Activating Deactivating groups

Activating - Substituent Effects on the Reactivity and Orientation of Electrophilic Aromatic Substitution Substituent groups already on the benzene

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Substituent Effects on the Reactivity and Orientation of Electrophilic Aromatic Substitution Substituent groups already on the benzene ring greatly influence both the reactivity of electrophilic attack, and the site ( ortho , meta , or para ) of attachment of the incoming electrophile. Classification of Substituents Substituents are classified as activating or deactivating relative to the reactivity of benzene. Substituents also are classified as ortho/para directing ( o/p directing) or meta directing ( m directing). There is a fundamental theoretical connection between the reactivity influence and site direction of a substituent group.
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Inductive Electron Withdrawal Electron Donation by Hyperconjugation
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Donation of electrons through a σ bond is called inductive electron donation An alkyl group is more electron donating than hydrogen because of hyperconjugation Withdrawal of electrons through a σ bond is called inductive electron withdrawal The NH 3 group is more electronegative than a hydrogen
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Resonance Electron Donation and Withdrawal Substituents such as NH 2 , OH, OR, and Cl donate electrons by resonance; they also withdraw electrons inductively
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Substituents such as C=O, C Ξ N, SO 3 H, and NO 2 withdraw electrons by resonance; they delocalize the π electrons of the ring onto the substituents
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Electron-donating substituents increase the reactivity of the benzene ring toward electrophilic aromatic substitution Electron-withdrawing substituents decrease the reactivity of the benzene ring toward electrophilic aromatic substitution
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The strongly activating substituents make the benzene ring more reactive toward electrophilic substitution Electron donation into the ring by resonance is more significant than their inductive electron withdrawal from the ring Strongly activating substituents
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The moderately activating substituents donate electrons into the ring by resonance and withdraw electrons inductively Overall, they donate electrons by resonance more strongly than they withdraw electrons inductively The substituents can donate electrons into the ring and away from the ring
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These substituents are less effective in donating electrons into the ring because…
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These substituents are less effective in donating electrons into the ring because…
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This note was uploaded on 12/10/2010 for the course CHE 179582 taught by Professor Rzayev during the Spring '09 term at SUNY Buffalo.

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Activating - Substituent Effects on the Reactivity and Orientation of Electrophilic Aromatic Substitution Substituent groups already on the benzene

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