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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 1. State the type of reaction in step 1. Give the name of the reagent nee... 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
Give the reagents needed and give equations for step 2 and step 3.
Answer
For step 2, the reagent needed is an alkoxide, typically generated from sodium hydroxide (NaOH).
The equation for step 2 can be represented as:
In step 3, the reagent needed is ethanedioyl dichloride (also known as oxalyl chloride).
The equation for step 3 can be represented as:
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
The mechanism will involve the nucleophile attacking the carbonyl carbon of ethanedioyl dichloride, followed by the departure of the leaving group (Cl⁻), leading to the formation of an ester link:
- The alkoxide ion attacks the electrophilic carbon in the carbonyl.
- A tetrahedral intermediate forms.
- The intermediate collapses, expelling Cl⁻ and forming the ester link.
Step 7
Suggest why chemists usually aim to design production methods with fewer steps.
Answer
Chemists aim for fewer steps to reduce costs and increase efficiency in synthetic processes. Fewer steps often lead to shorter reaction times, reduced labor, and minimized consumption of reagents. Moreover, simpler processes generally diminish the risk of side reactions and improve yields.
Step 8
Suggest why chemists usually aim to design production methods with a high percentage atom economy.
Answer
A high percentage atom economy is desirable as it indicates that most of the reactants are converted into useful products rather than waste. This efficiency minimizes environmental impact by reducing the generation of by-products and the need for excessive purification processes.