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Kinetics and Thermochemistry of the Cl((sup 2)P(sub J)) + C2Cl4 Association ReactionA laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the Cl(sup 2)P(sub j) + C2Cl4 association reaction as a function of temperature (231-390 K) and pressure (3-700 Torr) in nitrogen buffer gas. The reaction is found to be in the falloff regime between third and second order over the range of conditions investigated, although the second-order limit is approached at the highest pressures and lowest temperatures. At temperatures below 300 K, the association reaction is found to be irreversible on the experimental time scale of approximately 20 m-s. The kinetic data at T is less than 300 K have been employed to obtain falloff parameters in a convenient format for atmospheric modeling. At temperatures above 330 K, reversible addition is observed, thus allowing equilibrium constants for C2Cl5 formation and dissociation to be determined. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the association reaction: Delta-H(298) = -18.1 +/- 1.3 kcal/mol, Delta-H(0) = -17.6 +/- 1.3 kcal/mol, and Delta-S(298) = -27.7 +/- 3.0 cal/mol.K. In conjunction with the well-known heats of formation of Cl((sup 2)P(sub j)) and C2Cl4 the above Delta-H values lead to the following heats of formation for C2Cl5, at 298 and 0 K: Delta-H(f,298) = 8.0 +/- 1.3 kcal/mol and Delta-H(f,0) = 8.1 +/- 1.5 kcal/mol. The kinetic and thermochemical parameters reported above are compared with other reported values, and the significance of reported association rate coefficients for understanding tropospheric chlorine chemistry is discussed.
Document ID
Acquisition Source
Document Type
Reprint (Version printed in journal)
Nicovich, J. M.
(Georgia Inst. of Tech. Atlanta, GA United States)
Wang, S.
(Georgia Inst. of Tech. Atlanta, GA United States)
Mckee, M. L.
(Auburn Univ. AL United States)
Wine, P. H.
(Georgia Tech Research Inst. Atlanta, GA United States)
Date Acquired
August 17, 2013
Publication Date
April 9, 1997
Publication Information
Publication: Laboratory Investigations of Stratospheric Halogen Chemistry
Publisher: American Chemical Society
ISSN: 0022-3654
Subject Category
Inorganic And Physical Chemistry
Funding Number(s)
Distribution Limits
Work of the US Gov. Public Use Permitted.
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