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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This equation shows benzene reacting with propanoyl chloride in the presence of aluminum chloride to form the electrophile.
Step 2
Outline a mechanism for the reaction of this electrophile with benzene.
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Answer
The mechanism for the electrophilic substitution reaction proceeds through several steps:
Formation of the Electrophile: The AlCl₃ coordinates with the Cl atom of the acyl chloride, generating a more reactive electrophile (propanoyl cation).
Electrophilic Attack: The π electrons of benzene attack the carbon of the acyl group, forming a sigma complex.
Deprotonation: The sigma complex loses a proton to restore aromaticity, regenerating the aromatic system.
The overall mechanism can be summarized as:
Electrophilic substitution (E+)
Step 3
Give the IUPAC name of the alcohol.
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Answer
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 required for the conversion from the organic product to the alcohol is NaBH₄ (sodium borohydride). The mechanism for this reaction is known as nucleophilic addition.
Step 5
Describe what would be observed when the alcohol reacts with ethanoyl chloride.
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Answer
When the alcohol reacts with ethanoyl chloride, misty fumes or a sweet smell will be observed due to the formation of the ester and the release of hydrogen chloride 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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Answer
The structure of the ester formed from the reaction is:
