Chemical and photochemical generated carbon-centered radical intermediate and its reaction with desoxyribonucleic acid

Justo, Giselle Z.; Livotto, Paolo Roberto; Durán, Nélson

doi:10.1016/0891-5849(95)00036-w

Cited by 7 publications

(4 citation statements)

References 25 publications

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“…Among the key intermediates involved in reactions R1−R3 are the 1- and 2-phenylethyl radicals, which are produced in the pyrolysis and combustion of ethylbenzene and its α-substituted derivatives . The 2-phenylethyl radical ( 1 , Figure ) is also generated during in vivo oxidation of a tranquilizing drug phenelzine (phenylethylhydrazine), and it is used as a model radical to study the metabolism of hydrazine derivatives as well as protein and DNA damage by C-centered radicals . In turn, the 1-phenylethyl radical ( 2 ) is used in the chemistry of polymers as a mimetic compound for studying the selectivity of reactions of the growing polystyrene radical with different monomers .…”

Section: Introductionmentioning

confidence: 99%

Combined Quantum Chemical/RRKM-ME Computational Study of the Phenyl + Ethylene, Vinyl + Benzene, and H + Styrene Reactions

Tokmakov

Lin

2004

J. Phys. Chem. A

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Reactions of phenyl radicals with ethylene (R1), vinyl radicals with benzene (R2), and H-atoms with styrene (R3) are important prototype processes pertinent to the formation and degradation of aromatic hydrocarbons in high-temperature environments. Detailed mechanisms for these reactions are elucidated with the help of quantum chemical calculations at the G2M level of theory. Reactions R1−R3 initially produce chemically activated intermediates interconnected by isomerization pathways on the extended [C8H9] potential energy surface. All kinetically important transformations of these isomeric C8H9 radicals are explicitly characterized and utilized in the construction of multichannel kinetic models for reactions R1−R3. Accurate thermochemistry is evaluated for the key intermediates from detailed conformational and isodesmic analyses. An examination of the G2M energetic parameters for reactions R1−R3 and for briefly revisited C6H5 + C2H2 and C6H6 + H addition reactions reveals common theoretical deficiencies and suggests that the quality of theoretical predictions can be improved by small systematic corrections. Theoretical molecular and adjusted energetic parameters are used in a consistent way to calculate the total rate constants and product branching for reactions R1−R3 by weak collision master equation/RRKM analysis (addition channels) and transition state theory with Eckart tunneling corrections (abstraction channels). The available experimental kinetic data for reactions R1 and R2 is surveyed and found in good agreement with the best theoretical estimates.

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Section: Introductionmentioning

confidence: 99%

Combined Quantum Chemical/RRKM-ME Computational Study of the Phenyl + Ethylene, Vinyl + Benzene, and H + Styrene Reactions

Tokmakov

Lin

2004

J. Phys. Chem. A

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“…As one of the simplest unsaturated hydrocarbons, ethylene (C 2 H 4 ) and its reaction with C 6 H 5 and products on the corresponding PES have been recognized as important in various fields. The radical addition product, 2-phenylethyl radical, has been used as a carbon-centered radical interacting with DNA to study the metabolic activation of hydrazine derivatives. − Another radical adduct formed through 2-phenylethyl radical isomerization is 1-phenylethyl radical, and it has been selected as a model species to react with various monomers to understand their reactivity toward the polystyrene radical. − In this reaction network, styrene can be generated through the well-skipping reaction from C 6 H 5 + C 2 H 4 and H-elimination from radical adducts.…”

Section: Introductionmentioning

confidence: 99%

Direct Kinetics and Product Measurement of Phenyl Radical + Ethylene

et al. 2020

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The phenyl + ethylene (C6H5 + C2H4) reaction network was explored experimentally and theoretically to understand the temperature dependence of the reaction kinetics and product distribution under various temperature and pressure conditions. The flash photolysis apparatus combining laser absorbance spectroscopy (LAS) and time-resolved molecular beam mass spectrometry (MBMS) was used to study reactions on the C8H9 potential energy surface (PES). In LAS experiments, 505.3 nm laser light selectively probed C6H5 decay, and we measured the total C6H5 consumption rate coefficients in the intermediate temperature region (400–800 K), which connects previous experiments performed in high-temperature (pyrolysis) and low-temperature (cavity-ring-down methods) regions. From the quantum chemistry calculations by Tokmakov and Lin using the G2M(RCC5)//B3LYP method, we constructed a kinetic model and estimated phenomenological pressure-dependent rate coefficients, k(T, P), with the Arkane package in the reaction mechanism generator. The MBMS experiments, performed at 600–800 K and 10–50 Torr, revealed three major product peaks: m/z = 105 (adducts, mostly 2-phenylethyl radical, but also 1-phenylethyl radical, ortho-ethyl phenyl radical, and a spiro-fused ring radical), 104 (styrene, co-product with a H atom), and 78 (benzene, co-product with C2H3 radical). Product branching ratios were predicted by the model and validated by experiments for the first time. At 600 K and 10 Torr, the yield ratio of the H-abstraction reaction (forming benzene + C2H3) is measured to be 1.1% and the H-loss channel (styrene + H) has a 2.5% yield ratio. The model predicts 1.0% for H-abstraction and 2.3% for H-loss, which is within the experimental error bars. The branching ratio and formation of styrene increase at high temperature due to the favored formally direct channel (1.0% at 600 K and 10 Torr, 5.8% at 800 K and 10 Torr in the model prediction) and the faster β-scission reactions of C8H9 isomers. The importance of pressure dependence in kinetics is verified by the increase in the yield of the stabilized adduct from radical addition from 80.2% (800 K, 10 Torr) to 88.9% (800 K, 50 Torr), at the expense of styrene + H. The pressure-dependent model developed in this work is well validated by the LAS and MBMS measurements and gives a complete picture of the C6H5 + C2H4 reaction.

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“…On the basis of quantum chemical and statistical calculations, Lin et al proposed that the reaction involved an initial addition of the phenyl radical to the carbon−carbon double bond of the ethylene molecule via a phenylethyl radical, C 6 H 5 C 2 H 4 , followed by atomic hydrogen elimination . Note that this radical intermediate is utilized in polymer chemistry as a model compound to understand the region selectivity of polysterene radicals. − Also, the phenylethyl radial is formed during the in vivo oxidation of the drug phenylethylhydrazine and is often utilized to understand the metabolism of hydrazine and analogues compounds as well as DNA damage by carbon-centered radicals. − …”

Section: Introductionmentioning

confidence: 99%

“…[40][41][42] Also, the phenylethyl radial is formed during the in vivo oxidation of the drug phenylethylhydrazine and is often utilized to understand the metabolism of hydrazine and analogues compounds as well as DNA damage by carbon-centered radicals. [43][44][45][46] Despite the central role of the phenyl-ethylene reaction in the formation of PAHs, and the role of potential phenylethyl radical intermediates in polymer science and medicinal chemistry, the theoretical investigations have never been verified experimentally under single collision conditions, i.e., experimental conditions in which the outcome of a single collision can be observed without any wall effects. Here, we present the very first crossed molecular beam study of the reaction of the phenyl radical, C…”

Section: Introductionmentioning

confidence: 99%

Reaction Dynamics on the Formation of Styrene: A Crossed Molecular Beam Study of the Reaction of Phenyl Radicals with Ethylene

Zhang

Guo

et al. 2007

J. Org. Chem.

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The reaction dynamics of phenyl radicals (C6H5) with ethylene (C2H4) and D4-ethylene (C2D4) were investigated at two collision energies of 83.6 and 105.3 kJ mol-1 utilizing a crossed molecular beam setup. The experiments suggested that the reaction followed indirect scattering dynamics via complex formation and was initiated by an addition of the phenyl radical to the carbon-carbon double bond of the ethylene molecule forming a C6H5CH2CH2 radical intermediate. Under single collision conditions, this short-lived transient species was found to undergo unimolecular decomposition via atomic hydrogen loss through a tight exit transitions state to synthesize the styrene molecule (C6H5C2H3). Experiments with D4-ethylene verified that in the corresponding reaction with ethylene the hydrogen atom was truly emitted from the ethylene unit but not from the phenyl moiety. The overall reaction to form styrene plus atomic hydrogen from the reactants was found to be exoergic by 25 +/- 12 kJ mol(-1). This study provides solid evidence that in combustion flames the styrene molecule, a crucial precursor to form polycyclic aromatic hydrocarbons (PAHs), can be formed within a single neutral-neutral collision, a long-standing theoretical prediction which has remained to be confirmed by laboratory experiments under well-defined single collision conditions for the last 50 years.

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Chemical and photochemical generated carbon-centered radical intermediate and its reaction with desoxyribonucleic acid

Cited by 7 publications

References 25 publications

Combined Quantum Chemical/RRKM-ME Computational Study of the Phenyl + Ethylene, Vinyl + Benzene, and H + Styrene Reactions

Combined Quantum Chemical/RRKM-ME Computational Study of the Phenyl + Ethylene, Vinyl + Benzene, and H + Styrene Reactions

Direct Kinetics and Product Measurement of Phenyl Radical + Ethylene

Reaction Dynamics on the Formation of Styrene: A Crossed Molecular Beam Study of the Reaction of Phenyl Radicals with Ethylene

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