Chemistry 9701 · AS & A Level · Carbonyl compounds

Carbonyl compounds — practice question

Propanone, $\text{CH}_3\text{COCH}_3$, is a significant organic reagent. Fig. 4.1 illustrates several reactions of propanone and its derivatives.
(a(i))[3]

Reaction 1 is a nucleophilic addition reaction. Finish Fig. 4.2 so that it shows the mechanism for producing A from propanone. Include charges, dipoles, lone pairs of electrons and curly arrows where needed.

(a(ii))[1]

Explain why A fails to show optical isomerism.

(b)[1]

Suggest suitable reagents and conditions for reaction 2.

(c(i))[1]

Reaction 3 is a reduction reaction. Write an equation to represent reaction 3. Use $[\text{H}]$ to show one atom of hydrogen from the reducing agent.

(c(ii))[1]

Name compound C.

(d)[1]

State the observation in reaction 4.

(e)[1]

Explain why Fehling’s reagent fails to react with propanone.

(f)

Infrared spectroscopy can be used to tell compounds A, B and C apart. Fig. 4.3 displays the infrared spectrum of one of the compounds.

(f(i))[1]

Explain why the absorptions at $2850$-$2950\ \text{cm}^{-1}$ are not useful to help determine which of the compounds A, B or C produces the infrared spectrum in Fig. 4.3. Use Table 4.1 to answer this question.

(f(ii))[1]

Identify which of compounds A, B or C matches the infrared spectrum in Fig. 4.3. Explain your answer.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: Curly arrows from $\text{CN}^-$ to the carbonyl carbon, from $\text{C}=\text{O}$ to O, plus proton transfer

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