1,2-Dibromoethane on Cu(100): Bonding structure and transformation to C2H4

Temperature-programmed reaction/desorption, mass spectrometry, reflection-absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and density functional theory calculations have been employed to explore the reaction and bonding structure of 1,2-C2H4Br2 on Cu(100). Both the trans and gauche conformers are found to dissociate by breaking the C-Br bonds on clean Cu(100) at 115 K, forming C2H4 and Br atoms. Theoretical investigations for the possible paths of 1,2-C2H4Br2 → C2H4 + 2Br on Cu(100) suggest that the barriers of the trans and gauche molecules are in the ranges of 0–4.2 and 0–6.5 kcal/mol, respectively. The C-Br scission temperature of C2H4Br2 is much lower than that (∼170 K) of C2H5Br on Cu(100). Adsorbed Br atoms can decrease the dissociation rate of the 1,2-C2H4Br2 molecules impinging the surface. The 1,2-C2H4Br2 molecules adsorbed in the first monolayer are structurally distorted. Both the trans and gauche molecules exist in the second monolayer, but with no preferential adsorption o...