2019 A Level H2 Chemistry Paper 1 Question 21 - Determine Functional Groups that React with NaOH
Here's 2019 A Level H2 Chemistry Paper 1 Question 21.
The functional groups present in thyroxine (and mentioned in the options) are:
- carboxylic acid
The reactions to consider with NaOH are as follows:
1. Acid-base or neutralisation of acidic functional groups
We should be familiar with the acidity of carboxylic acids, phenols and alcohols.
For students who are interested, check out a previous video comparing acidity of organic compounds:
The reactions of acids, phenols and alcohols with bases are given below:
Acids and phenols are acidic enough to react with NaOH.
2. Nucleophilic Substitution of halogenoalkanes
Since the iodine atoms are attached to benzene, they are resonance stabilised hence will not undergo nucleophilic substitution.
3. Hydrolysis of nitriles, esters and amides
There are no functional groups in thyroxine that can be hydrolysed.
Hence we can conclude only -COOH and -OH(phenol) groups will react with NaOH and the answer to this question is option D.
Topic: Carboxylic Acids and Derivatives, Organic Chemistry, A Level Chemistry, Singapore
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