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Fernholz C, Bodi A, Hemberger P. Threshold Photoelectron Spectrum of the Phenoxy Radical. J Phys Chem A 2022; 126:9022-9030. [DOI: 10.1021/acs.jpca.2c06670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christin Fernholz
- Laboratory for Synchtrotron Radiation and Femtochemistry, Paul Scherrer Institute, Forschungsstrasse 111, CH-5232Villigen, Switzerland
| | - Andras Bodi
- Laboratory for Synchtrotron Radiation and Femtochemistry, Paul Scherrer Institute, Forschungsstrasse 111, CH-5232Villigen, Switzerland
| | - Patrick Hemberger
- Laboratory for Synchtrotron Radiation and Femtochemistry, Paul Scherrer Institute, Forschungsstrasse 111, CH-5232Villigen, Switzerland
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Li Y, Chen W, Zhu L, Wang H, Guan J, Shan X, Liu F, Wang Z. Intramolecular CH 3-migration-controlled cation reactions in the VUV photochemistry of 2-methyl-3-buten-2-ol investigated by synchrotron photoionization mass spectrometry and theoretical calculations. Phys Chem Chem Phys 2021; 23:10456-10467. [PMID: 33890587 DOI: 10.1039/d1cp00490e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
2-Methyl-3-buten-2-ol (MBO232) is a biogenic volatile organic compound (BVOC), and has a large percentage of emission into the atmosphere. The vacuum ultraviolet (VUV) photochemistry of BVOCs is of great importance for atmospheric chemistry. Studies have been carried out on several BVOCs but have not extended to MBO232. In the present report, the photoionization and dissociation processes of MBO232 in the energy range of 8.0-15.0 eV have been studied by tunable VUV synchrotron radiation coupled with a time-of-flight mass spectrometer. By measuring the photoionization spectra, the adiabatic ionization energy (AIE) of MBO232 and the appearance energies (AEs) of the eight identified fragment ions (i.e., C4H7O+, C3H7O+, C5H9+, C3H6O+, CH3CO+, CH3O+, C4H5+, and C3H5+) were determined. High-level quantum chemistry calculations suggest that there are 3 direct channels and 5 indirect channels via transition states and intermediates accountable for these fragments. Among the reaction channels, the direct elimination of CH3 is the most dominant channel and produces the resonance-stabilized radical cation. Most interestingly, our results show that the CH3 selectively migrates towards the cation, which leads to the different indirect channels. The CH3 migration is a rare process in the dissociative photoionization of metal-free organic molecules. We explain the process by molecular orbital calculations and electron localization function analysis and explore the non-conventional dissociation channels via the CH3 roaming mechanism. We further perform kinetics analysis using RRKM theory for the channels of interest. The activation barrier, and rate constants are analyzed for the branching fractions of the products. These results provide important implications for the VUV photochemistry of BVOCs in the atmosphere.
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Affiliation(s)
- Yanbo Li
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China.
| | - Weiye Chen
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China.
| | - Long Zhu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China.
| | - Huanhuan Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China.
| | - Jiwen Guan
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China.
| | - Xiaobin Shan
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China.
| | - Fuyi Liu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China.
| | - Zhandong Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China.
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Wu X, Zhou X, Bjelić S, Hemberger P, Bodi A. Valence Photoionization and Energetics of Vanillin, a Sustainable Feedstock Candidate. J Phys Chem A 2021; 125:3327-3340. [PMID: 33872037 DOI: 10.1021/acs.jpca.1c00876] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We studied the valence photoionization of vanillin by photoelectron photoion coincidence spectroscopy in the 8.20-19.80 eV photon energy range. Vertical ionization energies by EOM-IP-CCSD calculations reproduce the photoelectron spectral features. Composite method calculations and Franck-Condon simulation of the weak, ground-state band yield the adiabatic ionization energy of the most stable vanillin conformer as 8.306(20) eV. The lowest energy dissociative photoionization channels correspond to hydrogen atom, carbon monoxide, and methyl losses, which form the dominant C8H7O3+ (m/z 151) and the less intense C7H8O2+ (m/z 124) and C7H5O3+ (m/z 137) fragment ions in parallel dissociation channels at modeled 0 K appearance energies of 10.13(1), 10.40(3), and 10.58(10) eV, respectively. On the basis of the breakdown diagram, we explore the energetics of sequential methyl and carbon monoxide loss channels, which dominate the fragmentation mechanism at higher photon energies. The 0 K appearance energy for sequential CO loss from the m/z 151 fragment to C7H7O2+ (m/z 123) is 12.99(10) eV, and for sequential CH3 loss from the m/z 123 fragment to C6H4O2+ (m/z 108), it is 15.40(20) eV based on the model. Finally, we review the thermochemistry of the bi- and trifunctionalized benzene derivatives guaiacol, hydroxybenzaldehyde, anisaldehyde, and vanillin. On the basis of isodesmic functional group exchange reactions, we propose new enthalpies of formations, among them ΔfH°298K(vanillin, g) = -383.5 ± 2.9 kJ mol-1. These mechanistic insights and ab initio thermochemistry results will support analytical works to study lignin conversion involving vanillin.
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Affiliation(s)
- Xiangkun Wu
- Paul Scherrer Institute, 5232 Villigen, Switzerland.,Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoguo Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Saša Bjelić
- Paul Scherrer Institute, 5232 Villigen, Switzerland
| | | | - Andras Bodi
- Paul Scherrer Institute, 5232 Villigen, Switzerland
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Weidner P, Ray AW, Bodi A, Sztáray B. Dissociative Photoionization of Methyl Vinyl Ketone-Thermochemical Anchors and a Drifting Methyl Group. J Phys Chem A 2021; 125:848-856. [PMID: 33464085 DOI: 10.1021/acs.jpca.0c10665] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The dissociative photoionization of methyl vinyl ketone (MVK), an important intermediate in the atmospheric oxidation of isoprene, has been studied by photoelectron photoion coincidence spectroscopy. In the photon energy range of 9.5-13.8 eV, four main fragment ions were detected at m/z 55, 43, 42, and 27 aside from the parent ion at m/z 70. The m/z 55 fragment ion (C2H3CO+) is formed from ionized MVK by direct methyl loss, while breaking the C-C bond on the other side of the carbonyl group results in the acetyl cation (CH3CO+, m/z 43) and the vinyl radical. The m/z 42 fragment ion is formed via a CO-loss from the molecular ion after a methyl shift. The lightest fragment ion, the vinyl cation (C2H3+ at m/z 27), is produced in two different reactions: acetyl radical loss from the molecular ion and CO-loss from C2H3CO+. Their contributions to the m/z 27 signal are quantified based on the acetyl and vinyl fragment thermochemical anchors and quantum chemical calculations. Based on the experimentally derived appearance energy of the m/z 43 fragment ion, a new, experimentally derived heat of formation is proposed herein for gaseous methyl vinyl ketone (ΔfH0K = -94.3 ± 4.8 kJ mol-1; ΔfH298K = -110.5 ± 4.8 kJ mol-1), together with cationic heats of formation and bond dissociation energies.
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Affiliation(s)
- Peter Weidner
- Department of Chemistry, University of the Pacific, Stockton, California 95211, United States
| | - Amelia W Ray
- Department of Chemistry, University of the Pacific, Stockton, California 95211, United States
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, Villigen 5232, Switzerland
| | - Bálint Sztáray
- Department of Chemistry, University of the Pacific, Stockton, California 95211, United States
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Hemberger P, Pan Z, Bodi A, Bokhoven JA, Ormond TK, Ellison GB, Genossar N, Baraban JH. The Threshold Photoelectron Spectrum of Fulvenone: A Reactive Ketene Derivative in Lignin Valorization. Chemphyschem 2020; 21:2217-2222. [DOI: 10.1002/cphc.202000477] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 06/29/2020] [Indexed: 11/07/2022]
Affiliation(s)
- Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry Paul Scherrer Institute CH-5232 Villigen PSI Switzerland
| | - Zeyou Pan
- Laboratory for Synchrotron Radiation and Femtochemistry Paul Scherrer Institute CH-5232 Villigen PSI Switzerland
- Institute for Chemical and Bioengineering Department of Chemistry and Applied Biosciences ETH Zurich Zurich Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry Paul Scherrer Institute CH-5232 Villigen PSI Switzerland
| | - Jeroen A. Bokhoven
- Institute for Chemical and Bioengineering Department of Chemistry and Applied Biosciences ETH Zurich Zurich Switzerland
- Laboratory for Catalysis and Sustainable Chemistry Paul Scherrer Institute CH-5232 Villigen PSI Switzerland
| | - Thomas K. Ormond
- Department of Chemistry and Biochemistry University of Colorado Boulder Colorado 80309-0215 United States
| | - G. Barney Ellison
- Department of Chemistry and Biochemistry University of Colorado Boulder Colorado 80309-0215 United States
| | - Nadav Genossar
- Department of Chemistry Ben Gurion University of the Negev Beer Sheva 84105 Israel
- Israel Atomic Energy Commission Tel Aviv 61070 Israel
| | - Joshua H. Baraban
- Department of Chemistry Ben Gurion University of the Negev Beer Sheva 84105 Israel
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Wu X, Zhou X, Hemberger P, Bodi A. Conformers, electronic states, and diabolical conical intersections in the valence photoelectron spectroscopy of halocyclohexanes. J Chem Phys 2020; 153:054305. [DOI: 10.1063/5.0018293] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Xiangkun Wu
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoguo Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
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Suwannakham P, Sagarik K. Unimolecular photolysis mechanisms of formamide: the effect of thermal energy. Phys Chem Chem Phys 2020; 22:25789-25802. [DOI: 10.1039/d0cp03718d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The C–N dissociation is the most favorable in S1 state, and radical products (1) are precursors in other channels.
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Affiliation(s)
- Parichart Suwannakham
- School of Chemistry
- Institute of Science, Suranaree University of Technology
- Nakhon Ratchasima 30000
- Thailand
| | - Kritsana Sagarik
- School of Chemistry
- Institute of Science, Suranaree University of Technology
- Nakhon Ratchasima 30000
- Thailand
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