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Title: Simultaneous adjustment of experimentally based enthalpies of formation of CF{sub 3}X, X = nil, H, Cl, Br, I, CF{sub 3}, CN, and a probe of G3 theory

Abstract

The enthalpies of formation of the title compounds have been determined by simultaneous least-squares solution of a thermochemical network containing 28 experimental measurements extracted from the literature. The new enthalpies differ considerably from the older tabulated values and now show a high degree of internal consistency achieved through excellent agreement with newer experiments, as well as older calorimetric determinations. The fitted values are: {Delta}H{sub 1298}{degree}(CF{sub 3}) = {minus}111.3 {+-} 0.5 kcal/mol ({minus}110.6 {+-} 0.5 kcal/mol at 0 K), {Delta}H{sub 1298}{degree}(CF{sub 3}H) = {minus}165.6 {+-} 0.5 kcal/mol ({minus}163.9 {+-} 0.5 kcal/mol at 0 K) {Delta}H{sub 1298}{degree}(CF{sub 3}Cl) = {minus}169.5 {+-} 0.7 kcal/mol ({minus}168.3 {+-} 0.7 kcal/mol at 0 K), {Delta}H{sub 1298}{degree}(CF{sub 3}Br) = {minus}155.3 {+-} 0.5 kcal/mol (152.4 {+-} 0.5 kcal/mol at 0 K) {Delta}H{sub 1298}{degree}(CF{sub 3}I) = {minus}140.1 {+-} 0.5 kcal/mol ({minus}138.7 {+-} 0.5 kcal/mol at 0 K), {Delta}H{sub 1298}{degree} (C{sub 2}F{sub 6}) = {minus}321.3 {+-} 0.8 kcal/mol ({minus}319.3 {+-} 0.8 kcal/mol at 0 K), and {Delta}H{sub 1298}{degree}(CF{sub 3}CN) = {minus}118.4 {+-} 0.4 kcal/mol ({minus}117.5 {+-} 0.4 kcal/mol at 0 K). Theoretical calculations at the Gaussian-3 (G3) level of theory have been performed for a subgroup of these molecules, which were problematic at the Gaussian-2 (G2) level of theory. Inmore » comparison to G2 theory, the G3 results show a remarkable improvement in accuracy and agree with experiment within <2 kcal/mol. An isodesmic bond-separation scheme brings the calculated values even closer to the experiment. In addition, the G3 value for the ionization energy of CF{sub 3}, 9.08 eV, was found to be in good agreement with the recent experimental value of 9.05{sub 5} {+-} 0.01{sub 1} eV. Further indications that the experimental value for {Delta}H{sub f}{degree}(C{sub 2}F{sub 4}) is probably too high are also presented.« less

Authors:
; ; ;  [1];  [2]
  1. Argonne National Lab., IL (United States). Chemistry Div.
  2. Lucent Technologies, Murray Hill, NJ (United States). Bell Labs.
Publication Date:
Research Org.:
Argonne National Laboratory (ANL), Argonne, IL
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
320825
DOE Contract Number:  
W-31109-ENG-38
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory
Additional Journal Information:
Journal Volume: 102; Journal Issue: 52; Other Information: PBD: 24 Dec 1998
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; FORMATION HEAT; HALOGENATED ALIPHATIC HYDROCARBONS; HALIDES; CYANIDES; DATA ANALYSIS; LEAST SQUARE FIT; DISSOCIATION HEAT; VERIFICATION; CALORIMETRY

Citation Formats

Ruscic, B, Michael, J V, Redfern, P C, Curtiss, L A, and Raghavachari, K. Simultaneous adjustment of experimentally based enthalpies of formation of CF{sub 3}X, X = nil, H, Cl, Br, I, CF{sub 3}, CN, and a probe of G3 theory. United States: N. p., 1998. Web. doi:10.1021/jp983237e.
Ruscic, B, Michael, J V, Redfern, P C, Curtiss, L A, & Raghavachari, K. Simultaneous adjustment of experimentally based enthalpies of formation of CF{sub 3}X, X = nil, H, Cl, Br, I, CF{sub 3}, CN, and a probe of G3 theory. United States. doi:10.1021/jp983237e.
Ruscic, B, Michael, J V, Redfern, P C, Curtiss, L A, and Raghavachari, K. Thu . "Simultaneous adjustment of experimentally based enthalpies of formation of CF{sub 3}X, X = nil, H, Cl, Br, I, CF{sub 3}, CN, and a probe of G3 theory". United States. doi:10.1021/jp983237e.
@article{osti_320825,
title = {Simultaneous adjustment of experimentally based enthalpies of formation of CF{sub 3}X, X = nil, H, Cl, Br, I, CF{sub 3}, CN, and a probe of G3 theory},
author = {Ruscic, B and Michael, J V and Redfern, P C and Curtiss, L A and Raghavachari, K},
abstractNote = {The enthalpies of formation of the title compounds have been determined by simultaneous least-squares solution of a thermochemical network containing 28 experimental measurements extracted from the literature. The new enthalpies differ considerably from the older tabulated values and now show a high degree of internal consistency achieved through excellent agreement with newer experiments, as well as older calorimetric determinations. The fitted values are: {Delta}H{sub 1298}{degree}(CF{sub 3}) = {minus}111.3 {+-} 0.5 kcal/mol ({minus}110.6 {+-} 0.5 kcal/mol at 0 K), {Delta}H{sub 1298}{degree}(CF{sub 3}H) = {minus}165.6 {+-} 0.5 kcal/mol ({minus}163.9 {+-} 0.5 kcal/mol at 0 K) {Delta}H{sub 1298}{degree}(CF{sub 3}Cl) = {minus}169.5 {+-} 0.7 kcal/mol ({minus}168.3 {+-} 0.7 kcal/mol at 0 K), {Delta}H{sub 1298}{degree}(CF{sub 3}Br) = {minus}155.3 {+-} 0.5 kcal/mol (152.4 {+-} 0.5 kcal/mol at 0 K) {Delta}H{sub 1298}{degree}(CF{sub 3}I) = {minus}140.1 {+-} 0.5 kcal/mol ({minus}138.7 {+-} 0.5 kcal/mol at 0 K), {Delta}H{sub 1298}{degree} (C{sub 2}F{sub 6}) = {minus}321.3 {+-} 0.8 kcal/mol ({minus}319.3 {+-} 0.8 kcal/mol at 0 K), and {Delta}H{sub 1298}{degree}(CF{sub 3}CN) = {minus}118.4 {+-} 0.4 kcal/mol ({minus}117.5 {+-} 0.4 kcal/mol at 0 K). Theoretical calculations at the Gaussian-3 (G3) level of theory have been performed for a subgroup of these molecules, which were problematic at the Gaussian-2 (G2) level of theory. In comparison to G2 theory, the G3 results show a remarkable improvement in accuracy and agree with experiment within <2 kcal/mol. An isodesmic bond-separation scheme brings the calculated values even closer to the experiment. In addition, the G3 value for the ionization energy of CF{sub 3}, 9.08 eV, was found to be in good agreement with the recent experimental value of 9.05{sub 5} {+-} 0.01{sub 1} eV. Further indications that the experimental value for {Delta}H{sub f}{degree}(C{sub 2}F{sub 4}) is probably too high are also presented.},
doi = {10.1021/jp983237e},
journal = {Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory},
number = 52,
volume = 102,
place = {United States},
year = {1998},
month = {12}
}