Electrophilic Aromatic Substitution (EAS): Mechanism and Directing Effects

Master EAS with a step-by-step mechanism (sigma complex) and a clear directing effects framework. Predict products for nitration, sulfonation, halogenation, and Friedel–Crafts reactions with practice.

• Mechanism core: Attack → sigma complex → deprotonation restores aromaticity
• Rate-determining: Formation of sigma complex (loss of aromaticity)
• Directing effects: EDG donate → ortho/para + activation; EWG withdraw → meta + deactivation
• Exception: Halogens are deactivating but ortho/para directing
• Exam type: Predict the major product
• Exam type: Choose conditions
• Exam type: Failure modes / distractors