The reactivity of [C₃H₃⁺] ions; a thermochemical study

Abstract

The loss of halogen atom from the molecular ions of compounds of formulae C3H3Cl and C3H3Br produces the cyclopropenium cation as daughter ion. Each reaction takes place with appreciable reverse activation energy, most of which is partitioned into translational degrees of freedom of the products. In marked contrast, the iodo-analogues generate [propargyl]+ as daughter ions at the thermochemical threshold (i.e. Erev for these fragmentations is ∼0). It is proposed that the reason for this behaviour lies in a large activation energy for the reaction [cyclo-C3H3]+ + I• → [C3H3I]+•

A comparative ion chemistry study of acetone, diacetone alcohol, and mesityl oxide

“…The corresponding ions in 2-propanone would be CSHI I + , m / z 71, which was not observed, and C4H90+, m / z 73, which was observed. Thus we conclude that either reaction [12] [I21 CsD902+* + C4D90+ + CO AH1* or reaction [13] occurs or both occur, where AHl2 and A H l 3 are the enthalpy changes for reaction [I21 and [13], respectively. As either reaction [12] or reaction [13] may account for the observations, it is appropriate to consider the energetics of the processes bearing in mind that a small fraction of stored ions may acquire translational energy from the three-dimensional quadrupole field and produce minor amounts of fragment ions in super-thermal collisions.…”

“…As either reaction [12] or reaction [13] may account for the observations, it is appropriate to consider the energetics of the processes bearing in mind that a small fraction of stored ions may acquire translational energy from the three-dimensional quadrupole field and produce minor amounts of fragment ions in super-thermal collisions. As reactions 1121 and [13] produce a common daughter ion with an assumed common structure, and the heats of formation of CO and C2H2 are -110 and 227 kJ mol-', respectively, then for reaction [13] to occur the heat of formation of C6D110+ plus internal excitation must exceed the heat of formation of C5D9O2+ plus iniernal excitation of 337 kJ mol-', provided that AH12 = AHl3. Thus the occurrence of reaction [13] is less probable than reaction [12].…”

“…As reactions 1121 and [13] produce a common daughter ion with an assumed common structure, and the heats of formation of CO and C2H2 are -110 and 227 kJ mol-', respectively, then for reaction [13] to occur the heat of formation of C6D110+ plus internal excitation must exceed the heat of formation of C5D9O2+ plus iniernal excitation of 337 kJ mol-', provided that AH12 = AHl3. Thus the occurrence of reaction [13] is less probable than reaction [12].…”

Dissociation dynamics of propargyl chloride molecular ion near the reaction threshold: manifestation of quantum mechanical tunneling

“…19,20 In our previous study of this reaction, 1 it was found that reaction (1a) was responsible for the reactions on a microsecond time scale. Through quantum chemical and kinetic calculations, it was proposed that the observed reaction (MID-MIKES) was due to quantum mechanical tunneling occurring below the threshold for the rate-determining isomerization step.…”

“…Occurrence of reaction (1a) on the microsecond time scale has also been reported in previous MID studies, even though the spectra were not completely free from interferences. 19,20 In the present study, dissociation of PGC has been reinvestigated using the MIKES technique. The kinetic energy release distribution (KERD) arising in the dissociation has been determined.…”