Propanone, CH₃COCH₃, is an important organic reagent. [Figure 4.1] shows some reactions of propanone and its derivatives. propanone O // H₃C—C—CH₃ KCN and HCN reaction 1 A OH | H₃C—C—CH₃ | CN reaction 2 B OH | H₃C—C—COOH | CN 2,4-DNPH reaction 4 products [H] reaction 3 C OH | H₃C—C—CH₃ | H

1. (a)(i)Reaction 1 is a nucleophilic addition reaction. Complete [Figure 4.2] to show the mechanism for the formation of A from propanone. Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate. propanone O=C H₃C CH₃ Θ :CN A OH | H₃C—C—CH₃ | CN[3]
2. (a)(ii)Explain why A does not show optical isomerism.[1]
3. (b)Suggest the reagents and conditions for reaction 2.[1]
4. (c)(i)Reaction 3 is a reduction reaction. Construct an equation to represent reaction 3. Use [H] to represent one atom of hydrogen from the reducing agent.[1]
5. (c)(ii)Name C.[1]
6. (d)State what is observed in reaction 4.[1]
7. (e)Explain why Fehling's reagent does not react with propanone.[1]
8. (f)(i)Compounds A, B and C can be distinguished using infrared spectroscopy. [Figure 4.3] shows the infrared spectrum of one of the compounds. Explain why the absorptions at 2850–2950cm⁻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.[1]
9. (f)(ii)Identify which of compounds A, B or C produces the infrared spectrum in Fig. 4.3. Explain your answer. compound explanation[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.