Adiabatic and Nonadiabatic Reaction Pathways of the O(3P) with Propyne

详细信息    查看全文

• 作者：Shaolei Zhao ; Weiqiang Wu ; Hongmei Zhao ; Huan Wang ; Chunfan Yang ; Kunhui Liu ; Hongmei Su
• 刊名：Journal of Physical Chemistry A
• 出版年：2009
• 出版时间：January 8, 2009
• 年：2009
• 卷：113
• 期：1
• 页码：23-34
• 全文大小：480K
• 年卷期：v.113,no.1(January 8, 2009)
• ISSN：1520-5215

文摘

For the reaction of O(³P) with propyne, the product channels and mechanisms are investigated both theoretically and experimentally. Theoretically, the CCSD(T)//B3LYP/6-311G(d,p) level of calculations are performed for both the triplet and singlet potential energy surfaces and the minimum energy crossing point between the two surfaces are located with the Newton−Lagrange method. The theoretical calculations show that the reaction occurs dominantly via the O-addition rather than the H-abstraction mechanism. The reaction starts with the O-addition to either of the triple bond carbon atoms forming triplet ketocarbene ³CH₃CCHO or ³CH₃COCH which can undergo decomposition, H-atom migration or intersystem crossing from which a variety of channels are open, including the adiabatic channels of CH₃CCO + H (CH₂CCHO + H), CH₃ + HCCO, CH₂CH + HCO, CH₂CO + CH₂, CH₃CH + CO, and the nonadiabatic channels of C₂H₄ + CO, C₂H₂ + H₂ + CO, H₂ + H₂CCCO. Experimentally, the CO channel is investigated with TR-FTIR emission spectroscopy. A complete detection of the CO product at each vibrationally excited level up to v = 5 is fulfilled, from which the vibrational energy disposal of CO is determined and found to consist with the statistical partition of the singlet C₂H₄ + CO channel, but not with the triplet CH₃CH + CO channel. In combination with the present calculation results, it is concluded that CO arises mainly from the singlet methylketene (¹CH₃CHCO) dissociation following the intersystem crossing of the triplet ketocarbene adduct (³CH₃CCHO). Fast intersystem crossing via the minimum energy crossing point of the triplet and singlet surfaces is shown to play significant roles resulting into nonadiabatic pathways for this reaction. Moreover, other interesting questions are explored as to the site selectivity of O(³P) atom being added to which carbon atom of the triple bond and different types of internal H-atom migrations including 1,2-H shift, 3,2-H shift, and 3,1-H shift involved in the reaction.