Reaction Rate Constants and Mechanistic Detail of the Ni+ + Butanone Reaction

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• 作者：Ivanna E. Laboren ; Otsmar J. Villarroel ; S. Jason Dee ; Vanessa A. Castleberry ; Kevin Klausmeyer ; Darrin J. Bellert
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：March 17, 2011
• 年：2011
• 卷：115
• 期：10
• 页码：1810-1820
• 全文大小：983K
• 年卷期：v.115,no.10(March 17, 2011)
• ISSN：1520-5215

文摘

The unimolecular decomposition kinetics of the jet-cooled Ni⁺鈭抌utanone cluster ion has been monitored over a range of internal energies (16000鈭?8800 cm^鈭?). First-order rate constants are acquired for the precursor ion dissociation into three product channels. The temporal growth of each fragment ion is selectively monitored in a custom instrument and yields similar valued rate constants at a common ion internal energy. The decomposition reaction is proposed to proceed along two parallel reaction coordinates. Each dissociative pathway is rate-limited by the initial Ni⁺ oxidative addition into either the C鈭扖H₃ or C鈭扖₂H₅ 蟽-bond in the butanone molecule. Ratios of integrated product ion intensities as well as the measured rate constants are used to determine values for each 蟽-bond activation rate constant. The lowest energy measurement presented in this study occurs when the binary complex ion possesses an internal energy of 16000 cm^鈭?. Under this condition, the Ni⁺ assisted decomposition of the butanone molecule is rate limited by k_act^{C鈭扖₂H₅} = (0.92 卤 0.08) 脳 10⁵ s^鈭? and k_act^C鈭扖H₃ = (0.37 卤 0.03) 脳 10⁵ s^鈭?. The relative magnitudes of the two rate constants reflect the greater probability for reaction to occur along the C鈭扖₂H₅ 蟽-bond insertion pathway, consistent with thermodynamic arguments. DFT calculations at the B3LYP/6-311++G(d,p) level of theory suggest the most likely geometries and relative energies of the reactants, intermediates, and products.