State-Specific Reactions of Cu+(1S, 3D) with CH3X and CF3X (X = Cl, Br, I): Exploring the Influence of Dipole Orientation on Association and C鈥揦

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• 作者：William S. Taylor ; Micah L. Abrams ; Cullen C. Matthews ; Seth Byers ; Scott Musial ; Charles M. Nichols
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：April 26, 2012
• 年：2012
• 卷：116
• 期：16
• 页码：3979-3988
• 全文大小：340K
• 年卷期：v.116,no.16(April 26, 2012)
• ISSN：1520-5215

文摘

The reactions of gas-phase Cu⁺(¹S) and Cu⁺(³D) with CF₃X and CH₃X (X = Cl, Br, and I) have been examined experimentally using the drift cell technique at 3.5 Torr in He at room temperature. State-specific product channels and overall bimolecular rate constants for depletion of the two Cu⁺ states were determined using electronic state chromatography. The results showed that Cu⁺(¹S) participates exclusively in association with all of these neutrals, whereas, depending on the neutral, Cu⁺(³D) initiates up to three bimolecular processes, resulting in the formation of CuX⁺, CuC(H/F)₃⁺, and C(H/F)₃X⁺. Possible structures for the singlet association products were explored using density functional methods. These calculations indicated that Cu⁺ preferentially associates with the labile halogen (Cl, Br, I) with all neutrals except CF₃Cl, for which a 鈥渂ackside鈥?geometry occurs in which Cu⁺(¹S) is weakly bound to the 鈭扖F₃ end of the molecule. All products observed on the triplet reaction surface can be understood in terms of either known or calculated thermochemical requirements. Product distributions and overall reaction efficiencies for C鈥揦 bond activation (X = Br, I) through Cu⁺(³D) suggest that the orientation of the neutral dipole has little or no effect in controlling access to specific product channels. Likewise, second-order rate constants for reactions with X = Br and I indicate efficient depletion of Cu⁺(³D) and do not exhibit the dramatic variations in reaction efficiency previously observed with CH₃Cl and CF₃Cl. These results suggest that C鈥揦 bond activation proceeds through a bond-insertion mechanism as opposed to direct abstraction.