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Title: On the heat of formation of carbonyl fluoride, CF{sub 2}O

Abstract

In light of the recent controversy surrounding its heat of formation, CF{sub 2}O was reexamined by photoionization mass spectrometry. In particular, the CO{sup +} fragment ion yield curve from CF{sub 2}O was interpreted in terms of a retarded CO{sup +}+F{sub 2} process, and a more facile two-step fragmentation to CO{sup +}+2F. The former process produces a weak, slowly growing tail region without a clear onset, while the latter occurs at higher energy and causes a pronounced growth with a conspicuous onset, which was found to occur at {le}20.87{sup +0.03}/{sub {minus}0.07} eV at 0 K by fitting with a model curve that incorporates {open_quote}{open_quote}fluctuations{close_quote}{close_quote} associated with second-generation fragments. This onset leads to {Delta}{ital H}{sub {ital f}}{sup {degree}}{sub 298}(CF{sub 2}O) {ge}{minus}149.1{sup +1.4}/{sub {minus}0.7} kcal/mol, and indicates that the older experimental values for this quantity are too low by at least 3{endash}4 kcal/mol. While the F{sub 2} elimination is retarded by competition with lower energy processes, the two-step process derives its strength from the FCO{sup +} fragment, which assumes the role of a pseudoparent. Thus, the onset of CO{sup +}+2F is expected to appear reasonably close to the thermochemical threshold. Such an interpretation indicates that recently calculated {ital ab} {ital initio} values ofmore » {minus}145.3{plus_minus}1.7 kcal/mol and {minus}145.6{plus_minus}1.0 kcal/mol are very likely too high by 3{endash}4 kcal/mol. In addition, the adiabatic ionization potential of CF{sub 2}O was refined to 13.024{plus_minus}0.004 eV, while the 0 K appearance potential of the FCO{sup +} fragment was found by fitting to be {le}14.752{plus_minus}0.005 eV. (Abstract Truncated)« less

Authors:
; ;  [1]
  1. Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439-4831 (United States)
Publication Date:
OSTI Identifier:
397443
DOE Contract Number:  
W-31-109-ENG-38
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 105; Journal Issue: 22; Other Information: PBD: Dec 1996
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; ORGANIC FLUORINE COMPOUNDS; FORMATION HEAT; CARBONYL RADICALS; PHOTOIONIZATION; MASS SPECTROSCOPY; THERMODYNAMICS; IONIZATION POTENTIAL; POTENTIAL ENERGY SURFACES

Citation Formats

Asher, R L, Appelman, E H, and Ruscic, B. On the heat of formation of carbonyl fluoride, CF{sub 2}O. United States: N. p., 1996. Web. doi:10.1063/1.472848.
Asher, R L, Appelman, E H, & Ruscic, B. On the heat of formation of carbonyl fluoride, CF{sub 2}O. United States. doi:10.1063/1.472848.
Asher, R L, Appelman, E H, and Ruscic, B. Sun . "On the heat of formation of carbonyl fluoride, CF{sub 2}O". United States. doi:10.1063/1.472848.
@article{osti_397443,
title = {On the heat of formation of carbonyl fluoride, CF{sub 2}O},
author = {Asher, R L and Appelman, E H and Ruscic, B},
abstractNote = {In light of the recent controversy surrounding its heat of formation, CF{sub 2}O was reexamined by photoionization mass spectrometry. In particular, the CO{sup +} fragment ion yield curve from CF{sub 2}O was interpreted in terms of a retarded CO{sup +}+F{sub 2} process, and a more facile two-step fragmentation to CO{sup +}+2F. The former process produces a weak, slowly growing tail region without a clear onset, while the latter occurs at higher energy and causes a pronounced growth with a conspicuous onset, which was found to occur at {le}20.87{sup +0.03}/{sub {minus}0.07} eV at 0 K by fitting with a model curve that incorporates {open_quote}{open_quote}fluctuations{close_quote}{close_quote} associated with second-generation fragments. This onset leads to {Delta}{ital H}{sub {ital f}}{sup {degree}}{sub 298}(CF{sub 2}O) {ge}{minus}149.1{sup +1.4}/{sub {minus}0.7} kcal/mol, and indicates that the older experimental values for this quantity are too low by at least 3{endash}4 kcal/mol. While the F{sub 2} elimination is retarded by competition with lower energy processes, the two-step process derives its strength from the FCO{sup +} fragment, which assumes the role of a pseudoparent. Thus, the onset of CO{sup +}+2F is expected to appear reasonably close to the thermochemical threshold. Such an interpretation indicates that recently calculated {ital ab} {ital initio} values of {minus}145.3{plus_minus}1.7 kcal/mol and {minus}145.6{plus_minus}1.0 kcal/mol are very likely too high by 3{endash}4 kcal/mol. In addition, the adiabatic ionization potential of CF{sub 2}O was refined to 13.024{plus_minus}0.004 eV, while the 0 K appearance potential of the FCO{sup +} fragment was found by fitting to be {le}14.752{plus_minus}0.005 eV. (Abstract Truncated)},
doi = {10.1063/1.472848},
journal = {Journal of Chemical Physics},
number = 22,
volume = 105,
place = {United States},
year = {1996},
month = {12}
}