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Updated: Jul 15, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Evidence for beta-chlorocarbenium and beta-bromocarbenium ions
Brian K Ohta1, Ruth E Hough, Jeffrey W Schubert
1Department of Chemistry, Villanova University, Villanova, Pennsylvania 19085, USA. brian.ohta@villanova.edu
Abstract:
Isotopic perturbation of degenerate equilibrium is used to determine whether tetramethylethylenechloronium and tetramethylethylenebromonium ions are closed 1,2-bridged structures or rapid equilibria of open beta-halocarbenium ions. The observed 13C NMR isotope shifts are consistent with a combination of large equilibrium shifts and small upfield intrinsic shifts. The presence of equilibrium shifts in both halonium ions indicates that these ions are not closed 1,2-bridged structures. Rather, they are best represented by equilibria of beta-halocarbenium ions.
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