Water-Catalyzed Interconversion of Conventional and Distonic Radical Cations: Methanol and Methyleneoxonium Radical Cations

摘要

Conversion of the isolated methanol radical cation (1) to the methyleneoxonium radical cation (2) requires 108 kJ mol~(-1) (Figure 1). If a "spectator" water molecule is bound to the hydroxyl hydrogen, the barrier for the transformation of the hydrated methanol radical cation 6 to the hydrated methyleneoxonium radical cation 7 is actually increased slightly to 115 kJ mol~(-1) (Figure 2), but the TS for this rearrangement lies slightly below the energy of separated CH_3OH~(·+) + H_2O. The best water-catalyzed transformations, involving in particular a C—H-hydrated species 10, occur well below the energy of separated CH_3OH~(·+) + H_2O (Figure 3). The water-catalyzed transformation of methanol radical cation to methyleneoxonium radical "cation does indeed represent an elegant example of proton-transport catalysis.