Comparison of the Reactions of Branched Alcohols and Aldehydes on Rh(111) Academic Article uri icon

abstract

  • Alcohols adsorbed on the Rh(111) surface have been suggested to decompose via unstable surface oxametallacycle intermediates rather than via aldehydes. The chemistry of alcohols and aldehydes containing multiple methyl groups at the β-position was examined in this study to determine whether metallacycle formation could be blocked. Temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) studies demonstrated that complete substitution of β-hydrogens with methyl groups did lead to common alcohol and aldehyde decomposition pathways. 2,2-Dimethyl-1-propanol and 2,2-dimethyl-1-propanal decarbonylated to deposit isobutene on the surface; the sequence of subsequent dehydrogenation steps was the same, whether adsorbed isobutene was generated from these oxygenates, from f-butanol, or by isobutene exposure. In contrast, partial substitution at the β-position did not produce a common path for alcohol and aldehyde decarbonylation. 2-Methyl-1-propanol decomposition resulted in fragmentation of the hydrocarbon backbone of the molecule, generating Ci and Cz fragments from the reaction of the oxametallacycle intermediate. 2-Methyl-1-propanal, however, decarbonylated cleanly to form surface propylidyne intermediates, analogous to the chemistry observed for other aldehydes on Rh(111). These results illustrate the importance of β-CH activation in producing the oxametallacycle-mediated reaction pathways characteristic of alcohols on the Rh(111) surface. © 1996 American Chemical Society.

author list (cited authors)

  • Brown, N. F., & Barteau, M. A.

citation count

  • 24

publication date

  • January 1996