A temperature-dependent selected ion flow tube study of anions reacting with SF5CF3

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Rate constants and product distributions were measured for the reactions of trifluoromethyl sulfurpentafluoride (SF5CF3) with I I anions using two selected ion flow tube instruments. The reaction of O-2(-) was studied from 240 to 500 K and was found to proceed at approximately 30% of the collisional rate, yielding SF5- as the only product ion, presumably via a dissociative electron transfer mechanism. The reaction of OH- proceeds predominantly via nucleophilic attack at the carbon atom, displacing SF5- at approximately 25% of the collisional rate at 298 K. The rate constant exhibits a T-1.8 dependence from 240 to 500 K, suggesting the reaction occurs through a long-lived collision complex. The F- reaction, which proceeds at 70% the collisional rate at 298 K, also occurs via nucleophilic attack at the carbon atom, leading to the SF5- product ion. The O- ion reacts predominately by nucleophilic attack at the carbon atom and also via CF3 radical transfer to O-. The product branching fraction for the O- reaction did not vary with temperature, although the rate constant exhibits a 7(-1.6) dependence, similar to that of the OH- reaction. The ions SF6-, CF3-, NO2-, CO3-, Cl-, NO3-, and SF5- were found to be unreactive toward SF5CF3, despite the fact that sufficiently exothermic reactive channels exist for many of these ions. Published by Elsevier Science B.V.


Original languageEnglish
Pages (from-to)403-409
Number of pages7
JournalInternational Journal of Mass Spectrometry
Issue number1-3
Publication statusPublished - 1 Jan 2003


  • trifluoromethyl sulfurpentafluoride, SIFT, anion kinetics