Aromatic Sulfonation and Desulfonation as a Reversible EAS Tool: Mechanism + Exam Traps

Use sulfonation (SO3/H2SO4) to install –SO3H as a reversible, strongly deactivating meta-directing group; remove it by heating in dilute acid (desulfonation).

• Reaction: Aromatic Sulfonation and Desulfonation as a Reversible EAS Tool
• What it does: Use sulfonation (SO3/H2SO4) to install –SO3H as a reversible, strongly deactivating meta-directing group; remove it by heating in dilute acid (desulfonation).
• Typical reagents: SO3/H2SO4 (fuming sulfuric acid)
• Key intermediate: Varies / context-dependent
• Driving force: Formation of more stable bonds / products
• Exam type: Predict major product
• Exam type: Mechanism choice