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Title: On the heats of formation of trifluoromethyl radical CF{sub 3} and its cation CF{sub 3}{sup +}

Abstract

The CF{sup +} and CF{sub 3}{sup +} fragment ion yield curves from C{sub 2}F{sub 4} have been remeasured by photoionization mass spectrometry. Fits with appropriate model curves yield the appearance potentials AP{sub 0}(CF{sub 3}{sup +}C{sub 2}F{sub 4})=13.721{plus_minus}0.005 eV and AP{sub 0}(CF{sup +}/C{sub 2}F{sub 4})=13.777{plus_minus}0.005 eV and an accurate difference in ionization potentials, IP(CF){minus}IP(CF{sub 3})=0.055{plus_minus}0.003 eV. With the existing photoelectron value IP(CF)=9.11{plus_minus}0.01 eV, this produces IP(CF{sub 3})=9.05{sub 5}{plus_minus}0.01{sub 1} eV. The CF{sub 3}{sup +} fragments from CF{sub 3}Cl, CF{sub 3}Br, and CF{sub 3}I have also been remeasured, and their ion yield curves fitted with model functions. The experimentally derived AP{sub 0}(CF{sub 3}{sup +}/CF{sub 3}Cl){lt}12.867{plus_minus}0.008 eV has been found to be only an upper limit. The Analogous CF{sub 3}{sup 3}CF{sub 3}{sup +} fragment yield curves from CF{sub 3}Br and CF{sub 3}I produce AP{sub 0}(CF{sub 3}{sup +}/CF{sub 3}Br)=12.095{plus_minus}0.005 eV and AP{sub 0}(CF{sub 3}{sup +}/CF{sub 3}I)=11.384{plus_minus}0.005 eV, leading to D{sub 0}(CF{sub 3}{minus}Br)=70.1{plus_minus}0.3 kcal/mol (70.8{plus_minus}0.3 kcal/mol at 298 K) and D{sub 0}(CF{sub 3}{minus}I)=53.7{plus_minus}0.3 kcal/mol (54.3{plus_minus}0.3 kcal/mol at 298 K). Based on tabulated values for {Delta}H{sub f}{sup {circ}}(CF{sub 3}Br) and {Delta}H{sub f}{sup {circ}}(CF{sub 3}I), which appear to be inconsistent by {approximately}1 kcal/mol, a compromise value of {Delta}H{sub 298}{sup f{circ}}(CF{sub 3})={minus}111.4{plus_minus}0.9 kcal/mol ({minus}110.7{plus_minus}0.9 kcal/mol at 0 K)more » is selected, resulting in {Delta}H {sub 298}{sup f{circ}}(CF{sub 3}{sup +})=97.4{plus_minus}0.9 kcal/mol (98.1{plus_minus}0.9 kcal/mol at 0 K). Additionally, IP(CF{sub 4}){equivalent_to}AP{sub 0}(CF{sub 3}{sup +}/CF{sub 4})=14.67{plus_minus}0.04 eV can be inferred. (Abstract Truncated)« less

Authors:
;  [1]
  1. Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439-4831 (United States)
Publication Date:
OSTI Identifier:
435119
DOE Contract Number:  
W-31-109-ENG-38
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 106; Journal Issue: 1; Other Information: PBD: Jan 1997
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; CARBON FLUORIDES; FORMATION HEAT; ORGANIC COMPOUNDS; RADICALS; CATIONS; MOLECULAR IONS; POTENTIALS; PHOTOELECTRON SPECTROSCOPY; PHOTOIONIZATION; IONIZATION POTENTIAL

Citation Formats

Asher, R L, and Ruscic, B. On the heats of formation of trifluoromethyl radical CF{sub 3} and its cation CF{sub 3}{sup +}. United States: N. p., 1997. Web. doi:10.1063/1.473982.
Asher, R L, & Ruscic, B. On the heats of formation of trifluoromethyl radical CF{sub 3} and its cation CF{sub 3}{sup +}. United States. doi:10.1063/1.473982.
Asher, R L, and Ruscic, B. Wed . "On the heats of formation of trifluoromethyl radical CF{sub 3} and its cation CF{sub 3}{sup +}". United States. doi:10.1063/1.473982.
@article{osti_435119,
title = {On the heats of formation of trifluoromethyl radical CF{sub 3} and its cation CF{sub 3}{sup +}},
author = {Asher, R L and Ruscic, B},
abstractNote = {The CF{sup +} and CF{sub 3}{sup +} fragment ion yield curves from C{sub 2}F{sub 4} have been remeasured by photoionization mass spectrometry. Fits with appropriate model curves yield the appearance potentials AP{sub 0}(CF{sub 3}{sup +}C{sub 2}F{sub 4})=13.721{plus_minus}0.005 eV and AP{sub 0}(CF{sup +}/C{sub 2}F{sub 4})=13.777{plus_minus}0.005 eV and an accurate difference in ionization potentials, IP(CF){minus}IP(CF{sub 3})=0.055{plus_minus}0.003 eV. With the existing photoelectron value IP(CF)=9.11{plus_minus}0.01 eV, this produces IP(CF{sub 3})=9.05{sub 5}{plus_minus}0.01{sub 1} eV. The CF{sub 3}{sup +} fragments from CF{sub 3}Cl, CF{sub 3}Br, and CF{sub 3}I have also been remeasured, and their ion yield curves fitted with model functions. The experimentally derived AP{sub 0}(CF{sub 3}{sup +}/CF{sub 3}Cl){lt}12.867{plus_minus}0.008 eV has been found to be only an upper limit. The Analogous CF{sub 3}{sup 3}CF{sub 3}{sup +} fragment yield curves from CF{sub 3}Br and CF{sub 3}I produce AP{sub 0}(CF{sub 3}{sup +}/CF{sub 3}Br)=12.095{plus_minus}0.005 eV and AP{sub 0}(CF{sub 3}{sup +}/CF{sub 3}I)=11.384{plus_minus}0.005 eV, leading to D{sub 0}(CF{sub 3}{minus}Br)=70.1{plus_minus}0.3 kcal/mol (70.8{plus_minus}0.3 kcal/mol at 298 K) and D{sub 0}(CF{sub 3}{minus}I)=53.7{plus_minus}0.3 kcal/mol (54.3{plus_minus}0.3 kcal/mol at 298 K). Based on tabulated values for {Delta}H{sub f}{sup {circ}}(CF{sub 3}Br) and {Delta}H{sub f}{sup {circ}}(CF{sub 3}I), which appear to be inconsistent by {approximately}1 kcal/mol, a compromise value of {Delta}H{sub 298}{sup f{circ}}(CF{sub 3})={minus}111.4{plus_minus}0.9 kcal/mol ({minus}110.7{plus_minus}0.9 kcal/mol at 0 K) is selected, resulting in {Delta}H {sub 298}{sup f{circ}}(CF{sub 3}{sup +})=97.4{plus_minus}0.9 kcal/mol (98.1{plus_minus}0.9 kcal/mol at 0 K). Additionally, IP(CF{sub 4}){equivalent_to}AP{sub 0}(CF{sub 3}{sup +}/CF{sub 4})=14.67{plus_minus}0.04 eV can be inferred. (Abstract Truncated)},
doi = {10.1063/1.473982},
journal = {Journal of Chemical Physics},
number = 1,
volume = 106,
place = {United States},
year = {1997},
month = {1}
}