The nucleophilic silyl radical: Dual-parameter correlation analysis of the relative rates of bromine-atom abstraction reactions as measured by a rigorous methodology
✍ Scribed by Xi-Kui Jiang; William Fa-Xiang Ding; Yu-Huang Zhang
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- French
- Weight
- 571 KB
- Volume
- 53
- Category
- Article
- ISSN
- 0040-4020
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✦ Synopsis
the relative rates [ kR(Y) values ] of bromine-atom abstraction reactions of 13 p-Y-substituted benzyl bromides ( 1-Y's : Y = H, Et, tBu, Me3Si, MeS, Ph, F, CI, Br, CF 3 , CN, CO2Me, SO~Me ) by tris(trimethylsilyl) silyl radicals [(Me3Si )3Si ° ] in cyclohexane at 80 °C have been measured by a rigorous methodology. Correlation analysis of the kinetic data by the dual-parameter equation ( log k v / k H = pXcrx +p "c" )
shows that the silyl radical is distinctly nucleophilic and the transition states of the bromine-atom abstraction reactions are affected by both the polar and spindelocalization effects of the Y-substituents. Comparison of the [pp / pjj "[values suggests that the contribution of the spin-delocalization effects in this Br-atom abstraction reaction may be greater than the spin-delocalization effects in some Hatom abstraction reactions.