For each horizontal row of substituted benzenes, indicate
c. the one that yields the highest percentage of meta product in an electrophilic aromatic substitution reaction.

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Understand the concept of electrophilic aromatic substitution (EAS): This reaction involves the replacement of a hydrogen atom on a benzene ring with an electrophile. The reactivity of substituted benzenes in EAS depends on the electronic effects of the substituents present on the ring.

Identify the substituents on the benzene rings: Substituents can either activate or deactivate the benzene ring toward EAS. Activating groups (electron-donating groups) increase reactivity, while deactivating groups (electron-withdrawing groups) decrease reactivity.

Classify the substituents based on their electronic effects: Activating groups include -OH, -OCH₃, -NH₂, etc., which donate electrons through resonance or induction. Deactivating groups include -NO₂, -CF₃, -CN, etc., which withdraw electrons through resonance or induction.

Determine the least reactive benzene: The benzene with the strongest electron-withdrawing group (most deactivating substituent) will be the least reactive in an EAS reaction. Compare the substituents in the given row to identify the one with the strongest deactivating effect.

Conclude the analysis: Once the least reactive benzene is identified, confirm your reasoning by considering the resonance and inductive effects of the substituents. Ensure that the substituent's position (ortho, meta, or para) is also considered, as it can influence the reactivity.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

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.

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.

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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