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A computational study of the thermochemistry of bromine- and iodine-containing methanes and methyl radicals

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Article on a computational study of the thermochemistry of bromine- and iodine-containing methanes and methyl radicals.

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9 p.

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Marshall, Paul; Srinivas, G. N. & Schwartz, Martin June 28, 2005.

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Article on a computational study of the thermochemistry of bromine- and iodine-containing methanes and methyl radicals.

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9 p.

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Abstract: Bromo- and iodomethanes and the corresponding halogenated methyl radicals have been investigated by ab initio methods. Geometries and vibrational frequencies were derived with quadratic configuration interaction methods at the QCISD/6-311G(d,p) level of theory, and energies via QCISD(T)/6-311+G(3df,2p). Core electrons were represented with relativistic effective potentials. Anharmonicity of the out-of-plane bending modes in the methyl radicals was taken into account by numerical integration of the Schrödinger equation with potentials derived from relaxed scans of these modes. The results are in good accord with experimental data where available. Thermochemistry derived via isodesmic reactions referenced to CH3, CH4, and monohalomethanes yields excellent accord with new experiments on dihalomethanes and provides recommendations for the more poorly characterized tri- and tetrahalomethanes and halomethyl radicals. For the methanes CH2Br2, CHBr3, CBr4, CH2I2, CHI3, CI4, CH2BrI, CHBr2I, and CHBrI2 we compute ΔfH°298 values of 4.3, 51.6, 110.6, 108.1, 208.5, 321.3, 56.8, 104.8, and 157.1 kJ mol-1, respectively. For the methyl radicals CH2Br, CHBr2, CBr3, CH2I, CHI2, CI3, CHBrI, CBr2I, and CBrI2 we compute ΔfH°298 values of 166.6, 191.7, 224.0, 217.2, 290.4, 369.1, 241.6, 320.8, and 272.3 kJ mol-1, respectively. Recommended confidence limits are ±3 kJ mol-1 per Br or I atom. Trends in these values and the corresponding C−H bond strengths are discussed and compared with prior experiments, empirical estimation schemes, and ab initio calculations.

Reprinted with permission from the Journal of Physical Chemistry A. Copyright 2005 American Chemical Society.

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  • Journal of Physical Chemistry A, 2005, Washington D.C.: American Chemical Society, pp. 6371-6379

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  • Publication Title: Journal of Physical Chemistry A
  • Volume: 109
  • Issue: 28
  • Page Start: 6371
  • Page End: 6379
  • Pages: 9
  • Peer Reviewed: Yes

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  • June 28, 2005

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  • March 17, 2015, 10:38 a.m.

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Marshall, Paul; Srinivas, G. N. & Schwartz, Martin. A computational study of the thermochemistry of bromine- and iodine-containing methanes and methyl radicals, article, June 28, 2005; [Washington, D.C.]. (digital.library.unt.edu/ark:/67531/metadc501401/: accessed January 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.