 

CH4 + Br2 → CH3Br + HBr

 

methane + bromine → bromomethane + hydrogen bromide

 

  • Chlorine will also react with alkanes to form chloromethane

 

CH4 + Cl2 → CH3Cl + HCl

 

methane + chlorine → chloromethane + hydrogen chloride

 

  • The products belong to a family called halogenoalkanes or haloalkanes
  • Halogenoalkanes have many uses a solvents, refrigerants, propellants and pharmaceuticals

 

Exam Tip

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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