The gas phase reactivity of the dimethylchloronium ion with alkylbenzenes

Abstract

The reactivity of the dimethylchloronium ion with a series of aromatic hydrocarbons has been studied in a high pressure mass spectrometer ion source using the technique of reactant ion monitoring. Benzene is unreactive but all others, from toluene to mesitylene, react by CH3+ transfer to yield σ-bonded complexes. The relative rate of reaction increases with increasing exothermicity in line with current theories of nucleophilic displacement reactions.

The gas phase reactivity of chloronium ions by high pressure mass spectroscopy

“…The significantly higher reactivity of 2-chloropyridine compared with the more basic pyridine suggests that electrophilic attack on this compound may be occurring at C1 as well as at N. The alkyl aromatics show a wide range of reactivity with both halonium ions. The order of increasing reactivity is the same as we found previously for CH3ClCH3' with a much more limited set of compounds (2). The relative reactivities do not compare too well, however, with these previous values ( Table 2) and neither does the value of 0.1 1 for benzene (calculated using Fig.…”

“…The field free ion source and the quadrupole ion detection system have been described (2,11). RIM experiments were carried out in the manner which has been described in detail (2,5) and will therefore only be briefly described.…”

“…RIM experiments were carried out in the manner which has been described in detail (2,5) and will therefore only be briefly described.…”

“…min-'. The monitored ion current appears like an inverted gc trace (2). The relative reactivity RA/RB of two compounds, A and B, with a given reactant ion is (5) Can.…”

“…For example, CH3C1CH3' transfers a methyl cation to alkyl aromatics (ArR) in the gas phase with a reaction efficiency which increases with increasing exothermicity of reaction [l] [I] CH,ClCH,' + ArR + CH,Cl + A~RCH, ' We used the technique of Reactant Ion Monitoring (RIM) (2,5) to determine the relative rates of these reactions in the high pressure ion source of a mass spectrometer and found the relative reactivity of ArR to increase in the order toluene < xylenes < mesitylene. Neither benzene nor fluorobenzene was obsewed to react but in a subsequent publication Sen Sharma and Kebarle (3) showed that benzene does indeed react, but very slowly ( k -10-l2 cm3 molecule-' s-' at 298 K).…”