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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 23, Number 2
BKCSDE 23(2)
February 20, 2002 

Product-Resolved Photodissociations of Iodotoluene Radical Cations
Seung Koo Shin, Byungjoo Kim, Russell L. Jarek, Seung-Jin Han
FT-ICR, Time-resolved photodissociation, Iodotoluene, Tolyl cation, Product-resolved photodissociation.
Photodissociations of o-, m-, and p-iodotoluene radical cations were investigated by using Fourier-transform ion cyclotron resonance (FT-ICR) spectrometry. Iodotoluene radical cations were prepared in an ICR cell by a photoionization charge-transfer method. The time-resolved one-photon dissociation spectra were obtained at 532 nm and the identities of C7H7+ products were determined by examining their bimolecular reactivities toward toluene-d8. The two-photon dissociation spectra were also recorded in the wavelength range 615-670 nm. The laser power dependence, the temporal variation, and the identities of C7H7+ were examined at 640 nm. The mechanism of unimolecular dissociation of iodotoluene radical cations is elucidated: the lowest barrier rearrangement channel leads exclusively to the formation of the benzyl cation, whereas the direct C-I cleavage channel yields the tolyl cations that rearrange to both benzyl and tropylium cations with dissimilar branching ratios among o-, m-, and p-isomers. With a two-photon energy of 3.87 eV at 640 nm, the direct C-I cleavage channel results in the product branching ratio, [tropylium cation]/[benzyl cation], in descending order, 0.16 for meta > 0.09 for ortho > 0.05 for para.
267 - 270
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