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Title: Photodissociation and photoisomerization of {alpha}-fluorotoluene and 4-fluorotoluene in a molecular beam

Abstract

The photodissociation of jet-cooled {alpha}-fluorotoluene and 4-fluorotoluene at 193 and 248 nm was studied using vacuum ultraviolet (vuv) photoionization/multimass ion imaging techniques as well as electron impact ionization/photofragment translational spectroscopy. Four dissociation channels were observed for {alpha}-fluorotoluene at both 193 and 248 nm, including two major channels C{sub 6}H{sub 5}CH{sub 2}F{yields}C{sub 6}H{sub 5}CH{sub 2} (or C{sub 7}H{sub 7})+F and C{sub 6}H{sub 5}CH{sub 2}F{yields}C{sub 6}H{sub 5}CH (or C{sub 7}H{sub 6})+HF and two minor channels C{sub 6}H{sub 5}CH{sub 2}F{yields}C{sub 6}H{sub 5}CHF+H and C{sub 6}H{sub 5}CH{sub 2}F{yields}C{sub 6}H{sub 5}+CH{sub 2}F. The vuv wavelength dependence of the C{sub 7}H{sub 7} fragment photoionization spectra indicates that at least part of the F atom elimination channel results from the isomerization of {alpha}-fluorotoluene to a seven-membered ring prior to dissociation. Dissociation channels of 4-fluorotoluene at 193 nm include two major channels C{sub 6}H{sub 4}FCH{sub 3}{yields}C{sub 6}H{sub 4}FCH{sub 2}+H and C{sub 6}H{sub 4}FCH{sub 3}{yields}C{sub 6}H{sub 4}F+CH{sub 3} and two minor channels C{sub 6}H{sub 4}FCH{sub 3}{yields}C{sub 6}H{sub 5}CH{sub 2} (or C{sub 7}H{sub 7})+F and C{sub 6}H{sub 4}FCH{sub 3}{yields}C{sub 6}H{sub 5}CH (or C{sub 7}H{sub 6})+HF. The dissociation rates for {alpha}-fluorotoluene at 193 and 248 nm are 3.3x10{sup 7} and 5.6x10{sup 5} s{sup -1}, respectively. The dissociation rate for 4-fluorotoluene atmore » 193 nm is 1.0x10{sup 6} s{sup -1}. An ab initio calculation demonstrates that the barrier height for isomerization from {alpha}-fluorotoluene to a seven-membered ring isomer is much lower than that from 4-fluorotoluene to a seven-membered ring isomer. The experimental observed differences of dissociation rates and relative branching ratios between {alpha}-fluorotoluene and 4-fluorotoluene may be explained by the differences in the six-membered ring to seven-membered ring isomerization barrier heights, F atom elimination threshold, and HF elimination threshold between {alpha}-fluorotoluene and 4-fluorotoluene.« less

Authors:
; ; ; ; ; ; ;  [1]
  1. Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10617 (China)
Publication Date:
OSTI Identifier:
20864301
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 125; Journal Issue: 13; Other Information: DOI: 10.1063/1.2219445; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BRANCHING RATIO; DISSOCIATION; ELECTRONS; FAR ULTRAVIOLET RADIATION; HYDROFLUORIC ACID; ISOMERIZATION; ISOMERS; MOLECULAR BEAMS; ORGANIC FLUORINE COMPOUNDS; PHOTOCHEMISTRY; PHOTOIONIZATION; PHOTOLYSIS; REACTION KINETICS; SPECTROSCOPY; TOLUENE

Citation Formats

Huang, C -L, Jiang, J -C, Dyakov, Yuri A, Lin, M -F, Tseng, C -M, Lin, S H, Lee, Yuan T, and Ni, C -K. Photodissociation and photoisomerization of {alpha}-fluorotoluene and 4-fluorotoluene in a molecular beam. United States: N. p., 2006. Web. doi:10.1063/1.2219445.
Huang, C -L, Jiang, J -C, Dyakov, Yuri A, Lin, M -F, Tseng, C -M, Lin, S H, Lee, Yuan T, & Ni, C -K. Photodissociation and photoisomerization of {alpha}-fluorotoluene and 4-fluorotoluene in a molecular beam. United States. https://doi.org/10.1063/1.2219445
Huang, C -L, Jiang, J -C, Dyakov, Yuri A, Lin, M -F, Tseng, C -M, Lin, S H, Lee, Yuan T, and Ni, C -K. Sat . "Photodissociation and photoisomerization of {alpha}-fluorotoluene and 4-fluorotoluene in a molecular beam". United States. https://doi.org/10.1063/1.2219445.
@article{osti_20864301,
title = {Photodissociation and photoisomerization of {alpha}-fluorotoluene and 4-fluorotoluene in a molecular beam},
author = {Huang, C -L and Jiang, J -C and Dyakov, Yuri A and Lin, M -F and Tseng, C -M and Lin, S H and Lee, Yuan T and Ni, C -K},
abstractNote = {The photodissociation of jet-cooled {alpha}-fluorotoluene and 4-fluorotoluene at 193 and 248 nm was studied using vacuum ultraviolet (vuv) photoionization/multimass ion imaging techniques as well as electron impact ionization/photofragment translational spectroscopy. Four dissociation channels were observed for {alpha}-fluorotoluene at both 193 and 248 nm, including two major channels C{sub 6}H{sub 5}CH{sub 2}F{yields}C{sub 6}H{sub 5}CH{sub 2} (or C{sub 7}H{sub 7})+F and C{sub 6}H{sub 5}CH{sub 2}F{yields}C{sub 6}H{sub 5}CH (or C{sub 7}H{sub 6})+HF and two minor channels C{sub 6}H{sub 5}CH{sub 2}F{yields}C{sub 6}H{sub 5}CHF+H and C{sub 6}H{sub 5}CH{sub 2}F{yields}C{sub 6}H{sub 5}+CH{sub 2}F. The vuv wavelength dependence of the C{sub 7}H{sub 7} fragment photoionization spectra indicates that at least part of the F atom elimination channel results from the isomerization of {alpha}-fluorotoluene to a seven-membered ring prior to dissociation. Dissociation channels of 4-fluorotoluene at 193 nm include two major channels C{sub 6}H{sub 4}FCH{sub 3}{yields}C{sub 6}H{sub 4}FCH{sub 2}+H and C{sub 6}H{sub 4}FCH{sub 3}{yields}C{sub 6}H{sub 4}F+CH{sub 3} and two minor channels C{sub 6}H{sub 4}FCH{sub 3}{yields}C{sub 6}H{sub 5}CH{sub 2} (or C{sub 7}H{sub 7})+F and C{sub 6}H{sub 4}FCH{sub 3}{yields}C{sub 6}H{sub 5}CH (or C{sub 7}H{sub 6})+HF. The dissociation rates for {alpha}-fluorotoluene at 193 and 248 nm are 3.3x10{sup 7} and 5.6x10{sup 5} s{sup -1}, respectively. The dissociation rate for 4-fluorotoluene at 193 nm is 1.0x10{sup 6} s{sup -1}. An ab initio calculation demonstrates that the barrier height for isomerization from {alpha}-fluorotoluene to a seven-membered ring isomer is much lower than that from 4-fluorotoluene to a seven-membered ring isomer. The experimental observed differences of dissociation rates and relative branching ratios between {alpha}-fluorotoluene and 4-fluorotoluene may be explained by the differences in the six-membered ring to seven-membered ring isomerization barrier heights, F atom elimination threshold, and HF elimination threshold between {alpha}-fluorotoluene and 4-fluorotoluene.},
doi = {10.1063/1.2219445},
url = {https://www.osti.gov/biblio/20864301}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 13,
volume = 125,
place = {United States},
year = {2006},
month = {10}
}