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Titolo:
Solvation of cyclopentadienyl and substituted cyclopentadienyl radicals insmall clusters. III. Pre-reactive clusters
Autore:
Fernandez, JA; Yao, J; Bernstein, ER;
Indirizzi:
Colorado State Univ, Dept Chem, Ft Collins, CO 80523 USA Colorado State Univ Ft Collins CO USA 80523 hem, Ft Collins, CO 80523 USA
Titolo Testata:
JOURNAL OF CHEMICAL PHYSICS
fascicolo: 11, volume: 110, anno: 1999,
pagine: 5183 - 5188
SICI:
0021-9606(19990315)110:11<5183:SOCASC>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
TRANSITION-STATE THEORY; LASER-INDUCED FLUORESCENCE; THERMAL RATE CONSTANTS; CROSSED-BEAM REACTION; HIGH-PRESSURE RANGE; ELECTRONIC SPECTROSCOPY; NONADIABATIC PREDISSOCIATION; HYDROCARBON MOLECULES; VANDERWAALS MOLECULE; CHEMICAL-DYNAMICS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
59
Recensione:
Indirizzi per estratti:
Indirizzo: Fernandez, JA Colorado State Univ, Dept Chem, Ft Collins, CO 80523 USA Colorado State Univ Ft Collins CO USA 80523 s, CO 80523 USA
Citazione:
J.A. Fernandez et al., "Solvation of cyclopentadienyl and substituted cyclopentadienyl radicals insmall clusters. III. Pre-reactive clusters", J CHEM PHYS, 110(11), 1999, pp. 5183-5188

Abstract

The hydrogen abstraction reaction between cyclopentadienyl radicals [Xcpd,X=H, CH3 (m) F, CN] and substituted methanes (CH4, C2H6, CH3CH2OH, CH3Cl, CH2F2, CHF3, and CH3OH) is studied for the isolated one-to-one van der Waals clusters created in a supersonic expansion. Three different types of fluorescence excitation spectra are characterized for these cluster systems: (1) sharp spectra are observed for some clusters, suggesting no cluster chemistry for either the ground or excited electronic states of Xcpd-CNcpd/CH3Cl, CH2F2, CHF3, CH3OH; (2) broad spectra are observed suggesting initiation of cluster chemistry on the excited state cluster potential energy surface-CNcpd-CH4, Fcpd-CHF2Cl, CHF3; and (3) only a greatly reduced bare radical signal is observed, but no cluster emission can be detected-cpd, mcpd/all substituted methanes, Fcpd-CH2F2,CH3Cl, CH3CH2OH, CH3OH, C2H6, and CNcpd/C2H6,CH3CH2OH. These results, taken together, suggest that the Xcpd radicals undergo an excited electronic state electrophilic hydrogen abstraction reaction with substituted methanes. The radical reactivities are in the order mcpd similar to cpd>Fcpd>CNcpd and the substituted methane reactivities are inthe order C2H6>C2H5OH>CH4>CH3Cl similar to CH3OH>CH2F2>CHF2Cl>CHF3. All Xcpd radicals show intense, sharp spectra with CF4. This indication of an excited state Xcpd radical hydrogen abstraction reaction with substituted methanes is further explored by ab initio quantum chemistry techniques at the (7X7) CASSCF/6-31G (complete active space self-consistent field) and cc-pVDZlevels for cpd-CH4. Calculations confirm the idea that the ground state cluster has a reaction barrier (approximately +170 kJ/mol) and a positive free energy of reaction (similar to 80 kJ/mol). The excited cpd radical, however, can react with CH4 along a barrierless path to generate substantial hotground product states (C5H6 and CH3). Experimental data are consistent with an Xcpd-C2H4 addition reaction, as well. (C) 1999 American Institute of Physics. [S0021-9606(99)01410-5].

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Documento generato il 21/09/20 alle ore 12:56:03