Acyl chlorides are useful reagents in synthesis - AQA - A-Level Chemistry - Question 7 - 2018 - Paper 2
Question 7
Acyl chlorides are useful reagents in synthesis. They react with aromatic compounds and also with alcohols.
1. CH₃CH₂COCl reacts with benzene in the presence of AlC... show full transcript
Worked Solution & Example Answer:Acyl chlorides are useful reagents in synthesis - AQA - A-Level Chemistry - Question 7 - 2018 - Paper 2
Step 1
Give an equation for the reaction of CH₃CH₂COCl with AlCl₃ to form the electrophile.
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Answer
The equation for the reaction is:
C3H7Cl+AlCl3→C3H7++AlCl4−
Here, CH₃CH₂COCl (propanoyl chloride) reacts with AlCl₃ to produce the electrophile, the propanoyl cation (C₃H₇⁺).
Step 2
Outline a mechanism for the reaction of this electrophile with benzene.
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Answer
Electrophilic Attack: The electrophile, the propanoyl cation, attacks the π bond of benzene, forming a sigma complex (arenium ion).
Rearrangement: The sigma complex undergoes rearrangement to stabilize the ion, if necessary.
Deprotonation: The complex loses a proton to restore aromaticity, resulting in the acylated benzene product.
Step 3
Give the IUPAC name of the alcohol.
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The IUPAC name of the alcohol is 1-phenylpropan-1-ol.
Step 4
Give the reagent needed for this reaction and name the mechanism.
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Answer
The reagent needed is LiAlH₄ (Lithium aluminum hydride).
The name of the mechanism is reduction.
Step 5
Describe what would be observed when the alcohol reacts with ethanoyl chloride.
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When the alcohol reacts with ethanoyl chloride, misty fumes are observed, indicating the release of HCl gas.
Step 6
Name the mechanism for the reaction to form the ester.
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The mechanism for the reaction to form the ester is nucleophilic addition-elimination.
Step 7
Draw the structure of the ester.
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