Photo-Fries rearrangements of 1-naphthyl (R)-2-phenylpropanoate in poly(vinyl acetate) and ethyl acetate. Influence of medium polarity and polymer relaxation on motions of singlet radical pairs.
نویسندگان
چکیده
Both the regio- and stereo-chemistries of the photoreactions of 1-naphthyl (R)-2-phenylpropanoate have been investigated in poly(vinyl acetate) films in their glassy (at 5 degrees C) and melted (at 50 degrees C) states and in ethyl acetate. These results are compared with those from irradiations in polyethylene films and in n-hexane. The regioselectivity of the intermediate 1-naphthoxy/(R)-2-phenylpropanoyl radical pair combinations is much higher in both the melt and glassy states of poly(vinyl acetate) films than that in the melt state of completely amorphous polyethylene films, but the stereoselectivity of intermediate prochiral 1-naphthoxy/1-phenylethyl radical pair combinations is much lower in poly(vinyl acetate). The results emphasize the need to control the ratio between the rates of radical tumbling and translation, as well as the ratio between the rates of in-cage motions and cage-escape, if high stereo- and regio-selectivities of combination products are to be achieved. A mechanistic picture of how the radicals of the intermediate pairs are affected by and interact with the various media is advanced.
منابع مشابه
Reaction cavities of liquid and solid phases of a long n-alkane, n-nonadecane, as probed by the regio- and stereo-chemical fates of two singlet radical pairs.
The regio- and stereo-chemistries of photo-Fries reactions of 1-naphthyl (R)-2-phenylpropanoate ((R)-1) and photo-Claisen reactions of 1-naphthyl (R)-1-phenylethyl ether ((R)-2) have been investigated in the liquid and solid phases of n-nonadecane. The results are compared with those obtained in a lower and higher viscosity liquid n-alkane. Irradiation of (R)-1 yields a prochiral singlet 1-naph...
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ورودعنوان ژورنال:
- Anais da Academia Brasileira de Ciencias
دوره 78 1 شماره
صفحات -
تاریخ انتشار 2006