Mechanistic and Kinetic Approach on the Propargyl Radical (CH) with the Criegee Intermediate (CHOO).

The detailed reaction mechanism and kinetics of the CH + CHOO 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 CH + CHOO system. The CH + CHOO reaction leading to the CH-[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 CH + CHOO → CH-[cyc-CCHCHOO] + H decreases at low pressures (1-76 Torr), but it increases with rising temperature if the pressure ≥ 760 Torr. Rate constants of the three reaction channels CH + CHOO → CHCCHCHO + OH, CH + CHOO → OCHCHCHCHO + H, and CH + CHOO → CHCHCHO + CHO fluctuate with temperatures. The branching ratio of the CH + CHOO → CH-[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 + CHO) 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 CHOO-related systems under atmospheric and combustion conditions.