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α-Stabilization of Carbanions: Fluorine Is More Effective than the Heavier Halogens


  • We thank the Netherlands Organization for Scientific Research (NWO-CW), the Fonds der Chemischen Industrie (FCI), and the Deutsche Forschungsgemeinschaft (DFG), Sonderforschungsbereich 260, for financial support.


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Ready steady go! The basicity of the carbanions CH2X decreases continuously in the series X=F, Cl, Br, I. However, contrary to the common assumption, this occurs not because of the increasing α-stabilization of CH2X: F stabilizes CH2Xmore effectively than Cl, Br, and I (see picture). This apparent contradiction results from the usually ignored stabilization of the corresponding acids CH3X by X.

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