Thermometrische Prüfung von Bromadditionsreaktionen zur StrukturaufklÄrung und quantitativen Analyse

Zusammenfassung Durch Direktthermometrie lie\en sich organische Substanzen mit Doppelbindung z. B. verschiedene Arzneien, wie Chinin, Vasalgin mittels Bromwasserreagens quantitativ bestimmen. Die Ermittlung der Werte der ReaktionswÄrmen oder WÄrmeent-wicklungsgeschwindigkeiten ermöglicht eine schnelle Unterscheidung der cis- und trans-Isomeren wie Fumar- und MaleinsÄure, öl- und ElaidinsÄure usw.

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Organic substances containing double bonds, e.g. allyl alcohol, and different medicaments (quinine, vasalgin), were determined with bromine water by direct injection enthalpimetry. Measurement of the reaction heat or the rate of evolution of heat permits simple and rapid distinction of cis and trans isomers: fumaric and maleic acid, or oleic and elaidinic acid.

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Résumé Des substances organiques à liaisons doubles (par ex. l'alcool allylique, médicaments divers, la quinine, la vasalgine) ont été dosés par l'eau de brome, en utilisant la thermométrie directe. La mesure des chaleurs de réaction ou des vitesses du dégagement calorifique permettent une distinction rapide entre les isomères cis et trans: les acides fumarique et maléique, oléique et élaÏdique.

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, , , , (, ) . - -: , .

     

Thermal behaviour of polyetherimide peek blends

PEEK is characterised by high impact and fatigue resistance andT _g of 145C. Blends of PEEK and PEI have been made and scanning electron micro-graphs of the broken specimen show that the two polymers are completely miscible in all proportions. The study also shows that PEEKPEI 5050 blend, can be used as matrix for composite applications with appreciable enhancement ofT _g to 177C.     

On theC v toC p conversion for solid linear macromolecules

TheC _v toC _p conversion for solid linear macromolecules via the Nernst-Lindemann equationC _p -C _v =A ₀,C _p ² T/T_m is discussed on hand of data for 10 crystals and seven glasses. An average value ofA ₀=(5.11±2.41) · 10^–3 mol K J^–1 was calculated if the mole is assumed to refer to heavy atoms only. ThisA ₀ is numerically equal to the original Nernst—Lindemann constant.

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Zusammenfassung An Hand von sich auf 10 Kristalle und 7 Gläser beziehenden Daten wird die Umrechnung vonC _v -inC _p -Werte für feste lineare Makromoleküle mittels der Nernst-Lindemann-GleichungC _p -C _v =A ₀ C _p ² T/T _m diskutiert. Ein Durchschnittswert vonA ₀=(5.11±2.41) · 10^–3 mol K J^–1 wurde unter der Annahme berechnet, daß sich das Mol nur auf schwere Atome bezieht. DieserA ₀-Wert ist numerisch gleich der ursprünglichen Nerns-Lindemann-Konstanten.

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10 , - C _v C _p , —C _p –C _v = _{0 p} ² / . , , ₀ (5.11±2.41) · 10^–3 · ^–1. ₀ — .

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Support by the National Science Foundation, Polymers Program (Grant No. DMR 83-17097) is gratefully acknowledged.     

Empirical equations of state for adsorption layer: Alkylthiopolyoxyethylene glycols

Surface tension isotherms ofn-alkylthiopolyoxyerhylene glycols:n-C _x H_2x+1S(CH₂CH₂O) _y H, wherex=5 to 8,y=3 or 4, were approximated with orthogonal polynomials to get good quality values of surface pressure (II) and molar area of the adsorbed layer (). The modified Volmer (*(–₀)=Z*R*T) van der Waals and virial equations of state were used to correlate and in terms of real two-dimensional gas. The combination of Volmer and van der Waals equations of state made it possible to determine the interaction energy, , which was prescribed to cohesion of hydrophobic chains in the adsorption layer. The value of for the amphiphiles in question was in the range 0.97–1.91R*T and the average contribution per methylene group was ca. 0.21R*T.The Lennard-Jones potentials calculated from second virial coefficient were of the same range as , but no clear relation was found between their values and number of structure elements of the alkylthiopolyoxyethlene glycols.Presented during 7th International Conference: Surface and Colloid Science, July 7–13, 1991, Compiegne, France     

Reactivity of coordinated O2? towards. One-electron oxidants

Ion-radical complexes Ti(IV) (O ₂ ^– ) are unreactive towards most oxidants except Ce(IV) and Cr₂O ₇ ^2– . The one-electron redox potential for the O_{2 coord.}/O _{2 coord.} ^– couple lies between 1 and 1.6 V.

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- O ₂ ^– Ti(IV) , Ce(IV) Cr₂ O ₇ ^2– . - O_{2 .}/O ₂ ^– . 1 1,6 .

     

Thermochemical studies on the systems ACl/CeCl3 (A=Na-Cs)

The pseudobinary systems ACl/CeCl₃ (A=Na-Cs) were reinvestigated by means of DTA. The following compounds were found and identified through their X-ray patterns (primarily detected compounds in italics):NaCe _1.67 Cl ₆; K₃CeCl₆, K₂CeCl₅,KCe _1.67 Cl ₆;Rb ₃ CeCl ₆, Rb₂CeCl₅,RbCe ₂ Cl ₇; Cs₃CeCl₆, Cs₂CeCl₅,CsCe ₂ Cl ₇. The compounds A₂CeCl₅ crystallize with the K₂PrCl₅ structure. The high-temperature modifications of the compounds A₃CeCl₆ have the cubic elpasolite structure. The hexagonal unit cell of KCe_1.67Cl₆ is related to the CeCl₃ structure: 0.33 Ce³⁺ are substituted by one K^s+. The structure of CsCe₂Cl₇ can be described with a hexagonal subcellZ=4,a=9.72 andc=14.94 Å; however, small superstructure reflexions reduce the symmetry.The thermodynamic functions for the reactionsnACl+CeCl₃=A _n CeCl _n+3(A=K, Rb) were determined by means of e.m.f. measurements.Measurements of the e.m.f.E vs. T yielded the Gibbs enthalpiesG ^r . The temperature-dependence was found to be linear.The most important result is the formation of the elpasolites (A₃CeCl₆) and ACe₂Cl₇.

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Zusammenfassung Die pseudobinären Systeme ACl/CeCl₃ (A=Na-Cs) wurden mittels Differenzthermoanalyse (DTA) neu untersucht. Folgende Verbindungen wurden gefunden und durch ihre Röntgenbeugungsmuster charakterisiert (erstmalig nachgewiesene Verbindungen sind kursiv):NaCe _1.67 Cl ₆; K₃CeCl₆, K₂CeCl₅,KCe _1.67 Cl ₆;Rb ₃ CeCl ₆, Rb₂CeCl₅,RbCe ₂ Cl ₇; Cs₃CeCl₆, Cs₂CeCl₅,CsCe ₂ Cl ₇. Die Verbindungen A₂CeCl₅ kristallisieren im K₂PrCl₅-Typ. Die Hochtemperaturmodifikationen der Verbindungen A₃CeCl₆ liegen in der kubischen Elpasolith-Struktur vor. Die hexagonale Elementarzelle des KCe_1.67Cl₆ ist mit der CeCl₃-Struktur verwandt: 0,33 Ce³⁺ sind durch ein K⁺ ersetzt. Die Struktur des CsCe₂Cl₇ kann mit einer hexagonalen Pseudozelle beschrieben werden:a=9,72;c=14,94Å;Z=4; schwache Überstrukturreflexe reduzieren jedoch die Symmetrie. Die thermodynamischen Funktionen für die Reaktionen:n ACl + CeCl₃=A _n CeCl _n+3 (A=K, Rb) wurden durch EMK-Messungen bestimmt. Messungen der Abhängigkeit von e. m. f.E gegenT ergaben die Gibbs-EnthalpienG ^r . Es wurde eine lineare Temperaturabhängigkeit gefunden. Als wichtigstes Resultat ist die Bildung von Elpasoliten (A₃CeCl₆) und von Verbindungen (ACe₂Cl₇) anzusehen.

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ACl/CeCl₃, A . - ( ):NaCe _1.67 Cl ₆; K₃CeCl₆, K₂CeCl₅,KCe _1.67 Cl ₆;Rb ₃ CeCl ₆, Rb₂CeCl₅,RbCe ₂ Cl ₇; Cs₃CeCl₆, Cs₂CeCl₅ CsCe ₂Cl₇. A₂CeCl₅ K₂PrCl₅. A₃CeCl₆ . KCe_1.67Cl₆ CeCl₃, 0,33 Ce³⁺ . CsCe₂Cl₇ a=9,72 Å,c=14,94 Å Z=4. , . n ACl + CeCl₃=A _n CeCl _n+3(A=K, Rb) . . . . . .E , G ^r . ACe₂Cl₇.

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Presented as a poster at the 8th ICTA, Bratislava, 1985.

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This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.     

Influence of sodium on the catalytic properties of bismuth-molybdenum oxide catalysts

In the ammoxidation of propylene, the presence of a normal NaBi(MoO₄)₂ phase in bismuth molybdenum oxide catalysts decreases the acrylonitrile yield due to its oxidation

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NaBi(MoO₄)₂ -- .

     

Triterpene Glycosides of Astragalus and Their Genins. LXI. Occurrence of Cycloartane 6-O-Monodesmosides

Cyclosiversigenin 6-O--L-rhamnopyranoside and 6-O--D-glucopyranoside were isolated fromAstragalus coluteocarpusBoiss. (Leguminosae) andAstragalus dissectusB. Fedtsch. et N. Ivanova, respectively. Cyclosiversigenin 5-O--L-rhamnopyranoside was shown to be an artifact forAstragalus coluteocarpus.Thus, the cyclosiversigenin 6-O--D-glucopyranoside that was isolated from certainAstragalusspecies is hypothesized also to be an artifact. Glycosylation of the 6 -hydroxyl group of cycloartanes by D-glucose and D-xylose, in contrast with other substituents, does not change the low-field position of the PMR signal of the 4-CH ₃ group (1.65 2.01 ppm) that is caused by the influence of deuteropyridine directly on the 6 -hydroxyl. Obviously one of the hydroxyls of the -D-glucopyranoside or -D-xylopyranoside residues has the same effect in this instance.     

Catalytic decomposition of N2O on La2CuO4 in the presence of LaNi5 alloy

Decomposition of N₂O has been studied on pure La₂CuO₄, La₂CuO₄ with 5 and 10 wt. % LaNi₅ and oxidized LaNi₅ in the temperature range of 240–490 °C at 50 and 200 Torr initial pressures of N₂O. The addition of LaNi₅ decreases the energy of activation compared to that of La₂CuO₄ which has been explained based on the dispersity of NiO over La₂CuO₄.

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N₂O La₂CuO₄ La₂CuO₄ LaNi₅ 5–10 .%, 240–490°C N₂O 50 200 . LaNi₅ , . NiO La₂CuO₄.

     

Thermoanalytical studies of substances liberating aggressive gases

A modification to the derivatograph has been designed that allows thermoanalytical investigations of chemical compounds, including sulphides and acids, that evolve aggressive gases such as CO, SO₂, S, etc. during warming. Application of this modification is exemplified by studies on the thermal dehydrogenation of titanium hydride (TiH_1.85) and on the interaction of rhenium disulphide (ReS₂) with concentrated sulphuric acid.

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Zusammenfassung Es wird über die Modifizierung eines Derivatografen berichtet, die die Thermoanalyse von Stoffen ermöglicht, die wie z. B. Sulfide oder Säuren beim Erhitzen aggressive Gase wie z. B. CO, SO₂, S usw. freisetzen. Als Beispiel für die Anwendung dieser Modifizierung dienten Untersuchungen der thermischen Dehydrogenierung von Titanhydrid (TiH_1.85) und des Einwirkens von konzentrierter Schwefelsäure auf Rheniumsulfid (ReS₂).

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, , , , , SO₂, S . . 2- , - (³_1,85) (ReS₂) (H₂SO₄).

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Presented as a poster at ESTAC-4, Jena, GDR, 1987.     

Thermal properties of thio-and selenocyanatocopper(II) complexes with bipyridine and phenanthroline

The paper deals with the thermal properties of complex compounds of the general formula CuL₂(NCX)₂ (whereL=bipy or phen,X=S or Se). The phenanthroline complexes exhibit a higher thermal stability than those with bipyridine. For the latter complexes thermal decomposition begins with the release of bipyridine molecules, while for the phenanthroline complexes redox reactions of pseudohalogenide ligands with Cu(II) take place. The redox reactions start at a lower temperature for the selenocyanate complexes than for the thiocyanate complexes.

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Zusammenfassung Vorliegende Arbeit behandelt die thermischen Eigenschaften von Komplexverbindungen der allgemeinen Formel CuL₂(NCX)₂ (mitL=Bipyridin oder Phenanthrolin undX=S oder Se). Die Phenanthrolinkomplexe zeigen eine grössere thermische Stabilität als die Bipyridinkomplexe. Die thermiscne Zersetzung letzterer beginnt mit der Abgabe von Bipyridinmolekülen, während bei den Phenanthrolinkomplexen Redoxreaktionen von Pseudohalogenidliganden·mit Cu(II) stattfinden. Diese Redoxreaktionen beginnen bei den Selenozyanatkomplexen bei niedrigeren Temperaturen als bei den Thiozyanatkomplexen.

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CuL₂(NCX)₂, L= , X= . . , — . - , .

     

Scattering from concentration fluctuations in polymer blends: A monte carlo investigation

The collective scattering function S_coll( ), which describes light (neutron-, x-ray) scattering under wavevector , is obtained from Monte Carlo simulations for a symmetrical polymer mixture. The polymers are modelled by self-avoiding walks ofN _A=N_B=N steps on a simple cubic lattice, where a fraction _V of sites is left vacant, and an attractive energy occurs if two neighboring sites are taken by the same kind of monomer. Spinodal curves are estimated from linear extrapolation of S _coll ^–1 (0) vs./k _B T, whereT is the temperature. Also the single chain structure factor is obtained and the de Gennes random phase approximation (RPA) can thus be tested. Unexpectedly, strong deviations are found if one species is very dilute. The estimation of an effective Flory-Huggins-parameter from scattering data is also discussed.Contributed paper delivered at the Tagung der Deutschen Physikalischen Gesellschaft, Fachausschuß Polymerphysik, Hamburg, March 14–16, 1987.     

The Dissociation Constants of 1,1′-Bis (pyridinium-4-aldoxime)trimethylene dibromide

Summary. The dissociation constants of the two oxime groups of 1,1-bis(pyridinium-4-aldoxime)trimethylene dibromide (TMB-4) were determined using spectrophotometric data. Two numerical methods were applied to treat the overlapping equilibria. The results obtained by both agreed with each other and their mean values at 25°C corrected for the ionic strength of 0.05moldm^–3 are pK_a1=7.49±0.11 and pK_a2=8.96±0.09. These values were discussed in terms of the pK_as of 1,1-bis(pyridinium-4-aldoxime)oxydimethylene dichloride (Toxogonin), a similar dioxime, which were derived by extrapolation of literature data.     

Kinetics and mechanism of OsO4 catalyzed oxidation of chalcones by Ce4 in aqueous acetic sulfuric acid media

Kinetics of OsO₄ catalyzed oxidation of chalcones by Ce⁴⁺ has been studied in aqueous acetic-sulfuric acid medium in the temperature range 313 to 338 K. The order in [oxidant] is zero while the order with respect to [substrate] and [catalyst] are each fractional. The rate of the reaction decreased with increase in percentage of acetic acid while [H⁺] had practically no effect on the rate The rates of various substituted chalcones (with substituents in the phenyl. ring attached to the moiety) are in the orderp-CH₃>m-CH₃>H>p-Cl>m-Cl>m-NO₂>p-NO₂. A mechanism in which formation of a cyclic ester between chalcone and OsO₄ in a fast step followed by its decomposition in a rate-determining step is envisaged.

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Ce⁴⁺, OsO₄, - 313–338 . —, —. , [H⁺] . ( , : -CH₃>-CH₃>H>-Cl>-NO₂>-NO₂. , OsO₄ , , .

     

Influence of sodium salt addition on the morphological and catalytic properties (ethane hydrogenolysis) of aluminasupported cobalt

NaNO₃ addition to Co/Al₂O₃ results in an increase in the reducibility, in a smaller dispersity of the metal and in a decrease in the ethane hydrogenolysis rate due to a decorative effect.

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NaNO₃ Co/Al₂O₃ ,

     

Temperature programmed desorption of NH3 and H2O from NH4NaX and CoNH4NaX zeolites

A study has been made of temperature programmed desorption (TPD) of NH₃ and H₂O from samples of NH₄X and CoNH₄X zeolites of various degree of exchange. NH₃ TPD peaks could be explained by interaction of NH₃ with different Brönsted and Lewis acidic centers. Moreover a water peak at high temperatures allowed interpretations of the dehydroxylation, and by reason of the characteristic desorption temperatures a particular state of the Co²⁺ ions in the CoNH₄X zeolites is postulated.

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- () NH₃ H₂O NH₄X CoNH₄X . NH₃ NH₃ =qs . . Co²⁺ CoNH₄X.

     

Effect of an admixture on the electrical and thermal properties of triglycine sulphate crystals

The influence of chloroacetic acid amide (AC) on the temperature-dependence of the electrical conductivity (), thermal expansion (_ij) and specific heat ((C _p) of triglycine sulphate crystals was studied in the phase transition range (T _c=49°). The addition of isostructural AC increased the electrical conductivity, decreased the thermal expansion and changed theC _p peak. The mechanism is discussed on a thermodynamic basis.

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Zusammenfassung Der Einfluß der Zumischung von Chloressigsäureamid (AC) auf die Temperaturabhängigkeit der elektrischen Leitfähigkeit, der Wärmeausdehnung _ij und der spezifischen WärmeC _p von Triglycinsulfat-Kristallen wurde im Phasenübergangsgebiet (T _c=49 °C) untersucht. Die Beimischung von isostrukturellem AC erhöht die elektrische Leitfähigkeit und vermindert die Wärmeleitfähigkeit, während derC _p-Peak verändert wird. Der Mechanismus kann thermodynamisch diskutiert werden.

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(), () _ij) () , T _c=49°. , , , , C _p. .

     

Crystallization,melting and spherulitic structure of Β-nucleated random propylene copolymers

The characteristics of crystallization, melting and spherulitic growth of a random propylene copolymer (PRC) containing small amount of ethylene were studied in the presence of a selective -nucleating agent (calcium pimelate). It was established that the products of isothermal and non-isothermal crystallization are very rich in -modification but have mixed polymorphic composition. The formation of -modification may be attributed to -transition on the surface of growing -spherulites resulting in -twin-spherulites. During melting of PRC of -modification, the characteristics observed with -nucleated propylene homopolymers, namely, a -recrystallization of recooled samples and separated melting of non-recooled samples (i.e. the melting memory effect), as well as a -recrystallization leading to a perfection of the structure within the -modification, are also demonstrated. The disturbance of regularity of the polymer chain highly reduces the tendency to -crystallization. In contrast to the observations with propylene homopolymers, the growth rate of -modification (G ) is higher than that of -modification (G ) and no critical crossover temperature can be found (T()=413 K) below whichG >G . The experimental results show that a partial disturbance of chain regularity by incorporation of comonomer units considerably reduces the tendency to -crystallization.This research was supported by the National Scientific Research Fund (OTKA), the author is grateful for it. Thanks are due to Professor Géza Bodor for his help in X-ray diffractometric investigations and to Ms. Tünde Lócska for her prudential technical assistance in the optical experiments.     

A mechanistic study of cycloaddition of carbon dioxide to propyne over supported Rh4 and Fex Rhy carbonyl cluster derived catalysts

CO₂ undergoes cycloaddition to propyne on a cationic rhodium site with the assistance of O^2–/OH^– of support or iron oxide over Rh₄ and Fex Rhy carbonyl clusterderived catalysts.¹³CO₁₂ labeling and FTIR studies suggest that monodentate carbonate formed on the catalyst surface is most likely a key species to offer an active CO₂ to be converted into a carbonyl intermediate prior to the product 4,6-dimethyl-2-pyrone.

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CO₂ O^2–/OH Rh₄ Fex Rhy. ¹³CO₂ , CO₂ , 4,6--2-.

     

On expectation value calculations of one-electron properties using the coupled cluster wave functions

The ability of various approximate coupled cluster (CC) methods to provide accurate first-order one-electron properties calculated as expectation values is theoretically analysed and computationally examined for BH and CO. For actual calculations the infinite number of terms of the expectation value expansion (O=¦exp (T ⁺)O exp (T)¦_c) was truncated so that T ₁ T ₂, T ₃, and (1/2) T ₂T₂ clusters were retained on both sides of O. The role of individual clusters is carefully discussed. Inclusion of T ₁, is unavoidable, but if triples are essential in the energy evaluation, they may play an even more important role in the property expansion, as shown in the case of CO. It is shown that the CC wave function, which is exact to second order, effectively satisfies the Hellmann-Feynman theorem.