title: Reaction mechanism in crystalline solids: kinetics and conformational dynamics of the Norrish type II biradicals from α-adamantyl-p-methoxyacetophenone.
abstract: 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 α-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-lattice 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.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1559, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Kuzmanich
authors.forename: Cortnie S
authors.initials: CS
authors.lastname: Vogelsberg
authors.forename: Emily F
authors.initials: EF
authors.lastname: Maverick
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Netto-Ferreira
authors.forename: J C
authors.initials: JC
authors.lastname: Scaiano
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Garcia-Garibay