OrgoChem II

Aromatic Chemistry

EAS directing effects and synthesis order

Summary

Pick directing group then choose order of steps to control substitution. Full reference is on the external link.

What you need to know:

This topic covers aromatic chemistry. Focus on mastering the key concepts in the "Must know checklist" below. Follow the study steps systematically, and use practice problems to reinforce your understanding. The external reference provides comprehensive coverage of all concepts.

Video Tutorial

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Electrophilic Aromatic Substitution Reactions Made Easy!

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Must know checklist

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AromaticityHückel's rule (4n+2 π electrons), planar, cyclic, conjugated; benzene is aromatic (6 π e-); antiaromatic (4n π e-); nonaromatic (not fully conjugated)
Electrophilic Aromatic Substitution Reactions Made Easy!→
EAS mechanismelectrophile attacks aromatic ring → σ-complex (arenium ion, sp3 carbon) → loss of H+ regenerates aromaticity; rate-determining step is σ-complex formation
Aromaticity and Hückel's Rule→
Directing effectsactivating groups (OH, OR, NH2, alkyl) = ortho/para directors (donate electrons); deactivating groups (NO2, CN, C=O) = meta directors (withdraw electrons); halogens = weakly deactivating but ortho/para directors
Ortho Meta Para Directors - Activating and Deactivating Groups→
Common EAS reactionsnitration (HNO3/H2SO4), sulfonation (SO3/H2SO4), halogenation (X2/FeX3), Friedel-Crafts alkylation (RCl/AlCl3), Friedel-Crafts acylation (RCOCl/AlCl3)
EAS Mechanism - Sigma Complex Formation→
Synthesis strategyorder matters! Activating groups go first (faster), then deactivating; meta-directors block ortho/para; plan sequence to avoid wrong substitution patterns
EAS Synthesis Strategy - Order of Substitution→

Common mistakes

Wrong order of EAS steps (activating first, then deactivating)

Putting meta director ortho to another substituent and expecting ortho product

Forgetting Friedel-Crafts fails with strongly deactivated rings