Controlling tunnelling in methane loss from acetone ions by deuteration

Bodi, Andras; Baer, Tomas; Wells, Nancy K.; Fakhoury, Daniel; Klecyngier, David; Kercher, J. P.

doi:10.1039/c5cp02944a

Cited by 22 publications

(27 citation statements)

References 35 publications

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“…S12 of the ESI (right), most of this channel indeed corresponds to a DPI product according to its broad velocity distribution perpendicular to the molecular beam propagation axis in the VMI at 738 K. The major dissociative photoionization product of acetone, another expected pyrolysis product, 21 at energies higher than 10.3 eV is m/z 43 by the loss of a methyl radical to form C2H3O + . 73,100 Because of the hot pyrolysis products, a significant red shift in the appearance of the m/z 43 fragment ion is to be expected. 67 These findings are considered in the temperature-dependent species profiles, later in this study.…”

Section: Dpi Of Pyrolysis Productsmentioning

confidence: 99%

Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation

Grimm

Baik

Hemberger

et al. 2021

Phys. Chem. Chem. Phys.

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Section: Dpi Of Pyrolysis Productsmentioning

confidence: 99%

Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation

Grimm

Baik

Hemberger

et al. 2021

Phys. Chem. Chem. Phys.

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“…The most stable dissociation products, the 1‐butene cation and carbon monoxide, are only accessible after surmounting an energetic 3,5‐hydrogen‐transfer transition state at 11.18 eV. However, these hydrogen‐transfer processes may be enhanced by tunneling, similar to the less dominant methane‐loss process in acetone, which could also explain the low and slowly rising rate constant associated with 28 amu loss. The first, α‐bond breaking step in the parent ion may also be accompanied by simultaneous 3,2‐hydrogen‐atom transfer over a transition state (11.17 eV) that is virtually isoenergetic with the 3,5‐hydrogen‐transfer transition state mentioned earlier.…”

Section: Resultsmentioning

confidence: 99%

Dissociative Ionization and Thermal Decomposition of Cyclopentanone

Pastoors

Bodi

Hemberger

et al. 2017

Chemistry A European J

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Despite the growing use of renewable and sustainable biofuels in transportation, their combustion chemistry is poorly understood, limiting our efforts to reduce harmful emissions. Here we report on the (dissociative) ionization and the thermal decomposition mechanism of cyclopentanone, studied using imaging photoelectron photoion coincidence spectroscopy. The fragmentation of the ions is dominated by loss of CO, C2H4, and C2H5, leading to daughter ions at m/z 56 and 55. Exploring the C5H8O. + potential energy surface reveals hydrogen tunneling to play an important role in low‐energy decarbonylation and probably also in the ethene‐loss processes, yielding 1‐butene and methylketene cations, respectively. At higher energies, pathways without a reverse barrier open up to oxopropenyl and cyclopropanone cations by ethyl‐radical loss and a second ethene‐loss channel, respectively. A statistical Rice–Ramsperger–Kassel–Marcus model is employed to test the viability of this mechanism. The pyrolysis of cyclopentanone is studied at temperatures ranging from about 800 to 1100 K. Closed‐shell pyrolysis products, namely 1,3‐butadiene, ketene, propyne, allene, and ethene, are identified based on their photoion mass‐selected threshold photoelectron spectrum. Furthermore, reactive radical species such as allyl, propargyl, and methyl are found. A reaction mechanism is derived incorporating both stable and reactive species, which were not predicted in prior computational studies.

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“…The density of states of the reactant ion,

ρ (E)

, and the number of states of the transition state,

N^{\neq} (E - E_{0})

, are obtained based on ab initio harmonic vibrational frequencies and rotational constants. Neglecting tunneling, which may account for an apparent red shift of the appearance energy by about 100 meV, the water‐loss dissociation barrier is expected to correspond to the activation energy of H transfer to the carboxylic OH group.…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

The Distant Double Bond Determines the Fate of the Carboxylic Group in the Dissociative Photoionization of Oleic Acid

et al. 2017

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The valence threshold photoionization of oleic acid has been studied using synchrotron VUV radiation and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. An oleic acid aerosol beam was impacted on a copper thermodesorber, heated to 130 °C, to evaporate the particles quantitatively. Upon threshold photoionization, oleic acid produces the intact parent ion first, followed by dehydration at higher energies. Starting at ca. 10 eV, a large number of fragment ions slowly rise suggesting several fragmentation coordinates with quasi-degenerate activation energies. However, water loss is the dominant low-energy dissociation channel, and it is shown to be closely related to the unsaturated carbon chain. In the lowest-barrier process, one of the four allylic hydrogen atoms is transferred to the carboxyl group to form the leaving water molecule and a cyclic ketone fragment ion. A statistical model to analyze the breakdown diagram and measured rate constants yields a 0 K appearance energy of 9.77 eV, which can be compared with the density functional theory result of 9.19 eV. Alternative H-transfer steps yielding a terminal C=O group are ruled out based on energetics and kinetics arguments. Some of the previous photoionization mass spectrometric studies also reported 2 amu and 26 amu loss fragment ions, corresponding to hydrogen and acetylene loss. We could not identify such peaks in the mass spectrum of oleic acid.

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Controlling tunnelling in methane loss from acetone ions by deuteration

Cited by 22 publications

References 35 publications

Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation

Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation

Dissociative Ionization and Thermal Decomposition of Cyclopentanone

The Distant Double Bond Determines the Fate of the Carboxylic Group in the Dissociative Photoionization of Oleic Acid

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