Naming organic compounds with IUPAC rulesIB MYP Chemistry: Subtopic test

1. 1
   A chemist is labelling bottles in a laboratory store. Every organic compound must carry its IUPAC name, in which the stem shows the number of carbon atoms in the longest chain and the ending shows the family of the compound.

   (a)

   Which prefix shows a chain of seven carbon atoms?

   [1 mark]

   • Ahept-
   • Bhex-
   • Coct-
   • Dpent-

   (b)

   What is the IUPAC name of CH₃CH=CHCH₃?

   [1 mark]

   • ABut-1-ene
   • BBut-3-ene
   • CBut-2-ene
   • DButane

   (c)

   Give the name of CH₃CH₂CH₂OH and state what the ending -ol shows about the compound.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student is studying 2-methylpropane, which has the molecular formula C₄H₁₀ and the condensed structural formula CH₃CH(CH₃)CH₃.

   (a)

   Butane, CH₃CH₂CH₂CH₃, has the same molecular formula as 2-methylpropane. Which term describes the two compounds?

   [1 mark]

   • AIsotopes
   • BAllotropes
   • CHomologues
   • DStructural isomers

   (b)

   How many carbon atoms are in the longest chain of 2-methylpropane?

   [1 mark]

   • A2
   • B3
   • C4
   • D5

   (c)

   Explain what the parts 'propane' and 'methyl' tell you about the structure of 2-methylpropane.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student must name two compounds from their condensed structural formulae. Compound X is CH₃CH₂COOH and compound Y is CH₃COOCH₂CH₃.

   (a)

   Name compound X and compound Y, and state the functional group in compound X.

   [3 marks]

   (b)

   Pentane, CH₃CH₂CH₂CH₂CH₃, has two structural isomers. Name both isomers, write the condensed structural formula of the one with a single methyl branch, and explain why all three compounds are structural isomers.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A camping-gas cylinder contains a mixture of butane and 2-methylpropane, both with the molecular formula C₄H₁₀, stored as liquids under pressure. A student looks up boiling points: butane −0.5 °C, 2-methylpropane −11.7 °C, pentane 36 °C, 2-methylbutane 28 °C and 2,2-dimethylpropane 9.5 °C. She hypothesises that, for compounds with the same molecular formula, the more branched compound has the lower boiling point.

   (a)

   Describe the patterns in the data and evaluate the student's hypothesis.

   [6 marks]

   (b)

   Discuss and evaluate the use of butane and 2-methylpropane as a fuel for camping stoves.

   [6 marks]

   Total for question 4: 12 marks

End of questions