Reaction Mechanism in Crystalline Solids: Kinetics and Conformational Dynamics of the Norrish Type II Biradicals from 伪-Adamantyl-p-Methoxyacetophenone

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• 作者：Gregory Kuzmanich ; Cortnie S. Vogelsberg ; Emily F. Maverick ; Jos茅 Carlos Netto-Ferreira ; J. C. Scaiano ; Miguel A. Garcia-Garibay
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：January 18, 2012
• 年：2012
• 卷：134
• 期：2
• 页码：1115-1123
• 全文大小：489K
• 年卷期：v.134,no.2(January 18, 2012)
• ISSN：1520-5126

文摘

In an effort to determine the details of the solid-state reaction mechanism and diastereoselectivity in the Norrish type II and Yang cyclization of crystalline 伪-adamantyl-p-methoxyacetophenone, we determined its solid-state quantum yields and transient kinetics using nanocrystalline suspensions. The transient spectroscopy measurements were complemented with solid-state NMR spectroscopy spin鈥搇attice relaxation experiments using isotopically labeled samples and with the analysis of variable-temperature anisotropic displacement parameters from single-crystal X-ray diffraction to determine the rate of interconversion of biradical conformers by rotation of the globular adamantyl group. Our experimental findings include a solid-state quantum yield for reaction that is 3 times greater than that in solution, a Norrish type II hydrogen-transfer reaction that is about 8 times faster in crystals than in solution, and a biradical decay that occurs on the same time scale as conformational exchange, which helps to explain the diastereoselectivity observed in the solid state.