Homochirality in space – Selective enrichment of chiral molecules on chiral surfaces

Laboratoire de Chimie Théorique, UPMC (Univ. Paris VI), UMR-CNRS 7616, France

Abstract

Life on Earth, as we know it to day, is inseparable from homochirality. The presence of an enantiomeric excess in carbonaceous chondrites is well documented; among the different hypotheses considered to explain this undisputed fact, we chose to investigate the possibilities open by a selective adsorption on a chiral surface that would engage a process of enantiomeric enrichment. The chiral surface is that of the α-quartz $\left\{10\overline{10}\right\}$ and the chiral molécule is lactic acid, HOCH(CH₃)COOH. In this theoretical work we rely on numerical simulations based on Density Functional Theory (DFT) that proved efficient in the super-molecule and periodic approaches to this category of phenomena. In view of the different types of adsorption sites, a statistical treatment was necessary; it shows that (S)-lactic acid is preferentially adsorbed with a selectivity of ~0.7 kcal/mol with respect to the (R) isomer.