0%

DP IB Chemistry: SL

Topic Questions

Home / IB / Chemistry: SL / DP / Topic Questions / 11. Measurements & Data Processes / 11.1 Spectroscopic Identification / Structured Questions: Paper 2


11.1 Spectroscopic Identification

Question 1a

Marks: 2
a)
Three isomers of pentane are shown below.

1

   Give the IUPAC names of isomers B and C.

[2]

    Assess your score
      
    Key Concepts
    Nomenclature

    Question 1b

    Marks: 3
    b)
    Predict the number of different hydrogen environments in each of the isomers from part (a).
    [3]
      Assess your score
        
      Key Concepts
      Chemical environments

      Question 1c

      Marks: 2
      c)
      The displayed formula of propanal is shown.

      WGbWjbT6_2

      State the number of 1H NMR signals that would appear in the 1H NMR of propanal and state the ratio of the area under the peaks in which they would appear.

      [2]

        Assess your score
          

        Question 1d

        Marks: 2
        d)
        Propanal and propanone, shown below, both have the same molecular formula C3H6O.
        3
        Explain how propanone gives a different  1H NMR spectrum compared to propanal.
        [2]
          Assess your score
            

          Question 1e

          Marks: 1
          e)
          Using section 27 of the data booklet, state the chemical shift for the 1H NMR of propanone.
          [1]
            Assess your score
              
            Key Concepts
            Chemical environments

            Question 2a

            Marks: 2
            a)
            Using section 27 of the data booklet, state the chemical shift for hydrogens a and b  in the 1H NMR of propanal.

            4

              Assess your score
                
              Key Concepts
              Chemical environments

              Question 2b

              Marks: 1
              b)
              The structure of the amino acid glycine is shown below.

              5

                   State the number of peaks found in the 1H NMR spectrum of glycine.

              [1]

                Assess your score
                  

                Question 2c

                Marks: 1

                c)   State the ratio of the areas under the hydrogen peaks for glycine.

                [1]

                  Assess your score
                    

                  Question 2d

                  Marks: 1
                  d)
                  The chemical shift for the protons in the NH2 protons in glycine is 1.0 - 4.5 ppm.
                  Using section 27 of the data booklet, predict the other 1H NMR chemical shifts for glycine.
                  [1]
                    Assess your score
                      
                    Key Concepts
                    Chemical environments

                    Question 3a

                    Marks: 1

                    a)    Deduce the hydrogen deficiency of but-1-ene.

                    But-1-ene IB SL SQ 10.2 E Q5a

                      Assess your score
                        

                      Question 3b

                      Marks: 1
                      b)
                      Phenol acid has the molecular formula C6H6O.
                      Deduce the index of hydrogen deficiency of phenol.
                      [1]
                        Assess your score
                          

                        Question 3c

                        Marks: 1
                        c)
                        Under certain conditions, butan-1-ol can be oxidized to the compound with the infrared spectrum shown below.

                        ir-spectrum

                        Using section 26 of the data booklet, state the name of the compound that has produced the spectrum shown.

                        [1]

                          Assess your score
                            

                          Question 3d

                          Marks: 1
                          d)
                          State what the molecular (parent) ion, M+ peak, in the mass spectrum of a hydrocarbon containing 12C and 1H represents.
                          [1]
                            Assess your score
                              

                            Question 4a

                            Marks: 2

                            a)   Geraniol is an organic molecule that contains alkene and alcohol functional groups.

                                  The mass spectrum of geraniol is shown below.

                            mass-spectrum-geraniol

                            i)    State how this mass spectrum can be used to confirm the molar mass of geraniol. [1]


                            ii)    Give the formula of an ion that could be responsible for the peak at m/ z = 69. [1]

                              Assess your score
                                

                              Question 4b

                              Marks: 1
                              b)
                              A sample of propan-2-ol was heated under reflux with potassium dichromate(VI) acidified with sulfuric acid, and then the mixture was distilled. 

                              Apart from the peaks due to the C—C and C—H bonds, what peak(s) would be present in the infrared spectrum of the distillate.

                              [1]

                                Assess your score
                                  

                                Question 4c

                                Marks: 2
                                c)
                                The compound shown below can be analysed to obtain infrared and mass spectra.

                                heptane

                                Using section 28 of the data booklet, suggest the molecular formulae of the ions responsible for peaks in the mass spectrum with the following m/e values.

                                i)        15 [1]

                                ii)       100 [1]

                                  Assess your score
                                    
                                  Key Concepts
                                  Fragmentation patterns

                                  Question 4d

                                  Marks: 2
                                  d)
                                  The mass spectrum shown below was obtained for propanal, CH3CH2CHO.

                                  UzoggQTO_mass-spectrum-q

                                  i)    Use the mass spectrum to show that the empirical and the molecular formulae of the compound mentioned are the same. [1]

                                  ii)   Using section 28 of the data booklet, suggest the species responsible for the peak at m/z = 29. [1]

                                    Assess your score
                                      

                                    Question 5a

                                    Marks: 2

                                    a)   This question is about some isomeric alcohols with the molecular formula C5H12O.

                                          Some alcohols were heated with potassium dichromate(VI) and sulfuric acid. The organic compounds were separated from the reaction mixtures and purified.

                                          The infrared spectra of two of these organic compounds are shown below.

                                    compound-y-and-z

                                          Using section 26 of the data booklet, deduce the type of compound responsible for each spectrum.

                                          Include in your answer references to wavenumbers and their corresponding bonds.

                                    [2]

                                      Assess your score
                                        

                                      Question 5b

                                      Marks: 2
                                      b)
                                      State what is meant by the term ‘fingerprint region’ on infrared spectra and explain how this can be used to identify primary, secondary and tertiary halogenoalkanes.
                                      [2]
                                        Assess your score
                                          

                                        Question 5c

                                        Marks: 1

                                         c)   The infrared spectrum a student obtained of an organic molecule which contains carbon, hydrogen and oxygen atoms is shown below.

                                        ir-spectrum-2

                                              Use section 26 of the data booklet and information from the infrared spectrum to explain how the student deduced that the spectrum shows the presence of a carbonyl group.

                                        [1]

                                          Assess your score
                                            

                                          Question 5d

                                          Marks: 2

                                          d)   In an experiment to prepare a sample of ethanal, CH3CHO, ethanol, C2H5OH, is reacted with acidified potassium dichromate (VI) and the reaction mixture is distilled. The infrared spectra for ethanol and ethanal are shown below.

                                          ethanol-ir-spectrum

                                          ethanal-ir-spectrum

                                          i)    State the bonds that give rise to the absorption in the ethanol spectrum at 3400 cm-1 and the absorption in the ethanal spectrum at 1720 cm-1. [1]

                                           

                                          ii)    Explain why the absorption at 3400 cm-1 in the ethanol spectrum does not appear in the spectrum for ethanal. [1]

                                           

                                            Assess your score