Mechanistic and Kinetic Approach on the Propargyl Radical (C₃H₃) with the Criegee Intermediate (CH₂OO)

Abstract

The detailed reaction mechanism and kinetics of the C 3 H 3 + CH 2 OO system have been thoroughly investigated. The CBS-QB3 method in conjunction with the ME/ vRRKM theory has been applied to figure out the potential energy surface and rate constants for the C 3 H 3 + CH 2 OO system. The C 3 H 3 + CH 2 OO reaction leading to the CH 2 -[cyc-CCHCHOO] + H product dominates compared to the others. Rate constants of the reaction are dependent on temperatures (300−2000 K) and pressures (1−76,000 Torr), for which the rate constant of the channel C 3 H 3 + CH 2 OO → CH 2 -[cyc-CCHCHOO] + H decreases at low pressures (1−76 Torr), but it increases with rising temperature if the pressure P ≥ 760 Torr. Rate constants of the three reaction channels C 3 H 3 + CH 2 OO → CHCCH 2 CHO + OH, C 3 H 3 + CH 2 OO → OCHCHCHCHO + H, and C 3 H 3 + CH 2 OO → CHCHCHO + CH 2 O fluctuate with temperatures. The branching ratio of the C 3 H 3 + CH 2 OO → CH 2 -[cyc-CCHCHOO] + H channel is the highest, accounting for 51−98.7% in the temperature range of 300−2000 K and 760 Torr pressure, while those of the channels forming the products PR10 (OCHCHCHCHO + H) and PR11 (CHCHCHO + CH 2 O) are the lowest, less than 0.1%, indicating that the contribution of these two reaction paths to the title reaction is insignificant. The proposed temperature-and pressure-dependent rate constants, together with the thermodynamic data of the species involved, can be confidently used for modeling CH 2 OO-related systems under atmospheric and combustion conditions.

A Computational Study of the Mechanism and Kinetics of the 4-Methyl Aniline Reaction with OH Radicals

“…The high-cost method known as CCSD(T) [31,32] was employed to compute singlepoint energies (E sp ) for each species on the potential energy surface (PES). Therefore, the total enery of each substance was the sum of E sp and zero-point vibrational energy (E zp ), in which E zp was scaled by a 0.971 factor [33][34][35]. The reason to use the CCSD(T) method is that it gives very accurate results, with an error of only about 4 kJ•mol −1 [36,37].…”

Study on Mechanism and Kinetics of the H2O-Abstraction Reactions Between C3H4 Isomers and •OH Radicals

“…[3][4][5] Notably, these reactions may yield propargyl radical ( • C 3 H 3 ), the smallest resonantly stabilized hydrocarbon radical, initiating the formation of the initial aromatic ring. [6][7][8][9][10] Consequently, the interactions of hydroxyl radicals with allene and propyne play a pivotal role in the comprehensive oxidation pathway of these molecules. 11 Many experiments and calculations have been undertaken to elucidate the chemical kinetics of allene and propyne.…”