1. 1
   A research group is studying three compounds: but-2-ene (CH₃CH=CHCH₃), 1,2-dichlorocyclopropane (a three-membered carbon ring with one chlorine atom on each of two adjacent ring carbons) and 2-bromobutane (CH₃CHBrCH₂CH₃).

   (a)

   Which compound shows cis–trans isomerism?

   [1 mark]

   • ABut-1-ene
   • B2-methylbut-2-ene
   • C1,1-dichloroethene
   • DBut-2-ene

   (b)

   Which statement about the two enantiomers of 2-bromobutane is correct?

   [1 mark]

   • AThey rotate plane-polarised light by equal angles in opposite directions.
   • BThey have different boiling points.
   • CThey are superimposable mirror images.
   • DAn equimolar mixture of the two rotates plane-polarised light more than either pure enantiomer.

   (c)

   Explain why 1,2-dichlorocyclopropane exists as cis and trans isomers.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A technician is labelling bottles in a store room. They include ethanamide (CH₃CONH₂), ethylamine (CH₃CH₂NH₂) and a halogenoalkane with the condensed formula CH₃CH₂CH(CH₃)CH₂Cl.

   (a)

   Which functional group is present in ethanamide?

   [1 mark]

   • AAmino
   • BAmido
   • CHydroxyl
   • DCarboxyl

   (b)

   What is the IUPAC name of CH₃CH₂CH(CH₃)CH₂Cl?

   [1 mark]

   • A1-chloro-3-methylbutane
   • B4-chloro-3-methylbutane
   • C1-chloro-2-methylbutane
   • D1-chloropentane

   (c)

   Deduce the condensed structural formula and IUPAC name of one position isomer of CH₃CH₂CH(CH₃)CH₂Cl.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An unknown compound W contains only carbon, hydrogen and oxygen. Its infrared spectrum shows a very broad absorption between 2500 and 3000 cm⁻¹ and a strong, sharp absorption at 1710 cm⁻¹. Its mass spectrum has a molecular ion peak at m/z = 74 and fragment peaks at m/z = 57, 45 and 29.

   (a)

   Deduce what the infrared absorptions show about the bonds and functional group in W.

   [3 marks]

   (b)

   Use the mass spectrum to deduce the structure of W, identifying the species responsible for each fragment peak.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Two esters, T and U, both have the molecular formula C₄H₈O₂. Their ¹H NMR spectra each show three signals. T: 1.2 ppm (triplet, relative area 3), 2.0 ppm (singlet, relative area 3), 4.1 ppm (quartet, relative area 2). U: 1.1 ppm (triplet, relative area 3), 2.3 ppm (quartet, relative area 2), 3.7 ppm (singlet, relative area 3). Both infrared spectra show a strong absorption at 1740 cm⁻¹ and C–H absorptions near 2900–3000 cm⁻¹, but no broad O–H absorption. The most abundant fragment in the mass spectrum of T is at m/z = 43, and in the mass spectrum of U it is at m/z = 57.

   (a)

   Deduce the structure of T, explaining how the number of signals, chemical shifts, relative areas and splitting patterns support your answer.

   [6 marks]

   (b)

   Deduce the structure of U. Evaluate how the infrared and mass spectrometry data support the structures of both T and U, including why infrared spectroscopy alone cannot distinguish them.

   [6 marks]

   Total for question 4: 12 marks

End of questions