- Homogenous Gas-Phase Formation and Destruction of Anthranil from o-Nitrotoluene Decomposition
-
Dilute quantities of o-nitrotoluene and anthranil have been pyrolyzed in comparative rate single pulse shock tube experiments.Rather than C-NO2 bond cleavage and NO2 isomerization found as major channels in p-nitrotoluene decomposition, we demonstrate that the important pathway for pyrolysis involves the formation of anthranil with the following overall rate expression: k(o-nitrotoluene -> anthranil) = 1.2 x 1013 exp(-26020/T)/s.The anthranil that is formed is very unstable under our conditions; the rate expression for disappearence has been found to be the following: k(anthranil)d = 3.7 x 1015 exp(-25800/T)/s.Arguments are presented that suggest that the first rate expression is representative of a retroene reaction and the second expression is for the breaking of the N-O bond in anthranil.These conclusions emphasize the difference in results from shock tube and laser pyrolysis experiments.Their implications on the initiation reactions in the decomposition of nitroaromatic explosives are discussed.
- He, Y. Z.,Cui, J. P.,Mallard, W. G.,Tsang, W.
-
-
Read Online
- Excess Energy and Structural Dependence of the Rate of Energy Redistribution during the Photodissociation of Iodotoluenes
-
The ortho (2-), meta (3-), and para (4-) iodotoluenes (C7H7I) are photodissociated at 266 and 304 nm and studied with state-selective one-dimensional photofragment translational spectroscopy.Angular, velocity, and translational energy distributions are obtained for the ground state I(2P3/2) and spin-orbit excited state I*(2P1/2) iodine atoms produced upon photodissociation.As has been observed in iodobenzene, the ground-state I channel observed in each isomer of iodotoluene exhibits both a prompt alkyl iodide-like dissociation channel following a parallel excitation to the alkyl iodide 3Q0(n,?*) repulsive state and curve crossing to the 1Q1(n,?*) state, and a slower, indirect dissociation channel following a competitive excitation to aromatic charge-transfer (?,?*) predissociative excited states at both 266 and 304 nm.The I* channel observed at both 266 and 304 nm for each isomer results from a prompt dissociation resulting from parallel absorption to an alkyl iodide type 3Q0(n,?*) state.The rapid I and I* dissociative channels observed for each isomer are found to exhibit strong dependence on the excess excitation.This is discussed in terms of a strong coupling between the dissociation coordinate and the more dense vibrational states of the toluene ring.Dissociation times and rates of internal energy redistribution (IER) from the slow dissociative channel (β) are estimated for each isomer.For 2-iodotoluene, the rate of IER for the slow I channel increases from 20 kcal/mol*ps at 304 nm to 30 kcal/mol*ps at 266 nm, while the rates of IER for 3- and 4-iodotoluene (16 kcal/mol*ps and 15 kcal/mol*ps, respectively) remain unchanged as the photon energy is increased.The difference in the observed excess energy dependence of the rates of IER in these isomers is discussed in terms of the complex coupling schemes between the optical doorway states and the n,?* repulsive states that produce the iodine atoms, monitored in the experiment.
- Freitas, John E.,Hwang, Hyun Jin,El-Sayed, M. A.
-
-
Read Online
- Investigating the mechanisms of aromatic amine-induced protein free radical formation by quantitative structure-activity relationships: Implications for drug-induced agranulocytosis
-
Aromatic amine drugs have been associated with agranulocytosis (neutrophil depletion) for which the mechanism is unknown. We have previously shown that the metabolism of two aromatic amine drugs by human myeloperoxidase (MPO) results in phenyl radical metabolite formation and also in protein free radical formation on MPO. Because the concentration of drug required to produce a maximum signal for MPO protein free radical (MPO?) detection was different for each drug, this prompted us to consider that other aromatic amines may also show varying degrees of ability to induce MPO? formation. Immunoassay experiments using the immuno-spin-trapping technique were performed, which evaluated the potency of different aromatic amines containing the aniline substructure to generate the MPO?. Each reaction contained equal amounts of H2O2, 5,5-dimethyl-1-pyrroline- N-oxide, MPO, and variable concentrations of aniline derivatives. Several physicochemical parameters for aniline derivatives were used to derive quantitative structure-activity relationship equations, which showed that the Hammett constant (-) best correlated with the MPO? formation for all aniline derivatives. More statistically robust equations were derived if the anilines were separated into mono- and disubstituted groups. However, some aniline derivatives did not induce MPO? formation. Using electron spin resonance spectroscopy, we evaluated the ability of all aniline derivatives tested to produce phenyl radical metabolites, as previously shown by spin trapping for the aromatic amine drugs. Interestingly, we found that only those aniline derivatives that produced a phenyl radical also formed MPO ?. We propose that the phenyl radical is the reactive free radical metabolite responsible for generating the MPO?+.
- Siraki, Arno G.,Jiang, Jinjie,Mason, Ronald P.
-
experimental part
p. 880 - 887
(2011/03/17)
-
- Magnetic Field Effects on the Photodissociation Reaction of Triarylphosphine in Nonviscous Homogeneous Solutions
-
The magnetic field effects (MFEs) on the photodecomposition reactions of triphenylphosphine and its halogen and methyl derivatives are investigated in fluid solutions. The yield of diarylphosphinyl radicals decreased with increasing magnetic field from 0.1 to 5 T but was stationary below 0.1 T and above 5 T. The MFE becomes larger by the substitution of halogen atoms and the 3- or 4-methyl group. In cyclohexane, the yields of the escaped diarylphosphinyl radicals at 1 T are reduced to 0.69, 0.55, 0.59, and 0.56 of those at 0 T for triphenylphosphine and its tris(4-chloro), tris(3-methyl), and tris(4-methyl) derivatives, respectively. This magnetic field dependence was ascribed to originate from the deactivation process of the excited triplet state, which is a variant of the d-type triplet mechanism originally proposed by Steiner. The interaction between the closely lying nπ* and ππ* states makes their solvent dependence complicated.
- Sakaguchi, Yoshio,Hayashi, Hisaharu
-
p. 3421 - 3429
(2007/10/03)
-