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Effect of protonation exothermicity on the chemical ionization mass spectra of some alkylbenzenes
Author(s) -
Herman Jan A.,
Harrison Ale X. G.
Publication year - 1981
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210161002
Subject(s) - alkylbenzenes , chemistry , protonation , alkyl , mass spectrum , fragmentation (computing) , chemical ionization , reagent , medicinal chemistry , proton affinity , deprotonation , photochemistry , ion , hydride , electron ionization , polyatomic ion , mass spectrometry , ionization , organic chemistry , benzene , hydrogen , computer science , operating system , chromatography
The H 2 , N 2 /H 2 , CO 2 /H 2 , N 2 O/H 2 , CO/H 2 and CH 4 chemical ionization mass spectra of thirteen C 8 to C 11 alkylbenzenes are reported. Characteristic hydride and alkide ion abstraction 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 .