Textbook Question
Predict the major products formed when benzene reacts (just once) with the following reagents.
(h) benzoyl chloride + AlCl3
19. Reactions of Aromatics: EAS and Beyond
Electron Withdrawing Groups
6:10 minutesProblem 53c
Textbook Question
Predict the major products of the following reactions.
(c) nitrobenzene + fuming sulfuric acid
Verified step by step guidance1
Step 1: Analyze the reactants. Nitrobenzene (C6H5NO2) is an aromatic compound with a nitro group (-NO2) attached to the benzene ring. Fuming sulfuric acid is a mixture of sulfuric acid (H2SO4) and sulfur trioxide (SO3), which is used for sulfonation reactions.
Step 2: Understand the reaction mechanism. Sulfonation of aromatic compounds involves the electrophilic substitution of a hydrogen atom on the benzene ring with a sulfonic acid group (-SO3H). The nitro group (-NO2) is an electron-withdrawing group, which deactivates the benzene ring and directs incoming electrophiles to the meta position relative to itself.
Step 3: Predict the major product. Since the nitro group is meta-directing, the sulfonic acid group (-SO3H) will be introduced at the meta position relative to the nitro group on the benzene ring.
Step 4: Compare the provided options. Among the given structures (A, B, C, D), identify the one where the sulfonic acid group (-SO3H) is at the meta position relative to the nitro group (-NO2).
Step 5: Confirm the correct structure. Based on the sulfonation mechanism and the directing effects of the nitro group, the major product will be the structure where the -SO3H group is meta to the -NO2 group. This corresponds to option C in the provided image.
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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. In this process, the aromaticity of the ring is preserved, and the reaction typically involves the formation of a sigma complex. Understanding EAS is crucial for predicting the products of reactions involving aromatic compounds, such as nitrobenzene with fuming sulfuric acid.
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Activating and Deactivating Groups
In EAS reactions, substituents on the aromatic ring can either activate or deactivate the ring towards further substitution. Activating groups, such as -OH or -NH2, increase the electron density of the ring, making it more reactive, while deactivating groups, like -NO2 or -SO3H, withdraw electron density and make the ring less reactive. Recognizing the nature of substituents is essential for predicting the major products of the reaction.
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Ortho/Para vs. Meta Directing Effects
The position at which a new substituent is added to an aromatic ring during EAS is influenced by the existing substituents. Ortho and para directing groups favor substitution at the 2 or 4 positions relative to themselves, while meta directing groups favor substitution at the 3 position. This concept is vital for determining the specific products formed when nitrobenzene reacts with fuming sulfuric acid, as the existing nitro group will influence the site of new substitution.
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