Theoretical Analysis of the Fragmentation of (CO)5: A Symmetry-Allowed Highly Exothermic Reaction that Follows a Stepwise Pathway

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• 作者：Jiajun Liu ; Xiaoguang Bao ; David A. Hrovat ; Weston Thatcher Borden
• 刊名：Journal of Organic Chemistry
• 出版年：2015
• 出版时间：December 4, 2015
• 年：2015
• 卷：80
• 期：23
• 页码：11788-11793
• 全文大小：336K
• ISSN：1520-6904

文摘

B3LYP and CCSD(T) calculations, using an aug-cc-pVTZ basis set, have been carried out on the fragmentation of 1,2,3,4,5-cyclopentanepentone, (CO)₅, to five molecules of CO. Although this reaction is calculated to be highly exothermic and is allowed to be concerted by the Woodward鈥揌offmann rules, our calculations find that the D_5h energy maximum is a multidimensional hilltop on the potential energy surface. This D_5h hilltop is 16鈥?0 kcal/mol higher in energy than a C₂ transition structure for the endothermic cleavage of (CO)₅ to (CO)₄ + CO and 11鈥?5 kcal/mol higher than a C_s transition structure for the loss of two CO molecules. The reasons for the very high energy of the D_5h hilltop are discussed, and the geometries of the two lower energy transition structures are rationalized on the basis of mixing of the e₂鈥?HOMO and the a₂鈥?LUMO of the hilltop.