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When looking at the GC/MS for Allylthiobenzene aka allyl phenyl sulphide, two clear peaks are seen at 91 m/z and 65 m/z, most common for 7 membered and 5 membered carbon rings respectively. The problem is that the substituent group associated to this compound begins with a sulphur, which, when integrated into the ring, does not produce a signal at 91. Is it possible for this to be cleaved and a different carbon (possibly from the tail swinging around) to be integrated?

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    $\begingroup$ Welcome to chemSE. The likely cations mz=65 and m/z=91 are $\ce{C5H5+}$ and $\ce{C7H7+}$ (tropylium?), respectively. There is the possibility that the initial event is a Claisen rearrangement. This would form a $\ce{C10}$ framework from which the fragments arise. $\endgroup$
    – user55119
    Commented Jun 15, 2023 at 17:52
  • $\begingroup$ It is also true that the MS of toluene, thioanisole and allylbenzene all show the presence of m/z=65 and m/z=91 fragments. Look here. $\endgroup$
    – user55119
    Commented Jun 15, 2023 at 22:49

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