Inter- and intra-annular proton exchange in gaseous benzylbenzenium ions (protonated diphenylmethane)
作者:Dietmar Kuck、Wolfgang Bather
DOI:10.1002/oms.1210210802
日期:1986.8
AbstractTwo distinct proton exchange reactions occur in metastable gaseous benzylbenzenium ions, generated by isobutane chemical ionization of diphenylmethane and four deuterium‐labelled analogues. Whereas the proton ring‐walk at the benzenium moiety is fast giving rise to a completely random intraannular proton exchange, the interannular proton exchange is surprisingly slow and competes with the elimination of benzene. A kinetic isotope effect of kH/kD= 5 has been determined for the interannular proton transfer, and a particularly high energy barrier of 50–75 kJ mol−1 has been estimated. These observations are attributed to steric restrictions of the ring‐to‐ring proton transfer in benzylbenzenium ions and contrasted to the fast interannular proton exchange in the higher homologues.