Chemistry 9701 · AS & A Level · Carboxylic acids and derivatives

Carboxylic acids and derivatives — practice question

(a)[3]

Ethanoic acid, $\text{CH}_3\text{CO}_2\text{H}$, and trichloroethanoic acid, $\text{CCl}_3\text{CO}_2\text{H}$, are both carboxylic acids. Ethanoic acid may be used to prepare ethanamide, $\text{CH}_3\text{CONH}_2$. Put these three compounds in order from least acidic to most acidic. Explain your answer.

(b(i))[1]

State which, if any, of ethanoic acid, methanoic acid and ethanedioic acid reacts with Fehling’s reagent.

(b(ii))[1]

State which, if any, of ethanoic acid, methanoic acid and ethanedioic acid react with warm acidified manganate(VII) ions.

(c(i))[2]

Compound $A$ contains chlorine. Give the structural formula and the name of $A$.

(c(ii))[2]

Suggest suitable reagents for steps 1 and 2 in the synthesis. step 1 step 2

(d(i))[1]

Explain why $\text{CDCl}_3$ is used as a solvent instead of $\text{CHCl}_3$.

(d(ii))[2]

Complete the diagram by adding the chemical shifts, $\delta$, for the labelled protons in the $\text{CH}_3\text{CONHC}_2\text{H}_5$ molecule.

(d(iii))[2]

State and explain how the proton NMR spectrum of the amide $\text{CH}_3\text{CONHC}_2\text{H}_5$ changes when it is dissolved in $\text{D}_2\text{O}$ instead of $\text{CDCl}_3$.

(e)[1]

The mass spectrum of the amide $\text{CH}_3\text{CONHC}_2\text{H}_5$ shows a fragment ion at $m/e$ 58. Give the molecular formula of this fragment ion.

(f(i))[1]

Identify reagent $B$.

(f(ii))[1]

State the number of separate absorptions in the carbon-13 NMR spectrum of diethylamine.

Worked solution & mark scheme

This 17-mark question has a full step-by-step worked solution and mark scheme. One marking point: ethanamide first, then ethanoic acid, then trichloroethanoic acid

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