Calorimetric study of the proximity effect in aliphatic diesters

Excess molar enthalpies,H ^E , at atmospheric pressure and 303.15 K are reported for binary mixtures of 1-chlorohexane with diethyl oxalate, diethyl malonate, diethyl succinate, diethyl glutarate, diethyl adipate, diethyl pimelate and diethyl sebacate. These experimental results, together with those obtained previously on the excess enthalpies of aliphatic diester+n-hexane mixtures, are interpreted in terms of molecular surface interactions between aliphatic, chlorinated and carboxylate groups. Comparison of the enthalpy interchange parameters reveals a decrease of the intermolecular interactions with decreasing intramolecular COO-COO distance in the diester molecule.

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Zusammenfassung Bei Atmosphärendruck und 303,15 K gemessene molare Überschußenthalpien (H ^E werden für binäre Gemische von 1-Chlorhexan mit Diäthyloxalat, Diäthylmalonat, Diäthylsuccinat, Diäthylglutarat, Diäthyladipat, Diäthylpimelat bzw. Diäthylsebacat angegeben. Diese experimentellen Ergebnisse werden zusammen mit den früher für Gemische von aliphatischen Diestern und n-Hexan erhaltenen Resultaten als molekulare Oberflächenwechselwirkungen zwischen aliphatischen, chlorierten und Carboxylatgruppen interpretiert. Ein Vergleich der Enthalpieaustauschparameter läßt eine Verminderung der intermolekularen Wechselwirkungen mit abnehmendem intramolekularem Abstand zwischen den COO-Gruppen erkennen.

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(H ^E ) 303,15 K 1- , , , , , . , + -, , . COO-COO .

     

Oxidation of aroyl hydrazines, III. Kinetics and mechanism of the oxidation of nicotinoyl and isonicotinoyl hydrazine by iodine

The title reaction was studied in aqueous hydrochloric acid at high iodide concentations. The reaction is first order with respect to both oxidant and substrate though diisonicotinoyl hydrazines are the products apart from nitrogen. The reaction is markedly inhibited by H⁺ and I^– ions. An I^– ion independent path is also noticed.

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. , , -() , . H⁺ I^–. , , I^–.

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Part II: Indian J. Chem. (In press)     

Thermal effects of contamination,adsorbed water and annealing on the DTA of powdered quartz

During the grinding of quartz, water is adsorbed from the atmosphere, but this water gave no detectable thermal effect on DTA because it was evolved uniformly up to 1000°. However, in conjunction with an iron contaminant, the adsorbed water was involved in an oxidation reaction causing noticeable thermal effects for quartz powdered in a vibration mill constructed of steel parts. When powdered so finely that the - inversion peak at 573° had disappeared, annealing caused a partial redevelopment of the peak but recrystallization of disrupted quartz was too small an effect to give any detectable exothermic peak on DTA.

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Zusammenfassung Während des Vermahlens von Quartz wird Wasser aus der Atmosphäre adsorbiert, jedoch ergab dieses Wasser keinen nachweisbaren thermischen Effekt in der DTA, da es bis zu 1000° gleichmässig freigesetzt wird. Im Zusammenhang mit einer Eisen-Verunreinigung wurde jedoch das adsorbierte Wasser in eine Oxidationsreaktion einbezogen, welche beim in einer aus Stahlteilen gefertigten Vibrationsmühle zerpulvertem Quartz nachweisbare thermische Effekte verursachten. Wenn so fein pulverisiert wurde, daß der --Inversions-Peak bei 573° verschwunden war, verursachte eine Wärmebehandlung eine teilweise Wiederentwicklung des Peaks, jedoch war die Rekristallisation des zerstörten Quartzes zu geringfügig um einen nachweisbaren exothermen Peak in der DTA-Kurve zu ergeben.

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Résumé Lors du broyage du quartz, il se produit une adsorption de l'eau atmosphérique mais cette eau ne donne pas d'effet thermique décelable par ATD car elle se dégage régulièrement jusqu'à 1000°. Cependant, en présence de fer comme contaminant, l'eau adsorbée intervient dans une réaction d'oxydation qui donne des effets thermiques perceptibles dans le cas de quartz pulvérisé dans un vibrobroyeur en acier. Si le quartz est en poudre assez fine pour que le pic d'inversion - à 573° disparaisse, le recuit provoque la réapparition partielle du pic. La recristallisation du quartz est cependant trop faible pour donner un effet exothermique décelable par ATD.

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, , 1000°. , , . - 573° , , , - .

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We are grateful to the Science Research Council for supporting this work.     

Syntheses and properties of mixed dinuclear copper(II) complexes with heterocyclic dithiocarbamates and a cyclic octadentate tertiary amine

Five new Cu^II complexes of general formula [Cu₂(Rdtc)tpmc](ClO₄)₃, (1)–(5), where tpmc and Rdtc ^– refer to N,N,N,N-tetrakis(2-pyridylmethyl)-1,4,8,11-teraazacyclotetradecane and piperidine- (Pipdtc), 4-morpholine- (Morphdtc), 4-thiomorpholine- (Timdtc), piperazine- (Pzdtc) or N-methylpiperazine- (N-Mepzdtc) dithiocarbamates, respectively, have been prepared. Elemental analyses, conductometric and magnetic measurements, u.v./vis, i.r., e.p.r. and mass spectroscopy have been employed to characterize them. The complexes adopt an exo coordination of Cu^II ions and tpmc. The dithiocarbamate ion joins both the sulphur and the copper atoms acting as a bridging ligand The presence of different heteroatoms in the piperidine ring influences the (C=N) and (C=S) vibrations which decrease in the order of the complexes: Pipdtc>N-Mepipdtc>Pzdtc>Morphdtc>Timdtc ligands. Attention has been paid to the detailed mechanism of the mass spectral fragmentation of the complexes. The g _eff factors of the complexes have been also estimated by e.p.r. spectra. Finally, the complexes obtained demonstrate microbiologycal activity against some bacteria.     

New Insight into the Structure of CTAB Micelles in the Presence of Cyclodextrins, Using Non-Steroidic Anti-Inflammatory Agents – Nabumetone, Naproxen – as Fluorescent Probes

The structure of CTAB micelles in the presence of -, - and hydroxypropyl--cyclodextrin has been investigated by means of conductivity and spectroscopic measurements – absorption and steady state fluorescence – using Naproxen, Nabumetone and pyrene as probes. In the presence of the three cyclodextrins, two types of micelles have been detected. The first type is a pure surfactant micelle, while the other is formed by surfactant monomers complexed with cyclodextrins. The presence of cyclodextrins produces a decrease in the cmc of the pure micelle. The second type of micelle is formed at higher cmc* values, 25.6 × 10^-4 M, 27.8 × 10^-4 M and 38.9 × 10^-4 M for -, -, and HPCD respectively. A significant increase in the ionisation degree has been detected. The aggregation number is strongly increased, being 92 ± 3 , 97 ± 3 and 80 ± 2 for for -, -, and HPCD respectively. The polarity of this micelle decreases, indicating that it becomes tighter and its hydrophobic region becomes less polar.     

Study of the reaction K4Fe(CN)6·3H2O→K4Fe(CN)6+3H2O by the derivatograph and dielectric constant measurements

K₄Fe(CN)₆·3H₂O was studied by a derivatograph in the temperature range +20° to +300° and dielectric constant () measured from –80° to +150°. The loss of the three water molecules occurs at 105° and the vs T curve shows a Debye relaxation behavior. By using Mason's theory it was possible to classify K₄Fe(CN)₆·3H₂O in the temperature range –25° to +100° C as a para-electric order-disorder crystal.

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Zusammenfassung K₄[Fe(CN)₆].3 H₂O wurde mit dem Derivatograph im Temperaturbereich von+20° bis+300° untersucht und die dielektrische Konstante () im Bereich von –80° und +150° gemessen. Die Abspaltung der drei Wassermoleküle erfolgt bei 105°. Die Kurve von als Funktion vonT zeigt ein Relaxationsverhalten nach Debye. Bei Anwendung der Theorie von Mason gelang es K₄[Fe(CN)₆].3 H₂O im Temperaturbereich von –25° bis 100° als para-elektrischen, geordneten-ungeordneten Kristall einzuordnen.

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Résumé Etude de K₄Fe(CN)₆·3H₂O à l'aide d'un «Derivatograph» entre +20 et +300° mesure de la constante diélectrique () entre –80 et+150°. La perte des trois molécules d'eau a lieu à 105° et la courbe en fonction deT montre un comportement de relaxation Debye. D'après la théorie de Mason, il est possible de classer K₄Fe(CN)₆·3H₂O comme cristal paraélectrique ordre-désordre entre –25 et +100°.

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K₄[Fe(CN)₆] · 3H₂O +20° +300° –80° +150°. 105°, -T . , , K₄[Fe(CN)₆] · 3H₂O –25° +100° .

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Work partially supported by Banco Nacional de Desenvolvimento Econômico and Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul.

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P. da R. Andrade deceased on December 16, 1974.     

Apparent inconsistencies in acid-base behavior of ZnO

Acidic behavior of ZnO is observed in spectroscopic experiments (Zn–H band at 1708 cm^–1, XPS O 1s binding energy 530/532 eV, pyridine Lewis band at 1452 cm^–1), basic behavior in catalytic reactions of alcohols (98% dehydrogenation). This is ascribed to a high sensitivity to experimental conditions.

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ZnO ( Zn–H 1708 ^–1, XPS O 1s 530/532 .., 1452 ^–1), (98% ). .

     

Rapid determination of vapor adsorption properties of ultramicroporous solids: An application to the zeolite affinity of adsorption

Adsorption capacities of zeolites are rapidly determined by a vapor sorption apparatus which can be used as an ultramicroporosimeter. From the sorption data, it is possible to calculate the zeolite affinities toward various adsorbates in comparison with water. The n-hexane affinity index of the new ZSM zeolites has values always higher than those of X, Y or Zeolon zeolites. This fact is attributed to the unusual framework structure of the silica-rich ZSM zeolites.

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, . . - ZSM , X, Y . ZSM , .

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Presented in part at the I⁰ Convegno nazionale di Catalisi-II⁰ Simposio Italo/Cecoslovacco di Catalisi, held in Bologna (Italy) on June 1979.     

Thermal decomposition of palladium-imidazole complexes

Two Pd-imidazole complexes have been synthesized following the reaction of PdCl₂ and imidazole at 12 and 14 metal ligand ratios. Elemental and thermogravimetric analytical data obtained from these compounds illustrate that they have the formulae Pd(IMDAH)₂Cl₂ · 4H₂O and Pd(IMDAH)₃Cl₂ (IMDAH = imidazole), respectively. The mechanism of thermal decomposition for these complexes in air involves initial dissociation of H₂O and IMDAH ligands in the 120–340 °C range, subsequent dissociation of the chloride atoms to form PdO in the 530–570 °C range, and finally formation of Pd metal at 820–840 °C.

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Zusammenfassung In einer Reaktion von PdCl₂ mit Imidazol wurde bei einem metall-Ligandenverhältnis von 12 bzw. 14 zwei Pd-Imidazolkomplexe dargestellt. Auf Grund der Ergebnisse von Elementaranalyse und Thermogravimetrieuntersuchungen besitzen die Verbindungen die Formeln Pd(IMDAH)₂Cl₂·4H₂O bzw. Pd(IMDAH)₃Cl₂ (IMDAH=Imidazol). Der Mechanismus der thermischen Zersetzung dieser Komplexe in Luft umschliesst eine anfängliche Dissoziation (Abgabe von Wasser und IMDAH-Liganden) im Temperaturbereich 120–340 °C, gefolgt von der Bildung von PdO unter Abspaltung der Chloratome bei 530–570 °C sowie die letztendliche Bildung von metallischem Pd bei 820–840 °C.

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, 12 14, . , d()₂l₂· 4₂ d()₃l₂. 120–340°, 530–570°. 820–840°.

     

Inhomogeneity of strong Lewis acid centers on Al2O3 surface

Specificity of the bands at 1630–1620 cm^–1 in IR spectra of coordinatively bonded pyridine has been studied. Three strong Lewis-type acid centers have been revealed on Al₂O₃ surface.

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- 1630–1620 ^–1.

     

Isomerization of 1-methylnaphthalene on magnesium modified NaY zeolites

The conversions of 1-methylnaphthalene on NaY zeolite and its magnesium modifications with different degrees of ion exchange and various Si/Al ratios have been studied at 310 and 350 °C. The investigated catalysts are highly active for positional isomerization. The observed changes in their catalytic activity are explained by the promotion of proton formation and by the absorption properties of magnesium cations as well as by their localization in cations as well as by their localization in the crystal lattice of the zeolite.

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1- NaY Si/Al 310 350°C. . , .

     

Thermal conductivity of cemented carbides

The hypothetical salts Li₄SiN₂O and Li₇SiN₃O were sought in the course of studies on the reactions of Li₂SiN₂ and Li₅SiN₃ with lithium oxide, and of LiSiNO with lithium nitride.

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Zusammenfassung In einer Reihe von Studien der Reaktionen von Li₂SiN₂ und Li₅SiN₃ mit Lithiumoxid bzw. LiSiNO mit Lithiumnitrid wurde nach den hypothetischen Salzen Li₄SiN₂O und Li₇SiN₃O gesucht.

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Li₂SiN₂ Li₅SiN₃ LiSiNO Li₄SiN₂O Li₇SiN₃O.

     

α-(3-Indolyl)-β-hydroxyethylamine and its derivatives

The reduction of oximes of 3-hydroxyacetylindole, 3-benzyloxyacetylindole, and 3-ethoxy-acetylindole (mixtures of syn and anti isomers) gave -(3-indolyl--hydroxyethylamine, -(3-indolyl)--benzyloxyethylamine, and -(3-indolyl)--ethoxyethylamine, the structures of which were confirmed by PMR and mass spectrometry.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 778–781, June, 1971.     

Investigation of the interaction between zinc oxide and phosgene

It has been shown that in the interaction of zinc oxide and phosgene, the most active are the samples having oxygen vacancies. A mechanism for this process is suggested.

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, , . .

     

Oligomeric proanthocyanidin glycosides ofClementsia semenovii. II

The structures of proanthocyanidins CS-3 and CS-4, isolated from the roots ofClementsia semenovii have been established on the basis of chemical and spectral studies. CS-3 is 7-O-(6-O-galloyl--D-Glcp O--D-Glcp O--D-Glcp O--D-Glcp O--D-Glcp)-(+)-catechin-(4—8)-(–)-epigallocatechin-(4—8)-(+)-catechin-(4—8)-(–)-epigaLLocatechin-(4—8)-(–)-epigallocatechin-(4—8)-(–)-epigallocatechin, and CS-4 is 3-O-galloyl-7-O-[6-O-galloyl--D-Glcp O--D-Glcp O--D-Glcp-(+)-gallocatechin-(4—8)-[(+)-catechin-(4—8)-(3-O-galloyl-(–)-epigallocatechin]₂-(4—8)-(–)-epicatechin.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 50–58, January–February, 1999.     

Four types of relaxation in chemical kinetics (linear case)

According to results obtained previously for the linear equations of chemical kinetics, the relation between the steady-state reaction rate and the relaxation time has been studied.

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, , .

     

On-line glucose monitoring by using microdialysis sampling and amperometric detection based on ‘wired’ glucose oxidase in carbon paste

In-vitro on-line glucose monitoring is described, based on microdialysis sampling and amperometric detection operated in a flow-injection system. Samples were injected into a two-electrode microcell containing an Ag/AgCl quasi-reference electrode and a glucose enzyme electrode as the working electrode, operated at + 0.15 Vvs. Ag/AgCl. The enzyme electrode is constructed by mixing the wired glucose oxidase into carbon paste. {Poly[1-vinylimidazole osmium(4,4-dimethylbipyridine)₂Cl)]}^+/2+ was used to wire the enzyme. The non-coated electrodes, cross-linked with poly(ethylene glycol) diglycidyl ether, responded linearly to glucose concentrations up to 60 mM, and were characterized by a sensitivity of 0.23 A mM^–1 cm^–2, when operated in flow injection mode and of 5.4 AmM ^–1 cm^–2 in steady-state conditions. This sensitivity of the resulting enzyme electrode was 50% lower than that of similarly prepared but non-cross-linked electrodes. However, the cross-linked electrodes showed superior operational and storage stabilities, which were further improved by coating the electrodes with a negatively charged Eastman AQ film. An in-house designed microdialysis probe, equipped with a polysulphone cylindrical dialysis membrane, yielded a relative recovery of 50–60% at a perfusion rate of 2.5 l/min^–1 in a well stirred glucose solution. The on-line set up effectively rejected common interferences such as ascorbic acid and 4-acetaminophen when present at their physiological concentrations.     

Determination of Proteins at Nanogram Levels Using the Resonance Light Scattering Technique with a Novel PVAK Nanoparticle

A novel functionalized polyvinyl alcohol keto-derivative nanoparticle (PVAK) has been prepared in a one-step method using oxidation and degradation under ultrasonic irradiation. The nanoparticle is water-soluble, chemically stable, non-toxic and biocompatible. The surface of the nanoparticle is covered with abundant hydroxyl, carbonyl and carboxyl. At pH 3.0, the interactions of PVAK with different proteins can result in obviously enhanced RLS signals at 380nm. Under optimal conditions, the calibration graphs are linear over the range of 0.024.0µgmL^–1 for human serum albumin (HSA), 0.023.5µgmL^–1 for bovine serum albumin (BSA), and 0.053.5µgmL^–1 for human -globulin (-G), respectively. Detection limits were 6.4ngmL^–1 for HSA, 9.2ngmL^–1 for BSA, and 12.5ngmL^–1 for -G, respectively. The method was employed for the determination of total proteins in human serum with satisfactory results.     

Photochemically induced fluorescence investigation of aβ-cyclodextrin: Azure A inclusion complex and determination of analytical parameters

The photooxidation of Azure A and fluorescence properties of Azure A and its photoproduct have been investigated in aqueous media and in the presence of-cyclodextrin (-CD). The fluorescence intensity of the complex formed between the photoproduct and -CD was found to be three times higher than that of the uncomplexed Azure A photoproduct. A complex formation constant of 110±40 M^–1 was calculated using the Benesi-Hildebrand treatment of the fluorescence emission data. Although the stoichiometry of the Azure A photoproduct: -CD complex was found to be 1: 1, it seems that the Azure A structure is only partially included. Calibration graphs were plotted for the free Azure A photoproduct and the photogenerated product included in -CD. The analytical parameters and quantification limits were determined.     

Micro-Determination of Protein Containing SH– and –S–S– Groups Based on the Polarographic wave of an Electroactive Derivative

This paper presents a new simple and sensitive method for the micro-determination of protein containing SH– and –S–S– groups based on the single sweep polarographic wave of an electroactive derivative. In 0.04molL^–1 Na₃PO₄ and 0.2% ascorbic acid solution, protein is heated in a boiling water bath for 15min, the reaction product giving a sensitive reduction wave at –0.70V (vs. SCE). The wave height is linearly proportional to the concentration of protein. The calibration curves of bovine serum albumin (BSA), human serum albumin (HSA), ovalbumin (OVA) and lysozyme (Lyso) are constructed under the optimal conditions. For BSA and HSA, the linear ranges and detection limits are 0.05–24mgL^–1 and 0.02mgL^–1, respectively. The method has been applied to the determination of protein in human serum samples with satisfactory results. The mechanism of the polarographic wave was also studied, and the results show that S^2– ion is released from the protein molecule during the derivatization reaction, the wave being attributed to the reduction of HgS.