6711-19-9Relevant articles and documents
Time- and product-resolved photodissociations of bromotoluene radical cations
Kim, Byungjoo,Shin, Seung Koo
, p. 1411 - 1417 (1997)
Photodissociations of o-, m-, and p-bromotoluene radical cations have been studied in the wavelength range 575-475 nm using Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry. The parent ions were prepared by charge-transfer reactions of bromotoluenes with toluene-d8 radical cations produced by two-photon ionization of toluene-d8 at 266 nm. Bromotoluene radical cations dissociate to C7H7+ by loss of Br. The dissociation rates were measured by time-resolved photodissociation spectroscopy. Structures of C7H7+ from one-photon dissociation were identified by their bimolecular reactivities with toluene-d8. The C7H7+ products from all three isomers were identified as the benzyl cation. No unreactive tropylium ions were detected within experimental limits. The rate constants measured in this work were combined with the previous photoelcctron-photoion-coincidence results to refine activation parameters for the Rice-Ramsperger-Kassel-Marcus rate-energy curves, k(E), for the low barrier rearrangement process. The activation barriers are estimated to be 1.66, 1.80, and 1.78 eV for the o-, m-, and p-bromotoluene radical cations, respectively, whereas the entropy changes for the activation, ΔS?(1000 K), are -9.6, -7.2, and -5.6 eu., respectively. The mechanism of the rearrangement process is presented to account for the predominant formation of the benzyl cation.
Identification of Chemi-ions Formed by Reactions of Deuterated Fuels in the Reflected Shock Zone
Kern, R. D.,Singh, H. J.,Xie, K.
, p. 3333 - 3335 (1990)
Dilute mixtures of various fuels with and without oxygen were analyzed dynamically from the reflected shock zone by time-of-flight mass spectrometry to test for the presence of chemi-ions.The identity of the major chemi-ion species and the amounts produced depended upon the fuel/O2 ratio, temperature, observation time, and the cleanliness of the shock tube-mass spectrometer system.Chemi-ions were readily observed in oxidative mixtures of acetylene, ethylene, benzene, and acetaldehyde.Deuterated compounds of these fuels were employed to demonstrate the absence of chemi-ions in oxygen-free mixtures.It follows that the radical-molecule mechanism for soot formation is dominant in pyrolytic reaction systems.
Collisional stabilization and thermal dissociation of highly vibrationally excited C9H12+ ions from the reaction O 2+ + C9H12 → O2 + C9H12+
Fernandez, Abel I.,Viggiano,Miller, Thomas M.,Williams,Dotan,Seeley,Troe
, p. 9652 - 9659 (2008/04/18)
Highly vibrationally excited n-propylbenzene cations, C9H 12+*, were prepared by the charge transfer reaction O2+ + C9H12 → O2 + C9H12+* in a turbulent ion flow tube. The subsequent competition between fragmentation of C9H 12+* into C7H7+ + C2H5 and stabilization in collisions with N2 was studied at temperatures in the range 423-603 K and at pressures between 15 and 200 Torr. Most of the C7H7+ is the aromatic benzylium isomer, while the fraction of the minor species, seven-membered-ring tropylium, increases with T, from 5 to 20%. Minor fragments are C 6H6+, C7H8+, and C8H9+, Energy-transfer step sizes (ΔE) for collisional deactivation are obtained by combining the stabilization versus fragmentation ratios measured as a function of pressure in this study with fragmentation rates from the literature. The values are compared with related information for other excited molecular ions and are similar to those of their neutral analogues. At the highest temperatures, C 9H12+ was also observed to pyrolyze after collisional stabilization. Employing unimolecular rate theory, the derived rate constants for thermal dissociation of C9H12+ are related to values derived from the specific rate constants k(E,J) for fragmentation. Good agreement is found between measured and predicted pyrolysis rate constants. This allows us to confirm the dissociation energy of C 9H12+ into C7H7 + (benzylium) and C2H5 as 166.9 (±2.2) kJ mol-1 (at 0 K).
Mass-spectrometric study on ion-molecule reactions of CH5+, C2H5+, and C3H5+ with C9-C19 alkylbenzenes in an ion trap
Tanaka, Yuki,Tsuji, Masaharu
, p. 241 - 252 (2007/10/03)
Chemical ionization of alkylbenzenes (PhCxH2x + 1 = M: x = 3-13) by the CH5+, C2H5+, and C3H5+ ions has been studied under a reactant-ion selective mode of an ion-trap type of GC/MS. The dominant product ions for short-chain reagents (x +, [Phil + H]+, and CxH2x + 1+ ions, produced through proton-transfer to benzene ring. On the other hand, the dominant product ions for long-chain reagents (x ≥ 7) were CyH2y + 1+ (y yH2y+ (y ≤ x) ions. The former ions are produced through the attack of the reactant ions on the alkyl chain and/or the benzene ring, while the latter ones are exclusively formed through the attack of the reactant ions on the alkyl chain. Major formation processes of CyH2y + 1+ and PhCyH2y+ ions in each reaction were discussed on the basis of observed distributions and calculated thermochemical data.
