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Titolo:
A combined crossed molecular beam and ab initio investigation of C-2 and C-3 elementary reactions with unsaturated hydrocarbons - pathways to hydrogen deficient hydrocarbon radicals in combustion flames
Autore:
Kaiser, RI; Le, TN; Nguyen, TL; Mebel, AM; Balucani, N; Lee, YT; Stahl, F; Schleyer, PV; Schaefer, HF;
Indirizzi:
Univ York, Dept Chem, York YO10 5DD, N Yorkshire, England Univ York York N Yorkshire England YO10 5DD O10 5DD, N Yorkshire, England Tech Univ Chemnitz Zwickau, Dept Phys, D-09107 Chemnitz, Germany Tech UnivChemnitz Zwickau Chemnitz Germany D-09107 07 Chemnitz, Germany Acad Sinica, Inst Atom & Mol Sci, Taipei 107, Taiwan Acad Sinica Taipei Taiwan 107 a, Inst Atom & Mol Sci, Taipei 107, Taiwan Univ Perugia, Dipartimento Chim, I-06123 Perugia, Italy Univ Perugia Perugia Italy I-06123 rtimento Chim, I-06123 Perugia, Italy Univ Erlangen Nurnberg, Inst Organ Chem, D-91054 Erlangen, Germany Univ Erlangen Nurnberg Erlangen Germany D-91054 -91054 Erlangen, Germany Univ Georgia, Ctr Computat Quantum Chem, Athens, GA 30602 USA Univ Georgia Athens GA USA 30602 putat Quantum Chem, Athens, GA 30602 USA
Titolo Testata:
FARADAY DISCUSSIONS
, volume: 119, anno: 2001,
pagine: 51 - 66
SICI:
1364-5498(2001)119:<51:ACCMBA>2.0.ZU;2-8
Fonte:
ISI
Lingua:
ENG
Soggetto:
CHEMICAL-DYNAMICS; CARBON-ATOMS; TEMPERATURE-DEPENDENCE; INTERSTELLAR C3H; LASER PHOTOLYSIS; C4H6 ISOMERS; C(P-3(J)); C-2; KINETICS; STARS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
71
Recensione:
Indirizzi per estratti:
Indirizzo: Kaiser, RI Univ York, Dept Chem, York YO10 5DD, N Yorkshire, England Univ York York N Yorkshire England YO10 5DD Yorkshire, England
Citazione:
R.I. Kaiser et al., "A combined crossed molecular beam and ab initio investigation of C-2 and C-3 elementary reactions with unsaturated hydrocarbons - pathways to hydrogen deficient hydrocarbon radicals in combustion flames", FARADAY DIS, 119, 2001, pp. 51-66

Abstract

Crossed molecular beam experiments on dicarbon and tricarbon reactions with unsaturated hydrocarbons acetylene, methylacetylene, and ethylene were performed to investigate the dynamics of channels leading to hydrogen-deficient hydrocarbon radicals. In the light of the results of new ab initio calculations, the experimental data suggest that these reactions are governed byan initial addition of C-2/C-3 to the pi molecular orbitals forming highlyunsaturated cyclic structures. These intermediates are connected via various transition states and are suggested to ring open to chain isomers which decompose predominantly by displacement of atomic hydrogen, forming C4H, C5H, HCCCCCH2, HCCCCCCH3, H2CCCCH and H2CCCCCH. The C-2((1)Sigma (+)(g)) + C2H4 reaction has no entrance barrier and the channel leading to the H2CCCCH product is strongly exothermic. This is in strong contrast with the C-3((1)Sigma (+)(g)) + C2H4 reaction as this is characterized by a 26.4 kJ mol(-1)threshold to form a HCCCCCH2 isomer. Analogous to the behavior with ethylene, preliminary results on the reactions of C-2 and C-3 with C2H2 and CH3CCH showed the H-displacement channels of these systems to share many similarities such as the absence/presence of an entrance barrier and the reaction mechanism. The explicit identification of the C-2/C-3 vs. hydrogen displacement demonstrates that hydrogen-deficient hydrocarbon radicals can be formed easily in environments like those of combustion processes. Our work is a first step towards a systematic database of the intermediates and the reaction products which are involved in this important class of reactions. Thesefindings should be included in future models of PAH and soot formation in combustion flames.

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Documento generato il 06/04/20 alle ore 08:36:36