Electron-Transfer Chemistry of the Merostabilized 3,5,5-Trimethyl-2-morpholinon-3-yl Radical

Article abstract of DOI:10.1021/ja00394a020

Reductions of 5,6-dihydro-5,5-dimethyl-3-phenyl-1,4-oxazin-2-one (6) to 5,5-dimethyl-3-phenyl-2-morpholinone (8), 2-benzoyl-4,4-dimethyl-2-oxazoline (9) to 2-(hydroxyphenylmethyl)-4,4-dimethyl-2-oxazoline (10), 4-(diphenylmethylene)-2,5-cyclohexadienone (12a) to diphenyl(p-hydroxyphenyl)methane (14a), 4--2,5-cyclohexadienone (12b) to tris(p-hydroxyphenyl)methane (14b), benzil (17) to benzoin, and substituted benzils (17a-c) to substituted benzoins by 3,5,5-trimethyl-2-morpholinon-3-yl radical are described.Intermediate radicals 5,5-dimethyl-3-phenyl-2-morpholinon-3-yl (7), diphenyl(p-hydroxyphenyl)methyl (13a), and tris(p-hydroxyphenyl)methyl (13b) are characterized by EPR spectroscopy.Kinetic analyses of the reductions of 6, 9, 17, and 17a-c are described, and mechanisms and rate laws are shown in Schemes II, III, and VII.Reduction reactions most likely occur by electron transfer.Evidence for electron transfer includes an isotope effect for disproportionation of 1 equal to 1.10 +/- 0.09, correlation of the logarithm of the relative rates of reduction of benzils with ?⁺ with a ρ of 1.7 +/- 0.1, and observation of electron transfer from 1 to tetracyanoethylene, dianisyloxoammonium perchlorate (21), and paraquat (20).