Interaction of NH2 radical with alkylbenzenes

Kamal Siddique, Mohammednoor Altarawneh, Anam Saeed, Zhe Zeng, Jeff Gore, Bogdan Z. Dlugogorski

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Abstraction of a hydrogen atom from the alkyl side chain, attached to a benzene ring, by the amidogen radical (NH2), plays a critical importance in thermal processes that involve the presence of alkylbenzene species and NH2-containing species, as in the pyrolysis of biomass. Yet, literature provides no thermo-kinetic account of this important category of reactions. In this contribution, we compute standard reaction (Δr298) and activation enthalpies (Δ298) for H removal from the alkyl side chains in toluene, ethylbenzene and n-propylbenzene, as well as addition of NH2 at the four possible sites of the phenyl ring in toluene and ethylbenzene. Abstraction of the benzylic H atom in toluene constitutes the sole feasible channel at all temperatures. The same finding applies to ethylbenzene, albeit with a gradual increase of the contribution from the channel of abstraction of primary's H with increasing temperatures. The rate constant of the abstraction of benzylic H in n-propylbenzene dominates that of the primary and secondary H atoms. Computed branching ratios confirm the dominance of H abstraction corridors over the addition channels, even at low temperatures. For primary's H abstraction reactions, comparing reaction rate constants of alkylbenzenes with those of the analogous sites in alkanes indicates a noticable influence of the aromatic ring on the reaction rate constants. The results of the present calculations apply to any branched aromatic hydrocarbon interacting with the NH2 radical.

Original languageEnglish
Pages (from-to)85-96
Number of pages12
JournalCombustion and Flame
Volume200
Issue numberFebruary
Early online date23 Nov 2018
DOIs
Publication statusPublished - 1 Feb 2019
Externally publishedYes

Fingerprint

Ethylbenzene
Toluene
toluene
Rate constants
Atoms
Reaction rates
rings
reaction kinetics
Aromatic Hydrocarbons
corridors
Alkanes
Aromatic hydrocarbons
interactions
biomass
Benzene
Paraffins
Temperature
alkanes
pyrolysis
atoms

Cite this

Siddique, K., Altarawneh, M., Saeed, A., Zeng, Z., Gore, J., & Dlugogorski, B. Z. (2019). Interaction of NH2 radical with alkylbenzenes. Combustion and Flame, 200(February), 85-96. https://doi.org/10.1016/j.combustflame.2018.11.002
Siddique, Kamal ; Altarawneh, Mohammednoor ; Saeed, Anam ; Zeng, Zhe ; Gore, Jeff ; Dlugogorski, Bogdan Z. / Interaction of NH2 radical with alkylbenzenes. In: Combustion and Flame. 2019 ; Vol. 200, No. February. pp. 85-96.
@article{067437164a2a4e3a91d036061d5979b4,
title = "Interaction of NH2 radical with alkylbenzenes",
abstract = "Abstraction of a hydrogen atom from the alkyl side chain, attached to a benzene ring, by the amidogen radical (NH2), plays a critical importance in thermal processes that involve the presence of alkylbenzene species and NH2-containing species, as in the pyrolysis of biomass. Yet, literature provides no thermo-kinetic account of this important category of reactions. In this contribution, we compute standard reaction (ΔrH°298) and activation enthalpies (Δ⧧H°298) for H removal from the alkyl side chains in toluene, ethylbenzene and n-propylbenzene, as well as addition of NH2 at the four possible sites of the phenyl ring in toluene and ethylbenzene. Abstraction of the benzylic H atom in toluene constitutes the sole feasible channel at all temperatures. The same finding applies to ethylbenzene, albeit with a gradual increase of the contribution from the channel of abstraction of primary's H with increasing temperatures. The rate constant of the abstraction of benzylic H in n-propylbenzene dominates that of the primary and secondary H atoms. Computed branching ratios confirm the dominance of H abstraction corridors over the addition channels, even at low temperatures. For primary's H abstraction reactions, comparing reaction rate constants of alkylbenzenes with those of the analogous sites in alkanes indicates a noticable influence of the aromatic ring on the reaction rate constants. The results of the present calculations apply to any branched aromatic hydrocarbon interacting with the NH2 radical.",
keywords = "Amidogen radical (NH), Aromatic hydrocarbon, Bond dissociation enthalpies, Reaction rate constants",
author = "Kamal Siddique and Mohammednoor Altarawneh and Anam Saeed and Zhe Zeng and Jeff Gore and Dlugogorski, {Bogdan Z.}",
year = "2019",
month = "2",
day = "1",
doi = "10.1016/j.combustflame.2018.11.002",
language = "English",
volume = "200",
pages = "85--96",
journal = "Combustion and Flame",
issn = "0010-2180",
publisher = "Elsevier",
number = "February",

}

Siddique, K, Altarawneh, M, Saeed, A, Zeng, Z, Gore, J & Dlugogorski, BZ 2019, 'Interaction of NH2 radical with alkylbenzenes', Combustion and Flame, vol. 200, no. February, pp. 85-96. https://doi.org/10.1016/j.combustflame.2018.11.002

Interaction of NH2 radical with alkylbenzenes. / Siddique, Kamal; Altarawneh, Mohammednoor; Saeed, Anam; Zeng, Zhe; Gore, Jeff; Dlugogorski, Bogdan Z.

In: Combustion and Flame, Vol. 200, No. February, 01.02.2019, p. 85-96.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Interaction of NH2 radical with alkylbenzenes

AU - Siddique, Kamal

AU - Altarawneh, Mohammednoor

AU - Saeed, Anam

AU - Zeng, Zhe

AU - Gore, Jeff

AU - Dlugogorski, Bogdan Z.

PY - 2019/2/1

Y1 - 2019/2/1

N2 - Abstraction of a hydrogen atom from the alkyl side chain, attached to a benzene ring, by the amidogen radical (NH2), plays a critical importance in thermal processes that involve the presence of alkylbenzene species and NH2-containing species, as in the pyrolysis of biomass. Yet, literature provides no thermo-kinetic account of this important category of reactions. In this contribution, we compute standard reaction (ΔrH°298) and activation enthalpies (Δ⧧H°298) for H removal from the alkyl side chains in toluene, ethylbenzene and n-propylbenzene, as well as addition of NH2 at the four possible sites of the phenyl ring in toluene and ethylbenzene. Abstraction of the benzylic H atom in toluene constitutes the sole feasible channel at all temperatures. The same finding applies to ethylbenzene, albeit with a gradual increase of the contribution from the channel of abstraction of primary's H with increasing temperatures. The rate constant of the abstraction of benzylic H in n-propylbenzene dominates that of the primary and secondary H atoms. Computed branching ratios confirm the dominance of H abstraction corridors over the addition channels, even at low temperatures. For primary's H abstraction reactions, comparing reaction rate constants of alkylbenzenes with those of the analogous sites in alkanes indicates a noticable influence of the aromatic ring on the reaction rate constants. The results of the present calculations apply to any branched aromatic hydrocarbon interacting with the NH2 radical.

AB - Abstraction of a hydrogen atom from the alkyl side chain, attached to a benzene ring, by the amidogen radical (NH2), plays a critical importance in thermal processes that involve the presence of alkylbenzene species and NH2-containing species, as in the pyrolysis of biomass. Yet, literature provides no thermo-kinetic account of this important category of reactions. In this contribution, we compute standard reaction (ΔrH°298) and activation enthalpies (Δ⧧H°298) for H removal from the alkyl side chains in toluene, ethylbenzene and n-propylbenzene, as well as addition of NH2 at the four possible sites of the phenyl ring in toluene and ethylbenzene. Abstraction of the benzylic H atom in toluene constitutes the sole feasible channel at all temperatures. The same finding applies to ethylbenzene, albeit with a gradual increase of the contribution from the channel of abstraction of primary's H with increasing temperatures. The rate constant of the abstraction of benzylic H in n-propylbenzene dominates that of the primary and secondary H atoms. Computed branching ratios confirm the dominance of H abstraction corridors over the addition channels, even at low temperatures. For primary's H abstraction reactions, comparing reaction rate constants of alkylbenzenes with those of the analogous sites in alkanes indicates a noticable influence of the aromatic ring on the reaction rate constants. The results of the present calculations apply to any branched aromatic hydrocarbon interacting with the NH2 radical.

KW - Amidogen radical (NH)

KW - Aromatic hydrocarbon

KW - Bond dissociation enthalpies

KW - Reaction rate constants

UR - http://www.scopus.com/inward/record.url?scp=85056861810&partnerID=8YFLogxK

U2 - 10.1016/j.combustflame.2018.11.002

DO - 10.1016/j.combustflame.2018.11.002

M3 - Article

VL - 200

SP - 85

EP - 96

JO - Combustion and Flame

JF - Combustion and Flame

SN - 0010-2180

IS - February

ER -

Siddique K, Altarawneh M, Saeed A, Zeng Z, Gore J, Dlugogorski BZ. Interaction of NH2 radical with alkylbenzenes. Combustion and Flame. 2019 Feb 1;200(February):85-96. https://doi.org/10.1016/j.combustflame.2018.11.002