Wize University Organic Chemistry Textbook > Aromaticity (Arenes)
Considerations for Electrophilic Aromatic Substitutions
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Considerations for Electrophilic Aromatic Substitutions
The rate of an electrophilic aromatic substitution (EAS) reaction is greatly impacted by substituents on the aromatic ring. Electron-donating groups (have lone pairs) will activate the benzene ring and accelerate the reaction. Electron-withdrawing groups (have multiple bonds) will activate the benzene ring and decelerate the reaction. Some examples are below.
The substituents play a role in the regioselectivity of an EAS reaction. Electron-donating groups (EDG) will favour EAS reactions in the ortho and para positions. Stronger directors (amines, alcohols, ethers) will have the strongest directing effect. Electron-withdrawing groups (EWG) will favour EAS reactions in the meta position.
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Example: Directing Groups in Electrophilic Aromatic Substitution
Predict the products in the following reactions:
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Example: Directing Groups in Electrophilic Aromatic Substitution
Some directing groups have greater influence than others. Those will greater influence are called strong directors and those which have a lesser influence are called medium directors. Using resonance structures, explain the observation below.
