Equilibrium Adsorption of D- and L‐Alanine Mixtures on Naturally Chiral Cu{3,1,17} Surfaces

Equilibrium adsorption of gas phase mixtures of Dand Lalanine (Ala) onto the naturally chiral Cu{3,1,17} surfaces has been studied by both experiment and DFT-based modeling. Isotopically labeled *L-Ala (HO2 CCH(NH2)CH3) and unlabeled D-Ala allow mass spectrometric enantiodifferentiation of the adsorbed species during temperature-programmed decomposition, following equilibrium adsorption. Measurements of the relative equilibrium coverages of Dand *L-Ala on the Cu{3,1,17} surfaces, θD/R/θ*L/R = θ*L/S/θD/S, at gas phase partial pressure ratios of P*L/PD = 1/2, 1, and 2 indicate that the D-Ala and *L-Ala conglomerate phases are more energetically stable than a D*L-Ala racemate phase, but that their adsorption energies are not measurably enantiospecific, ΔΔEDL ≈ 0. Although the DFT simulations provide a self-consistent structure of Ala overlayers on Cu{3,1,17} they overestimate the enantiospecificity of the adsorption energetics.