| Abstract | Relative rates of hydrogen atom abstraction by photogenerated tert-butoxyl from a variety of cyclic and acyclic ethers, acetals, and orthoformates have been measured at -60°C by an EPR spectroscopic technique. There is a pronounced stereoelectronic effect which produces high rates of abstraction from those C-H bonds adjacent to oxygen which have a relatively small dihedral angle (ca. 30°) with respect to the p-type orbital(s) on the oxygen(s). For C-H bonds which have a large dihedral angle (ca. 90°) abstraction is very much slower. The barrier to inversion of the 2-methoxy-1,3-dioxolan-2-yl radical is ≥10 kcal/mol. © 1981 American Chemical Society. |
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