Activation: A group present in reactant that activates the ring, so aromatic ring reacts more
readily with electrophiles.
Deactivation: A group present in reactant that deactivates the ring, so aromatic ring reacts less
readily with electrophiles.
Activation and deactivation affects rate of reaction and position
of substitution. Deactivating may need more extreme conditions.
Directing Effect: Different groups can have directing effect on
any second substituent on benzene ring. All 2- and 4- directing
groups (ortho and para) are activating groups, apart from
halogens. All 3- directing groups (meta) are deactivating groups.
Table shows effect of first substituent on second substituent. E.g.
an –NH2 group on the reactant would direct the second
substituent to positions 2 or 4. NH2 would activate aromatic ring.
Proportions of Substituent Groups: 2 and 4 directing groups,
can be in 6 position, which is the same as 2 position. So would
expect twice as much 2- than 4-.
2, 3 and 6 positions monosubstituted- 3 different isomers.
Also means yield is less.
Need to learn table.
Planning Organic Synthesis: When carrying out reaction on an aromatic compound, have to
consider order of reactions to ensure correct substitution pattern and correct product. E.g. chose
a group for first substituent that will direct second substituent into correct position.
2- 4- directing groups creates mixture of products. Need to separate by distillation if water or if
solid recrystallization.
