The dissociative recombination of hydrocarbon ions . III . Methyl - substituted benzene ring compounds
Résumé
The recombination of electrons with cyclic ions produced via ion – molecule reactions between atomic precursor ions and methyl-substituted benzene ring compounds ͑(toluene , ortho-, and para-xylene and mesitylene) has been studied at 300 K using a flowing afterglow Langmuir probe-mass spectrometer apparatus. Differing amounts of energy can be deposited into the daughter ions depending upon which atomic precursor is used. It has been found that same-mass daughter ions formed from different precursors displayed different recombination rate coefficients indicating that different isomeric forms were reacting. In particular , the benzene ring of the toluene cation expands to a seven-membered ring following isomerization to the cycloheptatriene form. H atom abstraction allows two different isomeric daughter ions to be formed that do not interconvert and that display different recombination rates. A similar behavior was observed for the xylenes and for mesitylene. All recombination rates lie in the range from 10-7 to 10 -6 cm3 s-1 and display no apparent relation with size nor with the aromaticity of the ions .
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