Fragmentation of two dimethylaluminum peroxy radical isomers formed by the hypergolic reaction of trimethyl aluminum with O2

Trong Nghia Nguyen; Phuong H. Trac; M. C. Lin

doi:10.1016/j.comptc.2021.113436

Fragmentation of two dimethylaluminum peroxy radical isomers formed by the hypergolic reaction of trimethyl aluminum with O₂

Trong Nghia Nguyen, Phuong H. Trac, M. C. Lin^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

We have investigated computationally the kinetics and mechanisms for the fragmentation of the (CH₃)₂Al(O)O and CH₃Al(O)OCH₃ radicals formed by different O₂-for-CH₃ substitution reactions of (CH₃)₃Al with O₂ at the CCSD(T)//6-311++G(3df,2p)//B3LYP/6-311++G(3df,2p) level of theory. The fragmentation of these radicals may play a key role in the chain-propagation of hypergolic combustion of trimethyl aluminum in air under ambient conditions. Rate constants for various product channels have been calculated under different pressures between 100 and 7600 Torr at temperatures from 300 to 2000 K. Among the many fragmentation processes of the CH₃Al(O)OCH₃ radical, produced by the predominant (CH₃)₃Al + O₂ reaction, its exothermic isomerization to CH₂Al(OH)OCH₃ (−26.7 kcal/mol) with a small barrier (9.7 kcal/mol), to be followed by decomposition giving a reactive product pair CH₃AlOH + CH₂O with a small endothermicity of 15.8 kcal/mol is believed to be most important. The ensuing exothermic and barrierless reaction of CH₃AlOH with O₂ gives rise to a ring intermediate, cy_CH₃Al(O₂)OH (−70.5 kcal/mol), which readily fragments to HOAlO₂ + CH₃ with an overall exothermicity of 21.7 kcal/mol. The (CH₃)₂Al(O)O radical isomer, which is effectively the association complex of (CH₃)₂Al and O₂, on the other hand, is stable and has no low-energy exit paths to reactive products including its isomer CH₃Al(O)OCH₃. Rate constants for the three key reactions leading to the ultimate formation of CH₃ + HOAlO₂ + CH₂O have been calculated for combustion modeling applications.

Original language	English
Article number	113436
Journal	Computational and Theoretical Chemistry
Volume	1205
DOIs	https://doi.org/10.1016/j.comptc.2021.113436
State	Published - Nov 2021

Keywords

(CH)Al
(CH)AlO
Ab initio chemical kinetics
O

Access to Document

10.1016/j.comptc.2021.113436

Cite this

@article{240dcdcfdfe1415fa8196939de9951ed,

title = "Fragmentation of two dimethylaluminum peroxy radical isomers formed by the hypergolic reaction of trimethyl aluminum with O2",

abstract = "We have investigated computationally the kinetics and mechanisms for the fragmentation of the (CH3)2Al(O)O and CH3Al(O)OCH3 radicals formed by different O2-for-CH3 substitution reactions of (CH3)3Al with O2 at the CCSD(T)//6-311++G(3df,2p)//B3LYP/6-311++G(3df,2p) level of theory. The fragmentation of these radicals may play a key role in the chain-propagation of hypergolic combustion of trimethyl aluminum in air under ambient conditions. Rate constants for various product channels have been calculated under different pressures between 100 and 7600 Torr at temperatures from 300 to 2000 K. Among the many fragmentation processes of the CH3Al(O)OCH3 radical, produced by the predominant (CH3)3Al + O2 reaction, its exothermic isomerization to CH2Al(OH)OCH3 (−26.7 kcal/mol) with a small barrier (9.7 kcal/mol), to be followed by decomposition giving a reactive product pair CH3AlOH + CH2O with a small endothermicity of 15.8 kcal/mol is believed to be most important. The ensuing exothermic and barrierless reaction of CH3AlOH with O2 gives rise to a ring intermediate, cy_CH3Al(O2)OH (−70.5 kcal/mol), which readily fragments to HOAlO2 + CH3 with an overall exothermicity of 21.7 kcal/mol. The (CH3)2Al(O)O radical isomer, which is effectively the association complex of (CH3)2Al and O2, on the other hand, is stable and has no low-energy exit paths to reactive products including its isomer CH3Al(O)OCH3. Rate constants for the three key reactions leading to the ultimate formation of CH3 + HOAlO2 + CH2O have been calculated for combustion modeling applications.",

keywords = "(CH)Al, (CH)AlO, Ab initio chemical kinetics, O",

author = "Nguyen, {Trong Nghia} and Trac, {Phuong H.} and Lin, {M. C.}",

note = "Publisher Copyright: {\textcopyright} 2021",

year = "2021",

month = nov,

doi = "10.1016/j.comptc.2021.113436",

language = "English",

volume = "1205",

journal = "Computational and Theoretical Chemistry",

issn = "2210-271X",

publisher = "Elsevier BV",

}

TY - JOUR

T1 - Fragmentation of two dimethylaluminum peroxy radical isomers formed by the hypergolic reaction of trimethyl aluminum with O2

AU - Nguyen, Trong Nghia

AU - Trac, Phuong H.

AU - Lin, M. C.

PY - 2021/11

Y1 - 2021/11

N2 - We have investigated computationally the kinetics and mechanisms for the fragmentation of the (CH3)2Al(O)O and CH3Al(O)OCH3 radicals formed by different O2-for-CH3 substitution reactions of (CH3)3Al with O2 at the CCSD(T)//6-311++G(3df,2p)//B3LYP/6-311++G(3df,2p) level of theory. The fragmentation of these radicals may play a key role in the chain-propagation of hypergolic combustion of trimethyl aluminum in air under ambient conditions. Rate constants for various product channels have been calculated under different pressures between 100 and 7600 Torr at temperatures from 300 to 2000 K. Among the many fragmentation processes of the CH3Al(O)OCH3 radical, produced by the predominant (CH3)3Al + O2 reaction, its exothermic isomerization to CH2Al(OH)OCH3 (−26.7 kcal/mol) with a small barrier (9.7 kcal/mol), to be followed by decomposition giving a reactive product pair CH3AlOH + CH2O with a small endothermicity of 15.8 kcal/mol is believed to be most important. The ensuing exothermic and barrierless reaction of CH3AlOH with O2 gives rise to a ring intermediate, cy_CH3Al(O2)OH (−70.5 kcal/mol), which readily fragments to HOAlO2 + CH3 with an overall exothermicity of 21.7 kcal/mol. The (CH3)2Al(O)O radical isomer, which is effectively the association complex of (CH3)2Al and O2, on the other hand, is stable and has no low-energy exit paths to reactive products including its isomer CH3Al(O)OCH3. Rate constants for the three key reactions leading to the ultimate formation of CH3 + HOAlO2 + CH2O have been calculated for combustion modeling applications.

AB - We have investigated computationally the kinetics and mechanisms for the fragmentation of the (CH3)2Al(O)O and CH3Al(O)OCH3 radicals formed by different O2-for-CH3 substitution reactions of (CH3)3Al with O2 at the CCSD(T)//6-311++G(3df,2p)//B3LYP/6-311++G(3df,2p) level of theory. The fragmentation of these radicals may play a key role in the chain-propagation of hypergolic combustion of trimethyl aluminum in air under ambient conditions. Rate constants for various product channels have been calculated under different pressures between 100 and 7600 Torr at temperatures from 300 to 2000 K. Among the many fragmentation processes of the CH3Al(O)OCH3 radical, produced by the predominant (CH3)3Al + O2 reaction, its exothermic isomerization to CH2Al(OH)OCH3 (−26.7 kcal/mol) with a small barrier (9.7 kcal/mol), to be followed by decomposition giving a reactive product pair CH3AlOH + CH2O with a small endothermicity of 15.8 kcal/mol is believed to be most important. The ensuing exothermic and barrierless reaction of CH3AlOH with O2 gives rise to a ring intermediate, cy_CH3Al(O2)OH (−70.5 kcal/mol), which readily fragments to HOAlO2 + CH3 with an overall exothermicity of 21.7 kcal/mol. The (CH3)2Al(O)O radical isomer, which is effectively the association complex of (CH3)2Al and O2, on the other hand, is stable and has no low-energy exit paths to reactive products including its isomer CH3Al(O)OCH3. Rate constants for the three key reactions leading to the ultimate formation of CH3 + HOAlO2 + CH2O have been calculated for combustion modeling applications.

KW - (CH)Al

KW - (CH)AlO

KW - Ab initio chemical kinetics

KW - O

UR - http://www.scopus.com/inward/record.url?scp=85114509164&partnerID=8YFLogxK

U2 - 10.1016/j.comptc.2021.113436

DO - 10.1016/j.comptc.2021.113436

M3 - Article

AN - SCOPUS:85114509164

SN - 2210-271X

VL - 1205

JO - Computational and Theoretical Chemistry

JF - Computational and Theoretical Chemistry

M1 - 113436

ER -

Fragmentation of two dimethylaluminum peroxy radical isomers formed by the hypergolic reaction of trimethyl aluminum with O₂

Abstract

Keywords

Access to Document

Other files and links

Fingerprint

Cite this