Effect of protonation exothermicity on the chemical ionization mass spectra of some alkylbenzenes

The H2, N2/H2, CO2/H2, N2O/H2, CO/H2 and CH4 chemical ionization mass spectra of thirteen C8 to C11 alkylbenzenes are reported. Characteristic hydride and alkide ion ion reactions are observed with all reagent gases. The major fragmentation reactions of [MH]+ are olefin elimination to form a protona...

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Veröffentlicht in:Organic Mass Spectrometry 1981-10, Vol.16 (10), p.423-427
Hauptverfasser: Herman, Jan A., Harrison, Ale X. G.
Format: Artikel
Sprache:eng
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Zusammenfassung:The H2, N2/H2, CO2/H2, N2O/H2, CO/H2 and CH4 chemical ionization mass spectra of thirteen C8 to C11 alkylbenzenes are reported. Characteristic hydride and alkide ion ion reactions are observed with all reagent gases. The major fragmentation reactions of [MH]+ are olefin elimination to form a protonated arene and arene elimination to form an alkyl ion. From the effect of structure and protonation exothermicity it is concluded that rearrangement of primary alkyl groups to the more stable secondary or tertiary structure occurs prior to alkyl ion formation. A detailed fragmentation mechanism for protonated arenes is proposed. The ‘effective’ proton affinity of the methane‐derived reagent system is estimated to be ∼556 kJ mol−1.
ISSN:0030-493X
1096-9888
DOI:10.1002/oms.1210161002