Evidence for beta-chlorocarbenium and beta-bromocarbenium ions.
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.
Ohta
Brian K
BK
Department of Chemistry, Villanova University, Villanova, Pennsylvania 19085, USA. brian.ohta@villanova.edu
Hough
Ruth E
RE
Schubert
Jeffrey W
JW