In: Chemistry
Explain the mass fragmentation pattern of (organic
spectroscopy)
1) Benzene
2)Neopentane
3)n-butyl alcohol
4) Toluene
5)1-Butanol
6)Benzyl alcohol
In case of benzene, the loss of one electron forms the arenium ion which has a m/z ratio = 78 and we can observe the main peak at this position.
2. Neopentane forms stable tertiary butyl cation upon fragmentation with m/z ratio 57. (please see the figure attached)
3. n-Butyl alcohol being a primary alcohol can cleave in two prominent ways. One is through breaking bond and another by lose of water. The first mechanism give peak at m/z =31 and the second one at 46. Both mechanism are shown in the figure attached.
4. The fragmentation of toluene starts from benzyl cation (m/z=91) which forms tropylium ion with m/z =91which is a major peak, then it undergoes further rearrangements to eliminate acetylene to give a peak at m/z=65.
5. 1-Butanol is essentially n-butyl alcohol.
6. Benzyl alcohol undergoes fragmentation is a similar fashion as toluene but in this case the tropyliol cation is formed which has a m/z ratio of 107. This tropyliol cation then undergoes further elimination of CO and H2 to form fragments with m/z ratio of 79 and 77.
All the mechanism are shown in the attached figure.