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Title: Thermochemistry of the smallest QOOH radical from the roaming fragmentation of energy selected methyl hydroperoxide ions

Abstract

Here, the dissociative photoionization processes of methyl hydroperoxide (CH 3OOH) have been studied by imaging Photoelectron Photoion Coincidence (iPEPICO) spectroscopy experiments as well as quantum-chemical and statistical rate calculations. Energy selected CH 3OOH + ions dissociate into CH 2OOH +, HCO +, CH 3 +, and H 3O + ions in the 11.4–14.0 eV photon energy range. The lowest-energy dissociation channel is the formation of the cation of the smallest “QOOH” radical, CH 2OOH +. An extended RRKM model fitted to the experimental data yields a 0 K appearance energy of 11.647 ± 0.005 eV for the CH 2OOH + ion, and a 74.2 ± 2.6 kJ mol -1 mixed experimental-theoretical 0 K heat of formation for the CH 2OOH radical. The proton affinity of the Criegee intermediate, CH 2OO, was also obtained from the heat of formation of CH 2OOH + (792.8 ± 0.9 kJ mol -1) to be 847.7 ± 1.1 kJ mol -1, reducing the uncertainty of the previously available computational value by a factor of 4. RRKM modeling of the complex web of possible rearrangement-dissociation processes was used to model the higher-energy fragmentation. Supported by Born–Oppenheimer molecular dynamics simulations, we found that the HCO + fragmentmore » ion is produced through a roaming transition state followed by a low barrier. Lastly, H 3O + is formed in a consecutive process from the CH 2OOH + fragment ion, while direct C–O fission of the molecular ion leads to the methyl cation.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [1]
  1. Univ. of the Pacific, Stockton, CA (United States)
  2. Paul Scherrer Institute, Villigen (Switzerland)
  3. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1485834
Alternate Identifier(s):
OSTI ID: 1462769
Report Number(s):
SAND-2018-12912J
Journal ID: ISSN 1463-9076; PPCPFQ; 669829
Grant/Contract Number:  
AC04-94AL85000; NA0003525
Resource Type:
Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 20; Journal Issue: 32; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Covert, Kyle J., Voronova, Krisztina, Torma, Krisztián G., Bodi, Andras, Zádor, Judit, and Sztáray, Bálint. Thermochemistry of the smallest QOOH radical from the roaming fragmentation of energy selected methyl hydroperoxide ions. United States: N. p., 2018. Web. doi:10.1039/C8CP03168A.
Covert, Kyle J., Voronova, Krisztina, Torma, Krisztián G., Bodi, Andras, Zádor, Judit, & Sztáray, Bálint. Thermochemistry of the smallest QOOH radical from the roaming fragmentation of energy selected methyl hydroperoxide ions. United States. doi:10.1039/C8CP03168A.
Covert, Kyle J., Voronova, Krisztina, Torma, Krisztián G., Bodi, Andras, Zádor, Judit, and Sztáray, Bálint. Fri . "Thermochemistry of the smallest QOOH radical from the roaming fragmentation of energy selected methyl hydroperoxide ions". United States. doi:10.1039/C8CP03168A. https://www.osti.gov/servlets/purl/1485834.
@article{osti_1485834,
title = {Thermochemistry of the smallest QOOH radical from the roaming fragmentation of energy selected methyl hydroperoxide ions},
author = {Covert, Kyle J. and Voronova, Krisztina and Torma, Krisztián G. and Bodi, Andras and Zádor, Judit and Sztáray, Bálint},
abstractNote = {Here, the dissociative photoionization processes of methyl hydroperoxide (CH3OOH) have been studied by imaging Photoelectron Photoion Coincidence (iPEPICO) spectroscopy experiments as well as quantum-chemical and statistical rate calculations. Energy selected CH3OOH+ ions dissociate into CH2OOH+, HCO+, CH3+, and H3O+ ions in the 11.4–14.0 eV photon energy range. The lowest-energy dissociation channel is the formation of the cation of the smallest “QOOH” radical, CH2OOH+. An extended RRKM model fitted to the experimental data yields a 0 K appearance energy of 11.647 ± 0.005 eV for the CH2OOH+ ion, and a 74.2 ± 2.6 kJ mol-1 mixed experimental-theoretical 0 K heat of formation for the CH2OOH radical. The proton affinity of the Criegee intermediate, CH2OO, was also obtained from the heat of formation of CH2OOH+ (792.8 ± 0.9 kJ mol-1) to be 847.7 ± 1.1 kJ mol-1, reducing the uncertainty of the previously available computational value by a factor of 4. RRKM modeling of the complex web of possible rearrangement-dissociation processes was used to model the higher-energy fragmentation. Supported by Born–Oppenheimer molecular dynamics simulations, we found that the HCO+ fragment ion is produced through a roaming transition state followed by a low barrier. Lastly, H3O+ is formed in a consecutive process from the CH2OOH+ fragment ion, while direct C–O fission of the molecular ion leads to the methyl cation.},
doi = {10.1039/C8CP03168A},
journal = {Physical Chemistry Chemical Physics. PCCP (Print)},
number = 32,
volume = 20,
place = {United States},
year = {2018},
month = {7}
}

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