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Ring opening reaction of protonated polyfluorinated benzenes in the gas phase. A theoretical MNDO study
Author(s) -
Hrušák Jan
Publication year - 1990
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.1210251004
Subject(s) - mndo , protonation , chemistry , dissociation (chemistry) , fluorine , ion , hydrogen atom , computational chemistry , ring (chemistry) , photochemistry , hydrogen , medicinal chemistry , carbon atom , organic chemistry , molecule , alkyl
The MNDO calculations of protonated polyfluorobenzenes [Ph‐F n ]H + indicate the possibility of a relatively free migration of the hydrogen proton with energy barriers of 125–145 kJ mol −1 . At a higher degree of substitution ( n ) the protonation of the ipso carbon atom occupied by fluorine becomes energetically feasible, along with analogous migrations of fluorine, which, however, are energetically the most advantageous (Δ E a ∼ 230 kJ mol −1 ). In addition to bridged fluoronium ions, relatively stable cyclic intermediates were also found, which make possible a rearrangement to the difluoromethylenecyclopentadienyl cation and thus the elimination of CF 2 observed in collision‐induced dissociation mass spectra.