| Abstract
| - Sum frequency generation (SFG) vibrational spectroscopy was used to investigate the adsorption geometriesand surface reactions of various C6 hydrocarbons (n-hexane, 2-methylpentane, 3-methylpentane, and 1-hexene)on Pt(100). At 300 K and in the presence of excess hydrogen, n-hexane, 3-methylpentane, and 2-methylpentaneadsorb molecularly on Pt(100) mostly in “flat-lying” conformations. Upon heating the metal surface to 450K, the molecules underwent dehydrogenation to form new surface species in “standing-up” conformations,such as hexylidyne and metallacyclic species. 1-Hexene, however, dehydrogenated to form metallocycle Pt3⋮C-(CH2)5-Pt at 300 K in the presence of excess hydrogen and remained unreacted on the surface upon heatingthe metal surface to 450 K. Dehydrogenation was enhanced in the absence of excess hydrogen in the casesof n-hexane, 2-methylpentane, and 3-methylpentane to form metallocycle Pt3⋮C-(CH2)5-Pt; 2-methyl-1-penteneand 4-methyl-1-pentene; and metallacyclohexane, respectively, at 300 K. These surface species remainedunreacted after increasing the surface temperature to 450 K. The mechanisms for catalytic isomerization anddehydrocyclization of n-hexane were discussed on the basis of these results.
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