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1. Adsorption of acrolein and its hydrogenation products on Cu(111)

   https://doi.org/10.1039/D2CP03817J  

   Islam, Arephin; Molina, David L.; Trenary, Michael (October 2022, Physical Chemistry Chemical Physics)

   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. 

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2. Adsorption and reaction pathways of 7-octenoic acid on copper

   https://doi.org/10.1039/d1cp00167a  

   Bavisotto, Robert; Rana, Resham; Hopper, Nicholas; Olson, Dustin; Tysoe, Wilfred T. (March 2021, Physical Chemistry Chemical Physics)

   null (Ed.)

   The surface structure and reaction pathways of 7-octenoic acid are studied on a clean copper substrate in ultrahigh vacuum using a combination of reflection–absorption infrared spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption and scanning-tunneling microscopy, supplemented by first-principles density functional theory calculations. 7-Octenoic acid adsorbs molecularly on copper below ∼260 K in a flat-lying configuration at low coverages, becoming more upright as the coverage increases. It deprotonates following adsorption at ∼300 K to form an η 2 -7-octenoate species. This also lies flat at low coverages, but forms a more vertical self-assembled monolayer as the coverage increases. Heating causes the 7-octenoate species to start to tilt, which produces a small amount of carbon dioxide at ∼550 K and some hydrogen in a peak at ∼615 K ascribed to the reaction of these tilted species. The majority of the decarbonylation occurs at ∼650 K when CO 2 and hydrogen evolve simultaneously. Approximately half of the carbon is deposited on the surface as oligomeric species that undergo further dehydrogenation to evolve more hydrogen at ∼740 K. This leaves a carbonaceous layer on the surface, which contains hexagonal motifs connoting the onset of graphitization of the surface. 

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3. On the Origin of the Rate Enhancement by a R‐(+)‐1‐(1‐Naphthyl)‐Ethylamine‐Modified Pd(111) Model Catalyst for Methyl Pyruvate Hydrogenation

   https://doi.org/10.1002/cctc.202201078  

   Bavisotto, Robert; Roy, Sree_Pradipta; Tysoe, Wilfred_T (January 2023, ChemCatChem)

   Abstract Chiral modifiers of heterogeneous catalysts can function as activity promotors to minimize the influence of unmodified sites on the enantiomeric excess to obtain highly enantioselective catalysts. However, the origin on this effect is not well understood. It is investigated using a model catalyst of R‐(+)‐1‐(1‐naphthyl)‐ethylamine (R‐1‐NEA)/Pd(111) for the hydrogenation of methyl pyruvate (MP) to methyl lactate (ML). The activity of the model catalyst remains constant for multiple turnovers. No rate enhancement is found for R‐1‐NEA coverages below ∼0.5 monolayer (ML), but a significant increase is found at R‐1‐NEA coverages of ∼0.75 ML, with a rate approximately twice that of the unmodified catalyst. This is investigated using infrared spectroscopy to distinguish between MP monomers and dimers. MP titration experiments with hydrogen show a half‐order hydrogen pressure dependence, with the monomer reacting at twice the rate as the dimer. It is found that the dimer is the most abundant species on clean Pd(111), but the ratio of monomers to dimers increases as the R‐1‐NEA coverage increases due to surface crowding. The monomeric species is also found to be more stable on the crowded surface than on clean Pd(111); the chiral modifier also serves to stabilize the reactant. Finally, this model nicely explains the unusual 1‐NEA‐covergae dependence of the reactivity. 

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4. On the formation of complex organic molecules in the interstellar medium: untangling the chemical complexity of carbon monoxide–hydrocarbon containing ice analogues exposed to ionizing radiation via a combined infrared and reflectron time-of-flight analysis

   https://doi.org/10.1039/C9CP01793C  

   Abplanalp, Matthew J.; Kaiser, Ralf I. (August 2019, Physical Chemistry Chemical Physics)

   Recently, over 200 molecules have been detected in the interstellar medium (ISM), with about one third being complex organic molecules (COMs), molecules containing six or more atoms. Over the last few decades, astrophysical laboratory experiments have shown that several COMs are formed via interaction of ionizing radiation within ices deposited on interstellar dust particles at 10 K (H 2 O, CH 3 OH, CO, CO 2 , CH 4 , NH 3 ). However, there is still a lack of understanding of the chemical complexity that is available through individual ice constituents. The present research investigates experimentally the synthesis of carbon, hydrogen, and oxygen bearing COMs from interstellar ice analogues containing carbon monoxide (CO) and methane (CH 4 ), ethane (C 2 H 6 ), ethylene (C 2 H 4 ), or acetylene (C 2 H 2 ) exposed to ionizing radiation. Utilizing online and in situ techniques, such as infrared spectroscopy and tunable photoionization reflectron time-of-flight mass spectrometry (PI-ReTOF-MS), specific isomers produced could be characterized. A total of 12 chemically different groups were detected corresponding to C 2 H n O ( n = 2, 4, 6), C 3 H n O ( n = 2, 4, 6, 8), C 4 H n O ( n = 4, 6, 8, 10), C 5 H n O ( n = 4, 6, 8, 10), C 6 H n O ( n = 4, 6, 8, 10, 12, 14), C 2 H n O 2 ( n = 2, 4), C 3 H n O 2 ( n = 4, 6, 8), C 4 H n O 2 ( n = 4, 6, 8, 10), C 5 H n O 2 ( n = 6, 8), C 6 H n O 2 ( n = 8, 10, 12), C 4 H n O 3 ( n = 4, 6, 8), and C 5 H n O 3 ( n = 6, 8). More than half of these isomer specifically identified molecules have been identified in the ISM, and the remaining COMs detected here can be utilized to guide future astronomical observations. Of these isomers, three groups – alcohols, aldehydes, and molecules containing two of these functional groups – displayed varying degrees of unsaturation. Also, the detection of 1-propanol, 2-propanol, 1-butanal, and 2-methyl-propanal has significant implications as the propyl and isopropyl moieties (C 3 H 7 ), which have already been detected in the ISM via propyl cyanide and isopropyl cyanide, could be detected in our laboratory studies. General reaction mechanisms for their formation are also proposed, with distinct follow-up studies being imperative to elucidate the complexity of COMs synthesized in these ices. 

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5. Glycosidic linkage, N -acetyl side-chain, and other structural properties of methyl 2-acetamido-2-deoxy-β- D -glucopyranosyl-(1→4)-β- D -mannopyranoside monohydrate and related compounds

   https://doi.org/10.1107/S2053229620001515  

   Zhang, Wenhui; Meredith, Reagan J.; Oliver, Allen G.; Carmichael, Ian; Serianni, Anthony S. (March 2020, Acta Crystallographica Section C Structural Chemistry)

   null (Ed.)

   The crystal structure of methyl 2-acetamido-2-deoxy-β-D-glycopyranosyl-(1→4)-β-D-mannopyranoside monohydrate, C 15 H 27 NO 11 ·H 2 O, was determined and its structural properties compared to those in a set of mono- and disaccharides bearing N -acetyl side-chains in βGlcNAc aldohexopyranosyl rings. Valence bond angles and torsion angles in these side chains are relatively uniform, but C—N (amide) and C—O (carbonyl) bond lengths depend on the state of hydrogen bonding to the carbonyl O atom and N—H hydrogen. Relative to N -acetyl side chains devoid of hydrogen bonding, those in which the carbonyl O atom serves as a hydrogen-bond acceptor display elongated C—O and shortened C—N bonds. This behavior is reproduced by density functional theory (DFT) calculations, indicating that the relative contributions of amide resonance forms to experimental C—N and C—O bond lengths depend on the solvation state, leading to expectations that activation barriers to amide cis – trans isomerization will depend on the polarity of the environment. DFT calculations also revealed useful predictive information on the dependencies of inter-residue hydrogen bonding and some bond angles in or proximal to β-(1→4) O -glycosidic linkages on linkage torsion angles ϕ and ψ. Hypersurfaces correlating ϕ and ψ with the linkage C—O—C bond angle and total energy are sufficiently similar to render the former a proxy of the latter. 

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