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Title: A photoionization study of trifluoromethanol, CF{sub 3}OH, trifluoromethyl hypofluorite, CF{sub 3}OF, and trifluoromethyl hypochlorite, CF{sub 3}OCl

Abstract

CF{sub 3}OH, an important and controversial by-product of atmospheric decomposition of CF{sub 3}CFH{sub 2} (HFC-134a) and other hydrofluorocarbons, has been examined by photoionization mass spectrometry. The ionization onset is characterized by a broad Franck{endash}Condon distribution, arising primarily from a substantial elongation of the C{endash}O bond upon ionization. An upper limit to the adiabatic ionization potential (IP) of {le}13.08{plus_minus}0.05eV has been established. The appearance potentials (APs) of the first two fragments have been accurately determined by fitting with appropriate model functions as AP{sub 0}(CF{sub 2}OH{sup +}/CF{sub 3}OH){le}13.830{plus_minus}0.005eV and AP{sub 0}(CF{sub 3}{sup +}/CF{sub 3}OH){le}13.996{plus_minus}0.005eV. While the exact nature of the lowest-energy fragment (nominally CF{sub 2}OH{sup +}) is not clear, the CF{sub 3}{sup +} fragment threshold leads unambiguously to {Delta}H{sub f298}{sup {circ}}(CF{sub 3}OH){ge}{minus}217.2{plus_minus}0.9kcal/mol and D{sub 298}(CF{sub 3}{endash}OH){le}115.2{plus_minus}0.3kcal/mol. With previously derived {Delta}H{sub f298}{sup {circ}}(CF{sub 3}O)={minus}151.8{sub {minus}1.1}{sup +1.7}kcal/mol, this yields D{sub 298}(CF{sub 3}O{endash}H)=117.5{sub {minus}1.4}{sup +1.9}kcal/mol, very close to, or only slightly weaker than the O{endash}H bond energy in water: D{sub 298}(CF{sub 3}O{endash}H){endash}D{sub 298}(HO{endash}H)={minus}1.8{sub {minus}1.4}{sup +1.9}kcal/mol{approx}0kcal/mol. Similarly, with the recently redetermined value for {Delta}H{sub f}{sup {circ}}(CF{sub 2}O), this implies a 298 K reaction enthalpy for the 1,2-elimination of HF from CF{sub 3}OH of 2.8{sub {minus}1.1}{sup +1.7}kcal/mol. CF{sub 3}OF and CF{sub 3}OCl have also been examined bymore » photoionization. CF{sub 3}OF produces a very weak parent, with an apparent adiabatic IP(CF{sub 3}OF){le}12.710{plus_minus}0.007eV. (Abstract Truncated)« less

Authors:
; ; ; ; ;  [1]
  1. Argonne National Laboratory, Argonne, Illinois 60439-4831 (United States)
Publication Date:
Research Org.:
Argonne National Laboratory (ANL), Argonne, IL
OSTI Identifier:
503611
DOE Contract Number:  
W-31109-ENG-38
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 106; Journal Issue: 22; Other Information: PBD: Jun 1997
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; CHLOROFLUOROCARBONS; PHOTOCHEMICAL REACTIONS; ATMOSPHERIC CHEMISTRY; ORGANIC COMPOUNDS; MASS SPECTRA; REACTION HEAT; PHOTOIONIZATION; FLUORINATED ALIPHATIC HYDROCARBONS; CHLORINATED ALIPHATIC HYDROCARBONS; DECOMPOSITION

Citation Formats

Asher, R L, Appelman, E H, Tilson, J L, Litorja, M, Berkowitz, J, and Ruscic, B. A photoionization study of trifluoromethanol, CF{sub 3}OH, trifluoromethyl hypofluorite, CF{sub 3}OF, and trifluoromethyl hypochlorite, CF{sub 3}OCl. United States: N. p., 1997. Web. doi:10.1063/1.474017.
Asher, R L, Appelman, E H, Tilson, J L, Litorja, M, Berkowitz, J, & Ruscic, B. A photoionization study of trifluoromethanol, CF{sub 3}OH, trifluoromethyl hypofluorite, CF{sub 3}OF, and trifluoromethyl hypochlorite, CF{sub 3}OCl. United States. doi:10.1063/1.474017.
Asher, R L, Appelman, E H, Tilson, J L, Litorja, M, Berkowitz, J, and Ruscic, B. Sun . "A photoionization study of trifluoromethanol, CF{sub 3}OH, trifluoromethyl hypofluorite, CF{sub 3}OF, and trifluoromethyl hypochlorite, CF{sub 3}OCl". United States. doi:10.1063/1.474017.
@article{osti_503611,
title = {A photoionization study of trifluoromethanol, CF{sub 3}OH, trifluoromethyl hypofluorite, CF{sub 3}OF, and trifluoromethyl hypochlorite, CF{sub 3}OCl},
author = {Asher, R L and Appelman, E H and Tilson, J L and Litorja, M and Berkowitz, J and Ruscic, B},
abstractNote = {CF{sub 3}OH, an important and controversial by-product of atmospheric decomposition of CF{sub 3}CFH{sub 2} (HFC-134a) and other hydrofluorocarbons, has been examined by photoionization mass spectrometry. The ionization onset is characterized by a broad Franck{endash}Condon distribution, arising primarily from a substantial elongation of the C{endash}O bond upon ionization. An upper limit to the adiabatic ionization potential (IP) of {le}13.08{plus_minus}0.05eV has been established. The appearance potentials (APs) of the first two fragments have been accurately determined by fitting with appropriate model functions as AP{sub 0}(CF{sub 2}OH{sup +}/CF{sub 3}OH){le}13.830{plus_minus}0.005eV and AP{sub 0}(CF{sub 3}{sup +}/CF{sub 3}OH){le}13.996{plus_minus}0.005eV. While the exact nature of the lowest-energy fragment (nominally CF{sub 2}OH{sup +}) is not clear, the CF{sub 3}{sup +} fragment threshold leads unambiguously to {Delta}H{sub f298}{sup {circ}}(CF{sub 3}OH){ge}{minus}217.2{plus_minus}0.9kcal/mol and D{sub 298}(CF{sub 3}{endash}OH){le}115.2{plus_minus}0.3kcal/mol. With previously derived {Delta}H{sub f298}{sup {circ}}(CF{sub 3}O)={minus}151.8{sub {minus}1.1}{sup +1.7}kcal/mol, this yields D{sub 298}(CF{sub 3}O{endash}H)=117.5{sub {minus}1.4}{sup +1.9}kcal/mol, very close to, or only slightly weaker than the O{endash}H bond energy in water: D{sub 298}(CF{sub 3}O{endash}H){endash}D{sub 298}(HO{endash}H)={minus}1.8{sub {minus}1.4}{sup +1.9}kcal/mol{approx}0kcal/mol. Similarly, with the recently redetermined value for {Delta}H{sub f}{sup {circ}}(CF{sub 2}O), this implies a 298 K reaction enthalpy for the 1,2-elimination of HF from CF{sub 3}OH of 2.8{sub {minus}1.1}{sup +1.7}kcal/mol. CF{sub 3}OF and CF{sub 3}OCl have also been examined by photoionization. CF{sub 3}OF produces a very weak parent, with an apparent adiabatic IP(CF{sub 3}OF){le}12.710{plus_minus}0.007eV. (Abstract Truncated)},
doi = {10.1063/1.474017},
journal = {Journal of Chemical Physics},
number = 22,
volume = 106,
place = {United States},
year = {1997},
month = {6}
}