Experiments and theory on the thermal decomposition of CHC1{sub 3} and the thermal reactions of CC1{sub 2}.
Rate constants for the thermal decomposition of CHCl{sub 3} in Kr diuent have been measured by the laser schlieren density gradient method. The only decomposition process indicated is molecular elimination giving the singlet carbene, CCl{sub 2}, and HCl. Rate constants are determined under different conditions of density over the temperature range 1282-1878 K, giving k({+-}15%) = 4.26 x 10{sup 16} exp(-22 516 K/T) cm{sup 3} mol{sup -1} s{sup -1}. Electronic structure calculations have provided models for both the transition state and molecule. With these models, both semiempirical Troe and Rice-Ramsperger-Kassel-Marcus unimolecular theoretical calculations are carried out. The experimental results agree with theory provided E{sub 0} = 56.0 kcal mol{sup -1} and {Delta}E{sub down} = (820 {+-} 30) cm{sup -1}, suggesting that the barrier for back reaction is 3.8 kcal mol{sup -1}. Cl-atom atomic resonance absorption spectrometric (ARAS) experiments, also in Kr diluent, are then carried out, confirming that atom formation is entirely due to the thermal reactivity of CCl{sub 2}. On the basis of Cl-atom yield measurements, a mechanism for Cl-atom formation is devised. Chemical simulations of the absolute Cl-atom profile data then provide estimates of the temperature dependences for the rate constants used in the mechanism. These results are discussed in terms of unimolecular reaction rate theory suggesting that the heat of formation for CCl radicals is 100 {+-} 4 kcal mol{sup -1} at 0 K. Our calculated results (R-CCSD(T)) extrapolated to the complete basis set limit give values of {Delta}f = 53.0 and {Delta}f = 102.5 kcal mol{sup -1} and are consistent with the experimental results reported herein. Additionally, the results suggest that CCl{sub 2} undergoes dissociative recombination with a substantial activation energy.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- ER
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 938041
- Report Number(s):
- ANL/CHM/JA-26070
- Journal Information:
- J. Phys. Chem. A, Journal Name: J. Phys. Chem. A Journal Issue: 46 ; Nov. 13, 1997 Vol. 101; ISSN 1089-5639; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- ENGLISH
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