ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Ab initio calculations have been used to characterize the transition states for halogen abstraction by CH3 in reactions with CF4, CF3Cl, CF3Br, and CF3I (1-4). Geometries and frequencies were obtained at the HF/6-31G(d) and MP2=full/6-31G(d) levels of theory. Energy barriers were computed via the Gaussian-2 methodology, and the results were employed in transition state theory analyses to obtain the rate constants over 298-2500 K. There is good accord with literature measurements in the approximate temperature range 360-500 K for reactions (2-4), and the computed activation energies are accurate to within ±6 kJ mol-1. Recommended rate constant expressions for use in combustion modeling are k;1=1.6×10-19 (T/K)2.41 exp(-13150 K/T), k2=8.4×10-20(T/K)2.34 exp(-5000 K/T), k3=4.6×10-19 (T/K)2.05 exp(-3990 K/T), and k4=8.3×10-19 (T/K)2.18 exp(-1870 K/T) cm3 molecule-1 s-1. The results are discussed in the context of flame suppression chemistry. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 179-184, 1998.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
