Further dehydrogenation of 2‐cyclopenten‐1‐one may yield 2,4‐cyclopentadien‐1‐one. If the information still cannot be found, contact our Certificate of Analysis department at COFA@SpectrumChemical.com or call 800-772-8786 and select Option 6 then Option 2 and then Option 1. As shown in Figures 2 A and B, the model reproduces the observed ion abundances and dissociation rates quite well, thereby validating the dissociative photoionization mechanism. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. In the photoionization mass spectra reported by Chambreau et al.,37 products are also seen in the mass channels corresponding to vinylacetylene (C4H4) and vinyl (C2H3). IMPORTANT UPDATE - All sales after March 2, 2020 are final and non-returnable for COVID-19 related items. This MassBank Record with Accession JP002304 contains the MS mass spectrum of '2-(DIMETHOXYMETHYL)CYCLOPENTANONE'. A small contribution of propene to the overall m/z 42 ms‐TPES cannot be ruled out. Pallet), Pallet Charge (Plastic Journal of Analytical and Applied Pyrolysis. acknowledge funding by the Swiss Federal Office for Energy (BFE Contract number SI/501269‐01). Lastly, a noticeable difference lies in the CO‐loss channel. Please make sure the Catalog Number and Lot Number are entered and click the Enter button. In the breakdown diagram in Figure 2 A, the fractional abundance of parent and fragment ions detected in threshold photoionization of the room‐temperature sample is plotted as a function of photon energy. Dots correspond to experimental data, continuous lines represent the statistical model fits. 0.1 %), secondary reactions initiated by atomic hydrogen may have a small contribution to the formation of the observed products, or isomerization thereof. This work was further supported by NWO Exacte Wetenschappen (Physical Sciences) for the use of the supercomputer facilities at SurfSara. The experimental findings on the dissociative ionization are rationalized by hydrogen tunneling and a model is constructed to test the viability of this fragmentation mechanism. The m/z 56 peak exhibits a quasi‐exponential decay to higher TOF, which is indicative of fragmentation in the acceleration region of the mass spectrometer, and—in the experimental configuration used in this work—a unimolecular rate constant of 104–107 s−1. Create . Moreover, these studies were not sensitive to reactive intermediates, which could provide important clues to the overall chemistry. Time‐of‐flight mass spectrum of cyclopentanone pyrolysis products formed at about 1100 K and ionized at 10.5 eV constructed from coincidences of all photoelectrons regardless of their position on the detector (i.e., energy) with photoions. The pyrolysis of cyclic ketones has been studied in some detail. The fragmentation of the ions is dominated by loss of CO, C2H4, and C2H5, leading to daughter ions at m/z 56 and 55. Upon ionization through the X̃+ 2B←X̃ 1A transition, electron density is removed from the HOMO, leading to a 0.02 Å contraction of the C=O bond and a 0.03 Å elongation of the two (O=)C−C bonds, as predicted by B3LYP/6–311++G(d,p) geometry optimization of the neutral and ionic ground state. Coincidences between electrons and cations were plotted as a function of delay time to yield the TOF mass spectra. A list with that name already exists. Zaras et al.11 characterized the energetics of the unimolecular dissociation of cyclopentanone using the composite G3B3 method. Tariff … The mass spectrum was acquired on a EI-B with POSITIVE ionisation and has the SPLASH 'splash10-004i-9100000000-abeab23508923cc141f7'. J.B. acknowledges the Netherlands Organisation for Scientific Research (NWO) for a VENI grant (Grant number 722.013.014). Use the link below to share a full-text version of this article with your friends and colleagues. Due to the strong transition at 10.5 eV, the m/z 28 is assigned to ethylene.34 Carbon monoxide could contribute to this mass channel as well, but its ionization threshold is 14.01 eV,35 beyond the photon energy range of this study. specific. The peaks at 55 and 56 amu are attributed to dissociative photoionization of thermally excited cyclopentanone as described in the previous section, while all other products are formed by pyrolysis. Decomposition pathways of cyclopentanone and cyclopentenone through α‐, β‐, and γ‐cleavage. The mass spectra also establish the 55 and 56 amu ion signals as the sole dominant low‐energy dissociative photoionization products. 2020-10-24 . Cyclopentanone pyrolysis products are compared to those predicted in a previous computational study to pin down the underlying dissociation mechanism. In this study, ketene, allene, and propyne as well as the radicals allyl, propargyl, vinyl and methyl have also been identified. A pyrolysis mechanism is proposed and discussed in light of the recent findings on cyclohexanone pyrolysis. Computed bond dissociation energies (BDE) are taken from Zaras et al.11. Threshold photoelectron spectra were plotted by selecting only the central spot on the electron detector and subtracting the “hot” electron background.45 Cations were accelerated in the opposite direction in a Wiley‐McLaren type TOF configuration and detected with a microchannel plate (MCP) detector. Allene, propyne, and cyclopropene can be responsible for the fragment detected at m/z 40. In this work, we find that this channel is significantly higher (by 0.2 eV) in energy at 1.97 eV with respect to the cation (11.26 eV w.r.t. Literature data to validate the theoretical computations on cyclopentanone dissociation are scarce. The computational results on the neutral cyclopentanone potential energy surface (PES) were employed to calculate rate constants of the initial isomerization steps over the 800–2000 K temperature range by using Rice–Ramsperger–Kassel–Marcus (RRKM) modeling.
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