Thermal, Electron, and Photon Induced Chemistry of Acetone on Ag(111)

Sparks, Stacy Converse; Szabó, András; Szulczewski, Greg; Junker, K.; White, John

doi:10.1021/jp972005x

Cited by 20 publications

(12 citation statements)

References 21 publications

(57 reference statements)

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“…This suggests that some of the adsorbed acetone and acetic acid molecules desorb intact from the surface and some dissociate and leave fragments behind. Thermal dissociation of acetone and acetic acid on other solid surfaces has been observed, − but the details of dissociation and the chemical species created during the dissociation process are beyond the scope of this paper (a brief discussion is included in Section S2). Our aim was to determine the desorption temperatures for the intact molecules so as to be able to compare them with the DFT predictions.…”

Section: Resultsmentioning

confidence: 99%

Functional Group Adsorption on Calcite: I. Oxygen Containing and Nonpolar Organic Molecules

et al. 2016

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Considerable interest in calcite crystallization has prompted many studies on organic molecule adsorption. However, each study has explored only a few compounds, using different methods and conditions, so it is difficult to combine the results into a general model that describes the fundamental mechanisms. Our goal was to develop a comprehensive adsorption model from the behavior of a range of organic compounds by exploring how common functional groups interact with calcite and the effects of various side groups and hydrogen on adsorption. We used density functional theory, with semiempirical dispersion corrections (DFT-D2), to determine adsorption energy on calcite {10.4} for nonpolar (benzene, ethane, and carbon dioxide) and oxygen containing polar molecules (water, methanol, ethanol, phenol, formic acid, acetic acid, propanoic acid, benzoic acid, formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, dimethyl ether, acetone, and furan). From the adsorption energies, within the transition state theory approximation, we derived desorption temperature for each molecule. Then we used X-ray photoelectron spectroscopy (XPS) to determine the desorption temperature for four representative molecules and compared the experimental results with those predicted. Carboxylic acids (R-COOH) adsorb more strongly than water and alcohols (R−OH), which in turn adsorb more strongly than the aldehydes (R-CHO). Attachment of a hydrogen atom or a side group changes adsorption behavior for hydroxyl and aldehyde functional groups but does not affect the carboxyl functional group significantly.

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Section: Resultsmentioning

confidence: 99%

Functional Group Adsorption on Calcite: I. Oxygen Containing and Nonpolar Organic Molecules

et al. 2016

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“…The former path produces acetone diolate, while the latter path produces acetone enolate (CH 2 C(CH 3 )O – ). Acetone enolate, the formation of which is related to the well-known ketone–enol transformation, CH 3 COCH 3 ↔ CH 2 COHCH 3 , is a common product of acetone reactions in solutions and on the surface of various metals and oxides after adsorption of acetone. − …”

Section: Discussionmentioning

confidence: 99%

Insights into Acetone Photochemistry on Rutile TiO₂(110). 2. New Photodesorption Channel with CH₃ Ejection along the Surface Normal

Petrik

Henderson

2015

J. Phys. Chem. C

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Angle-resolved photon-stimulated desorption (PSD) combined with infrared reflection−absorption spectroscopy and temperature-programmed desorption reveal two distinct channels in the photochemistry of acetone on rutile TiO 2 (110). During UV irradiation of coadsorbed oxygen and acetone molecules, nonthermal methyl radicals (CH 3 ) are ejected in two different directions: (i) normal to the surface and (ii) off-normal at ∼±66°to the surface normal in the [11̅ 0] azimuth (i.e., perpendicular to the O and Ti rows). The direction of the "off-normal" PSD component is consistent with the orientation of the C−CH 3 bonds in the η 2 -acetone diolatea photoactive form of acetone chemisorption on the oxidized TiO 2 (110) surface proposed in earlier studies. The direction of the "normal" PSD component requires an orientation of a C−CH 3 bond which is not consistent with the η 2 -acetone diolate structure. The "off-normal" PSD component dominates at lower acetone coverage (<0.2 ML), but does not increase at higher coverages in accord with the acetone diolate peak intensity in the infrared reflection−absorption spectra. The "normal" PSD component grows with the acetone coverage up to 0.6 ML. Based on the H/D exchange experiments, the newly discovered "normal" PSD channel is tentatively assigned to a photoproduced η 2 -acetone enolate as a precursor. I. INTRODUCTIONIn the first paper of this two-part series, which we will refer to as part 1, 1 we investigated the photochemistry of acetone adsorbed on oxidized TiO 2 (110) for low coverages of acetone, that is, coverages comparable to the amount of chemisorbed oxygen. Infrared reflection−absorption spectroscopy (IRAS) and angle-resolved photon-stimulated desorption (AR-PSD) measurements provided compelling evidence for a model of the acetone photochemistry previously proposed by one us (M.A.H.). 2−4 In that model, acetone diolateformed by a thermal reaction between acetone and chemisorbed oxygenis the photoactive species:

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“…Experimental evidence partially supports this claim. [5][6][7] In addition to the possibility of generating unique molecular species, lowenergy, electron-induced chemistry may oen predominate over UV photoninduced chemistry depending on the incident ux and the identity and phase of the target molecules. Reaction cross sections can be several orders of magnitude larger for electrons than for photons, especially at incident energies corresponding to resonances associated with dissociative electron attachment (DEA), making it easier for electrons to initiate chemical reactions.…”

Section: Introductionmentioning

confidence: 99%

Low-energy electron-induced chemistry of condensed methanol: implications for the interstellar synthesis of prebiotic molecules

et al. 2014

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In the interstellar medium, UV photolysis of condensed methanol (CH3OH), contained in ice mantles surrounding dust grains, is thought to be the mechanism that drives the formation of "complex" molecules, such as methyl formate (HCOOCH3), dimethyl ether (CH3OCH3), acetic acid (CH3COOH), and glycolaldehyde (HOCH2CHO). The source of this reaction-initiating UV light is assumed to be local because externally sourced UV radiation cannot penetrate the ice-containing dark, dense molecular clouds. Specifically, exceedingly penetrative high-energy cosmic rays generate secondary electrons within the clouds through molecular ionizations. Hydrogen molecules, present within these dense molecular clouds, are excited in collisions with these secondary electrons. It is the UV light, emitted by these electronically excited hydrogen molecules, that is generally thought to photoprocess interstellar icy grain mantles to generate "complex" molecules. In addition to producing UV light, the large numbers of low-energy (< 20 eV) secondary electrons, produced by cosmic rays, can also directly initiate radiolysis reactions in the condensed phase. The goal of our studies is to understand the low-energy, electron-induced processes that occur when high-energy cosmic rays interact with interstellar ices, in which methanol, a precursor of several prebiotic species, is the most abundant organic species. Using post-irradiation temperature-programmed desorption, we have investigated the radiolysis initiated by low-energy (7 eV and 20 eV) electrons in condensed methanol at - 85 K under ultrahigh vacuum (5 x 10(-10) Torr) conditions. We have identified eleven electron-induced methanol radiolysis products, which include many that have been previously identified as being formed by methanol UV photolysis in the interstellar medium. These experimental results suggest that low-energy, electron-induced condensed phase reactions may contribute to the interstellar synthesis of "complex" molecules previously thought to form exclusively via UV photons.

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Thermal, Electron, and Photon Induced Chemistry of Acetone on Ag(111)

Cited by 20 publications

References 21 publications

Functional Group Adsorption on Calcite: I. Oxygen Containing and Nonpolar Organic Molecules

Functional Group Adsorption on Calcite: I. Oxygen Containing and Nonpolar Organic Molecules

Insights into Acetone Photochemistry on Rutile TiO₂(110). 2. New Photodesorption Channel with CH₃ Ejection along the Surface Normal

Low-energy electron-induced chemistry of condensed methanol: implications for the interstellar synthesis of prebiotic molecules

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Thermal, Electron, and Photon Induced Chemistry of Acetone on Ag(111)

Cited by 20 publications

References 21 publications

Functional Group Adsorption on Calcite: I. Oxygen Containing and Nonpolar Organic Molecules

Functional Group Adsorption on Calcite: I. Oxygen Containing and Nonpolar Organic Molecules

Insights into Acetone Photochemistry on Rutile TiO2(110). 2. New Photodesorption Channel with CH3 Ejection along the Surface Normal

Low-energy electron-induced chemistry of condensed methanol: implications for the interstellar synthesis of prebiotic molecules

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Insights into Acetone Photochemistry on Rutile TiO₂(110). 2. New Photodesorption Channel with CH₃ Ejection along the Surface Normal