How to Interpret a Mass Spectrum Containing Ions that Undergo Rearrangement - Part 2

The retro-Diels–Alder (rDA) reaction is the reverse of the Diels–Alder (DA) reaction, a [4+2] cycloelimination.


For cyclohexene derivatives, the π-electrons are excited and generate a charge site and a radical site upon gas chromatography-mass spectrometry (GC-MS) electron ionization (EI). It undergoes an rDA rearrangement to give diene and alkene (dienophile) fragment/product ions via two successive α-cleavages. The charge may be retained by either fragment as evident from the spectrum. This rearrangement may occur by a radical or an ionic mechanism.



Click to enlarge the image

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

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

References:

(1)    Wikipedia Contributors. Retro-Diels–Alder reaction. Wikipedia.

(2)    National Institute of Standards and Technology. NIST Chemistry WebBook - SRD 69. NIST. https://webbook.nist.gov/chemistry/.

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