ELECTRON SPIN RESONANCE STUDY OF PHOSPHORANYL RADICALS I. INFLUENCE OF STERIC AND ELECTRONIC EFFECTS ON RADICAL FORMATION IN SOLUTION |
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Authors: | A. E. H. De Keijzer H. M. Buck |
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Affiliation: | Department of Organic Chemistry , Eindhoven University of Technology , 5600 MB, Eindhoven, The Netherlands |
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Abstract: | Abstract An electron spin resonance study of phosphoranyl radicals, generated by u.v. irradiation of solutions containing a trialkylphosphite and a dialkylperoxide, enabled us to examine the influence of steric and electronic factors on radical formation. It was demonstrated that the influence of steric factors, such as α- or β-branching of the alkyl groups, on the magnitude of radical formation was present in both trialkyl- and methyldialkylphosphites, but not in dimethylalkylphosphites. Furthermore, the study of additional hetero atoms in the alkyl ligand of the dimethylalkylphosphites clearly revealed the influence of the gauche-effect. It was demonstrated that the presence of the gauche-effect, which causes a conformational preference in which a larger steric hindrance is produced, resulted in a decrease of radical formation. |
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Keywords: | Thiopyranthione cyclohexylidene malonitrile- isoquinoline derivatives |
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