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.     

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.     

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.     

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.     

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.     

Die IR-Spektren von B-Methoxy- und B-Trideuteromethoxyborazinen und-boroxinen und Tri[methoxy(d3)boran

Zusammenfassung In Methoxyverbindungen des Bors tritt eine Verminderung der Frequenz der B—O-Valenzschwingung gengenüber den entsprechenden Trideuteromethoxyverbindungen auf. Dies wird durch zufällige Entartung von B—O und CH₃ erklärt, die zu einer Abstoßung und zur Vermischung des Schwingungscharakters dieser beiden Schwingungen führt. Hiedurch werden die B—O-Valenzschwingungen zu tieferen und die CH₃-Deformationsschwingungen zu höheren Wellenzahlen verschoben. Ähnliche Erscheinungen sind auch in Methoxyborazinen durch Wechselwirkung von BN und CH₃ zu beobachten. Diese Deutung gibt auch Hinweise für Zuordnungen in den Spektren von N-Methylborazinderivaten.

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In methoxy substituted boron compounds bands arising from B—O stretching and (O)–CH₃ deformation modes show accidental degeneracy. The frequency of the CH₃ absorption is increased whereas BO is decreased compared to the corresponding CD₃-compounds. The spectra of B-methoxyborazines show similar effects between BN and (O)–CH₃ bands, which is analogous to interference between BN and (N)–CH₃ in N-methylborazines.

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Mit 7 Abbildungen     

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.     

Preparation and characterization of Ru?Pb supported catalysts

Decomposition of Mn₃Mo₂TeO₁₂ during oxidation of toluene to benzaldehyde was observed. Depending on the surface composition of the initial catalyst, the decomposition leads to less active but highly selective MnMoTeO₆ or to MnMoO₄ which is not selective in toluene oxidation.

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Mn₃Mo₂TeO₁₂ . , MnMoTeO₆, MnMoO₆.

     

Diffuse-Reflectance IR Spectra of Methane Adsorbed on NaZSM-5 and HZSM-5 Zeolites

Diffuse-reflectance IR spectra of methane adsorbed on high-silica NaZSM-5 and HZSM-5 zeolites point to a stronger adsorption of methane on sodium cations than on protons. For the asymmetric stretching vibration ₃, this form of adsorption is characterized by a doublet with band maxima at 2980 and 3010 cm^–1. For the fully symmetric stretching vibration ₁, it is characterized by a singlet with a maximum at 2880 cm^–1. Methane is also adsorbed on NaZSM-5 in a weaker form, which is characterized by absorption bands with maxima at 3002 (₃) and 2887 (₁) cm^–1. The weaker form of methane adsorption on acidic bridging hydroxy groups of HZSM-5 is characterized by absorption bands at 3001 and 2887 cm^–1 (₃ and ₁, respectively). A difference between this form of adsorption and weak adsorption on sodium-exchanged zeolite reveals itself in the somewhat higher intensity of the band at 2887 cm^–1. For methane adsorbed on NaZSM-5, the frequencies of deformational vibrations and a spectrum in the near IR region are obtained for the first time. It was found that the perturbance of adsorbed methane molecules is seen in the spectrum as in the low-frequency shifts of most of the bands that appear due to composite vibrations and overtones and as new adsorption bands that were not observed for gaseous methane.     

Vibrational spectra of the hexaalkyldielementooxanes-derivatives of the group IVB elements

Conclusions On the basis of the calculation of the frequencies and form of the normal vibrations for hexaalkyldielementooxanes (C₂H₅)₃MOM(C₂H₅)₃ (M is an element from the Group IVB) and the existence of a correlation between _as ^MOM and k_MO and _OH, it is shown that a change in the frequency of the antisymmetrical valence vibrations for the M-O-M group is mainly due to dynamic effects in the M-O-M system.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1042–1044, May, 1976.     

Association and relative acidities of 2-substituted 5-trifluoroacetylpyrroles

The acidities of 2-substituted 5-trifluoroacetylpyrroles were studied by IR spectroscopy from the shift of the frequency of the NH stretching vibration (_NH) in the presence of dimethylformamide (DMF) relative to the band of vibrations of free NH. The existence of a correlation relationship between _NH and _I constitutes evidence that the acidities of pyrroles are determined primarily by the inductive effect of the substituents in the 2 and 5 positions of the pyrrole ring. The low probability of the formation of an intramolecular NH... O=C hydrogen bond in the investigated molecules was demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 772–774, June, 1984.     

Complexation of three uranium(IV) ions at two α-B-[SbW9O33]9- trilacunary Keggin units: A spectroscopic investigation

The sandwich-type uranium(IV)-polyoxometalate Na₆ [U₃ (SbW₉ O₃₃ )₂ ]·22H₂ O was prepared and investigated by FT-IR and UV-VIS methods. The uranium(IV) coordination at the trilacunary Keggin units shifts the _as (W-O_b,c -W), _as (W=O_d ), _as (W-O_a ) antisymmetric stretching vibration bands in the 700 ÷ 950 cm^-1 region of the FT-IR spectrum of U(IV)-complex. The visible electronic absorption spectrum of the complex indicates a ³ H₄ electronic ground state of uranium ions and a quasicubic local symmetry around them. The UV electronic spectra of the U(IV)-POM complex and of the ligand present the broad bands assigned to p -d electronic transitions in the W=O bonds (at 46640 cm^-1 for the ligand and 47280 cm^-1 for the complex) and d -p -d transitions in tricentric W-O-W bonds (at 40880 cm^-1 for the ligand and 39920 cm^-1 for the complex).     

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.     

Influence of solvent on ir spectra of aroyl(hydroxymethyl)trifluorosilanes

Conclusions Dipole-dipole interaction of the solvent with molecules of aroyl (hydroxymethyl) trifluorosilanes 4-XC₆H₄COOCH₂SiF₃ is responsible for changes in frequency of the stretching vibrations of groups included in a five-membered ring, containing an intramolecular coordination bond Si 0 (the frequencies C=O and SiF _a , are lowered, and the frequencies _asCOC are raised). The value of the orientation-induction parameter in the Buckingham equation, reflecting the dependence of C=O and SiF _a on the parameters of the medium (, n), increases with increasing electron-donor capability of the substituent X, indicating an increase in the strength of the coordination bond. The coefficient in the Hammett equation is determined by the polar properties of the medium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2251–2254, October, 1984.     

Phase separation of poly(γ-benzyl L-glutamate) to liquid crystal and isotropic solution in various helicogenic solvents

Solvent effects on the phase separation of poly(-benzyl L-glutamate) to liquid crystal and isotropic solution have been observed in various helicogenic solvents. The temperature-composition phase diagrams have been determined for each solution. The critical concentrations, ₂ ^* , at which the phase separation occours have been compared in various solvents. In dimethylformamide in which the polymer is molecularly dispersed, the observed ₂ ^* value has agreed with that calculated by Flory's theory. In some solvents in which the polymer aggregates in a head-to-tail mode such as chloroform, the observed ₂ ^* values have been considerably small. It is assumed that the polymer aggregates behave as longer particles than the original particles. In dioxane in which the polymer aggregates highly both in a head-to-tail and a side-by-side modes, the ₂ ^* value has been a little larger than that in chloroform. In this case the relationship between the aggregation and the liquid crystal formation is so complicated that further investigation is necessary. In aromatic solvents such asm-cresol that dissolves the polymer almost molecularly, the ₂ ^* is smaller than that in dimethylformamide. Therefore, the intermolecular interactions between the phenyl groups in the side groups of the polymer and those in solvent molecules must be considered.The author is grateful to Mr. K. Sano and Mr. M. Watanabe for their observation of the liquid crystal formation.     

FT-Raman Spectra of 2-, 3-, and 4-Chlorostyrene Molecules Included in Cyclodextrins

FT-Raman spectra of 2-, 3-, and 4-chlorostyrene included in-cyclodextrin (CD),glycerol ether -CD, -CD,sulfated -CD, andglycerol ether -CD were recorded.In the inclusion complexes, the area of the vinyl(C=C) band decreased remarkably, whereasthe area of the phenyl (C=C) band increasedcompared to those of liquid 2-, 3-, and 4-chlorostyrene,respectively. From the results, the inclusion structures of2-, 3-, and 4-chlorostyrene were discussed.     

Infrared spectroscopy of hydrogen bond and substituent effects in electron donor molecules

The frequency shift, , of the O—H stretching mode in the IR spectra of the H-complexes of phenol with electron donor molecules BX_i (B is the n- or -donor center and X_i are substituents; a total of eight series), the change in the Gibbs free energy, G, due to H-complexation, and the parameter (a measure of the ability of BX_i molecules to donate an electron pair; two series) are determined by both the electrostatic interaction and charge transfer in the formation of H-complex. The , G, and values depend not only on the inductive and resonance effects, but also the polarizability of substituents characterized by the parameters.     

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.

     

Reaction mechanism and principles of choosing catalysts for selective oxidation at C?H bonds

Reaction mechanism for selective oxidation of organic compounds at C–H bonds is discussed. The criteria of selecting catalysts for these reactions have been formulated; 1) fast heterolytic activation of C–H bonds; 2) relatively slow primary activation of oxygen; 3) fast diffusion of oxygen vacancies; 4) fast electron transfer from the adsorbed substrate to catalyst.

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C–H . : 1) C–H ; 2) ; 3) ; 4) .

     

Oxidative coupling of 5-membered heterocycles catalyzed by a Pd(II)-heteropolyacid system in dimethylformamide

Oxidative coupling of thiophene and 2-methylfuran to the corresponding dihetaryls in DMFA medium occurs in the presence of the homogeneous catalytic system Pd(II)-molybdovanodophosphoric heteropolyacid (HPA). The data obtained show that HPA may act as a reversible oxidant in polar aprotic media.

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, Pd(II)- 2- . , .