Free Radicals in the Photolysis and Radiolysis of Polymers: IV. Radicals in γ- and UV-Irradiated Wood and Lignin

Free radicals formed in the radiolysis and photolysis of wood and lignin were studied using X-band and D-band EPR measurements. It was found that singlet spectra at g 2, which appeared upon the low-temperature (77 K) - and UV irradiation of wood and lignin, or singlets detected in a posteffect on heating the irradiated samples belong to radicals having conjugated carbon–carbon bonds. Formyl radicals in -irradiated wood and peroxide radicals in - and UV-irradiated wood were detected for the first time using EPR spectra. The radiation-chemical and quantum yields of radical formation reactions were determined. In wood at 77 K, G _R 3.2 1/100 eV and _R 2 × 10^–3.     

Einfluß der Anionensolvatation auf die Komplexbildung in Donorlösungsmitteln

Zusammenfassung Der Einfluß der Anionensolvatation auf die Komplexbildung in Donorlösungsmitteln wird folgendermaßen beschrieben: Der thermodynamische Solvatationseffekt hängt vom Verhältnis der freien Solvatationsenthalpien zur freien Enthalpie des Gesamtvorganges der Komplexbildung ab; d. h., je geringer die Akzeptorstärke des Akzeptors, um so mehr wird durch die Solvatation die Donorstärke eines Anions im Vergleich zu derjenigen des Neutraldonors erniedrigt. Der spezifische Solvatationseffekt bringt das spezifische Solvatisierungsvermögen eines Lösungsmittels gegenüber einem Anion (bei gegebenem Akzeptor) zum Ausdruck. Protonenhaltige Lösungsmittel, z. B. Wasser, Methanol, Essigsäure, Ameisensäure, Formamid, haben eine hohe Tendenz zur Wasserstoffbrückenwechselwirkung; sie solvatisieren Halogenid- und Pseudohalogenidionen wesentlich stärker als aprotische Donorlösungsmittel. Die Donorstärke eines anionischen Liganden wird in einem solchen Lösungsmittel entsprechend erniedrigt. Zum Vergleich der Stabilität eines Komplexes in verschiedenen Lösungsmitteln können ihre Donizitäten allein nicht herangezogen werden. Die solvatisierenden Eigenschaften von Donorlösungsmitteln nehmen ab: H₂O>ROHDMSOES>ANTMSNMDMF>DMA>HMPT.

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The influence of anion-solvation on complex formation in donor solvents

The said influence is described as follows: the thermodynamic solvation effect depends on the ratio of the free enthalpy of solvation to the free enthalpy of the complex forming reaction. It is increased by decreasing acceptor strength of the acceptor. The specific solvation effect is due to the specific solvating power of a solvent towards an anion (with given acceptor). Protonic solvents are known to have higher tendencies for hydrogen bridge interactions. They are stronger solvating agents for halide and pseudohalide ions than aprotic donor solvents. The donor properties of a donor anion is decreased in such solvents and the donicity alone is no longer a useful guide to estimate the relative stabilities of a complex in such media. The solvating properties of donor solvents decrease in the following order: H₂O>ROHDMSOES>ANTMSNMDMF>DMA>HMPT.

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Herrn Professor Dr.Richard Kieffer zum 65. Geburtstag gewidmet.     

Properties of aqueous salt solutions of poly(ethylene oxide). Cloud points, θ temperatures

The determination of the properties of aqueous salt solutions of poly(ethylene oxide) has been extended to the cloud point, and temperature measurements have been made at several concentrations for various salts (flourides, iodides, acetates, formates, phosphates, bromides, thiosulfates and perchlorates). The resulting dependency of the critical temperatures (mostly between 290–350 K) on the molar concentration can be expressed as sequences showing the decreasing effect of anion species or cation species in salting out the polymer. The decreasing order of effectiveness of the anions in reducing the temperature is PO ₄ > HPO ₄ > S₂O ₃ > H₂PO ₄ ^– >F^– > HCOO^– > CH₃COO^– > Br^– > I^–. The order for cations is K⁺ Rb⁺ Na⁺ Cs⁺ > Sr⁺⁺ > Ba⁺⁺ Ca⁺⁺ > NH ₄ ⁺ > Li⁺. The changes brought about in temperatures by the salts were found to be the results of the changes taking place in the hydrophilic and hydrophobic interactions among polymer, solvent and additive salts and of the change of water structure by structure making or structure breaking ions, and of the influence of salts on the hydration sheath of the polymer.     

Dehydration of lithium triphosphate pentahydrate,Li5P3O10· 5H2O

The kinetics of isothermal-isobaric dehydration of Li₅P₃O₁₀·5H₂O in vacuum (p=10^–1 hPa) and in water vapour atmosphere ( =23·hPa) was investigated by TG in the temperature range 40–140°. It was shown that the initial non-degradation removal of 1/10 of the crystal water, the rate of which is sensitive to , proceeds according to the laws of reversible topochemical reactions. In the next, irreversible degradation stage, where the bulk of the crystal water is removed, the kinetic characteristics of the process and the DSC effects exhibit a low sensitivity to the water vapour pressure. The peculiarities of Li₅P₃O₁₀·5H₂O dehydration were considered in comparison with the thermal behaviour of Na₅P₃O₁₀·6H₂O and K₅P₃O₁₀·4H₂O.

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Zusammenfassung Die Kinetik der isotherm-isobaren Dehydratisierung von Li₅P₃O₁₀·5H₂O in Vakuum (p=10^–4 hPa) und in Wasserdampfatmosphäre ( =23 hPa) wurde durch TG im Temperaturbereich von 40–140° untersucht. Es wurde gezeigt, daß die anfängliche, noch keine Zersetzung zur Folge habende Eliminierung von 1/10 des Kristallwassers, deren Geschwindigkeit von abhängt, nach den Gesetzen der reversiblen topochemischen Reaktionen abläuft. Im nächsten irreversiblen Zersetzungsschritt, in dem die Hauptmenge des Kristallwassers austritt, sind die kinetischen Kennwerte des Prozesses und die DSC-Effekte nur wenig vom Wasserdampfdruck abhängig. Die Besonderheiten der Dehydratisierung von Li₅P₃O₁₀·5H₂O werden im Vergleich mit dem thermischen Verhalten von Na₅P₃O₁₀·6H₂O und K₅P₃O₁₀·4H₂O erörtert.

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40–140° - Li₅P₃O₁₀ · 5₂ (=10^–4 ) (=23 ). , 1/10 , . , - . L₅₃₁₀·5₂ Na₅P₃O₁₀·6H₂O K₅₃₁₀·4₂.

     

Interaction of tribenzyltitanium with butadiene

It has been established that the interaction of (C₆H₅CH₂)₃Ti with butadiene does not change the parameters of ESR spectra. Only the hydrodynamic radius of this complex increases.

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, (C₆H₅CH₂)₃Ti . .

     

Spectrophotometric Determination of the Polyiodohalides of Organic Nitrogen-Containing Cations

The following biologically active diiodohalides of organic cations were studied: N-cetylpyridinium, trimethylbenzylammonium, triethylbenzylammonium, and N,N-dimethylmorpholinium diiodochlorides; N-cetylpyridinium, tetramethylammonium, tetrabutylammonium, and N,N-dimethylmorpholinium diiodobromides; and N,N-dimethylmorpholinium and butyroylcholinium triiodides. A simple and rapid procedure was proposed for the determination of the above compounds; it is based on the conversion of organic diiodohalides into the corresponding triiodides (_{300 nm} 4 × 10⁴; _{370 nm} 2 × 10⁴) in the presence of excess potassium iodide (RSD 2%). An extraction–spectrophotometric method was developed for the quantitative determination of the biologically active compounds in pharmaceutical dosage forms based on their ion associates with anionic dyes, erythrosine (m _min = 1.25–3.30 g; RSD 3%) and Bromothymol Blue (m _min = 3.85 g; RSD = 3%), or a cationic dye—1,3-dimethyl-2-(4-morpholinophenyl)azobenzimidazolium phenylsulfate (m _min = 2.32–8.26 g; RSD 4%). The developed procedures were used for monitoring drug substances in model pharmaceutical preparations (RSD 4%).     

Thermodynamic and magnetic resonance studies on the hydration of polymers: I. Interactions of water in a synthetic cation-exchange resin

Measurements of NMR spin-lattice relaxation times T ₁ were performed for sorbed H₂O and D₂O in a sulfonated ion-exchange resin at varying degrees of hydration with alkaline cations as counter ions. From the sorption isotherms at three different temperatures the partial molar enthalpies and entropies of sorption show a minimum for all alkaline cations at water concentrations of n 0.8, i.e., there are 0.8 water molecules per –SO ₃ ^– group. The first water molecules sorbed in the ion-exchange resin matrix are characterized by anisotrtopic rotational diffusion processes with correlation times of the order of ₁ 50 ns and ₂ 30 ps, respectively. This indicates that they are located in the electrostatic field between the corresponding ion pair. Although these two correlation times are very similar at a given temperature for all alkaline cations studied in the present investigation, the existence of a second spin-lattice relaxation time for sorbed H₂O at n=0.8 indicates that for Cs about 50% of the sorbed water diffuses between locations in the resin. This fraction decreases with ionic radii and with falling temperatures. For Li the amount is less than 20%.     

Glass transition and crystallization effects demonstrated by thermal analysis of liquid-quenched ternary glasses Te80Ge20−xA x V (AV=Sb,Bi)

In DSC studies of liquid-quenched ternary chalcogenide glasses Te₈₀Ge_20–xA _x ^V (A^V=Sb, Bi), the characteristic temperatures (glass transition and crystallization temperatures) were determined. Changes in the thermal stabilities of these glasses, depending on the element A (Sb, Bi) from group V of the periodic table and on its content in the alloy were evaluated. Moreover, the effect of changes in the glass composition on the glass formation ability expressed by the parameter K_g1 was determined.

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Zusammenfassung In DSC-Untersuchungen abgeschreckter ternärer Chalkogenidgläser des Typs Te₈₀Ge_20–xA _x ^v (A^x=Sb, Bi) wurden die charakteristischen Temperaturen (die GlasÜbergangs- und Kristallisationstemperaturen) bestimmt. Die Änderungen der Thermostabilität dieser Gläser wurden in Abhängigkeit von dem Element A (=Sb, Bi) aus der V Gruppe der Periodensystems und von seinem Gehalt in der Legierung ausgewertet. Ausserdem wurde der Einfluß der Änderungen in der Glaszusammensetzung auf die Glasbildungsfähigkeit, ausgedrückt durch den Parameter K_g1, bestimmt.

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Résumé On a déterminé par analyse calorimétrique différentielle (DSC) les températures caractéristiques (températures de transition vitreuse et de cristallisation), des verres ternaires à chalcogénures formés par trempe à partir du liquide, du type Te₈₀Ge_20–xA _x ^v (A^v=Sb, Bi). On a évalué la variation de la stabilité thermique de ces verres en fonction de l'élément A (=Sb, Bi) du Vème groupe du tableau périodique et de sa teneur dans l'alliage. De plus, on a déterminé l'effet des variations de la composition du verre sur la capacité de formation du verre qui s'exprime par le paramètreK _g1.

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Te₈₀Ge_20–xA _x ^v (A^v=Sb, Bi), , . A(=Sb,Bi) . , K _gl, .

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Research supported by the U. S. National Science Foundation under Grant No. GF 421 76     

m-Xylene conversion over dealuminated Y zeolites studied by the pulse method

m-Xylene conversion was studied over dealuminated Y type zeolites in hydrogen forms, SiO₂ to Al₂O₃ ratios were varied from 4.86 to 12.95.

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- . SiO₂/Al₂O₃ 4,86 12,95.

     

The advantage of anti-Compton counting in the measurement of low-level radioactivity by gamma-ray spectrometry

The inherent advantage of anti-Compton counting of low-level radioactivity is defined in terms of changes in the limits of decision, detection and determination. It appears that the advantage factor can be expressed in the experimentally observed reductions of peak area, compton continuum and natural background. For an array equipped with a sample changer, the advantage factor for interference by the compton continuum is 4, while that for interference by the natural background amounts to 3. By sacrificing the sample changer and closing its gap with NaI-plug, additional factors of 1.5 and 2 can be obtained for compton and natural background, respectively.     

Thermodynamics and thermochemistry of kinetic (real) phase diagrams involving solids

A theoretical analysis of the formation of materials with metastable microstructures under non-ideal and highly non-equilibrium conditions is presented.

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Zusammenfassung Es wird eine theoretische Untersuchung der Bildung von Stoffen mit metastabilen MikroStrukturen unter nichtidealen Bedingungen weitab vom Gleichgewicht dargelegt.

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Synthesis of dimethyl sulfide in the presence of zeolites

In the presence of zeolites, dimethyl sulfide is produced either through CH₃OH interaction with H₂S or via CH₃SH decomposition. In accordance with their activities, in both reactions, zeolites arrange in the same sequence: HZSMHNaY>NaXNaY. Realization of the reaction CH₃OH+H₂S is more difficult compared to methanethiol decomposition.

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CH₃OH H₂S CH₃SH. : HZSMHNaY>NaXNaY. CH₃OH+H₂S , .

     

Influence of structural promoters on reduction dilatograms of iron catalyst

In each reduction step, changes in the catalyst pellet volume during reduction of precipitated iron catalysts are determined by the concentration of structural promoters and the reaction temperature.

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, , .

     

The Coordination Number of Lu(III) in a Mixed System of Methanol and Water

The stability constants (_1(F)) of the monofluoro complex of Lu(III) and those (_1(Cl)) of the monochloride solvent-shared ion-pair of Lu(III) have been determined in mixed solvents of methanol and water at 0.10 and 1.00 mol·dm^–3 ionic strengths, respectively. The variation in ln_1(F) with an increase in the mole fraction of methanol (X _s) in the mixed solvent system showed an acute-angled convex inflection point at X _s 0.12, an acute-angled concave inflection point at X _s 0.22, and another acute-angled convex inflection point at X _s 0.27. It was concluded that the first and the second convex inflection points denoted the CN of Lu³⁺ from CN = 8 to a mixture of CN = 8 and 7 and from CN = 8 and 7 to a mixture containing CN = 6, respectively. The concave point is the starting point of a change in the CN of Lu(III) in LuF²⁺ from CN = 8 to a mixture of CN = 8 and 7. The values of two inflection points of the CN around Lu³⁺ are consistent with the inflection points of the variation in the values of ln_1(Cl) versus the dielectric constant of the mixed solvent.     

Effect of vanadium content on the character of acidic sites on V2O5/Al2O3 catalysts

By IR spectroscopy and TPD the effect of vanadium content on the relative proportion of strongly acidic sites of V₂O₅/Al₂O₃ catalyst was studied.

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- - V₂O₅/Al₂O₃.

     

On the limits of low level measurements of137Cs as a natural radiotracer

Study of¹³⁷Cs in rivers implies knowledge of its adsorption behaviour towards particulate matter and sediments and the possibility of low-level counting of water and solids. As the adsorption isotherms and kinetics will be discussed separately, this text focuses on the low level counting of¹³⁷Cs. The use of flat-ended Ge(Li) detectors is compared to that of an anticoincidence array after preconcentration of the cesium ions into a 0.5 ml solid aliquot. The lower limits of determination at a relative standard deviation of 10% are 10 Bq · kg^–1 for as received aliquots on a flat Ge(Li) detector and 10 mBq in case of preconcentration from water and counting in the anticoincidence facility. The eventual improvement of the accuracy by applying moving average and smoothing procedures are considered.     

Analysis of thermal desorption spectra of oxygen desorbed from rhodium

Thermal desorption spectra of oxygen desorbed from rhodium have been analyzed in terms of models accounting for the effect of lateral interactions between adsorbed particles and of their diffusion into the bulk of metal on the desorption kinetics of O₂. Complex configuration of these spectra is ascribed to the processes of formation/decomposition of surface Rh oxides and the diffusion of particles into the near-surface layers of metal and back to the surface.

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- , O₂ . - O₂ Rh - .

     

Mechanism of isotope exchange of dihydrogen with liquid water catalyzed by hydroxide ions

In the analysis of the reaction between dissolving hydrogen and aqueous alkali hydroxide solutions the interaction of hydrogen with the molecular ion (H₃O₂)^– should be studied. This interaction is analyzed by the interacting bonds method. The activation energy (E_a) is estimated.

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, (H₃O₂)^–. . (E_a).