Tutorial 1. Organic Chemistry III
Structure determination in Organic Chemistry 2021
Instruction: Provide answers for all the tasks that follow.
1. Draw the diagram of an electron-ionization, magnetic-sector mass spectrometer and label all
its parts.
2. Define/explain the following terms:
2.1. Parent peak 2.2. Base peak 2.3. Finger print region
3. Write the molecular formula for each product and label it as a cation, an ion-radical or a free
radical:
3.1. CH4 minus one electron
3.2. [CH4]+ minus H∙
3.3. [CH3CH2]+ minus H∙
3.4. [CH3CH2]+ minus H∙
4. Write the molecular formula for the molecular ion of:
4.1. CH4 and 4.2. CH3CH2CH2CH3
5. Give m/e value for each of the following particles:
5.1. [CH4]+∙
5.2. [(CH3)2CH]+
5.3. [O2] +∙
5.4. [H2O] +∙
6. Calculate the mass-to-charge ratio for the molecular ion of:
6.1. 1,2-dichloroethane
6.2. p-Bromophenol
7. Give the structures of the products formed in each case:
_ H2O
7.1. CH3CH2CH2OH +.
1
, Tutorial 1. Organic Chemistry III
Structure determination in Organic Chemistry 2021
_ e-
7.2.
7.3. +. _ H
OH
_
7.4. (CH3)2CHCl +. Cl
8. For each of the following compounds predict the structure and the mass-to-charge ratio value
for the molecular ion and the likely positively charged fragmentation products formed.
8.1. 2,5-Dimethylhexane 8.2. 2-Propanol
8.3. 2-Chloropropane 8.4. Butanal
8.5. Acetone
9. The mass spectrum of 2,2-dimethylpropane shows a base peak at m/z = 57.
9.1. Write the formula for the molecular ion of 2,2-dimethylpropane.
9.2. Draw the structure for the fragment ion with m/z = 57.
10. Suggest fragmentation patterns that account for the following observed peaks in the mass
spectra of:
10.1. n-butane m/e = 58, 57, 43, 29, 15
10.2. 1-bromopropane m/e = 124, 105, 79
10.3. C6H5CH2OCH3 m/e = 122, 121, 91, 77
10.4. 5-methyl-2-hexanone m/e = 71, 58, 43
11. Propose structures for compounds that fit the following data:
11.1. A ketone with M+· = 86 and fragments at m/z = 71 and m/z = 43
11.2. An alcohol with M+· = 88 and fragments at m/z = 73, m/z = 70 and m/z = 59
2
Structure determination in Organic Chemistry 2021
Instruction: Provide answers for all the tasks that follow.
1. Draw the diagram of an electron-ionization, magnetic-sector mass spectrometer and label all
its parts.
2. Define/explain the following terms:
2.1. Parent peak 2.2. Base peak 2.3. Finger print region
3. Write the molecular formula for each product and label it as a cation, an ion-radical or a free
radical:
3.1. CH4 minus one electron
3.2. [CH4]+ minus H∙
3.3. [CH3CH2]+ minus H∙
3.4. [CH3CH2]+ minus H∙
4. Write the molecular formula for the molecular ion of:
4.1. CH4 and 4.2. CH3CH2CH2CH3
5. Give m/e value for each of the following particles:
5.1. [CH4]+∙
5.2. [(CH3)2CH]+
5.3. [O2] +∙
5.4. [H2O] +∙
6. Calculate the mass-to-charge ratio for the molecular ion of:
6.1. 1,2-dichloroethane
6.2. p-Bromophenol
7. Give the structures of the products formed in each case:
_ H2O
7.1. CH3CH2CH2OH +.
1
, Tutorial 1. Organic Chemistry III
Structure determination in Organic Chemistry 2021
_ e-
7.2.
7.3. +. _ H
OH
_
7.4. (CH3)2CHCl +. Cl
8. For each of the following compounds predict the structure and the mass-to-charge ratio value
for the molecular ion and the likely positively charged fragmentation products formed.
8.1. 2,5-Dimethylhexane 8.2. 2-Propanol
8.3. 2-Chloropropane 8.4. Butanal
8.5. Acetone
9. The mass spectrum of 2,2-dimethylpropane shows a base peak at m/z = 57.
9.1. Write the formula for the molecular ion of 2,2-dimethylpropane.
9.2. Draw the structure for the fragment ion with m/z = 57.
10. Suggest fragmentation patterns that account for the following observed peaks in the mass
spectra of:
10.1. n-butane m/e = 58, 57, 43, 29, 15
10.2. 1-bromopropane m/e = 124, 105, 79
10.3. C6H5CH2OCH3 m/e = 122, 121, 91, 77
10.4. 5-methyl-2-hexanone m/e = 71, 58, 43
11. Propose structures for compounds that fit the following data:
11.1. A ketone with M+· = 86 and fragments at m/z = 71 and m/z = 43
11.2. An alcohol with M+· = 88 and fragments at m/z = 73, m/z = 70 and m/z = 59
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