2021 P1 Q23 - Deduce Structure of Amide X

Let Chemistry Guru, Singapore's top choice for JC Chemistry tuition, guide you through 2021 A Levels H2 Chemistry Paper 1 Question 23.

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.

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.

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.

Therefore the answer to this question is option A.

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

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