(a(i))[4]
State the structures of the organic compounds Q, R, S and T.
(a(ii))[1]
State the systematic name of compound P.
(a(iii))[1]
What do you observe when compound P is treated with 2,4-dinitrophenylhydrazine (2,4-DNPH)?
(b)[4]
Compound U has a chiral centre and the same molecular formula as compound P, $\text{C}_5\text{H}_8\text{O}$. Compound U decolourises a sample of bromine water readily. Compound U does not display cis-trans isomerism. When compound U is heated under reflux with excess acidified potassium dichromate(VI), the organic product gives the infra-red spectrum shown. Use the information given to suggest a structure for compound U. Explain your answer.