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

GÓMEZ, NICOLÁS D.; LAURA AZCÁRATE, M.; CODNIA, JORGE; COBOS, CARLOS J.

Computational and Theoretical Chemistry

Elsevier

Lugar: Amsterdam; Año: 2020 vol. 1176 p. 1 - 12

2210-271X

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 ofdensity 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 beexpressed 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.