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Title: From benzene to muconaldehyde: Theoretical mechanistic investigation on some tropospheric oxidation channels

Abstract

In the tropospheric oxidation of benzene and methylated benzenes, unsaturated dicarbonyls are commonly detected products. Aldehydes are known to contribute on their own to some aspects of air pollution, and hexa-2,4-dien-1,6-dial (muconaldehyde) in particular is interesting because of its multiform toxicity. This study investigates the likelihood of some benzene oxidation steps and is especially focused on ring opening and generation of muconaldehyde.; With sufficiently high NO{sub x} concentration, O abstraction by NO from the cis peroxyl group in the 2-hydroxy-cyclohexadienyl peroxyl radical can play a role. In fact, it is shown to open a facile cascade of oxidation steps by first forming the 2-hydroxy-cyclohexadienyl oxyl radical. This intermediate is prone to ring opening via {beta}-fragmentation and generates the open-chain delocalized 6-hydroxy-hexa-2,4-dienalyl radical, in which one terminus is the first carbonyl group of the final dialdehyde. The second one can form either by simple H abstraction operated by O{sub 2} or by O{sub 2} addition followed by HOO{sup {sm{underscore}bullet}}elimination. The overall free-energy drop is estimated to be 48 kcal mol{sup {minus}1}. Exploration of other pathways, possibly playing a major role in yielding aldehydes in the case of low NO{sub x} concentration, indicates that only ring closure of the 2-hydroxy-cyclohexadienyl peroxyl radicalmore » to the [3.2.1] bicyclic endo-peroxy allyl radical intermediate is promising. In this case, however, the outcome of a subsequent ring opening can ultimately be the production of 1,2 and 1,4 dialdehydes (as direct oxidation of muconaldehyde itself can actually do).« less

Authors:
;
Publication Date:
Research Org.:
Univ. de Torino (IT)
OSTI Identifier:
20000128
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 121; Journal Issue: 36; Other Information: PBD: 15 Sep 1999; Journal ID: ISSN 0002-7863
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; TROPOSPHERE; OXIDATION; BENZENE; CARBONYLS; PHENOLS; ALDEHYDES; CHEMICAL REACTION KINETICS; POLLUTANTS

Citation Formats

Ghigo, G., and Tonachini, G. From benzene to muconaldehyde: Theoretical mechanistic investigation on some tropospheric oxidation channels. United States: N. p., 1999. Web. doi:10.1021/ja990552l.
Ghigo, G., & Tonachini, G. From benzene to muconaldehyde: Theoretical mechanistic investigation on some tropospheric oxidation channels. United States. doi:10.1021/ja990552l.
Ghigo, G., and Tonachini, G. Wed . "From benzene to muconaldehyde: Theoretical mechanistic investigation on some tropospheric oxidation channels". United States. doi:10.1021/ja990552l.
@article{osti_20000128,
title = {From benzene to muconaldehyde: Theoretical mechanistic investigation on some tropospheric oxidation channels},
author = {Ghigo, G. and Tonachini, G.},
abstractNote = {In the tropospheric oxidation of benzene and methylated benzenes, unsaturated dicarbonyls are commonly detected products. Aldehydes are known to contribute on their own to some aspects of air pollution, and hexa-2,4-dien-1,6-dial (muconaldehyde) in particular is interesting because of its multiform toxicity. This study investigates the likelihood of some benzene oxidation steps and is especially focused on ring opening and generation of muconaldehyde.; With sufficiently high NO{sub x} concentration, O abstraction by NO from the cis peroxyl group in the 2-hydroxy-cyclohexadienyl peroxyl radical can play a role. In fact, it is shown to open a facile cascade of oxidation steps by first forming the 2-hydroxy-cyclohexadienyl oxyl radical. This intermediate is prone to ring opening via {beta}-fragmentation and generates the open-chain delocalized 6-hydroxy-hexa-2,4-dienalyl radical, in which one terminus is the first carbonyl group of the final dialdehyde. The second one can form either by simple H abstraction operated by O{sub 2} or by O{sub 2} addition followed by HOO{sup {sm{underscore}bullet}}elimination. The overall free-energy drop is estimated to be 48 kcal mol{sup {minus}1}. Exploration of other pathways, possibly playing a major role in yielding aldehydes in the case of low NO{sub x} concentration, indicates that only ring closure of the 2-hydroxy-cyclohexadienyl peroxyl radical to the [3.2.1] bicyclic endo-peroxy allyl radical intermediate is promising. In this case, however, the outcome of a subsequent ring opening can ultimately be the production of 1,2 and 1,4 dialdehydes (as direct oxidation of muconaldehyde itself can actually do).},
doi = {10.1021/ja990552l},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 36,
volume = 121,
place = {United States},
year = {1999},
month = {9}
}