Activation of Dioxygen by Halocarbon Ions

Abstract

Tandem mass spectrometry is used to show that low energy collisions of ionized halocarbenes, including CBr 2•+ and CBrCl •+ , with molecular oxygen lead to (i) decarbonation with formation of the dihalogen molecular cation and (ii) oxygenolysis yielding BrCO + . Both reactions may occur via the same ion-molecule addition product of molecular oxygen and the ionized carbene. Reaction is favored at low collision energies, such as are encountered in an ion trap. Insights into the energetics of the reactions of CBr 2•+ with O 2 are obtained from ab initio molecular orbital theory. Other aspects of the positive ion chemistry of dioxygen with various halogen-containing ions are also discussed. Dioxygen activation by halocarbon ions suggests additional channels that might affect the fate of halocarbons and the ozone balance in the atmosphere.

Gas-phase reactions of halogenated radical carbene anions with sulfur and oxygen containing species

“…Analogous to the above reactions with CS 2 , COS and CO 2 , where the displaced halide is also observed, this reaction most likely proceeds through an These dihalide anions could be formed from a mechanism similar to Scheme 4, where X atom abstraction occurs within the product ion-molecule complex before the initial products separate to form XY •− and CO 2 . Interestingly, the product ions formed in the reactions of CCl 2 •− and CBrCl •− with O 2 are comparable to the carbene cation reaction of CBr 2 •+ with O 2 , which has previously been studied by Cooks and co-workers [75]. In that work, the authors speculate that this reaction proceeds through a Br 2 CO 2 •+ intermediate, which can eliminate CO 2 to form Br 2 •+ .…”

Formation of Protonated ortho-Quinonimide from ortho-Iodoaniline in the Gas Phase by a Molecular-Oxygen-Mediated, ortho-Isomer-Specific Fragmentation Mechanism

“…One of the fundamentally interesting ion–molecule reactions that has been investigated is the deliberate, or sometimes undesired, addition of dioxygen to radical sites of distonic radical cations. ,− For example, both pyridine- and aniline-derived distonic radical cations are known to form peroxyl radical cations with molecular oxygen. , Similar O 2 addition reactions have been reported also for several distonic radical anions. − Moreover, molecular oxygen is known to add to radical ions formed by the cleavage of N–C α bonds of the amide backbone in peptides under electron-capture dissociation (ECD) or electron-transfer dissociation (ETD) conditions, to radical anions generated from iodotyrosine residues, to organometallic cobalt­(III) and aluminum­(III) complexes , and other inorganic ions. , …”

Isomerization and dissociation of C2X5+ and C2X4+· ions (X = Cl, F) from chlorofluoroethanes in an ion trap mass spectrometer

“…The interest in the ion chemistry of perfluoro‐ and chlorofluorocarbons is high, since ions derived from compounds belonging to these families are implicated in numerous processes which range from ionic degradation pathways in the mesosphere and low thermosphere1 to plasma‐based technologies 2. In the latter field, various ion‐etching techniques for microcircuit fabrication (ion milling, ion etching, sputter etching) should be mentioned, in addition to promising new technologies for the treatment of volatile organic compounds (VOCs) which make use of non‐thermal plasmas 3.…”