Electrophilic Aromatic Substitution (EAS)
Electrophilic Aromatic Substitution is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This reaction is crucial for modifying aromatic compounds and is influenced by the nature of substituents already present on the ring, which can either activate or deactivate the ring towards further substitution.
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Activating and Deactivating Substituents
Substituents on a benzene ring can be classified as activating or deactivating based on their electronic effects. Activating groups, such as -OH or -NH2, donate electron density to the ring, enhancing its reactivity towards electrophiles. In contrast, deactivating groups, like -NO2 or -CF3, withdraw electron density, making the ring less reactive in EAS reactions.
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Activating and deactivating groups
Ortho/Para vs. Meta Directing
The position of substituents on a benzene ring affects the orientation of subsequent electrophilic attacks. Activating groups typically direct new substituents to the ortho and para positions, while deactivating groups often direct them to the meta position. Understanding these directing effects is essential for predicting the reactivity and product distribution in EAS reactions.
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Ortho, Para major products