Radiation-induced gas-phase dealkylation and isomerization of p-tert-butyltoluene

D₃ ⁺ ions, produced by deuterium -radiolysis, were allowed to react with gaseous p-tert-butyltoluene. The excited arenium ions formed, if not collisionally stabilized, underwent predominantly dealkylation to form toluene and, to a minor extent, isomerization. The dependence of reaction product yields on the substrate pressure is discussed.     

The radiolysis of aqueous solution of bis/1,2-dicarbollyl/cobalt/III/ acid

The radiation-induced oxidation of bis/1,2-dicarbollyl/cobalt/III/ acid by OH radicals in deaerated/aerated aqueous solutions has been investigated. 8-Monohydroxy-, and 8,8-dihydroxy-derivatives have been identified as products of the -radiolysis. For the different conditions the following radiationchemical yields were observed: in the presence of N₂ atmosphere G/_OHDCC/=1.58, in aerated solution 2.11 and 3.04 in a solution saturated with CCl₃.     

Effect of iso-propanol on the radiolysis of aqueous solutions of periodate

The -radiolysis of IO ₄ ^– in aqueous solution and binary solutions containing iso-propanol has been studied as a function of reactant concentration and absorbed dose. The disappearance of periodate ion in the presence of alcohol is found to be higher as compared to that observed in the pure system. The trend in the G-values determined at various combinations of the reactant concentrations suggests the occurrence of a chain reaction in the radiolytic process.     

Effect of LET on the radiolysis of cyclopentane

The - and -radiolysis of cyclopentane were compared in the presence and absence of iodine scavenger. The G-values of the main hydrocarbon products, cyclopentene and bicyclopentyl are 2.22 and 0.56 molecule/100 eV in -radiolysis and 3.25 and 1.23, respectively, in -radiolysis. During high LET -irradiation the yields of products formed by a radical mechanism are much smaller (G=1.18) than in -radiolysis (G=2.68), whereas unimolecular cyclopentene formation is hardly influenced by LET (G=1.8 and 1.6, respectively).     

Effect of LET on radiolysis of C6−C8 cycloalkane systems

The - and -radiolysis of cyclohexane, cycloheptane and cyclooctane was investigated in the absence and presence of iodine scavenger. Comparison of the distributions of products formed revealed considerable differences between - and -radiolysis, and the decomposition of strainless cyclohexane and strained cycloheptane and cyclooctane.     

Effect of Temperature on the Yields of Final Products in the γ-Radiolysis of Formaldehyde Solutions in C1–C3 Alkanols

The effect of temperature on the yields of 1,2-alkanediols in the -radiolysis of the methanol(or ethanol)–formaldehyde (0.9 M) systems and on the yields of 1,2-alkanediols, carbonyl compounds, methanol, and ethanol in the -radiolysis of the 1-propanol(or 2-propanol)–formaldehyde (1 M) systems was studied over the range 373–473 K. It was found that the temperature dependence of the yields of 1,2-butanediol and 2-methyl-1,2-propanediol exhibited maximums at 423 and 373 K, respectively.     

Gamma radiolysis of Methyl Red solution and reaction induced by γ-irradiated NaCl in Methyl Red

The -radiolysis of Methyl Red solution in HCl medium at pH=2 has been studied along with energy transfer reaction brought about byF and hole centers of -irradiated NaCl. The G-values for degradation of the azo dye indicator by radiolysis and -irradiated salt were determined as 9·10^–1 and 4.8·10^–3, respectively. The kinetic rate constants (k) of degradation are evaluated as 2·10^–5 rad^–1 in the case of direct radiolysis, while for the irradiated salt it is 2·10^–7 rad^–1. The extent of degradation by direct -radiolysis is 100–200 times greater as compared to that by the -irradiated salt. The same mechanism is proposed for radiolysis as well as the reaction induced by -irradiated sodium chloride.     

Synthesis of two regiospecific isomers of monotosyl-γ-cyclodextrin

Tosylation of -cyclodextrin in an aqueous alkaline solution gave two regiospecific isomers (2-monotosyl--cyclodextrin(1) and 6-monotosyl--cyclodextrin(2)), that could recognize and catalyze small sized guest molecules; 2-monotosyl--CD recognized small sized guest molecules more effectively than did 6-monotosyl--CD.     

Radiation-Chemical Aspects of Radioactive Waste Management

Studies of radiation-chemical processes in model liquid radioactive waste are summarized. These processes are radiolytic transformations of various substances present in the waste (actinide ions (primarily, neptunium and plutonium ions), inorganic matter (for example, nitrate ions), and organic compounds (acetic acid, EDTA, etc.)) and radiolytic gas evolution. Attention was focused on the latter process. The volumes and compositions of gases formed in the -radiolysis of aqueous solutions that simulated intermediate-level and high-level liquid waste were determined. It was found that the nature and the radiation-chemical yields of released gases depend on the absorbed dose, the composition and concentration of solutions, the irradiation temperature, the presence of solid substances, etc. In a number of cases, data obtained with model solutions were compared to the results of studies of real liquid radioactive waste.     

Applied Aspects of the γ-Radiolysis of C1–C4 Alcohols and Binary Mixtures on Their Basis

Generalized data on the -radiolysis of aliphatic C₁–C₄ alcohols are summarized. These data can be used for solving practical problems in the related areas of research. In particular, a rate equation that relates the radiation-chemical yield of an 1 : 1 adduct formed from saturated and unsaturated components upon the -radiolysis of a binary system to the concentrations of these components was derived. An equation was obtained for estimating the reaction rate constants of decay of identical hydroxyalkyl radicals in collisions with each other from the reciprocal viscosity (fluidity) of corresponding alcohols. An empirical equation for calculating the concentration of the free (desolvated) form of formaldehyde in alcohol–formaldehyde systems at various temperatures and total formaldehyde concentrations and an equation for evaluating solvent concentrations in these systems were derived.     

The gamma-radiolysis of HEDTA in a simulated, mixed waste

The -radiolysis of the parent compound N-(2-hydroxyethyl)ethylenediaminetriaceticacid (HEDTA) in a simulant of a Hanford mixed waste, at a -dose of7.5 . 10₆±10% R, yielded 94.4% degradation. HEDTA radiolysisyielded four degradation products: glyoxylic acid, N-( nitroso)iminodiaceticacid (NIDA) and 2 dicarboxylic acids, ethandioic (oxalic) and propandioic(malonic) acids. Glyoxylic acid had been identified in previous studies byour laboratory as N-hydroxymethyl-N-methyliminoacetic acid (HMMIA). Promptedby studies from another laboratory, the chelator fragment previously reportedby our laboratory as N-(methylamine)iminodiacetic acid (MAIDA) is re-identifiedas NIDA. A methylamine moiety previously believed to be present in MAIDA,and several other chelator fragments, as well, has been re-identified as anitroso group.     

A study of the color reaction of iron with “TTA”

Summary TTA, or 2-Thenoyltrifluoroacetone, gives with ferric ion, in various concentrations colorations ranging from blood red to light pink. The advantages of this test are that it is simple to perform, that it is applicable in different acid media of fairly high concentrations, and that it is somewhat sensitive in the presence of ions that usually interfere with such tests. The sensitivity (limit of identification) was found to be 0,5 and the limit of concentration 1 : 100000 when a benzene solution of the reagent was reacted with a slightly acid solution of ferric ion on spot paper.

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Zusammenfassung TTA (2-Thenoyltrifluoraceton) gibt mit Ferriionen je nach Konzentration der letzteren eine blutrote bis blaßrosa Färbung. Die Probe ist einfach ausführbar und wird durch die Gegenwart von Säuren bis zu ziemlich hohen Konzentrationen sowie durch die Gegenwart störender Ionen wenig beeinträchtigt. Wenn eine Lösung des Reagens in Benzol zu einer leicht angesäuerten Ferrisalzlösung zugesetzt wird, beträgt die Erfassungsgrenze 0,5 bei einer Grenzkonzentration von 1 : 100000.

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Résumé Le TTA, thénoyl-2 trifluoracétone, donne avec les ions ferriques, suivant leur concentration, une coloration rouge sang à rose pâle. L'essai est simple à effectuer et à peine troublé par la présence des acides jusqu'à des concentrations passablement élevées et par la présence des ions gênants. Quand on ajoute une solution du réactif dans le benzène à une solution peu acide de sel ferrique, on observe une limite de sensibilité de 0,5 pour une limite de dilution de 1 : 100000.

     

Pulse radiolytic reduction studies of 1,4,4a,8a-tetrahydro-endo–1,4-methano-naphtha-5,8-dione (THMND): effect of tertiary structure

Radiolytic reduction of a substituted 5,8-naptha dione (THMND), synthesized in our laboratory, has been investigated by pulse radiolysis and steady-state -radiolysis in pure aqueous, aqueous-formate and in aqueous-2-propanol-acetone mixed solvent systems. The rate constants of formation of the semi-dione radicals were approx. 10⁹ dm³ mol^-1 s^-1 in aqueous-formate and aqueous-2-propanol-acetone mixed solvent. The semi-dione radicals decay by second order kinetics with rate constants (2k) of about 10⁹ and 10⁸ dm³ mol^-1 s^-1 in the above two solvents, respectively. The pK _a value of the radical was found to be 5.0 in aqueous-formate solution and 5.8 in the aqueous-2-propanol-acetone mixed solvent. The one-electron reduction potential (E ¹) value at pH 7, determined from the pulse-radiolysis experiment, was found to be –420 ± 20 mVvs. NHE at 298 K and was independent of solvent. Ab initio calculations on its one-electron reduction reaction suggest the formation of a radical, which is different from a semiquinone where the electron density is delocalised over the two oxygen atoms. Experimental absorption maxima of the radical in aqueous solution also agree very well with the ab initio calculated values. Steady-state -radiolysis of THMND produces the corresponding two-electron reduced species.     

Radiation-Chemical Behavior of C1-C4 Alcohols and Their Binary Mixtures

Data on -radiolysis of C₁-C₄ alcohols, practically significant for related fields of chemistry, were summarized.     

Study of radical species formed by radiolysis of polycrystalline calcium selenite (CaSeO3)

The paper presents spin density values on oxygen and selenium orbitals, derived from EPR spectra of SeO ₂ ^– radical, formed in the -radiolysis of calcium selenite (CaSeO₃). The kinetics of thermal annealing of radicals have been studied. A mechanism for radiolysis is proposed.     

Oxidation of Fe2+ ions by transfer of energy from γ-irradiated NaCl in aqueous Fricke solution

The oxidation of iron/II/ ions has been studied by dissolving -irradiated NaCl crystals in aqueous Fricke solution. The yield of iron/III/ ions was determined as a function of the amount of NaCl added, storage time, dose, concentration of iron/II/ ions and pH of the Fricke solution. The energy transfer parameter, , which is the ratio of G/Fe³⁺/ obtained by the addition of irradiated NaCl to that by direct radiolysis was evaluated.     

Reduction of nitrate during release of stored energy from γ-irradiated NaCl crystals in aqueous NaNO3 solution

Reduction of nitrate to nitrite takes place when the stored energy in the form of colour centres is released during dissolution of -irradiated NaCl crystals in aqueous sodium nitrate solution. Various parameters like dose, amount, storage time and particle size of irradiated NaCl salt which control the yield of nitrite have been studied. Similarly, the effect of concentration of NaNO₃ and the role of precipitation on the yields of nitrite in aqueous TlNO₃ and AgNO₃ have been investigated. The energy transfer parameter has been determined as the ratio of G/NO ₂ ^– / obtained by the addition of irradiated NaCl to that of direct -radiolysis. The data permit the evaluation of the concentration of colour centres in the irradiated NaCl crystals on the basis of the mechanism of reduction of nitrate.     

A Spectroscopic and Molecular Modelling Study of the Nature of the Association Complexes of Nile Red with Cyclodextrins

The polarity-sensitive fluorescent dye Nile Red forms association complexes with various cyclodextrins in aqueous solution. The formation of such association complexes has a significant effect on the Nile Red fluorescence, with the largest effect being observed in -cyclodextrin solution. When -cyclodextrin is used to increase the Nile Red concentration in solution, the absorption spectrum shows a large blue shift indicating the formation of an inclusion complex, but surprisingly the Nile Red fluorescence is strongly suppressed. A proposed explanation for this observation involves the formation of 1:2 host:guest complexes, in which the Nile Red guests are included as relatively non-fluorescent dimers. When the solutions were prepared by adding -cyclodextrinto a near-saturated aqueous solution of Nile Red (so that 1:1 or 2:1 complexation shouldbe favoured), significant fluorescence enhancement was observed. Analysis of thefluorescence enhancement as a function of host concentration indicated the formationof 2:1 host:guest complexes in these solutions. However, electrospray mass spectroscopic studies show no evidence for the formation of any such inclusion complexes. Furthermore, molecular modelling shows that the formation of a complex involving full insertion of Nile Red in the -cyclodextrin cavity is not stable, and will quickly eject the Nile Red guest molecule. These modelling results suggest that an association complex involving capping (via the association of Nile Red parallel to the cavity opening, or by partial insertion into the cavity) of the -cyclodextrin cavity by one or two Nile Red molecules is much more likely.     

Hydroxyl radical-mediated advanced oxidation processes for textile dyes: a comparison of the radiolytic and sonolytic degradation of the monoazo dye Acid Orange 7

Acid Orange 7, a textile azo dye, has been partially mineralized and degraded using -radiolysis and sonolysis. These two different advanced oxidation processes (AOP) are effective in producing OH radicals and cause complete destruction of the chromophore. The reaction mechanism of dye degradation has been probed by analyzing the reaction products with HPLC. In both cases, the final end products of degradation are oxalate and formate ions. The intermediates observed are all similar. While hydroxybenzenesulfonic acid is the major observed reaction intermediate in the oxidation processes, the pulse radiolysis studies indicate that the OH radical initiated pathway for attack occurs via the initial formation of 1,2-naphthaquinone and subsequent breakdown into oxalic acid.     

Effect of gamma-irradiation on the uncatalyzed bromate oscillator

The characteristics of uncatalyzed bromate oscillator are altered in presence of -irradiation. These alterations could not be accounted for in terms of substrates acting as scavengers for hydrogen atoms. The alteration of the effective activity of the key species in presence of -irradiation can also account for the changes observed in the oscillation characteristics.