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Type: Artigo de periódico
Title: Gas-phase chemistry of the sulfur hexafluoride fragment ions SFn+ (n=0-5) and SFn2+ (n=2, 4). Ab initio thermochemistry of novel reactions of S+. and SF+
Author: Sparrapan, R
Mendes, MA
Ferreira, IPP
Eberlin, MN
Santos, C
Nogueira, JC
Abstract: A systematic study of the gas-phase chemistry of the major positively charged ions produced by 70 eV dissociative electron ionization of SF6, i.e., SFn+ (n = 0-5) and SFn2+ (n = 2, 4), has been performed via pentaquadrupole (QqQqQ) mass spectrometric experiments in conjunction with G2(MP2) ab initio calculations. Comparison, under exactly the same 15 eV collision conditions, of the SFn+ proclivities to dissociate by F loss was accomplished via a tandem-in-space three-dimensional MS2 scan. The experimental SFn+ dissociation proclivities were found to correlate perfectly with those expected from G2(MP2) dissociation thresholds. Ion/molecule reactions of mass-selected SFn+ and SFn2+ were performed with O-2 and the oxygenated neutral gases H2O, CO, CO2, and N2O. The ions, under the very low energy (near zero) multiple collision conditions employed, undergo either dissociation by F loss or charge exchange, or participate in novel reactions that have been corroborated by both MS3 experiments and G2(MP2) ab initio thermochemistry. O-abstraction takes place in reactions of SF+ with O-2 and CO, and of S+. with CO2 and O-2 and the corresponding oxyions F-SO+ and SO+. are formed to great extents. CO-abstraction that yields ionized carbon oxysulfide (COS+.) also occurs to a minor extent in reactions of S+. with CO2. Reactions of SF+ with CO yields a minor COS+. product in a net sulfur cation (S+.) transfer reaction. Theory corroborates the experimental observations as the respective O-abstraction and S+. transfer reactions are predicted by G2(MP2) ab initio thermochemistry to be the most favorable processes.
Country: EUA
Editor: Amer Chemical Soc
Citation: Journal Of Physical Chemistry A. Amer Chemical Soc, v. 102, n. 27, n. 5189, n. 5195, 1998.
Rights: fechado
Identifier DOI: 10.1021/jp980876g
Date Issue: 1998
Appears in Collections:Unicamp - Artigos e Outros Documentos

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