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Title: Isomerization and dissociation in competition: The two-component dissociation rates of methyl propionate ions

Abstract

Threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy has been used to investigate the unimolecular chemistry of gas-phase methyl propionate ions. This ion undergoes isomerization to a lower energy enol structure, CH{sub 3}CHC(OH)OCH{sub 3}{sup {sm_bullet}+}, via two different pathways involving two distonic isomers, {sup {sm_bullet}}CH{sub 2}CH{sub 2}C{sup +}(OH)OCH{sub 3} and CH{sub 3}CH{sub 2}C{sup +}(OH)OCH{sub 2}{sup {sm_bullet}}. This isomerization reaction is in competition with the direct CH{sub 3}O{sup {sm_bullet}} loss reaction, which leads to two-component dissociation rates of the methyl propionate ions. Detailed modeling of this complex reaction permitted the extraction of the dissociative photoionization threshold for methyl propionate, which at 0 K is 10.83 {+-} 0.01 eV, as well as the isomerization barrier between the distonic CH{sub 3}CH{sub 2}C{sup +}(OH)OCH{sub 2}{sup {sm_bullet}} and enol CH{sub 3}CHC(OH)OCH{sub 3}{sup {sm_bullet}+} ions of 8.5 kcal/mol (relative to the methyl propionate ion). By combining this with the 0 K heats of formation of methyl propionate and the methoxy radical, the authors derive a 0 K heat of formation of the product propanoyl ion of 147 kcal/mol. Also measured was the adiabatic ionization energy of methyl propionate, 10.03 {+-} 0.05 eV.

Authors:
;  [1]
  1. Univ. of North Carolina, Chapel Hill, NC (United States). Chemistry Dept.
Publication Date:
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
349882
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory
Additional Journal Information:
Journal Volume: 103; Journal Issue: 9; Other Information: PBD: 4 Mar 1999
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; DISSOCIATION; IONS; METHOXY RADICALS; PROPIONIC ACID; PHOTOELECTRON SPECTROSCOPY; MASS SPECTROSCOPY; ISOMERIZATION; IONIZATION; REACTION KINETICS

Citation Formats

Mazyar, O A, and Baer, T. Isomerization and dissociation in competition: The two-component dissociation rates of methyl propionate ions. United States: N. p., 1999. Web. doi:10.1021/jp984322p.
Mazyar, O A, & Baer, T. Isomerization and dissociation in competition: The two-component dissociation rates of methyl propionate ions. United States. https://doi.org/10.1021/jp984322p
Mazyar, O A, and Baer, T. 1999. "Isomerization and dissociation in competition: The two-component dissociation rates of methyl propionate ions". United States. https://doi.org/10.1021/jp984322p.
@article{osti_349882,
title = {Isomerization and dissociation in competition: The two-component dissociation rates of methyl propionate ions},
author = {Mazyar, O A and Baer, T},
abstractNote = {Threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy has been used to investigate the unimolecular chemistry of gas-phase methyl propionate ions. This ion undergoes isomerization to a lower energy enol structure, CH{sub 3}CHC(OH)OCH{sub 3}{sup {sm_bullet}+}, via two different pathways involving two distonic isomers, {sup {sm_bullet}}CH{sub 2}CH{sub 2}C{sup +}(OH)OCH{sub 3} and CH{sub 3}CH{sub 2}C{sup +}(OH)OCH{sub 2}{sup {sm_bullet}}. This isomerization reaction is in competition with the direct CH{sub 3}O{sup {sm_bullet}} loss reaction, which leads to two-component dissociation rates of the methyl propionate ions. Detailed modeling of this complex reaction permitted the extraction of the dissociative photoionization threshold for methyl propionate, which at 0 K is 10.83 {+-} 0.01 eV, as well as the isomerization barrier between the distonic CH{sub 3}CH{sub 2}C{sup +}(OH)OCH{sub 2}{sup {sm_bullet}} and enol CH{sub 3}CHC(OH)OCH{sub 3}{sup {sm_bullet}+} ions of 8.5 kcal/mol (relative to the methyl propionate ion). By combining this with the 0 K heats of formation of methyl propionate and the methoxy radical, the authors derive a 0 K heat of formation of the product propanoyl ion of 147 kcal/mol. Also measured was the adiabatic ionization energy of methyl propionate, 10.03 {+-} 0.05 eV.},
doi = {10.1021/jp984322p},
url = {https://www.osti.gov/biblio/349882}, journal = {Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory},
number = 9,
volume = 103,
place = {United States},
year = {Thu Mar 04 00:00:00 EST 1999},
month = {Thu Mar 04 00:00:00 EST 1999}
}