title: Adsorption and ring-opening of lactide on the chiral metal surface Pt(321)(S) studied by density functional theory.
abstract: We study the adsorption and ring-opening of lactide on the naturally chiral metal surface Pt(321)(S). Lactide is a precursor for polylactic acid ring-opening polymerization, and Pt is a well known catalyst surface. We study, here, the energetics of the ring-opening of lactide on a surface that has a high density of kink atoms. These sites are expected to be present on a realistic Pt surface and show enhanced catalytic activity. The use of a naturally chiral surface also enables us to study potential chiral selectivity effects of the reaction at the same time. Using density functional theory with a functional that includes the van der Waals forces in a first-principles manner, we find modest adsorption energies of around 1.4 eV for the pristine molecule and different ring-opened states. The energy barrier to be overcome in the ring-opening reaction is found to be very small at 0.32 eV and 0.30 eV for LL- and its chiral partner DD-lactide, respectively. These energies are much smaller than the activation energy for a dehydrogenation reaction of 0.78 eV. Our results thus indicate that (a) ring-opening reactions of lactide on Pt(321) can be expected already at very low temperatures, and Pt might be a very effective catalyst for this reaction; (b) the ring-opening reaction rate shows noticeable enantioselectivity.
authors: Department of Physics, Campus Plaine - CP 231, Universite Libre de Bruxelles, 1050 Brussels, Belgium.
authors: J-H
authors: JH
authors: Franke
authors: Department of Physics, Campus Plaine - CP 231, Universite Libre de Bruxelles, 1050 Brussels, Belgium.
authors: D S
authors: DS
authors: Kosov
mesh_terms: D000327:Adsorption; D004146:Dioxanes / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D010984:Platinum / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism; D013499:Surface Properties
chemical_list: D004146:Dioxanes; D010984:Platinum; D006859:Hydrogen; C091880:dilactide