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

The present work represents the reaction mechanism and kinetics study of the 4-methyl-3-penten-2-one initiated by OH radicals. The geometries of all stationary points are optimized at the M06-2X/6-311+ +G(d,p) level of theory, and the energy values are refined by making single point energy calculation at the CCSD(T)/6-311++G(d,p) level of theory to construct an energy-level diagram. By employing conventional transition state theory along with a tunneling coefficient, the overall rate constants are calculated in the temperature range of 180−360 K and can be summarized by a modified Arrhenius three-parameter fit expression: k (T) = 6.72 × 10 −20 × T 2.5 × exp (2056.4/T) cm 3 molecule −1 s −1 . The rate constant obtained at 298 K is found to be 1.02 × 10 −10 cm 3 molecule −1 s −1 , which is in good agreement with the experimental data. In the atmosphere, the major oxidation products of the title reaction are acetone, methyl glyoxal, (CH 3 ) 2 COHC(O)H, CO 2 , and formaldehyde, which are in accordance with experimental detection. The atmospheric lifetime of 4-methyl-3-penten-2-one initiated by OH radicals and the impact of products on tropospheric chemistry have been provided in the paper.

Section: Resultsmentioning

confidence: 99%

Theoretical Investigations of the OH-Initialized Oxidation of 4-Methyl-3-Penten-2-One in the Atmosphere

Zhang

2022

“…The electronic partition function of the Cl• atoms was evaluated by considering the splitting of 881 cm –1 between the ground 2 P 3/2 and excited 2 P 1/2 electronic states of Cl• atoms . The CTST method developed by Singleton and Cvetanovic and Alvarez-Idaboy et al , has been successfully employed to a lot of similar reaction systems. − …”

Section: Methodsmentioning

confidence: 99%

Atmospheric Degradation of 3-Methoxy-1-propanol by Reaction with Hydroxyl Radicals and Chlorine Atoms

Du,

Zhu,

Zhang

2024

The BH&HLYP/6-311++G(d,p) level of theory has been employed to investigate the degradation of 3-methoxy-1-propanol (3M1POL) initiated by HO• radicals. Additionally, the CCSD(T)/6-311++G(d,p) method is used to recalculate the single-point energies for each stationary point. For the reaction of 3M1POL + Cl•, the potential energy surface profile has been constructed at the CCSD(T)/cc-pVTZ// MP2/6-311++G(d,p) + 0.95 × ZPE level of theory. The results reveal that the abstractions at three −CH 2 − groups of 3M1POL play an important role in the oxidation mechanisms of 3M1POL with HO• radicals and Cl• atoms, yielding three intermediates:

“…The rate coefficient of the title reaction has been calculated utilizing the method proposed by Singleton and Cvetanovic, and Alvarez-Idaboy et al, , which has been applied to similar reactions. − k = k 1 k − 1 k 2 = K eq k 2 where K eq is defined as the equilibrium constant between the 4M3B2O and OH reactants and the reactant complex (RC) and k 2 is the unimolecular rate coefficient for the formation of product (P).…”

Section: Methodsmentioning

confidence: 99%

Kinetics, Products, and Mechanisms Study of the Atmospheric Degradation of (E)-4-Methoxy-3-buten-2-one with Hydroxyl Radicals

Zhang

2023

High-level ab initio calculations have been conducted to investigate the mechanisms and kinetics of the oxidation of (E)-4-methoxy-3-buten-2-one by hydroxyl radicals (OH) in the atmosphere. Potential energy diagrams have been constructed at the CCSD(T)/6-311++G(d,p)//BH&HLYP/6-311++G(d,p) level of theory to characterize the overall reaction mechanism. Transition-state theory, in combination with Eckart tunneling, is employed to calculate the rate coefficients for the title reaction over the 180−360 K temperature range. Rate coefficients can then be fitted to a modified form of the Arrhenius equation: k = 2.00 × 10 −13 × exp(1960.4/T) cm 3 molecule −1 s −1 . The room temperature rate coefficient is calculated to be 1.41 × 10 −10 cm 3 molecule −1 s −1 , which matches well with the experimentally reported ones. The kinetic results imply that the reaction for OH radicals with (E)-4-methoxy-3-buten-2-one mainly leads to the formation of two hydroxyalkyl radicals by the initial addition of OH radicals to the >C�C< double bond. Under NO x -contaminated atmospheric environments, the hydroxyalkyl radicals can undergo further reactions to give various products such as methyl formate, methyl glyoxal, 2-hydroxy-2-methoxyacetaldehyde, peroxyacetyl nitrate (PAN), CO 2 , and a variety of peroxyalkyl nitrates and organic nitrates, which are in qualitative agreement with the experimental observations. A discussion on the atmospheric implications is also presented.