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The adsorption of acrolein and its hydrogenation products propanal, 1-propanol, and 2-propenol on Cu(111) was studied by reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD). The experimental RAIR spectra were obtained by adsorbing multilayers of each molecule at 85 K and then annealing the surface up to 200 K to desorb the multilayer and produce the most stable monolayer structure on the surface. Each of the four molecules adsorbs weakly to the surface and desorbs at temperatures below 225 K. Compared to acrolein and propanal, the two alcohols, 2-propenol and 1-propanol, have notably higher desorption temperatures and broadened and redshifted O-H stretches that reveal strong hydrogen bonding in the multilayers. Upon annealing to 160 K, the OH stretches of both 2-propenol and 1-propanol disappear, indicating the hydrogen bonding in the multilayers is not present in the monolayers. For 2-propenol, the hydrogen bonding in the multilayer correlates with the observation of the CC stretch at 1647 cm −1 , which is invisible for the monolayer. This suggests that the CC bond is parallel to the surface for monolayer coverages of 2-propenol. Similarly, for propanal, the CO stretch peak at 1735 cm −1 compared to those at 1671 and 1695 cm −1 is very weak at low coverages but becomes the most prominent peak for the multilayer, indicating a change in molecular orientation. For acrolein, the out-of-plane bending modes are more intense than the CO stretch at submonolayer coverages, indicating that the molecular plane is mainly parallel to the surface. In contrast, the opposite intensity trend was observed for multilayer acrolein, suggesting that the CO bonds are tilted away from the surface. 

Reflection absorption infrared spectroscopy and temperature programmed desorption were used to study the adsorption of acrolein, its partial hydrogenation products, propanal and 2-propenol, and its full hydrogenation product, 1-propanol on the Ag(111) surface. Each molecule adsorbs weakly to the surface and desorbs without reaction at temperatures below 220 K. For acrolein, the out-of plane bending modes are more intense than the CO stretch at all coverages, indicating that the molecular plane is mainly parallel to the surface. The two alcohols, 2-propenol and 1-propanol, have notably higher desorption temperatures than acrolein and display strong hydrogen bonding in the multilayers as revealed by a broadened and redshifted O–H stretch. For 1-propanol, annealing the surface to 180 K disrupts the hydrogen-bonding to produce unusally narrow peaks, including one at 1015 cm −1 with a full width at half maximum of 1.1 cm −1 . This suggests that 1-propanol forms a highly orderded monolayer and adsorbs as a single conformer. For 2-propenol, hydrogen bonding in the multilayer correlates with observation of the CC stretch at 1646 cm −1 , which is invisible for the monolayer. This suggests that for monolayer coverages, 2-propenol bonds with the CC bond parallel to the surface. Similarly, the CO stretch of propanal is very weak for low coverages but becomes the largest peak for the multilayer, indicating a change in orientation with coverage.