2021 P1 Q23 - Deduce Structure of Amide X

Let's take a look at 2021 A Levels H2 Chemistry Paper 1 Question 23.

2021 p1 q23 question

We are required to identify amide X given its reactions with LiAlH4 and warm HCl(aq).

1. Reduction with LiAlH4 to form C6H13N.

With strong reducing agent LiAlH4, amide (-CONH-) is reduced to amine (-CH2NH-) functional group.

We can determine the products formed for each option and see which ones give product with the correct molecular formula.

2021 p1 q23 reduction with LiAlH4

Notice only options A and B form amine with the correct molecular formula C6H13N.

Hence options C and D are rejected.

2. Hydrolysis with HCl(aq) to form salt C6H14NO2Cl.

This is the reagents and conditions for acidic hydrolysis and products will be carboxylic acid and salt of amine.

Let us deduce the products of acidic hydrolysis for options A and B.

2021 p1 q23 hydrolysis with HCl

Option A is a cyclic amide hence will hydrolyse to give only 1 product with the correct molecular formula.

Option B is an aliphatic amide and on hydrolysis will give an acid compound (C6H10O2) and ammonium chloride.

Hence option B is eliminated.

2021 p1 q23 answer

Therefore the answer to this question is option A.

Topic: Nitrogen Compounds and Proteins, Organic Chemistry, A Level Chemistry, Singapore

Back to list of questions for 2021 A Level H2 Chemistry Paper 1.

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