| Abstract
| - The reactivity of 1-methyl-1-cyclohexene (1MC6=) and methylene cyclohexane (MeC6) on a Pt(111) single-crystal surface was investigated by means of temperature-programmed desorption (TPD) and reflection−absorption infrared spectroscopy (RAIRS). Dehydrogenation of both compounds occurs via the formation ofa common 1-methyl cyclohexenyl species, as corroborated by supporting data from cyclohexene dehydrogenation and 3-bromo cyclohexene thermal activation on Pt(111), and leads to the ultimate formation oftoluene, which desorbs at 430 K. On the other hand, hydrogenation, isomerization, and H−D exchange reactionsall take place by following the so-called Horiuti−Polanyi mechanism and involve a common 1-methylcyclohexyl surface intermediate. 1MC6= and MeC6 display different reactivities, with MeC6 isomerizing to1MC6=, but both hydrogenate to methyl cyclohexane (MC6). These reactions are enhanced by the presenceof predosed hydrogen on the surface and undergo extensive early H−D exchange if deuterium is used instead.
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