Quantum chemical and kinetic study of the CCl2+HCl→CHCl3 insertion reaction

Abstract

The CCl2 + HCl → CHCl3 (1) insertion reaction has been investigated by ab initio molecular orbital and kinetic calculations. The geometries of reactants, products and transition state were optimized with a large number of density functional theory (DFT) formulations combined with the 6-311++G(3df,3pd) basis set. The reaction barriers calculated with G4(MP2)//DFT and G4//DFT theories of 1.16 ± 0.27 and 0.61 ± 0.26 kcal mol−1 are consistent with the barrier height of ΔE0# = 1.54 ± 0.30 kcal mol−1 estimated from the room temperature experimental rate constant. Calculated enthalpies of reaction of −53.97 ± 0.09 (G4(MP2)//DFT), −55.27 ± 0.09 (G4//DFT) and −56.52 ± 3.90 kcal mol−1 (DFT) agree well with experimental values. The obtained rate constants over the 300–2000 K temperature range at the high and low pressure limit can be expressed as k1,∞(G4(MP2)//DFT) = (4.8 ± 1.8) × 10−14 (T/300 K)2.12±0.19 and k1,∞(G4//DFT) = (9.8 ± 3.4) × 10−14 (T/300 K)1.77±0.16 in cm3 molecule−1 s−1, and k1,0 = [HCl] 3.40 × 10−27 (T/300 K)−6.57 exp(−2218 K/T) cm3 molecule−1 s−1. Falloff curves for the intermediate pressure range obtained for the reactions (1, −1) with these rate constants and a derived central broadening factor of Fcent = 0.16 + 0.84 exp(−T/331 K) + exp(−7860 K/T) were compared with reported experimental rate data.