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This question is about making a diester from cyclohexanol - AQA - A-Level Chemistry - Question 8 - 2021 - Paper 2
Question 8
This question is about making a diester from cyclohexanol. Step 1 Step 2 Step 3 Step 4 --- 08.1 State the type of reaction in step 1. Give the name of the reagent... show full transcript
Worked Solution & Example Answer:This question is about making a diester from cyclohexanol - AQA - A-Level Chemistry - Question 8 - 2021 - Paper 2
Step 1
Step 2
Step 3
State the reagents needed and give equations for step 2 and step 3.
Answer
For step 2, the reagent needed is bromine in water, which adds across the double bond of the alkene formed in step 1. The equation is:
ightarrow C_6H_{10}Br_2$$ In step 3, the reagent is ethanedioyl dichloride (also known as oxalyl chloride) for forming the diester. The equation is: $$C_6H_{10}Br_2 + (COCl)_2 ightarrow C_6H_{10}(COO)_2 + 2HCl$$Step 4
Step 5
Step 6
Complete the mechanism to show the formation of one ester link in the first step of this reaction.
Answer
In the first step of the reaction, the mechanism can be illustrated as follows:
- The nucleophile attacks the carbonyl carbon, and a tetrahedral intermediate is formed showing the negative charge on oxygen.
- The intermediate collapses, leading to the elimination of the leaving group (Cl), resulting in the formation of the ester link. The mechanism can be summarized as:
OH OH
| |
C---C---C
| | Cl
`"/
O C=O
Step 7
Suggest why chemists usually aim to design production methods with fewer steps.
Answer
Fewer steps in a production method minimize cost, time, and resource expenditure, leading to more efficient synthesis processes. Additionally, reducing the number of steps can decrease the risk of side reactions, ultimately enhancing yield.
Step 8
Suggest why chemists usually aim to design production methods with a high percentage atom economy.
Answer
A high percentage atom economy indicates that a larger proportion of reactants are converted into the desired product, which is beneficial for sustainability. It reduces waste and conserves resources as all atoms from reactants are effectively utilized in the final product.