Kinetics and Mechanism for the Thermal Chlorination of Chloroform in the Gas Phase: Inclusion of HCl Elimination from CHCl 3

Document Type

Article

Publication Date

12-1-2003

Abstract

HCl elimination from chloroform is shown to be the lowest energy channel for initiation in the thermal conversion of chloroform to CCl 4, with chlorine gas in the temperature range of 573-635 K. Literature data on this reaction is surveyed and we further estimate its kinetic parameters using ab initio and density functional calculations at the G3//B3LYP/6-311G(d,p) level. Rate constants are estimated and reported as functions of pressure and temperature using quantum RRK theory for k(E) and master equation analysis for fall-off. The high-pressure limit rate constant of this channel is k(CHCl 3 → 1CCl 2 + HCl) = 5.84 × 10 40 × T -8.7 exp(-63.9 kcal/mol/RT) s -1which is in good agreement with literature values. The reactions of 1CCl 2with itself, with CCl 3, and with CHCl 3 are incorporated in a detailed mechanistic analysis for the CHCl 3 + Cl 2 reaction system. Inclusion of these reactions does not significantly change the mechanism predictions of Cl 2 concentration profiles in previous studies (Huybrechts, Hubin, and Van Mele, Int J Chem Kinet 2000, 32, 466) over the temperature range of 573-635 K; but Cl 2, CHCl 3, C 2Cl 6 species profiles are significantly different at elevated temperatures. Inclusion of the 1CCl 2 + Cl 2 → CCl 3 + Cl reaction (abstraction and chain branching), which is found to have dramatic effects on the ability of the model to match to the experimental data, is discussed. © 2003 Wiley Periodicals, Inc.

Identifier

0345306697 (Scopus)

Publication Title

International Journal of Chemical Kinetics

External Full Text Location

https://doi.org/10.1002/kin.10159

ISSN

05388066

First Page

647

Last Page

660

Issue

12

Volume

35

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