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Kinetics and mechanism for the thermal chlorination of chloroform in the gas phase: Inclusion of HCl elimination from CHCl 3
Author(s) -
Zhu Li,
Bozzelli Joseph W.
Publication year - 2003
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.10159
Subject(s) - chemistry , chloroform , reaction rate constant , atmospheric temperature range , kinetics , activation energy , chlorine , reaction mechanism , ab initio , kinetic energy , chlorine atom , computational chemistry , thermodynamics , medicinal chemistry , organic chemistry , catalysis , physics , quantum mechanics
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 → 1 CCl 2 + HCl) = 5.84 × 10 40 × T −8.7 exp(−63.9 kcal/mol/ RT ) s −1 , which is in good agreement with literature values. The reactions of 1 CCl 2 with 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 2 Cl 6 species profiles are significantly different at elevated temperatures. Inclusion of the 1 CCl 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. Int J Chem Kinet 35: 647–660, 2003