I'm having troubles assigning the signals m/z = 41 and 56 of the compound 1,5 pentanediol. I tried the basic fragmentations (McLafferty, loss of OH radical, etc.) but I can't figure the structure of these signals.

1,5-Pentanediol Mass Spectrum

Thank you.

  • $\begingroup$ Worth noting that $\ce{C3H5+}$ has an $m/z$ of 41.039. Not sure where 56 is coming from. I'm not sure that $\ce{C3H5+}$ really is the ion in this spectrum, but if it is, one way to get there would be by double dehydration of the alcohols, forming 1,4-pentadiene or an ion derived therefrom, followed by C-C bond breaking. The MS spectrum of 1,4-pentadiene does have a peak at 41, but admittedly it is not he main peak. $\endgroup$ – Curt F. Dec 9 '20 at 17:48
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    $\begingroup$ I found this paper doi.org/10.1002/oms.1210120113 that helped me a lot. Basically, there is an initial rearrangement and then the fragmentation occurs. $\endgroup$ – Matthew_Adams Dec 10 '20 at 18:23

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