Gas-phase reactions of oxide and superoxide anions with CF4, CF3Cl, CF3Br, CF3I, and C2F4 at 298 and 500 K

Article abstract of DOI:10.1063/1.463941

Rate constants and product branching fractions have been measured for the gas-phase reactions of oxide (O^-) and superoxide (O2^-) anions with the halocarbons CF4, CF3Cl, CF3Br, CF3I, and C2F4 using a variable temperature-selected ion flow tube (VT-SIFT) instrument operated at 298 and 500 K.The reactions of O^- with CF3X (X = Cl, Br, I) are fast and produce F^-, XF^-, and XO^- for all X.For CF3Cl and CF3Br, X^- is also formed.For CF3I, CF3^- and IOF^- are minor products.O^- reacts rapidly with C2F4 producing F^- as the major ionic product, along with contributions from reactive detachment and minor formation of FCO^-, CF3^-, and C2F3O^-.The reaction of O2^- with CF3Cl is slow, and both clustering and X^- formation were observed.For CF3Br and CF3I, the reactions with O2^- are fast, and nondissociative charge transfer was observed in addition to X^- formation.O2^- reacts rapidly with C2F4 by reactive detachment, in addition to producing F^- as the major ionic product with smaller amounts of F2^-, FCO^-, FCO2^-, CF3O^-, and C2F4O^-.O^- and O2^- were both found to be unreactive with CF4 at 298 and 500 K.The efficiencies of the reactions of both O^- and O2^- with CF3X are greater for the heavier halides at both 298 and 500 K.The rate constants for the reactions of O2^- with CF3X appear to correlate both with the rates of thermal electron attachment to CF3X and with the electron affinities of CF3X, indicating that the O2^- + CF3X reaction mechanism may involve initial electron transfer followed by dissociation.Thus the negative electron affinity of CF3Cl may explain the very slow rate for reaction with O2^- despite the available exothermic pathways.

Full text of DOI:10.1063/1.463941

Gasphase reactions of oxide and superoxide anions with CF4, CF3Cl, CF3Br, CF3I,
and C2F4 at 298 and 500 K
Robert A. Morris
Citation: The Journal of Chemical Physics 97, 2372 (1992); doi: 10.1063/1.463941
View online: http://dx.doi.org/10.1063/1.463941
View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/97/4?ver=pdfcov
Published by the AIP Publishing
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This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
128.193.164.203 On: Tue, 23 Dec 2014 17:04:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
128.193.164.203 On: Tue, 23 Dec 2014 17:04:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
128.193.164.203 On: Tue, 23 Dec 2014 17:04:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
128.193.164.203 On: Tue, 23 Dec 2014 17:04:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
128.193.164.203 On: Tue, 23 Dec 2014 17:04:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
128.193.164.203 On: Tue, 23 Dec 2014 17:04:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
128.193.164.203 On: Tue, 23 Dec 2014 17:04:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
128.193.164.203 On: Tue, 23 Dec 2014 17:04:37