Reactions of strong bases with vinyl fluoride formation and characterization of 1-fluorovinyl anion and the fluoride-acetylene hydrogen-bonded complex |
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Authors: | John J Rabasco Steven R Kass |
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Institution: | 1. Department of Chemistry, University of Minnesota, Minneapolis, Minnesota, MN 55455, USA
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Abstract: | Vinyl fluoride reacts with strong bases to afford I-fluorovinyl anion (1a) and a fluoride-acetylene cluster (1b). The former ion can be prepared independently, and cleanly, by the fluorodesilylation of 1-(trimethylsilyl) fluoroethylene. Reactions of 1a are reported, and its proton affinity is assigned (387 ± 3 kcal mol?1). Vinyl fluoride is 22 kcal mol?1 more acidic than ethylene. This unusually large substituent effect is reproduced by ab initio calculations, and can be accounted for by geometric changes which minimize the electron-electron repulsion in 1a. Computations on 2-fluorovinyl anions (1c and 1d) have also been carried out, and both ions are only slightly less stable than 1a. The cis isomer (1c) has a larger barrier for fluoride elimination and is a reasonable target for preparation. |
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