Contain polar bonds as the halogens are more electronegative than carbon atoms, drawing electron density towards the halogen and forming δ+ and δ- regions
Nucleophiles
Species that contain a lone electron pair attracted to δ+ regions of molecules
Examples: CN-, :NH3, -:OH
Nucleophilic Substitution
1. Nucleophile attacks δ+ carbon, electrons transferred to halogen
2. Can produce alcohols or amines from halogenoalkanes
Elimination
Nucleophile acts as a base, accepts a proton and removes a hydrogen atom, resulting in elimination of the halide and formation of a carbon-carbon double bond
Greater Mr of halogen in polar bond
Lower bond enthalpy, faster rate of reaction
Nucleophilic substitution reactions can only occur for 1° (primary) and 2° (secondary) halogenoalkanes
Elimination reactions can only occur from 2° and 3° (tertiary) halogenoalkanes
Ozone depletion
Ozone in the atmosphere absorbs UV radiation, CFCs also absorb UV radiation, breaking down the carbon-halogen bonds to form free radicals that can catalyse ozone depletion
CFC-free solvents are now being produced to prevent them entering the atmosphere, helping minimise ozone depletion and global warming
