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This question is about 2-methylbut-1-ene - AQA - A-Level Chemistry - Question 3 - 2022 - Paper 2
Question 3
This question is about 2-methylbut-1-ene. 1. Name the mechanism for the reaction of 2-methylbut-1-ene with concentrated sulfuric acid. Outline the mechanism for thi... show full transcript
Worked Solution & Example Answer:This question is about 2-methylbut-1-ene - AQA - A-Level Chemistry - Question 3 - 2022 - Paper 2
Step 1
Name the mechanism for the reaction of 2-methylbut-1-ene with concentrated sulfuric acid.
Answer
The mechanism for the reaction of 2-methylbut-1-ene with concentrated sulfuric acid is known as Electrophilic Addition. In this reaction, the alkene undergoes protonation by sulfuric acid, leading to carbocation formation.
Step 2
Outline the mechanism for this reaction to form the major product.
Answer
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Protonation: The double bond of 2-methylbut-1-ene attacks the proton (H⁺) from sulfuric acid, leading to the formation of the more stable carbocation at the more substituted carbon.
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Nucleophilic attack: The bisulfate ion (HSO₄⁻) attacks the carbocation, forming alkyl hydrogen sulfate.
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Hydrolysis: The alkyl hydrogen sulfate can then be hydrolyzed to form the major alcohol product by reacting with water.
Step 3
Draw the structure of the minor product formed in the reaction in Question 03.1. Explain why this is the minor product.
Answer
The minor product formed is a less stable carbocation that leads to an alternative alcohol structure.
Structure of Minor Product: The structure can be represented as:
H OH
\ |
C--C--C
/
H H
Explanation: This is the minor product due to the formation of a less stable, secondary carbocation compared to the more stable tertiary carbocation formed in the major product.
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