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Titolo:
Products, rate constants and mechanisms of gas-phase reactions of CX3+, CX2+, CX+ (X = F and/or Cl) and Cl+ with 1,1,1- and 1,1,2-trichlorotrifluoroethane
Autore:
Marotta, E; Paradisi, C;
Indirizzi:
CNR, Ctr Studio Meccanismi Reaz Organ, Dipartimento Chim Organ, I-35131 Padua, Italy CNR Padua Italy I-35131 n, Dipartimento Chim Organ, I-35131 Padua, Italy
Titolo Testata:
JOURNAL OF MASS SPECTROMETRY
fascicolo: 11, volume: 36, anno: 2001,
pagine: 1195 - 1202
SICI:
1076-5174(200111)36:11<1195:PRCAMO>2.0.ZU;2-N
Fonte:
ISI
Lingua:
ENG
Soggetto:
IONIZATION; MIXTURES; IONS; SI;
Keywords:
gas-phase ion-molecule reactions; ion trap mass spectrometry; chlorofluorocarbons; Cl+; chlorofluoroethanes;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
20
Recensione:
Indirizzi per estratti:
Indirizzo: Paradisi, C CNR, Ctr Studio Meccanismi Reaz Organ, Dipartimento Chim Organ, Via Marzolo 1, I-35131 Padua, Italy CNR Via Marzolo 1 Padua Italy I-35131 1, I-35131 Padua, Italy
Citazione:
E. Marotta e C. Paradisi, "Products, rate constants and mechanisms of gas-phase reactions of CX3+, CX2+, CX+ (X = F and/or Cl) and Cl+ with 1,1,1- and 1,1,2-trichlorotrifluoroethane", J MASS SPEC, 36(11), 2001, pp. 1195-1202

Abstract

The gas-phase ion chemistry of 1,1,1- and 1,1,2-trichlorotrifluoroethane was investigated with an ion trap mass spectrometer. Following electron ionization both compounds (M) fragment to [M - Cl](+), CX3+, CX2+, CX+ (X = F and/or Cl) and Cl+. The reactivity of each of these fragments towards their neutral precursors was studied to obtain product and kinetic data. Whereas [M - CI](+), CCl3+ and CCl2F+ cations are unreactive under the experimentalconditions used, all other species react via halide abstraction to give [M- Cl](+) and, to a far lesser extent, [M - F](+). In addition, CX2+ ions form CClX2+ in a process which formally amounts to chlorine atom abstraction, but more likely involves chloride ion abstraction followed by charge transfer. CX+ ions also form minor amounts of CX3+ product ions, possibly via chloride abstraction followed by or concerted with dihalocarbene eliminationfrom the (incipient) [M - Cl](+) ion. Trivalent carbenium ions are less reactive than divalent species, which in turn are less reactive than the monovalent ions (reaction efficiencies are given in parentheses): CF3+(0.70) < CF2+(0.78} < CF+(0.96). More interestingly, within each family of ions reactivity increases with the number of fluorine substituents (e.g. CF2+ > CFCl > CCl2+ and CF+ > CCl+), i.e. reactivity increases with the ion thermochemical stability, as measured by available standard free enthalpies of formation. Evaluation of the energetics involved shows that reactions are largely driven by the stability of the neutrals more than of the ions. Finally, the products observed in the reaction of Cl+ are attributed to ionization ofthe neutral via charge transfer and fragmentation. Copyright (C) 2001 JohnWiley & Sons, Ltd.

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Documento generato il 29/11/20 alle ore 03:24:05