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Title: Reaction of the C2H radical with 1-butyne (C4H6): Low Temperature Kinetics and Isomer-Specific Product Detection

Abstract

The rate coefficient for the reaction of the ethynyl radical (C{sub 2}H) with 1-butyne (H-C{triple_bond}C-CH{sub 2}-CH{sub 3}) is measured in a pulsed Laval nozzle apparatus. Ethynyl radicals are formed by laser photolysis of acetylene (C{sub 2}H{sub 2}) at 193 nm and detected via chemiluminescence (C{sub 2}H + O{sub 2} {yields} CH (A{sup 2}{Delta}) + CO{sub 2}). The rate coefficients are measured over the temperature range of 74-295 K. The C{sub 2}H + 1-butyne reaction exhibits no barrier and occurs with rate constants close to the collision limit. The temperature dependent rate coefficients can be fit within experimental uncertainties by the expression k = (2.4 {+-} 0.5) x 10{sup -10} (T/295 K)-(0.04 {+-} 0.03) cm{sup 3} molecule{sup -1}s{sup -1}. Reaction products are detected at room temperature (295 K) and 533 Pa using a Multiplexed Photoionization Mass Spectrometer (MPIMS) coupled to the tunable VUV synchrotron radiation from the Advanced Light Source at the Lawrence Berkeley National Laboratory. Two product channels are identified for this reaction: m/z = 64 (C{sub 5}H{sub 4}) and m/z = 78 (C{sub 6}H{sub 6}) corresponding to the CH{sub 3}- and H-loss channels, respectively. Photoionization efficiency (PIE) curves are used to analyze the isomeric composition of both product channels.more » The C{sub 5}H{sub 4} products are found to be exclusively linear isomers composed of ethynylallene and methyldiacetylene in a 4:1 ratio. In contrast, the C{sub 6}H{sub 6} product channel includes two cyclic isomers, fulvene 18({+-}5)% and 3,4-dimethylenecyclobut-1-ene 32({+-}8)%, as well as three linear isomers, 2-ethynyl-1,3-butadiene 8({+-}5)%, 3,4-hexadiene-1-yne 28({+-}8)% and 1,3-hexadiyne 14({+-}5)%. Within experimental uncertainties, we do not see appreciable amounts of benzene and an upper limit of 10% is estimated. Diacetylene (C{sub 4}H{sub 2}) formation via the C{sub 2}H{sub 5}-loss channel is also thermodynamically possible but cannot be observed due to experimental limitations. The implications of these results for modeling of planetary atmospheres, especially of Saturn's largest moon Titan, are discussed.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
Chemical Sciences Division
OSTI Identifier:
983173
Report Number(s):
LBNL-3312E
Journal ID: ISSN 0022-3654; JPCHAX; TRN: US1004569
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry
Additional Journal Information:
Journal Name: Journal of Physical Chemistry; Journal ID: ISSN 0022-3654
Country of Publication:
United States
Language:
English
Subject:
99; 37; ACETYLENE; ADVANCED LIGHT SOURCE; BENZENE; CHEMILUMINESCENCE; DETECTION; EFFICIENCY; ISOMERS; KINETICS; LASERS; MASS SPECTROMETERS; NOZZLES; PHOTOIONIZATION; PHOTOLYSIS; PLANETARY ATMOSPHERES; RADICALS; SYNCHROTRON RADIATION; Reaction, radical, butyne, Low Temperature Kinetics, Isomer-Specific, Detection

Citation Formats

Soorkia, Satchin, Trevitt, Adam J, Selby, Talitha M, Osborn, David L, Taatjes, Craig A, Wilson, Kevin R, and Leone, Stephen R. Reaction of the C2H radical with 1-butyne (C4H6): Low Temperature Kinetics and Isomer-Specific Product Detection. United States: N. p., 2009. Web.
Soorkia, Satchin, Trevitt, Adam J, Selby, Talitha M, Osborn, David L, Taatjes, Craig A, Wilson, Kevin R, & Leone, Stephen R. Reaction of the C2H radical with 1-butyne (C4H6): Low Temperature Kinetics and Isomer-Specific Product Detection. United States.
Soorkia, Satchin, Trevitt, Adam J, Selby, Talitha M, Osborn, David L, Taatjes, Craig A, Wilson, Kevin R, and Leone, Stephen R. Tue . "Reaction of the C2H radical with 1-butyne (C4H6): Low Temperature Kinetics and Isomer-Specific Product Detection". United States. https://www.osti.gov/servlets/purl/983173.
@article{osti_983173,
title = {Reaction of the C2H radical with 1-butyne (C4H6): Low Temperature Kinetics and Isomer-Specific Product Detection},
author = {Soorkia, Satchin and Trevitt, Adam J and Selby, Talitha M and Osborn, David L and Taatjes, Craig A and Wilson, Kevin R and Leone, Stephen R},
abstractNote = {The rate coefficient for the reaction of the ethynyl radical (C{sub 2}H) with 1-butyne (H-C{triple_bond}C-CH{sub 2}-CH{sub 3}) is measured in a pulsed Laval nozzle apparatus. Ethynyl radicals are formed by laser photolysis of acetylene (C{sub 2}H{sub 2}) at 193 nm and detected via chemiluminescence (C{sub 2}H + O{sub 2} {yields} CH (A{sup 2}{Delta}) + CO{sub 2}). The rate coefficients are measured over the temperature range of 74-295 K. The C{sub 2}H + 1-butyne reaction exhibits no barrier and occurs with rate constants close to the collision limit. The temperature dependent rate coefficients can be fit within experimental uncertainties by the expression k = (2.4 {+-} 0.5) x 10{sup -10} (T/295 K)-(0.04 {+-} 0.03) cm{sup 3} molecule{sup -1}s{sup -1}. Reaction products are detected at room temperature (295 K) and 533 Pa using a Multiplexed Photoionization Mass Spectrometer (MPIMS) coupled to the tunable VUV synchrotron radiation from the Advanced Light Source at the Lawrence Berkeley National Laboratory. Two product channels are identified for this reaction: m/z = 64 (C{sub 5}H{sub 4}) and m/z = 78 (C{sub 6}H{sub 6}) corresponding to the CH{sub 3}- and H-loss channels, respectively. Photoionization efficiency (PIE) curves are used to analyze the isomeric composition of both product channels. The C{sub 5}H{sub 4} products are found to be exclusively linear isomers composed of ethynylallene and methyldiacetylene in a 4:1 ratio. In contrast, the C{sub 6}H{sub 6} product channel includes two cyclic isomers, fulvene 18({+-}5)% and 3,4-dimethylenecyclobut-1-ene 32({+-}8)%, as well as three linear isomers, 2-ethynyl-1,3-butadiene 8({+-}5)%, 3,4-hexadiene-1-yne 28({+-}8)% and 1,3-hexadiyne 14({+-}5)%. Within experimental uncertainties, we do not see appreciable amounts of benzene and an upper limit of 10% is estimated. Diacetylene (C{sub 4}H{sub 2}) formation via the C{sub 2}H{sub 5}-loss channel is also thermodynamically possible but cannot be observed due to experimental limitations. The implications of these results for modeling of planetary atmospheres, especially of Saturn's largest moon Titan, are discussed.},
doi = {},
journal = {Journal of Physical Chemistry},
issn = {0022-3654},
number = ,
volume = ,
place = {United States},
year = {2009},
month = {12}
}