Analysis of the Temperature and Composition Dependence of Viscosimetric Properties of 2-Butanone <Emphasis Type="Bold">+</Emphasis> 2-Butanol Solvent Mixtures

Kinematic viscosities were measured for 2-butanone + 2-butanol binary liquid mixtures with a capillary Ubbelohde routine viscometer in the temperature range from 273.15 to 353.15 K at atmospheric pressure, and covering the whole miscibility field (0x_i1). Experimental data have been correlated by means of different empirical or semiempirical relationships, such as =(T), =(x_i), and =(T, x_i). Viscosity deviations, , from ideal behavior are negative at all experimental conditions, confirming that structure breaking effects prevail in the liquids. Furthermore, the thermodynamics of viscous flow and excess Gibbs energy of activation of viscous flow, G*^E, have been calculated. As an alternative and complementary approach to such investigations, the fluidity () of this binary system has been analyzed by the modified—Batschinski theory. The results are discussed in terms of the specific molecular interactions between the mixture components.     

Far infrared spectra (500–50 cm−1) of the 2,2′-bipyridine complexes of palladium and platinum halides

Summary The far-i.r. spectra of the title complexes have been examined. Band assignments are based on the shifts induced by ligand deuteration and halide substitution. Deuteration of bipyridine causes large shifts ( >10 cm^–1) in internal ligand modes, intermediate shifts between 2 and 9 cm^–1) in metal-nitrogen stretching and bending modes and small to zero shifts in metal-halide stretching and bending vibrations. Generally, the requirements for square planarC _2v synanetry [two (M–N) and two (M–X) bands] are observed. Previous ambiguities in the assignment of the (M–N) bands have been resolved by the isotopic labelling technique employed in this study.     

Some anomalies in the vibrational spectra of α, β-unsaturated ketones

Summary Some anomalies in the intensities of the bands of the C=C and C=O bonds in the vibrational spectra of , -unsaturated ketones have been explained by a difference in the sequence of the frequencies of the in-phase (_s) and out-of-phase (_as) vibrations of the multiple bonds in their cis (_s<_as) and trans (_s>_as) arrangements.     

Frequencies and integral intenstities of the lactone and ester carbonyls of natural guaianolides

The frequencies and integral intensities of the IR bands of the stretching vibrations of lactone and acyclic ester carbonyls at C-8 of ten natural guaianolides and their derivatives, and of three model compounds have been studied. The most probable interpretation of the change in the value of A_C=O and _C=O of the lactone carbonyl have been suggested. In elegin and some of its derivatives, acroptilin, chlorohyssopifolin B, and eleganin, a lowering of the values of A_C=0 and _C=0 in comparison with dihydroelegin, hexahydroelegin, and the hydroxylactone of cynaropicrin is caused by nonvalent interactions of the lactone carbonyl with the -exocyclic double bond. The increase in A_C=O and _C=O in dihydroelegin, hexahydroelegen, and the hydroxylactone of cynaropicrin is due to the angular strain of the -lactone ring. It has been shown that in an acyclic side chain at C-8 an increase in the integral intensity and in the frequency of the ,-unsaturated ester carbonyl relative to guaianolides in which the terminal vinyl group at C-17 is absent is due to a conjugation effect.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 805–811, November–December, 1987.     

Die PO-Bindung in den Phosphiten von Alkali- und Erdalkalimetallen

Zusammenfassung Auf Grund der Infrarotspektren der Phosphite von sieben Metallen der I. und II. Hauptgruppe des Periodischen Systems wurden die Werte der die PO-Bindung in den untersuchten Phosphiten charakterisierenden Parameter (Aufspaltung der Absorptionsbande der antisymmetrischen Valenzschwingung , Kraftkonstantenk _PO, Bindungslänger _PO und BindungsordnungN _PO) festgestellt. Es zeigte sich, daß die Kationen in der Abhängigkeit von ihrer Größe das Phosphitanion deformieren. Die Deformation des Anions erweist sich am deutlichsten in den Werten . Die Bindungsordnungen zeigen einen bedeutenden Anteil der -Bindungen in der PO-Bindung der untersuchten Phosphite.

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ThePO-bond in alkali metal phosphites and alkaline earth metal phosphites

The IR absorption spectra of seven phosphites of metals of groups I and II of the periodic table were recorded. From the spectra obtained, the values of the parameters characterizing the PO-bond in the compounds studied (splitting of the absorption band of the antisymmetric stretching vibration , force constantk _PO, bond lengthr _PO and bond orderN _PO) were calculated. It was shown that deformation of the phosphite anion by the cations is a function of the size of the latter. The deformation of the anion is revealed most clearly in the values . The values of the bond orderN _PO reveal a substantial degree of -bonding in the PO-bonds of the phosphites studied.

     

FT-Raman Spectra of o-, m-, and p-Nitrophenol Included in Cyclodextrins

FT-Raman spectra of o-, m-, and p-nitrophenol included in -cyclodextrin (CD), -CD, hydroxypropyl (HP) -CD, andsulfated -CD were recorded. The phenyl (C=C) band of o- and p-nitrophenol in the CD inclusion complexes was shifted to higher wavenumber thanthat of pure o- and p-nitrophenol,whereas the phenyl (C=C) band of m-nitrophenol in the CD inclusion complexes was shifted to lower wavenumber than that of pure m-nitrophenol. The ring CH peak of o-nitrophenol in the CD complexes was shifted to higher wavenumber than that of pure o-nitrophenol, whereas the ring CH peak of m- and p-nitrophenol in the CD complexes was shifted to lower wavenumber than that of pure m- and p-nitrophenol.     

Charge control of phenol complexation with unsaturated compounds containing organosilicon substituents. Thiophene derivatives

The frequency shifts of the O-H stretching modes and the resonance components _R of these shifts in the IR spectra of H-complexes of phenol with thiophene derivatives having organic and organosilicon substituents have been analyzed. Relationship of and _R parameters to values calculated by nonempirical methods that characterize the electronic effect of organic substituents on the effective charges of the thiophene ring atoms has been established. It has been shown that in the complexation of phenol (hard acid) with thiophene derivatives charge control prevails over frontier orbital control. The changes in the effective charges of the thiophene ring atoms due to the effect of organosilicon substituents have been calculated.For the previous publication of this series see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2163–2168, December, 1994.This work was supported by the Russian Foundation for Basic Research, Project No. 93-03-18725.     

IR Spectroscopic Study of Alkane Interaction with the Brønsted Acid Sites of Hydrogen-Exchanged Zeolites

Diffuse-reflectance IR spectroscopy is used to study the interaction of C₃ and C₆ alkanes (propane, n-hexane, 3-methylpentane, and cyclohexane) with the Brønsted acid sites of hydrogen-exchanged mordenite, ferrierite, ZSM-5, and faujasite. It is found that a shift of the absorption band of the stretching vibrations of acidic Si(OH)Al groups toward lower frequencies (OH) due to the formation of a hydrogen bond with adsorbed alkanes increases in the following series: OH(propane) < OH(n-hexane) = OH(3-methylpentane). The accessibility of Si(OH)Al groups to alkane molecules is determined by the dimension of rings through which molecules enter zeolite channels and cavities. It follows from the measured OH values that the strength of Brønsted acid sites decreases in the following series: HZSM-5 > H-mordenite H-ferrierite HY. The difference between the three high-silica zeolites is not great. The results obtained are compared with the published IR data on Si(OH)Al groups of zeolites with adsorbed alkanes and other weak bases.     

α BB Resonance in the ν8 Band of Borazine –10B

The high-resolution FTIR spectrum of the fundamental ₈ of borazine ¹⁰B₃ ¹⁴N₃ ¹H₆ was reanalyzed taking into account the ^BB resonance with the combination band (₁₀ + ₁₇). A parameter set for the states ₈ = 1 and ₁₀ = ₁₇ = 1, respectively, is given, reproducing the observed spectrum at least up to J = 30 with experimental accuracy.     

Investigation of supported WO3 catalysts for propene metathesis by diffuse reflectance spectroscopy

Diffuse reflectance spectra have been recorded for WO₃/SiO₂ and WO₃/-Al₂O₃ catalysts after various steps of treatment of these samples, in particular, after treatment of WO₃/SiO₂ by HCl. It is shown that for WO₃/-Al₂O₃ the temperatures of the onset of reaction and WO₃ reduction coincide.

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WO₃/SiO₂ WO₃/-Al₂O₃ , , WO₃/SiO₂ HCl. , WO₃/-Al₂O₃ .

     

Systematics of bonding in non-icosahedral carbon clusters

General formulas are presented for the vertex numbers, , of pentagon+hexagon polyhedra of icosahedral, tetrahedral or dihedral symmetries. Criteria for uniqueness of representation, isomer counts and grouping of pentagons are established. All polyhedra with 256 vertices or less and belonging to T, D ₅, D₆or their supergroups are listed. With the addition of C₃ to the dihedral and higher groups, at least one pentagon+hexagon cluster is found for all even 20 except for = 22 which is unrealisable in any symmetry, and = 46 (for which a C₃ polyhedron exists). Carbon clusters with closed electronic shells are shown to be generated by a geometrical leapfrog procedure: for all = 60+6k (where k is zero or greater than one) at least one closed shell structure is predicted. In dihedral symmetry closed shells also exist for some other values of . Separation of the 12 pentagonal faces is not sufficient to ensure a closed electronic shell but appears to be a necessary condition in dihedral or tetrahedral symmetry.     

Trinuclear,Oxo-Bridged,Mixed-Valence Iron Mercaptocarboxylates

Mixed carboxylates and mercaptocarboxylates of mixed-valence Fe^IIFe^III with general formula [Fe^II-Fe^III ₂O(OOCR)₃(OOCRSH)₃L₃](where R = C₁₃H₂₇, C₁₅H₃₁ or C₁₇H₃₅; R= CH₂ or C₆H₄ and L = pyridine) were successfully prepared by substitution of [Fe^IIFe^III ₂O(OAc)₆(H₂O)₃] with straight chain carboxylic acids and mercaptocarboxylic acids. The title products have been characterized by elemental analyses, molar conductances and magnetic susceptibility measurements, i.r., electronic and Mössbauer spectral data. The i.r. spectra showed resolved bands arising from the _asym(OCO) and _sym(OCO) vibrations of the bridging carboxylate and mercaptocarboxylate ligands along with the _asym(Fe₃O) vibrations. Mössbauer spectroscopic studies revealed two resolved quadrupole doublets due to Fe^II and Fe^III at 80, 200 and 295 K, confirming the valence-localized type of compound. This fact has also been supported by the observed electronic spectral bands in the complexes. Magnetic susceptibility measurements showed net anti-ferromagnetic coupling related to mixed-valence pairs. A structure for the complexes has been established on the basis of physico-chemical studies.     

Schrödinger Equation Solutions for the Central Field Power Potential Energy II. V(r) = −V 0(r/a 0)2ν−2, 0 ≤ ν ≤ 1, the Bound States

The bound states of the generalized Schrödinger equation system with radial potential energy V(r) = –V ₀(r/a ₀)^2–2, 0 1, are described. The solutions of the differential equation are related to the functions for the bound state problem with 1. The Green's function is constructed as well as its first iteration, the traces of both functions are calculated, and an upper and lower bound for the ground state is established. A WKB-like approximate solution for the eigenvalues and eigenfunctions is derived.     

Donor properties of the nitrone function in copper(II) complexes of some 2-hydroxy-1-naphthylnitrones

Summary Copper(II) complexes of the type CuL₂, 2H₂O and CuL₂. Py where L=-(2-hydroxy-1-naphthyl)-N-R-nitrone (R= methyl, phenyl and variously substituted phenyls) have been isolated and characterised. They have normal magnetic moments. Their ligand field spectra indicate an octahedral geometry for the dihydrates and a five-coordinate environment for the pyridine adducts. Increased (C=N) and considerably decreased (N-O) frequencies in these complexes reveal the presence of - and -interactions of the ligand with copper through nitrone oxygen. The effect of pyridine adduct formation is to increase the Cu-O -interaction.     

Diffusion Sensor of Mechanical Signals: Frequency Response at High Frequencies

The frequency response of a diffusion transducer with gauze electrodes, studied theoretically at high frequencies, is proportional to ^-3/2 starting with = D/R ² at < /R ² and to ^-1 at > /R ². Here, = 2f, f is the signal frequency, the electrolyte viscosity, D a diffusion coefficient, and R the radius of the gauze filaments. The calculation is compared with experiment.     

State of copper in massive Cu?V?Mo oxide systems

ESR data for X(CuO) V₂O₅·8.3 MoO₃ system heated at 400–550 °C indicate the occurrence of a copper state with d_Z ²-ground state. Copper ions are orbitally ordered apparently in –Cu²⁺–O–Cu¹⁺–O–Cu²⁺-chains.

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B X(CuO) V₂O₅·8,3 MoO₃ , 400–550°C d_Z ²- . , , –Cu²⁺–O–Cu¹⁺–O–Cu²⁺-.

     

Kinetics of Free Radical Generation in the Catalytic Oxidation of Methanol

The formation of free radicals over the surface of platinum-containing catalysts in the methanol oxidation reaction depending on the temperature, the composition of the reaction mixture, and the procedure used for introducing platinum was studied by the matrix isolation method technique. The nature and transformations of surface intermediates depending on the temperature and the presence of oxygen in the gas phase were studied by Fourier transform IR spectroscopy. The main surface intermediate was the methoxy group. The following three types of these groups were stabilized in alumina-based catalysts: (I) CH₃O–Al_oct (_s(–) = 2806 cm^–1), (II) CH₃O–Al_tetr (_s(–) = 2825 cm^–1), and (III) CH₃O < (Al)₂ (_S(–) = 2845 cm^–1, _s(–) = 1460 cm^–1, _s(–) = 1440 cm^–1, r _|| (₃) = 1185 cm^–1, and (–) = 1095 cm^–1). At the same time, isolated methoxy groups (_as(–) = 2997 cm^–1, _as(–) = 2959 cm^–1, _s(–) = 2857 cm^–1, and (₃) = 1450 cm^–1) and hydrogen-bonded groups ((–) = 3400–3550 cm^–1), which resulted from chemisorption at siloxane bridges, were stabilized in silica gel–based catalysts. It was found that CH₃O and CH₃OO radicals were formed only over the surfaces of pure supports (SiO₂ and Al₂O₃) and their mechanical mixtures with platinum. The total concentration of radicals was described by an extremal function of the composition of reactants, whereas the relative concentration depends on the nature of the support. This is conceivably due to the effect of coordinatively unsaturated cations of the support, which are formed by dehydroxylation in the course of catalyst pretreatment. An increase in the rate of formation of gas-phase radicals on mixed catalysts was explained by special properties of the platinum/support interface region, at which surface intermediates were formed in superequilibrium concentrations under reaction conditions.     

SIMS and XPS studies of Raney nickel catalysts

Chemical composition and structure of surface layers of Raney nickel catalysts prepared from NiAl₃ and Ni₂Al₃ intermetallides and Ni–Al (11) alloy have been studied by SIMS and XPS methods. A model structure of these catalysts is suggested.

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SIMS , NiAl₃, Ni₂Al₃ Ni–Al (11). .

     

Cleavage of 1,4-diphenylbuta-1,3-diyne on a ruthenium-cobalt cluster: Synthesis and molecular structure of Co2Ru3(μ4−C2Ph)(μ3−C2Ph)(μ-dppm)(μ-CO)2(CO)9

The reaction between Ru₃(₃-²-PhC₂C=CPh)(-dppm)(CO)₈ and Co₂(CO)₈ afforded dark red Co₂Ru₃(₄-C₂Ph)(₃-C₂Ph)(-dppm)(-CO)₂(CO)₉, shown by an X-ray structure determination to contain a strongly twisted Co₂Ru₃ bow-tie cluster (central Co), to which two PhC₂ units derived from cleavage of the original diyne are attached. One a these is strongly interacting with four metal atoms, the other being attached in the familiar ¹,2²-mode. The dppm ligand remains bridging two of the Ru atoms.