Rate Constants and Hydrogen Isotope Substitution Effects in the CH₃ + HCl and CH₃ + Cl₂

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Article on rate constants and hydrogen isotope substitution effects in the CH₃ + HCl and CH₃ + Cl₂ reactions.

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11 p.

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Eskola, Arkke J.; Timonen, Raimo S.; Marshall, Paul; Chesnokov, Evgeni N. & Krasnoperov, Lev N. July 23, 2008.

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Article on rate constants and hydrogen isotope substitution effects in the CH₃ + HCl and CH₃ + Cl₂ reactions.

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11 p.

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Abstract: The kinetics of the CH3 + Cl2 (k2a) and CD3 + Cl2 (k2b) reactions were studied over the temperature range 188−500 K using laser photolysis−photoionization mass spectrometry. The rate constants of these reactions are independent of the bath gas pressure within the experimental range, 0.6−5.1 Torr (He). The rate constants were fitted by the modified Arrhenius expression, k2a = 1.7 × 10−13(T/300 K)2.52exp(5520 J mol−1/RT) and k2b = 2.9 × 10−13(T/300 K)1.84exp(4770 J mol−1/RT) cm3 molecule−1 s−1. The results for reaction 2a are in good agreement with the previous determinations performed at and above ambient temperature. Rate constants of the CH3 + Cl2 and CD3 + Cl2 reactions obtained in this work exhibit minima at about 270−300 K. The rate constants have positive temperature dependences above the minima, and negative below. Deuterium substitution increases the rate constant, in particular at low temperatures, where the effect reaches ca. 45% at 188 K. These observations are quantitatively rationalized in terms of stationary points on a potential energy surface based on QCISD/6−311G(d,p) geometries and frequencies, combined with CCSD(T) energies extrapolated to the complete basis set limit. 1D tunneling as well as the possibility of the negative energies of the transition state are incorporated into a transition state theory analysis, an approach which also accounts for prior experiments on the CH3 + HCl system and its various deuterated isotopic substitutions [Eskola, A. J.; Seetula, J. A.; Timonen, R. S. Chem. Phys.2006, 331, 26].

Reprinted with permission from the Journal of Physical Chemistry A. Copyright 2008 American Chemical Society.

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  • Journal of Physical Chemistry A, 2008, Washington D.C.: American Chemical Society, pp. 7391-7401

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  • Publication Title: Journal of Physical Chemistry A
  • Volume: 112
  • Issue: 32
  • Page Start: 7391
  • Page End: 7401
  • Pages: 11
  • Peer Reviewed: Yes

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  • March 6, 2008

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  • June 4, 2008

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  • July 23, 2008

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  • Feb. 6, 2015, 9:38 a.m.

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Eskola, Arkke J.; Timonen, Raimo S.; Marshall, Paul; Chesnokov, Evgeni N. & Krasnoperov, Lev N. Rate Constants and Hydrogen Isotope Substitution Effects in the CH₃ + HCl and CH₃ + Cl₂, article, July 23, 2008; [Washington, D.C.]. (digital.library.unt.edu/ark:/67531/metadc499076/: accessed November 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.