Theoretical Study on the Reaction of the Methylidyne Radical, CH(X2螤), with Formaldehyde, CH2O

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• 作者：Hue Minh Thi Nguyen ; Huu Tho Nguyen ; Trong-Nghia Nguyen ; Hung Van Hoang ; Luc Vereecken
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：September 25, 2014
• 年：2014
• 卷：118
• 期：38
• 页码：8861-8871
• 全文大小：561K
• ISSN：1520-5215

文摘

A theoretical study of the mechanism and kinetics of the CH(X²螤) + H₂C鈺怬 reaction was carried out by ab initio molecular orbital theory based on the CCSD(T)/aug-cc-pVTZ//BHandHLYP/aug-cc-pVDZ method in conjunction with statistical theoretical kinetic VTST and RRKM Master Equation calculations. The potential energy surface for the cis/trans-HCOH + CH reactions was also examined. Calculated results show that the association reaction of CH and CH₂O occurs by addition of the CH radical onto the oxygen atom, cycloaddition onto the C鈺怬 bond, and, for a small fraction, insertion of CH into a C鈥揌 bond, forming CH₂C鈥揙鈥揅H, cyclic H₂COCH, and CH₂CHO, respectively. These channels are all barrierless, leading to a rate coefficient near the collision limit with a slight negative temperature dependence, in excellent agreement with experimental data. The intermediates can undergo extensive isomerization across seven C₂H₃O isomers, many with multiple conformers, prior to fragmentation. Eight fragmentation product sets were characterized, where H₂CCO + H and CH₃ + CO were found to be the major products at lower temperatures, while ³CH₂ + HCO started to contribute at higher temperatures. CCHO + H₂, C₂H + H₂O, HCCOH + H, C₂H₂ + OH, and HCCO + H₂ have negligible contributions for temperatures below 3000 K and pressures up to 100 atm. Collisional stabilization of the C₂H₃O isomers is negligible except at the highest of pressures and low temperatures.