These are Organic Chemistry 3 tutorial problems for extra practice and extra study materials for your upcoming tests and exams. These tutorials include Mass Spectrometry, IR Spectroscopy and Nuclear Magnetic Resonance (NMR).
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
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