X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, and temperature-programmed reaction/desorption have been employed to investigate the adsorption and reaction pathways of CH 2 =CHCOOH and CH 3 CHFCOOH on Cu(100) and oxygen-precovered Cu(100) [O/Cu(100)]. In the case of CH 2 =CHCOOH on O/Cu(100), CH 2 =CHCOO is the surface intermediate detected between 110 K and 400 K. CH 2 =CHCOO is adsorbed vertically and can change adsorption sites at a higher temperature. The propenoate (acrylate) decomposes at higher temperatures (>500 K), with formation of >C=C=O (ketenylidene) surface species and gaseous products. On Cu(100), CH 2 =CHCOOH is adsorbed in dimer form and can dissociate to generate CH 2 =CHCOO and CH 3 CHCOO intermediates on the surface. The CH 3 CHCOO continuously recombines with the H from deprotonation of CH 2 =CHCOOH, resulting in the formation CH 3 CH 2 COO. The co-existing CH 2 =CHCOO and CH 3 CH 2 COO further decompose at ∼550 K to evolve reaction products, but without >C=C=O being detected. On O/Cu(100), CH 3 CHFCOOH readily deprotonates to form CH 3 CHFCOO at 120 K. This intermediate reacts on the surface at ∼460 K to evolve gaseous products, also producing CH 2 =CHCOO. In the case of Cu(100), deprotonation of CH 3 CHFCOOH occurs at ∼250 K, forming CH 3 CHFCOO. Without oxygen on the surface, this intermediate decomposes into HF and CH 2 =CHCOO at ∼455 K.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry