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Ch. 17 - Reactions of Aromatic Compounds
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
Chapter 17, Problem 50j

Predict the major products formed when benzene reacts (just once) with the following reagents.
(j) nitric acid + sulfuric acid

Verified step by step guidance
1
Step 1: Recognize the type of reaction. The reaction of benzene with nitric acid (HNO₃) in the presence of sulfuric acid (H₂SO₄) is an electrophilic aromatic substitution reaction, specifically nitration.
Step 2: Understand the role of the reagents. Sulfuric acid acts as a catalyst and protonates nitric acid, generating the nitronium ion (NO₂⁺), which is the electrophile in this reaction. The reaction can be represented as: HNO_3 + H_2SO_4 → NO_2^+ + HSO_4^- + H_2O.
Step 3: Identify the electrophile and its interaction with benzene. The nitronium ion (NO₂⁺) attacks the π-electron cloud of benzene, forming a resonance-stabilized carbocation intermediate (arenium ion).
Step 4: Regenerate aromaticity. A proton (H⁺) is removed from the carbocation intermediate by the conjugate base (HSO₄⁻), restoring the aromaticity of the benzene ring and forming nitrobenzene as the major product.
Step 5: Summarize the major product. The major product of this reaction is nitrobenzene (C_6H_5NO_2), where a nitro group (-NO₂) is substituted onto the benzene ring.

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Key Concepts

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

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This process is crucial for understanding how benzene and its derivatives react, as the stability of the aromatic system allows for selective substitution rather than addition.
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Nitration of Benzene

Nitration is a specific type of electrophilic aromatic substitution where a nitro group (NO2) is introduced into the benzene ring. This reaction typically involves the use of a nitrating mixture, such as nitric acid and sulfuric acid, which generates the nitronium ion (NO2+), the active electrophile that attacks the aromatic ring.
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Benzene Nomenclature

Regioselectivity in Electrophilic Aromatic Substitution

Regioselectivity refers to the preference of an electrophilic substitution reaction to occur at specific positions on the aromatic ring. In the case of nitration of benzene, the nitro group can be introduced at different positions, but due to the stability of the intermediates formed, the major product is typically the nitrobenzene, with the nitro group being added to the ortho or para positions relative to the original hydrogen.
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