Polymerization and decarbonylation reactions of aldehydes on the Pd(111) surface

Article abstract of DOI:10.1021/ja00187a035

The adsorption and reaction of formaldehyde, acetaldehyde, and propanal were compared in temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) studies on a clean Pd(111) surface. Formaldehyde reacted upon adsorption at 170 K via decomposition to CO(a) and H(a) and polymerization to paraformaldehyde. In contrast, decomposition of the higher aldehydes required significantly higher temperatures. Acetaldehyde adsorbed on the clean surface in an η² configuration and reacted to form stable acetyl species which decomposed above 300 K to produce CO(a), H(a), and C₁ hydrocarbon fragments. Adsorbed acetyl groups were readily identified by the characteristic frequency of their CO stretch at 1565 cm^-1.