Topic 11: Halogenoalkanes
Nucleophillic Substitution
Halogenoalkanes contain polar bonds as the halogens are more electronegative than carbon
atoms. This means electron density is drawn towards the halogen forming ∂+ and ∂- regions.
Nucleophiles
These species are ‘positive liking’. They contain a lone electron pair that is attracted to ∂+
regions on molecules. Some of the most common nucleophiles are:
● CN:
● :NH
● :OH
They must be shown with the lone electron pair and a negative sign indicating they are
nucleophiles.
Nucleophilic Substitution
This is the reaction mechanism that shows how nucleophiles attack halogenoalkanes. It can
be used to produce alcohols or amines from halogenoalkanes.
Mechanism - Alcohol
The nucleophile attacks the ∂+ carbon and the electrons are transferred to the chlorine.
Mechanism - Amines
The intermediate formed has an N+ atom, so electrons are transferred to it causing a
hydrogen to be lost too.
Nucleophillic Substitution
Halogenoalkanes contain polar bonds as the halogens are more electronegative than carbon
atoms. This means electron density is drawn towards the halogen forming ∂+ and ∂- regions.
Nucleophiles
These species are ‘positive liking’. They contain a lone electron pair that is attracted to ∂+
regions on molecules. Some of the most common nucleophiles are:
● CN:
● :NH
● :OH
They must be shown with the lone electron pair and a negative sign indicating they are
nucleophiles.
Nucleophilic Substitution
This is the reaction mechanism that shows how nucleophiles attack halogenoalkanes. It can
be used to produce alcohols or amines from halogenoalkanes.
Mechanism - Alcohol
The nucleophile attacks the ∂+ carbon and the electrons are transferred to the chlorine.
Mechanism - Amines
The intermediate formed has an N+ atom, so electrons are transferred to it causing a
hydrogen to be lost too.
