Radiation-chemical stability of molecular systems; reactions of monomolecular detachment of hydrogen atoms and dissociative attachment of electrons

1985 ◽  
Vol 26 (5) ◽  
pp. 519-525 ◽  
Author(s):  
V.G. Plotnikov
Keyword(s):  
Chemical Stability ◽  
Hydrogen Atoms ◽  
Dissociative Attachment ◽  
Radiation Chemical ◽  
Molecular Systems

An ab initio and density functional theory study on neutral pterin radicals

Pteridines ◽  
2015 ◽  
Vol 26 (4) ◽  
pp. 135-142 ◽  
Author(s):  
Gilbert Reibnegger
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Electronic Structures ◽  
Density Functional ◽  
Electron System ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Molecular Systems ◽  
Phase Water ◽  
Planar Transition

AbstractThe electronic structures of the five radicals resulting from homolytic elimination of one of the hydrogen atoms from the most stable tautomeric form of neutral pterin were investigated in gas phase as well as in aqueous solution. Molecular wave functions obtained by density functional theory were analysed by quantum theory of atoms in molecules and electron localisation functions (ELF). Spin densities of the radicals as well as electrostatic potential functions were analysed. Radicals resulting from elimination of N-bonded hydrogen atoms are more stable in comparison with radicals obtained after abstraction of C-bonded hydrogen atoms. N-centred radicals show strong delocalisation of spin density over both heteroaromatic rings; in C-centred radicals delocalisation does not occur. ELF analyses showed that in N-derived radicals particularly the lone electron pair at N2′ is strongly involved into the bicyclic heteroaromatic π-electron system. Thereby, bonding geometry at N2′ in these radicals changes from pyramidal to planar. Transition from gas phase to solution phase (water) generally leads to increased polarity of the structures. Pterin-derived free radicals have been implicated in several biologically important reactions; so this investigation provides first insights into the detailed electronic structures of such molecular systems.

Radiation-chemical stability of TBP in solutions of hydrocarbons

1966 ◽  
Vol 21 (4) ◽  
pp. 946-950 ◽  
Author(s):  
E. P. Barelko ◽  
I. P. Solyanina ◽  
Z. I. Tsvetkova
Keyword(s):  
Chemical Stability ◽  
Radiation Chemical

ISOTOPE EFFECTS IN X-RAY-IRRADIATED ACIDIFIED H2O–D2O SOLUTIONS

1963 ◽  
Vol 41 (9) ◽  
pp. 2175-2186 ◽  
Author(s):  
Chava Lifshitz
Keyword(s):  
Isotope Effect ◽  
Molecular Hydrogen ◽  
Isotope Effects ◽  
Recombination Reaction ◽  
X Rays ◽  
Acid Solutions ◽  
Hydrogen Atoms ◽  
Radiation Chemical ◽  
X Ray ◽  
Molecular Product

H2O–D2O mixtures containing 0.1–1 N H2SO4 were irradiated by 200-kv X rays. The molecular isotope effect, [Formula: see text], was determined from experiments on KBr solutions. The atomic isotope effect, [Formula: see text], was determined from experiments on ethanol solutions. At 96% D2O, αA = 3.7 ± 0.5 and αM = 4.0 ± 0.2. The isotope effects are discussed in connection with the radiation-chemical reaction H3O+ + eH2O → H + 2H2O. The connection between the atomic and molecular hydrogen is discussed. It is concluded that the relation between the observed atomic and molecular isotope effects is not contrary to a hydrogen atom recombination reaction leading to the molecular product. Isotope effects due to the oxidation of Fe+2 ions by hydrogen atoms in acid solutions were measured and the mechanism of this reaction is discussed.

Antisymmetric features of atomic charge density: Their significance in studies of electron redistribution accompanying bonding, and their relevance to thegeneral problem of structure and properties of molecules

1965 ◽  
Vol 18 (5) ◽  
pp. 595 ◽  
Author(s):  
B Dawson
Keyword(s):  
Neutron Diffraction ◽  
Charge Density ◽  
Elevated Temperatures ◽  
Covalent Bond ◽  
Atomic Charge ◽  
Electronic Charge ◽  
Structure And Properties ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Molecular Systems

A discussion is given of aspects of atomic charge density which possess the property of antisymmetry about the reference nuclear centre. It is shown that components of electronic charge density displaying this property must be an integral part of all bonded atoms possessing non-centric environments. The significance of such components for detailed X-ray diffraction studies of the electron redistribution which characterizes covalent bond formation is demonstrated for the case of carbon in diamond, and it is shown that the so-called "forbidden" 222 reflexion there is a natural consequence of antisymmetric features required by the non-centric (tetrahedral) disposition of bonded atoms in this lattice. Detailed X-ray studies of anthracene, salicylic acid, and cyanuric acid are cited to illustrate the importance and generality of antisymmetry concepts in accurate examinations of molecular systems; their significance in explaining long-standing discrepancies in the location of hydrogen atoms by X-ray and neutron diffraction methods is also noted. The discussion also demonstrates the relevance of antisymmetry to recent important neutron diffraction studies of fluorite structures at different elevated temperatures. Here, the accessible aspects of atomic charge density are those of nuclear charge density, i.e. nuclear vibrational behaviour, and it is shown that the presence of significant anharmonicity in the anionic vibrational pattern is responsible for the unusual diffraction effects observed. This anharmonicity has the same antisymmetry characteristics as those responsible for the 222 reflexion observed in X-ray studies of diamond. It is predicted that .future neutron studies of diamond structures (C, Si, Ge) at elevated temperatures should reveal a range of "forbidden" reflexions produced by antisymmetric components in the nuclear motions about their equilibrium positions. The discussion concludes with brief comments on the multipolar nature of bonded atoms arising from antisymmetric components in their electronic charge densities. Preliminary remarks are made on the relevance of the multipole concept to general problems of structure and properties of molecular systems.

Radiolysis of transformer oil in presence of trichlorbenzen and nano-γ-Al2O3

2021 ◽  
Vol 2 ◽  
pp. 80-85
Author(s):  
Z. I. Iskenderova ◽  
Keyword(s):  
Absorbed Dose ◽  
Chemical Yield ◽  
Transformer Oil ◽  
Nano Particles ◽  
Electronic Excitation Energy ◽  
Hydrogen Atoms ◽  
Ph Indicator ◽  
Radiation Chemical ◽  
Initial Concentration ◽  
Main Components

In this work, a comparative study of the kinetics of changes in the pH indicator, the formation of H2O2 and CO2 depending on the absorbed dose at the radiolysis of TCB containing transformer oil in the presence and without nano-γ-Al2O3 under the action of γ radiation was carried out. During radiolysis of both systems (TСB + transformer oil and TСB + transformer oil + 0.1 g of nano-γ-Al2O3), the radiation-chemical yield of CO2 decreases with an increase in the initial concentration of TCB, although at the presence of nano-particles, the values of the radiation-chemical riels of CO2 become less. Unlike CO2, the radiation-chemical yields of H2O2 increase with an increase in the initial concentration of TCB, but their values are less in the presence of nano-γ-Al2O3. The results obtained are explained by the reactions of active particles, radiolysis of the main components of transformer oil, such as hydrogen atoms and hydrocarbon radicals with TCB and dissolved oxygen molecules. In addition, there is a transfer of electronic excitation energy from alkane and cycloalkane molecules to aromatic hydrocarbon molecules. The effect of nano-γ-Al2O3 on the radiolysis of the mixture is discussed on the basis of the reaction of electron and hole centers with the molecules of the components of the irradiated mixture.

Remarks on the diffuse interstellar lines

1967 ◽  
Vol 31 ◽  
pp. 91-93 ◽  
Author(s):  
G. Herzberg
Keyword(s):  
Hydrogen Atoms ◽  
Interstellar Gas

It is suggested that the diffuse interstellar lines are produced in the interstellar gas by molecules consisting of a few hydrogen atoms and one other atom, such as CH4+ or NH4. Diffuseness of the lines is assumed to result from predissociation of these molecules.

Role of the exosporial membrane in attachment and germination of C. sporogenes

1993 ◽  
Vol 51 ◽  
pp. 38-39
Author(s):  
B.J. Panessa-Warren ◽  
G.T. Tortora ◽  
J.B. Warren
Keyword(s):  
Enzymatic Degradation ◽  
Light Transmission ◽  
Extended Period ◽  
Growth Conditions ◽  
Clostridium Sporogenes ◽  
Radiation Chemical ◽  
Physical Trauma ◽  
Extended Contact ◽  
Cold Pressure

Some bacteria are capable of forming highly resistant spores when environmental conditions are not adequate for growth. Depending on the genus and species of the bacterium, these endospores are resistant in varying degrees to heat, cold, pressure, enzymatic degradation, ionizing radiation, chemical sterilants,physical trauma and organic solvents. The genus Clostridium, responsible for botulism poisoning, tetanus, gas gangrene and diarrhea in man, produces endospores which are highly resistant. Although some sporocides can kill Clostridial spores, the spores require extended contact with a sporocidal agent to achieve spore death. In most clinical situations, this extended period of treatment is not possible nor practical. This investigation examines Clostridium sporogenes endospores by light, transmission and scanning electron microscopy under various dormant and growth conditions, cataloging each stage in the germination and outgrowth process, and analyzing the role played by the exosporial membrane in the attachment and germination of the spore.

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