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

Abstract

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.

Investigating the Atmospheric Fate and Kinetics of OH Radical-Initiated Oxidation Reactions for Epoxybutane Isomers: Theoretical Insight

“…The overall rate coefficient, k (overall), decreases with the increase in temperature, indicating that it has a negative temperature dependence. Similar types of negative temperature dependency can be seen in reactions where PRC is formed, indicating that the PRC plays a very significant role in these types of reactions. , …”

“…Similar types of negative temperature dependency can be seen in reactions where PRC is formed, indicating that the PRC plays a very significant role in these types of reactions. 50,51 We have also calculated the branching ratios of these individual rate coefficients involved in A + • OH and B + • OH. The branching ratio (BR) is the ratio of the individual rate coefficient (k i ) to the total rate coefficient [k (overall)].…”

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

“…The oxidation of 4M3B2O in the atmosphere may be initiated by a reaction with OH and nitrate (NO 3 ) radicals, Cl atoms in coastal and marine regions, and ozone molecules, and the reaction with OH radicals may be the main degradation pathway of 4M3B2O in the daytime. A large number of kinetic and product data are available for the reaction of OH with unsaturated ketones in terms of experiment and theory, − yet, literature data on the atmospheric chemistry of 4M3B2O is scarce, and only one experimental study was devoted to the gas-phase reaction of 4M3B2O with OH radicals. In 2020, Gibilisco et al investigated the kinetics of the reaction of 4M3B2O with OH radicals at 298 ± 3 K and 1 atm of synthetic air by using the relative-rate technique and Fourier transform infrared spectroscopy (FTIR).…”