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- Author or Editor: J. Kuruc x
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Paramagnetic centers by X-ray-irradiation of aluminium hydroxide
Epr spectroscopy, radiation chemical yield and kinetics of thermal decay of paramagnetic centers
Abstract
EPR spectra of paramagnetic centers originating from X-ray-irradiation of aluminium hydroxide at room temperature have been measured. The EPR spectrum represents a superposition of EPR spectra of ionic centers O–, holes of type
spins.)=4.4±0.6) spins per 100 eV absorbed energy. The decay of paramagnetic centers in irradiated Al(OH)3 was oberved at 293 K. The rate constant of the paramagnetic centers decay in irradiated Al(OH)3 is K2=(0.0980±0.0019) kg·mol–1·min–1 and their half-life is 9.43±0.18 days.
Abstract
Gamma-radiolytically generated radicals of crown ethers /12-crown-4, 1; 15-crown-5, 2; dicyclohexano-24-crown-8, 3/ and the model compounds /tetrahydrofurane, 4 and 1,4-dioxane, 5/ were studied by the spin-trapping method using C-phenyl-N-methylnitrone /PBN/ as a spin-trapping agent giving rise to the sufficiently stable nitroxyl radicals. The spin adducts of radicals 2 and 3 are relatively stable up to the temperature 253 K and 453 K, respectively.
Abstract
The quantum yield of nitrobenzene disappearance has been determined. The mechanism of the photosubstitution of nitro group by the photolysis of nitrobenzene-tetrachloromethane mixture is discused.
Abstract
The method of low temperature ESR spectroscopy was used to study the free radicals generated by 
-irradiation of crown ethers: 12-crown-4 /1/; 15-crown-5 /2/; dicyclohexane-24-crown-8 /3/; and their analogues: tetrahydrofurane /4/ and 1,4-dioxane /5/. ESR spectra of radicals 4 and 5 taken at 77 K represent a simple singlet; ESR spectra of radicals generated from 1, 2 and 3 have a complex, multiplet structure. The kinetics of thermal decay of free radicals 4 in dependence on temperature starting from 103 K was investigated. The radicals 4 decay very fast at 253 K.
Abstract
The quantum yields of formation of chloride ions were determined in photolysis (
=254 nm) of watercarbon tetrachloride organic phase of 
CCl4(Cl–)=0.89±0.04 water-chlorobenzene (
PhCl(Cl–)=0.137± ±0.005) two-phase systems and saturated aqueous solutions of carbon tetrachloride (
CCl4(Cl–)=18.9±5.6 and chlorobenzene
PhCl(Cl–)=0.56±0.03. The quantum yields of chloride ions obtained from these systems are compared with partial radiation yields in the same systems. A mechanism for formation of Cl– ions is proposed.
Abstract
The influence of nitrobenzene and chlorobenzene on the total radiation yield of chloride ions in the 
-irradiation of water-carbon tetrachloride two-phase systems has been determined. Nitrobenzene at small concentrations shows a pronounced protective influence on the radiation destruction of carbon tetrachloride. Similar protective effect on the destruction of carbon tetrachloride is shown by chlorobenzene, too, but the decrease of radiation yields of chloride ions is smoother, which is explained by radiation decomposition of chlorobenzene itself. Protective effect of nitrobenzene and chlorobenzene on the radiation destruction of carbon tetrachloride is explained by transfer of energy from carbon tetrachloride molecules to the aromatic molecules.
Abstract
Various volatile products formed in the 
-radiolysis of water-nitrobenzene-carbon tetrachloride two phase systems have been identified using GC-MS and GC-FTIR systems. The conditions for the separation of the products are described in detail. It was found that product formation is dependent on the composition of the systems. In case when the volume ratio of carbon tetrachloride is higher, chlorobenzene appears to be one of the major radiolytic products. This means that substitution of the nitro group by chlorine atom occurs in the presence of water. Substitution of the nitro group and hydrogen atom by chlorine atom and/or HO free radical is also observed, depending on the composition of the mixture. Formation of phenyl isocyanate is proposed to be the result of interaction of dichlorocarbene and nitrobenzene. The mechanism of some main product formation is described briefly.
Abstract
Radicals formed at X- and 
-radiolysis of glass and liquid tri-n-butylphosphate /TBP/, di-n-butylphosphate /DBP/, di/2-ethylhexyl/phosphoric acid /DEHPA/, tri-p-tolylphosphate /TTP/ and di-n-butyl-n-butyl phopsphonate /DBBPN/ were studied using the technique of spin trap using C-phenyl-N-tert. butylnitrone /PBN/ and 2-methyl-2-nitrosopropane /MNP/ as spin trap agents. When using PBN, nitroxyl radicals generated by the spin trap of hydrogen atoms and labile radicals of phosphates or phosphonate were identified after irradiation in vacuum. Radiation-chemical yield of spin adducts was observed, as well as their thermal stability at 293 K, rate constants and half-time of decay and free activation energy of the decay of spin adducts. Mechanism of generation and decay of nitroxyl radicals is discussed. The spin adducts with MNP have a relatively low stability and superposition of some adducts spectra.
Abstract
A good deal of products formed in the 
-radiolysis of isomeric nitroaniline solutions in carbon tetrachloride have been identified using GC-FTIR-MS technique. Tetrachloroethylene, chloroeenzene, hexachloroethane isomeric di-, tri- and tetrachlorobenzenes and chloroisocyanatobenzenes are among the important products formed in the radiolysis. Formation of dichlorobenzene is the result of ipso-substitution of both the nitro and aniline group by chlorine atom and the subsequent chlorination of dichlorobenzene results in the formation of polychlorobenzenes. Chloroisocyanatobenzene is proposed to be the product arising from the interaction of dichlorocarbene and the nitro group of nitroaniline followed by chlorination of the resulting product, isocyanatobenzene. A 94% yield of undissolved 1,2-aminonitrobenzene chloride salt is obtained from the radiolysis of o-nitroaniline solution in carbon tetrachloride with a radiation yield of 1.83 molecules per 100 eV absorbed energy for an irradiation dose of 267 kGy.
Abstract
GC-MS method has been used for the determination of initial radiation yields of tetrachloroetyhelene, hexachloroethane and other volatile radiolyticalipso-substitued products including dichlorobenzenes, and chloronitrobenzenes formed in the 
-radiolysis of solutions of nitrobenzene, isomeric dinitrobenzenes, nitrophenols and nitroanilines in carbon tetrachloride. The decay of the solutes except nitrobenzene with dose is also considered by evaluating G(-solute) values. In almost all the solutions a decrease in the G-value of hexachloroethane is observed except inpara-dinitrobenzene andpara-nitrophenol solution where the G-value remains unaltered. The formation of tetrachloroethylene is not affected by the presence of nitroaromatics expect in the case ofortho-nitroaniline andortho-nitrophenol solutions, where an increase in the G-value is observed. This observation is explained in terms of energy transfer (quenching), charge transfer and scavenging of electrons by the nitroaromatic mmolecules.
