This question is about esters. Figure 4 shows an incomplete mechanism for the reaction of an ester with aqueous sodium hydroxide. Figure 4 1. Add three curly arrows to complete the mechanism in Figure 4. [3 marks] 2. Name the type of reaction shown in Figure 4. [1 mark] 3. Deduce the role of the CH3O- ion in step 3 shown in Figure 4. [1 mark] 4. A triester in vegetable oil reacts with sodium hydroxide in a similar way. Give a use for a product of this reaction. [1 mark]

A-Level AQA Chemistry Organic Mechanisms: This question is about esters.

This question is about esters - AQA - A-Level Chemistry - Question 7 - 2022 - Paper 2

Question 7

This question is about esters. Figure 4 shows an incomplete mechanism for the reaction of an ester with aqueous sodium hydroxide. Figure 4 1. Add three curly arro... show full transcript

Worked Solution & Example Answer:This question is about esters - AQA - A-Level Chemistry - Question 7 - 2022 - Paper 2

Step 1

Add three curly arrows to complete the mechanism in Figure 4.

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Answer

To complete the mechanism in Figure 4, three curly arrows are needed:

First Arrow: Draw an arrow from the carbon atom of the C=O bond to the oxygen atom, indicating nucleophilic attack by hydroxide.
Second Arrow: Place an arrow from the C-O bond to the adjacent carbon atom, showing the bond breaking.
Third Arrow: Draw an arrow from the O-H bond of the hydroxide ion to the carbonyl carbon to show the formation of the alkoxide.

Step 2

Name the type of reaction shown in Figure 4.

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Answer

The type of reaction shown in Figure 4 is an alkaline hydrolysis, also known as saponification.

Step 3

Deduce the role of the CH3O- ion in step 3 shown in Figure 4.

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Answer

In step 3, the CH3O- ion acts as a base. It accepts a proton from the hydroxyl group formed during the reaction, thereby stabilizing the intermediate and facilitating the completion of the hydrolysis reaction.

Step 4

Give a use for a product of this reaction.

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Answer

A product of this reaction is soap, which can be used for cleaning and emulsifying substances.

This question is about esters - AQA - A-Level Chemistry - Question 7 - 2022 - Paper 2

Worked Solution & Example Answer:This question is about esters - AQA - A-Level Chemistry - Question 7 - 2022 - Paper 2

Add three curly arrows to complete the mechanism in Figure 4.

Name the type of reaction shown in Figure 4.

Deduce the role of the CH3O- ion in step 3 shown in Figure 4.

Give a use for a product of this reaction.

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