Fragmentation of chlorpyrifos by thermal electron attachment: a likely relation to its metabolism and toxicity

2018 ◽  
Vol 20 (34) ◽  
pp. 22272-22283 ◽  
Author(s):  
Stanislav A. Pshenichnyuk ◽  
Alberto Modelli ◽  
Alexander S. Vorob’ev ◽  
Nail L. Asfandiarov ◽  
Ekaterina P. Nafikova ◽  
...  
Keyword(s):  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Electron Attachment ◽  
Negative Ions ◽  
Organophosphorus Insecticide ◽  
Dissociative Electron Attachment ◽  
Thermal Electron ◽  
Electron Transmission

The energies of formation and dissociative decays of temporary negative ions of the organophosphorus insecticide chlorpyrifos are studied using electron transmission, dissociative electron attachment spectroscopies and quantum-chemical calculations.

UV-Photoelectron, Electron Transmission, and Dissociative Electron Attachment Spectroscopies of Acetone Oximes

1998 ◽  
Vol 102 (41) ◽  
pp. 8037-8043 ◽  
Author(s):  
Dal Colle ◽  
Giuseppe Distefano ◽  
Alberto Modelli ◽  
Derek Jones ◽  
Maurizio Guerra ◽  
...  
Keyword(s):  
Electron Attachment ◽  
Dissociative Electron Attachment ◽  
Electron Transmission

On the structure of negative ions formed by dissociative electron attachment by monochlorophenol molecules

2003 ◽  
Vol 52 (9) ◽  
pp. 1974-1981 ◽  
Author(s):  
R. V. Khatymov ◽  
M. V. Muftakhov ◽  
P. V. Schukin ◽  
V. A. Mazunov
Keyword(s):  
Electron Attachment ◽  
Negative Ions ◽  
Dissociative Electron Attachment

scholarly journals Influence of electronic states of nanographs in carbon microcrystallines on surface chemistry of activated charcoal varieties

Surface ◽  
2021 ◽  
Vol 13(28) ◽  
pp. 15-38
Author(s):  
V.V. Strelko ◽  
◽  
Yu.I. Gorlov ◽  
Keyword(s):  
Quantum Chemical Calculations ◽  
Active Carbon ◽  
Quantum Chemical ◽  
Electronic States ◽  
Negative Ions ◽  
Chemical Transformations ◽  
Molecular Models ◽  
Heat Effects ◽  
Total Energies ◽  
Model Reactions

In this paper, the nature of the chemical activity of pyrolyzed nanostructured carbon materials (PNCM), in particular active carbon (AC), in reactions of electron transfer considered from a single position, reflecting the priority role of paramagnetic centers and edge defunctionaled carbon atoms of carbon microcristallites (CMC) due to pyrolysis of precursors. Clusters in the form of polycyclic aromatic hydrocarbons with open (OES) and closed (CES) electronic shells containing terminal hydrogen atoms (or their vacancies) and different terminal functional groups depending on specific model reactions of radical recombination, combination, replacement and elimination were used to model of nanographenes (NG) and CM. Quantum-chemical calculations of molecular models of NG and CMC and heat effects of model reactions were performed in frames of the density functional theory (DFT) using extended valence-splitted basis 6-31G(d) with full geometry optimization of concrete molecules, ions, radicals and NG models. The energies of boundary orbitals were calculated by means of the restricted Hartry-Fock method for objects with closed (RHF) and open (ROHF) electronic shells. The total energies of small negative ions (HOO-, HO-) and anion-radical О2•‾) were given as the sum of calculated total energies of these compounds and their experimental electron affinities. The estimation of probability of considered chemical transformations was carried out on the base on the well-known Bell-Evans-Polyani principle about the inverse correlation of the thermal effects of reactions and its activation energies. It is shown that the energy gap ΔЕ (energy difference of boundary orbitals levels) in simulated nanographens should depend on a number of factors: the periphery structure of models, its size and shape, the number and nature of various structural defects, electronic states of NG. When considering possible chemical transformations on the AC surface, rectangular models of NG were used, for which the simple classification by type and number of edge structural elements of the carbon lattice was proposed. Quantum chemical calculations of molecular models of NG and CNC and the energy of model reactions in frames of DTF showed that the chemisorption of free radicals (3O2 and N•O), as recombination at free radical centers (FRC), should occur with significant heat effects. Such calculations give reason to believe that FRC play an important role in formation of the functional cover on the periphery of NG in CMC of studied materials. On the base of of cluster models of active carbon with OES new ideas about possible reactions mechanisms of radical-anion О2•‾ formation and decomposition of hydrogen peroxide on the surface of active carbon are offered. Explanation of increased activity of AC reduced by hydrogen in H2O2 decomposition is given. It is shown that these PNCM models, as first of all AC, allow to adequately describe their semiconductor nature and acid-base properties of such materials.

scholarly journals Ring-Selective Fragmentation in the Tirapazamine Molecule upon Low-Energy Electron Attachment

2021 ◽  
Vol 22 (6) ◽  
pp. 3159
Author(s):  
Eugene Arthur-Baidoo ◽  
Joao Ameixa ◽  
Milan Ončák ◽  
Stephan Denifl
Keyword(s):  
Benzene Ring ◽  
Quantum Chemical ◽  
Electron Attachment ◽  
Oh Radical ◽  
Dissociative Electron Attachment ◽  
Triazine Ring ◽  
Beam Experiment ◽  
First Excited State ◽  
Low Energy Electron ◽  
The Common

We investigate dissociative electron attachment to tirapazamine through a crossed electron–molecule beam experiment and quantum chemical calculations. After the electron is attached and the resulting anion reaches the first excited state, D1, we suggest a fast transition into the ground electronic state through a conical intersection with a distorted triazine ring that almost coincides with the minimum in the D1 state. Through analysis of all observed dissociative pathways producing heavier ions (90–161 u), we consider the predissociation of an OH radical with possible roaming mechanism to be the common first step. This destabilizes the triazine ring and leads to dissociation of highly stable nitrogen-containing species. The benzene ring is not altered during the process. Dissociation of small anionic fragments (NO2−, CN2−, CN−, NH2−, O−) cannot be conclusively linked to the OH predissociation mechanism; however, they again do not require dissociation of the benzene ring.

scholarly journals Why Does the Type of Halogen Atom Matter for the Radiosensitizing Properties of 5-Halogen Substituted 4-Thio-2′-Deoxyuridines?

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2819 ◽  
Author(s):  
Paulina Spisz ◽  
Magdalena Zdrowowicz ◽  
Samanta Makurat ◽  
Witold Kozak ◽  
Konrad Skotnicki ◽  
...  
Keyword(s):  
Tumor Cell ◽  
Quantum Chemical ◽  
Halogen Atom ◽  
Activation Barrier ◽  
Electron Attachment ◽  
Remarkable Difference ◽  
Dissociative Electron Attachment ◽  
Chemical Studies ◽  
Quantum Chemical Studies ◽  
Tumor Cell Killing

Radiosensitizing properties of substituted uridines are of great importance for radiotherapy. Very recently, we confirmed 5-iodo-4-thio-2′-deoxyuridine (ISdU) as an efficient agent, increasing the extent of tumor cell killing with ionizing radiation. To our surprise, a similar derivative of 4-thio-2’-deoxyuridine, 5-bromo-4-thio-2′-deoxyuridine (BrSdU), does not show radiosensitizing properties at all. In order to explain this remarkable difference, we carried out a radiolytic (stationary and pulse) and quantum chemical studies, which allowed the pathways to all radioproducts to be rationalized. In contrast to ISdU solutions, where radiolysis leads to 4-thio-2’-deoxyuridine and its dimer, no dissociative electron attachment (DEA) products were observed for BrSdU. This observation seems to explain the lack of radiosensitizing properties of BrSdU since the efficient formation of the uridine-5-yl radical, induced by electron attachment to the modified nucleoside, is suggested to be an indispensable attribute of radiosensitizing uridines. A larger activation barrier for DEA in BrSdU, as compared to ISdU, is probably responsible for the closure of DEA channel in the former system. Indeed, besides DEA, the XSdU anions may undergo competitive protonation, which makes the release of X− kinetically forbidden.

scholarly journals Electron-Induced Decomposition of Uracil-5-yl O-(N,N-dimethylsulfamate): Role of Methylation in Molecular Stability

2021 ◽  
Vol 22 (5) ◽  
pp. 2344
Author(s):  
Eugene Arthur-Baidoo ◽  
Karina Falkiewicz ◽  
Lidia Chomicz-Mańka ◽  
Anna Czaja ◽  
Sebastian Demkowicz ◽  
...  
Keyword(s):  
Gas Phase ◽  
Quantum Chemical ◽  
Electron Attachment ◽  
Dissociative Electron Attachment ◽  
Stabilization Method ◽  
Radical Species ◽  
Molecular Stability ◽  
Resonance Stabilization ◽  
Induced Decomposition

The incorporation of modified uracil derivatives into DNA leads to the formation of radical species that induce DNA damage. Molecules of this class have been suggested as radiosensitizers and are still under investigation. In this study, we present the results of dissociative electron attachment to uracil-5-yl O-(N,N-dimethylsulfamate) in the gas phase. We observed the formation of 10 fragment anions in the studied range of electron energies from 0–12 eV. Most of the anions were predominantly formed at the electron energy of about 0 eV. The fragmentation paths were analogous to those observed in uracil-5-yl O-sulfamate, i.e., the methylation did not affect certain bond cleavages (O-C, S-O and S-N), although relative intensities differed. The experimental results are supported by quantum chemical calculations performed at the M06-2X/aug-cc-pVTZ level of theory. Furthermore, a resonance stabilization method was used to theoretically predict the resonance positions of the fragment anions O− and CH3−.

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