How to Interpret a Mass Spectrum Containing Ions that Undergo Rearrangement - Part 3

The gas chromatography-mass spectrometry (GC-MS) electron ionization (EI) may also result in ortho- rearrangement.


The same requirements for McLafferty rearrangement apply to ortho- rearrangement except for the strong α,β- C=C double bond. ortho- rearrangement, which initiates charge-site reaction, resulting in the loss of a small neutral molecule (water, HCl or the like), can be utilized to differentiate ortho- from para- and meta- isomers. This reaction is also observed for three unsaturated functional groups, viz., thioesters, esters and amides. Tropylium ion is formed due to a rearrangement from a molecule having a benzyl (PhCH2-) group, such as, o-Toluic acid as shown in the image below.



Click to enlarge the image

M = Molecular, OE = Odd-electron, EE = Even-electron

Is the infographic easy to comprehend❓ Let Chemaficionado know at mychemistryhomework@gmail.com❗

References:

(1)    Wikipedia Contributors. Mass spectral interpretation. Wikipedia.

‌(2)    SDBS, Spectral Database for Organic Compounds, AIST. sdbs.db.aist.go.jp. https://sdbs.db.aist.go.jp/.

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