Textbook Question
Predict the major products formed when benzene reacts (just once) with the following reagents.
(k) carbon monoxide, HCl, and AlCl3/CuCl
(l) CH2(COCl)2, AlCl3
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19. Reactions of Aromatics: EAS and Beyond
EAS:Friedel-Crafts Acylation Mechanism
5:10 minutesProblem 59
Textbook Question
Show two pairs of reagents that would each result in formation of the following compound:
Verified step by step guidance1
Step 1: Analyze the target compound. The structure contains a ketone group (C=O) attached to two aromatic rings: one is a benzene ring, and the other is a methyl-substituted benzene ring (toluene). This suggests the compound can be synthesized via a Friedel-Crafts acylation reaction.
Step 2: Identify the acyl group. The ketone group indicates the presence of a benzoyl group (C6H5CO-) attached to the methyl-substituted benzene ring. This implies that the acylating agent could be benzoyl chloride (C6H5COCl).
Step 3: Pair 1 of reagents: Use benzoyl chloride (C6H5COCl) as the acylating agent and methylbenzene (toluene, C6H5CH3) as the aromatic substrate. Combine these reagents in the presence of a Lewis acid catalyst, such as aluminum chloride (AlCl3), to facilitate the Friedel-Crafts acylation reaction.
Step 4: Pair 2 of reagents: Alternatively, use benzoic acid (C6H5COOH) as the acylating agent and methylbenzene (toluene, C6H5CH3) as the aromatic substrate. In this case, the reaction can be carried out using a dehydrating agent like phosphorus pentoxide (P2O5) or thionyl chloride (SOCl2) to convert the benzoic acid into an acylating intermediate.
Step 5: Ensure reaction conditions are optimized. For both pairs of reagents, maintain anhydrous conditions to prevent side reactions. Monitor the reaction progress using techniques like thin-layer chromatography (TLC) to confirm the formation of the desired ketone product.
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5mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
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Reagents are substances that participate in a chemical reaction to form new products. In organic synthesis, selecting the right reagents is crucial for achieving the desired transformation. Understanding the reactivity and compatibility of different reagents allows chemists to design effective synthetic pathways to create specific compounds.
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