Kinetic Applications of Electron Paramagnetic Resonance Spectroscopy. 36. Stereoelectronic Effects in Hydrogen Atom Abstraction from Ethers

Article abstract of DOI:10.1021/ja00393a018

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 deg 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 deg) with respect to the p-type orbital(s) on the oxygen(s).For C-H bonds which have a large dihedral angle (ca. 90 deg) abstraction is very much slower.The barrier to inversion of the 2-methoxy-1,3-dioxolan-2-yl radical is <*> 10 kcal/mol.