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DP IB Chemistry: HL

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Home / IB / Chemistry: HL / DP / Topic Questions / 20. Organic Chemistry (HL only) / 20.3 Stereoisomerism / Structured Questions: Paper 2


20.3 Stereoisomerism

Question 1a

Marks: 1
a)
Define the term stereoisomers.
[1]
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    Question 1b

    Marks: 2
    b)
    State the conditions needed for a compound to show cis-trans isomerism.
    [2]
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      Question 1c

      Marks: 2
      c)

      Draw the structural formulae for the E and Z stereoisomers of pent-2-ene.

      [2]

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        Question 1d

        Marks: 2
        d)

        2-bromo-1-chloropropene is a colourless, odourless liquid. 

        A student drew the two stereoisomers of 2-bromo-1-chloropropene below.

        ib-isomers-2

        State what is incorrect with their diagrams of these two stereoisomers.

        [2]

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          Question 2a

          Marks: 2
          a)

          Draw the E and Z stereoisomers for 2,3-dichlorobut-2-ene.

          [2]

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            Question 2b

            Marks: 2
            b)
            Name compounds C and D  using the E / Z naming system.
            compounds-c-and-d
            [2]
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              Question 2c

              Marks: 1
              c)

              Compound E is a derivative of compound C.

              compound-e-ib

              Suggest why the cis/trans naming system fails with compound E.

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                Question 2d

                Marks: 2
                d)
                Describe the difference between conformational and configurational stereoisomers.
                [2]
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                  Question 3a

                  Marks: 1
                  a)
                  The chemical and physical properties of optical isomers are identical. However, there are some other differences that can be used to distinguish isomers from each other.
                  In terms of properties, state one difference between optical isomers.
                  [1]
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                    Key Concepts
                    Polarimetry

                    Question 3b

                    Marks: 2
                    b)
                    Describe how you can detect optical activity in a sample.
                    [2]
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                      Key Concepts
                      Polarimetry

                      Question 3c

                      Marks: 1
                      c)

                      The structure of one optical isomer of a chlorofluorocarbon is shown below.

                      hydroflurocarbon-enantiomer

                      Draw the structure of the other enantiomer.

                      [1]

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                        Key Concepts
                        Optical Isomers

                        Question 4a

                        Marks: 1
                        a)

                        State what is meant by the term a chiral carbon.

                        [1]

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                          Key Concepts
                          Optical Isomers

                          Question 4b

                          Marks: 2
                          b)
                          The skeletal structure of an organic compound is shown below.
                          ib-isomers-5
                          Identify the chiral carbons. 
                          [2]
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                            Key Concepts
                            Optical Isomers

                            Question 4c

                            Marks: 1
                            c)
                            Explain why carbon a cannot be a chiral carbon.
                            ib-isomers-7a
                            [1]
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                              Key Concepts
                              Optical Isomers

                              Question 4d

                              Marks: 2
                              d)

                              The figure below identifies a different carbon, b, in the organic compounds structure.

                              ib-isomers-8a


                              Complete the figure below to show the 3D representations of the optical isomers formed at carbon b

                              ib-isomers-8b

                              [2]

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                                Key Concepts
                                Optical Isomers

                                Question 5a

                                Marks: 1
                                a)

                                Define the term racemic mixture.

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                                  Key Concepts
                                  Racemic Mixtures

                                  Question 5b

                                  Marks: 1
                                  b)
                                  Describe the composition of enantiomers when a reaction mixture is optically active.
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                                    Key Concepts
                                    Racemic Mixtures

                                    Question 5c

                                    Marks: 1
                                    c)

                                    Carvone is an optically active molecule which is found widely in plants, mostly in caraway seeds and spearmint leaves. The structure is shown below.

                                    carvone



                                    Mark on the diagram using an asterisk (*) the chiral carbon which causes this structure to exhibit optical isomerism.

                                    [1]

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                                      Key Concepts
                                      Optical Isomers

                                      Question 5d

                                      Marks: 1
                                      d)
                                      Draw the structure of the other optical isomer formed by carvone shown in part (c).
                                      [1]
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                                        Key Concepts
                                        Optical Isomers