Combinations of chiral and prochiral singlet radical-pairs in reaction cavities of polyethylene films. Control and analysis of radical tumbling and translation

The regio- and stereo-chemistries of combination products from chiral 1-naphthoxy/(R)-2-phenylpropanoyl and prochiral 1-naphthoxy/ 1-phenylethyl singlet radical- pairs ( radical- pairs A and B, respectively) have been studied at different temperatures in polyethylene ( PE) films with different crystallinities. The radical- pairs have been generated as intermediates along the photo-Fries reaction course of 1-naphthyl ( R)-2-phenylpropanoate ((R)-1) and the photo- Claisen reaction course of 1-naphthyl ( R)-1-phenylethyl ether (( R)-2). Radical-pair B was produced directly upon lysis of the first excited singlet state of ( R)-2 and indirectly after irradiation of ( R)-1 and subsequent decarbonylation of the 2-phenylpropanoyl radical of radical- pair A. Comparison of the fates of the directly and indirectly formed radical- pairs B provides detailed information about the nature of the reaction cavities within the polyethylene hosts and how the combinations of the radical- pairs are influenced by their initial locations within a cavity. The results, especially when taken with those from irradiations in n-alkanes, indicate that the PE cavities are "templated" by the ( R)-1 and ( R)-2 guest molecules and that the templated shapes are retained in some form for periods that are at least as long as the time required for decarbonylation of a 2-phenylpropanoyl radical. In addition, the enantiomeric excesses of the decarbonylated photoproducts from ( R)-1 ( 2, 2-(1-phenylethyl)-1-naphthol (2BN), and 4-(1-phenylethyl)-1-naphthol (4BN)) or 2BN and 4BN from ( R)-2 indicate different influences of temperature on translational and tumbling motions of the radicals of radical- pairs B within their polyethylene cages.