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Sunset Yellow is a yellow colouring agent used in food and drinks, which can be made by the following route - CIE - A-Level Chemistry - Question 7 - 2015 - Paper 1
Question 7
Sunset Yellow is a yellow colouring agent used in food and drinks, which can be made by the following route. In step 3 of this synthesis, a phenol-like compound, S,... show full transcript
Worked Solution & Example Answer:Sunset Yellow is a yellow colouring agent used in food and drinks, which can be made by the following route - CIE - A-Level Chemistry - Question 7 - 2015 - Paper 1
Step 1
Suggest structures for compounds R, S and T
Answer
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Compound R: The structure of compound R will be a primary amine, such as aniline, which has an amino group ( NH2) attached to a phenyl ring.
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Compound S: Compound S will be a diazonium salt formed after coupling with compound R, incorporating a phenolic structure similar to that of Sunset Yellow but with a diazonium group instead.
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Compound T: The structure for compound T will be a phenolic compound derived from the hydroxylation of compound S. This compound features a hydroxyl group attached to the aromatic ring.
Step 2
Suggest reagents and conditions for step 1.
Answer
Step 1 involves a reduction process. The reagents that can be used are Sn (tin) and HCl. The conditions include refluxing the mixture, maintaining a temperature of around 50°C, or using concentrated hydrochloric acid under mild conditions (around 20°C).
Step 3
Step 4
Step 5
Complete the table for the reactions of W.
Answer
For HCl:
- Reagent: HCl
- Structure of product: (C, H, N, O, Cl) - showing the nucleophilic substitution
- Type of reaction: Acid-base neutralisation.
For CH2CHBr:
- Reagent: CH2CHBr
- Structure of product: (C, H, N, Br)
- Type of reaction: Nucleophilic substitution.