REACTIONS OF PROTON-BOUND DIMERS

Thermal reactions of proton-bound dimers, (CH3CN)2H+, (CH3OCH3)2H+, an d (CH3COCH3)2H+, were studied using a selected ion flow tube. Reaction s observed include association, switching, and proton transfer. The as sociation channel was observed only for base molecules that had hydrog en bonding protons such as NH3, CH3NH2, (CH3)2NH, and CH3OH. An associ ation-insertion mechanism was proposed in which the central proton of the symmetrically bound dimers is replaced by a protonated base, for e xample, NH4+. These reactions are relatively slow, which demonstrates a central barrier along the potential energy surface. Ether-containing dimers do not demonstrate this insertion reaction, except for diether s, for example, CH3OCH2CH2OCH3, which can form stable bicyclic structu res. Dimers such as (HCOOH)2H+, which possess hydrogen bonding protons in the periphery, undergo switching reactions with ammonia and no ins ertion.