Understanding chloroethene chemisorption to iron surfaces using molecular mechanics and density functional theory

The thermodynamic favorability and resulting structures for chemical desorption of trichloroethylene (TCE) and tetrachloroethylene (PCE) to iron surfaces were studied using molecular mechanics and periodic density functional theory. PCE chemisorbed via pi and di-sigma bond formation between Fe and C atoms, while TCE chemisorbed via sigma and di-sigma bonds. Upon sigma and pi-bond formation, all C-Cl bonds became activated and the Cl atoms formed bonds with the iron surface. Sigma and pi bond formation also resulted in a shortening of the carbon-carbon bond by an amount consistent with the conversion of a double to a triple bond. Upon di-sigma bond formation, only one C-Cl bond on each C atom became activated, while the remaining bonds remained unchanged. Both angles and bond lengths indicated that there was no change in bond order of the carbon-carbon double bond upon di-sigma bond formation. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).