Advanced Topic 785 of 1102 Organic Chemistry
Directing Effects
Substituents direct incoming groups to ortho, para or meta positions.
In-depth explanation of Directing Effects
Substituents on a benzene ring direct incoming electrophiles to specific positions, and they also control the rate of substitution. Activating groups such as OH, NH2 and alkyl groups increase the rate and direct the new group to the ortho and para positions. Deactivating groups such as NO2, CN and C=O slow the reaction and direct the new group to the meta position. Halogens are unusual because they deactivate the ring by induction yet still direct ortho and para through resonance donation. These effects arise from how each substituent stabilizes or destabilizes the arenium ion intermediate.
Going deeper: Directing Effects
Key ideas: Activating ortho and para directors: -NH2, -OH, -OR, -NHCOR, -R. Deactivating meta directors: -NO2, -CN, -CHO, -COR, -COOH, -SO3H, -CF3, -NR3+. Halogens are deactivating but ortho and para directing. Judge by the stability of the sigma complex: donors stabilise ortho or para intermediates. Steric hindrance favours para with bulky groups such as tert-butyl.
Common mistakes and connections: Students think activating means meta directing, or that halogens are meta directors. Another mistake is considering only one group when two substituents exist; the stronger activator controls. Links to resonance, inductive effect and multistep synthesis order (nitrate first or reduce first).
Visualization of Directing Effects
Nitration of toluene gives mostly ortho and para products (58 and 38 percent) because the methyl group activates and directs there. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Nitration of toluene gives a mixture of ortho- and para-nitrotoluene, because the methyl group is an activating ortho and para director.
Frequently asked questions about Directing Effects
What is Directing Effects?
Substituents direct incoming groups to ortho, para or meta positions.
Is Directing Effects a beginner, intermediate or advanced topic?
Directing Effects is a advanced topic in Organic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Directing Effects?
Study these earlier topics in Organic Chemistry first: Electrophilic Aromatic Substitution, Nitration of Benzene, Friedel-Crafts Reactions.
What comes after Directing Effects?
The next topics in Organic Chemistry are Haloalkanes and SN1 Reaction.
Can I practise Directing Effects with quizzes?
Yes. The interactive lesson includes a self-check question on Directing Effects, and the Organic Chemistry quiz draws on every topic in this area.
Where Directing Effects fits in Organic Chemistry
Directing Effects is topic 57 of 148 in Organic Chemistry.