Hydroxyethanal, HOCH₂CHO, has been observed in dust clouds near the centre of our galaxy. [Figure 4.hydroxyethanal_structure]

1. (a)Predict the bond angles labelled x and y in the diagram of hydroxyethanal. [Figure 4.a.bond_angles][2]
2. (b)Hydroxyethanal reacts separately with 2,4-dinitrophenylhydrazine (2,4-DNPH) and with Tollens' reagent. State what you would observe in each reaction. reaction with 2,4-DNPH reaction with Tollens' reagent[2]
3. (c)(i)State the role of acidified Cr₂O₇²⁻ in this reaction.[1]
4. (c)(ii)State and explain any other necessary conditions for this reaction to be successful.[2]
5. (d)(i)Write an equation for the reduction of hydroxyethanal to (CH₂OH)₂. Use [H] to represent an atom of hydrogen from the reducing agent.[1]
6. (d)(ii)Identify a reagent for this reduction reaction.[1]
7. (d)(iii)(CH₂OH)₂ also forms when an alkene A reacts with cold, dilute, acidified manganate(VII) jons. Name A.[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.