Chemistry of Methoxonium on (2x1)Pt(110)

In a previous paper, (Chen, N.; Blowers, P.; Masel, R. I. Surf. Sci. 1998, 418, 329-341.) we found that methoxonium ions (CH3OH2)(+) can form when met hanol and hydrogen coadsorb on Pt(110). In this paper, we characterize the chemistry of methoxonium on (2 x I)Pt(110) using mainly TPD. We observe thr ee reaction pathways: a simple dehydrogenation to CO and hydrogen; an S(N)1 pathway to form water, methane, and adsorbed CH. groups; and an S(N)2 path way yielding dimethyl ether. The S(N)1 pathway shows a strong secondary iso tope effect implying that the transition state is ionic. The S(N)2 pathway is seen at high hydrogen coverages and shows kinetics typical for an S(N)2 process. This work demonstrates for the first time that cationic species on surfaces react via the same S(N)1 and S(N)2 pathways seen during reactions of cations in solution.