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Titolo:
Development and application of a possible mechanism for the generation of cis-pinic acid from the ozonolysis of alpha- and beta-pinene
Autore:
Jenkin, ME; Shallcross, DE; Harvey, JN;
Indirizzi:
AEA Technol PLC, Natl Environm Technol Ctr, Abingdon OX14 3ED, Oxon, England AEA Technol PLC Abingdon Oxon England OX14 3ED on OX14 3ED, Oxon, England Univ Bristol, Sch Chem, Bristol BS8 1TS, Avon, England Univ Bristol Bristol Avon England BS8 1TS Bristol BS8 1TS, Avon, England
Titolo Testata:
ATMOSPHERIC ENVIRONMENT
fascicolo: 18, volume: 34, anno: 2000,
pagine: 2837 - 2850
SICI:
1352-2310(2000)34:18<2837:DAAOAP>2.0.ZU;2-9
Fonte:
ISI
Lingua:
ENG
Soggetto:
GAS-PHASE REACTIONS; SECONDARY ORGANIC AEROSOL; NO3 RADICALS; PHOTOOXIDATION PRODUCTS; ATMOSPHERIC CHEMISTRY; OXIDATION-PRODUCTS; PARTICLE FORMATION; ABSORPTION-MODEL; PEROXY-RADICALS; OH RADICALS;
Keywords:
monoterpenes; alpha-pinene; beta-pinene; secondary-organic aerosol; pinic acid; carboxylic acids; acyl-oxy radicals; tropospheric oxidation chemistry; master chemical mechanism (MCM);
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Physical, Chemical & Earth Sciences
Citazioni:
61
Recensione:
Indirizzi per estratti:
Indirizzo: Jenkin, ME AEA Technol PLC, Natl Environm Technol Ctr, Abingdon OX14 3ED, Oxon, England AEA Technol PLC Abingdon Oxon England OX14 3ED , Oxon, England
Citazione:
M.E. Jenkin et al., "Development and application of a possible mechanism for the generation of cis-pinic acid from the ozonolysis of alpha- and beta-pinene", ATMOS ENVIR, 34(18), 2000, pp. 2837-2850

Abstract

Recent experimental studies have identified cis-pinic acid (a C-9 dicarboxylic acid) as a condensed-phase product of the ozonolysis of both alpha- and beta-pinene, and it is currently believed to be the most likely degradation product leading to the prompt formation of new aerosols by nucleation. The observed timescale of aerosol formation appears to require that cis-pinic acid is a first-generation product, and a possible mechanism for its formation has therefore been developed. The key step in the proposed mechanism requires that the isomerisation of a complex C-9 acyl-oxy radical by a 1,7 H atom shift is able to compete with the alternative decomposition to CO2 and a C-8 organic radical:[GRAPHICS]Thermodynamic and kinetic arguments are presented, on the basis of semi-empirical electronic structure calculations, which support this proposed mechanism, and thereby the competition between the two pathways. The transfer of the labile aldehydic H atom is shown to be especially facile in this casebecause it occurs though an unstrained transition state; this feature can in turn be attributed to the cis-substitution of the four-membered ring, which enforces the steric proximity of the acyl-oxy and aldehyde groups. The mechanism can explain the formation of cis-pinic acid from both alpha-and beta-pinene, because the acyl-oxy radical is likely to be formed following the decomposition of excited Criegee biradicals formed in both systems. It is also possible that a similar isomerisation reaction of a complex C-10 alpha-carbonyl oxy radical by a 1,8 H atom shift might explain the very recently observed formation of cis- 10-hydroxy-pinonic acid from alpha-pinene ozonolysis, and this possibility is also explored. An existing detailed schemedescribing the degradation of alpha-pinene (part of the Master Chemical Mechanism, MCM) is updated to include the proposed cis-pinic acid and cis-10-hydroxy-pinonic acid formation mechanisms, and the values of several uncertain parameters are adjusted on the basis of reported yields of a series of organic products from the ozonolysis of alpha-pinene. The updated degradation scheme is incorporated into a boundary layer box model, and representative ambient concentrations of the organic acids and other oxygenated products are calculated for a range of representative conditions appropriate to the boundary layer over central Europe. The simulated concentrations of the organic acids in general, and cis-pinic acid in particular, are strongly dependent on the level of NOx, and suggest that new aerosol formation from theoxidation of alpha-pinene is likely to be more favoured at lower NOx levels. (C) 2000 Elsevier Science Ltd. All rights reserved.

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Documento generato il 22/09/18 alle ore 01:03:18