X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, temperature-programmed reaction/desorption, and density functional theory calculations have been performed to investigate the reaction mechanisms and bonding structures of 3- and 2-bromopropanoic acids on Cu(100) and oxygen-precovered Cu(100). On Cu(100), the bond dissociation of C-Br and O-H in BrCH2CH2COOH is accelerated, occurring at 110 K, as compared to the monofunctional molecules. CH2CH2COOH, CH2CH2COO, and CH3CH2COO from the BrCH2CH2COOH reaction coexist on Cu(100) at 180 K. The CH2CH2COOH is not detected at 250 K, and CH3CH2COO predominates at 320 K. The CH2CH2COO is strongly bonded to the surface via the COO and terminal CH2 groups. In the presence of oxygen atoms on Cu(100), the C-Br scission is suppressed and BrCH2CH2COO is found to be predominant at 150 K. CH2CH2COO begins to form at 200 K and further reacts to produce CH3CH2COO and CH2-CHCOO at 320 K through disproportionation or sequential H loss at 2CH2 and hydrogenation at 3CH2. The reaction of CH3CHBrCOOH on Cu(100) also generates CH3CH2COO at 300 K via CH3CHCOOH and CH3CHCOO. The latter species could attach to the surface via the CHCOO or COO group. On O/Cu(100), dissociation of CH3CHBrCOOH forms CH3CHCOO between 200 and 400 K. CH3CHCOO on O/Cu(100) dehydrogenates, at 450 K, into CH2-CHCOO. A halogen (Cl and Br) effect is observed in the adsorption structure and reaction path of CH3CHCOO on O/Cu(100).
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films