TIME-DEPENDENT MASS-SPECTRA AND BREAKDOWN GRAPHS .17. NAPHTHALENE AND PHENANTHRENE

被引:105
作者
GOTKIS, Y
OLEINIKOVA, M
NAOR, M
LIFSHITZ, C
机构
[1] HEBREW UNIV JERUSALEM,DEPT PHYS CHEM,IL-91904 JERUSALEM,ISRAEL
[2] HEBREW UNIV JERUSALEM,FRITZ HABER RES CTR MOLEC DYNAM,IL-91904 JERUSALEM,ISRAEL
关键词
D O I
10.1021/j100149a031
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Time-resolved photoionization efficiency (PIE) curves were measured for C10H8.+, C10H7+, and C8H6.+ from naphthalene (and for the analogous ions in naphthalene-ds) and for C14H10.+ C14H9+, and C12H8.+ from phenanthrene. PIE curves were modeled by k(E) dependences via RRKM/QET calculations. Loose transition states were adopted for the H losses and for C2H2 loss from naphthalene. A tight transition state was found for the C2H2 elimination from phenanthrene. The most stable daughter ion isomeric structures are found namely, phenylacetylene.+ and acenaphthylene.+, by C2H2 elimination from naphthalene and phenanthrene, respectively. Disagreement between the present activation parameters for naphthalene and the ones adopted by Ruhl et al. (ref 3) are discussed. Large kinetic shifts have been observed. The conventional shift for C2H2 loss from phenanthrene is 4.0(7) eV, while the intrinsic shift, due to radiative decay in the infrared, is 3.2(5) eV. The following heats of formation were deduced: DELTAH(f)o 0(C8H6.+,phenylacetylene) = 280.6 +/- 1 kcal/mol, DELTAH(f)o 0-(C10H7+, naphthyl) = 275 +/- 3 kcal/mol, DELTAH(f)o 0(C12H8.+,acenaphthylene) less-than-or-equal-to 260.2 +/- 1 kcal/mol, and DELTAH(f)o 0-(C14H9+,phenanthryl) = 281 +/- 3 kcal/mol. The C-H bond energies are approximately 0.3-0.4 eV higher in naphthalene.+ and phenanthrene.+ than in benzene.+. The resilience of polycyclic aromatic hydrocarbons (PAHs) toward dissociation is understood on the basis of their high C-H and C-C bond energies and their large numbers of degrees of freedom. It can be partly overcome by ion trapping-as has been done in the present study. Formation of acenaphthylene.+ from phenanthrene.+ constitutes a possible example of a chemical link between PAHs and pentagonal-containing motifs of fullerenes.
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页码:12282 / 12290
页数:9
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