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Home ©NIST, 2013 Accessibility information

Reaction:   CHCl₃ + H· → Products
Reaction order:   2
Temperature:   200 - 5000 K
Rate expression:   2.76x10^-13 [cm³/molecule s] (T/298 K)^2.77 e^{-10327 [J/mole]/RT}
Category:  Theory
Data type:   Ab initio
Comments:   Used density functional theory (DFT) and ab initio quantum calculations to determine reaction pathways for reactions of H atoms with CCl4 and CHCl3. Employed BH&HLYP/6-311G(d,p) geometries/frequencies and PM4/6-311+G(3df,2p) energies. Rate expressions calculated using Truhlars Polyrate program employing CVT/SCT tunneling correction.

The calculated barrier for CCl4+H = CCl3+HCl was about 6.5 kcal/mol. For reaction with CHCl3, there are two reaction channels, abstraction of H atom with a barrier of about 6.8 kcal/mol and abstraction of Cl with a barrier of about 8.0 kcal/mol. The H atom abstraction channel dominates at low temperature, at about 670 K the two channels are about equal, and at high temperatures (2000 K) the Cl atom abstraction is about 65% of the total rate.

For CCl4+H, the calculated rate expression is about 2-3 lower than experimental rate constants (2001 Bryukov, Slagle, and Knyazev) and for CHCl3, the calculated total rate expression is only about 10-30% lower than the experimental values (same reference).

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Rate constant values calculated from the Arrhenius expression: