the figure show the gc-ms of essentail oil extracted from the seeds and leaves of plant. Guide me how to explain this especially base peak 55 and 97 what do they represent ?
ot tell me how to explain this ?
The ions in question (55 and 97) are the most abundant for your compound, but also at relatively low mass given the molecular weight of this substance being 280. They are also part of the a characteristic low mass ion series and thus represent the low mass, stable products following secondary, tertiary, etc. fragmentations of the original molecule. The most prominent series seems to be 67, 81, 95, 109 as indicative of the fact they are all separated by CH2, typical of an aliphatic series. Its hard to say exactly what these masses represent since there are various formulas they could correspond to, such as C5H7+ or C4H3O+, both of which could make sense given the structure of this molecule. There also is a notable odd electron ion series at m/z 68, 82, 96, 110. Otherwise there aren't many obvious fragments directly from the molecular ion aside from slight M-OH, M-H2O, and M-C2O2H4.
The ions in question (55 and 97) are the most abundant for your compound, but also at relatively low mass given the molecular weight of this substance being 280. They are also part of the a characteristic low mass ion series and thus represent the low mass, stable products following secondary, tertiary, etc. fragmentations of the original molecule. The most prominent series seems to be 67, 81, 95, 109 as indicative of the fact they are all separated by CH2, typical of an aliphatic series. Its hard to say exactly what these masses represent since there are various formulas they could correspond to, such as C5H7+ or C4H3O+, both of which could make sense given the structure of this molecule. There also is a notable odd electron ion series at m/z 68, 82, 96, 110. Otherwise there aren't many obvious fragments directly from the molecular ion aside from slight M-OH, M-H2O, and M-C2O2H4.
Hello Yasir, maybe a look into the appendix of Fred McLafferty's book is helpful (https://books.google.de/books/about/Interpretation_Of_Mass_Spectra.html?id=xQWk5WQfMQAC&redir_esc=y)
55 is due to C=O=OH+. Non bonding electron are the choice for charge retention
95 is due to fragmentation of the alkene portion, one mechanism is CH3-CH2-CH2-CH2-CH=CH+ this is an even election ion with mass 97 and losses a hydrogen molecule to give m/z 95
Hi Yasir,
You may check the MS list Gerrit van der Honing provided in another RG question (3rd answer). See the link attached.
Hope you find something.
Cheers,
Marcus
https://www.researchgate.net/post/What_may_be_the_reason_if_I_am_getting_higher_mass_calculated_mass_42060_experimentally_447_in_mass_spectrometry
The main fragmentations observed such as m/z 55, 67, 81, 95, 109 are due to the complex hydrogen transfer. The postulated fragmentation mechanisms are attached. Note that the ions due to McLafferty's rearrangement such as m/z 60 and 101 are not observed probably because of the structure with 2 double bonds.
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