Microwave Spectrum of 1,3-Dioxolane. Potential Function of Hindered Pseudorotation and Molecular Conformation

Vibrational and rotational transitions of c type with 24 ≥ J ≥ 18 between the pseudorotational states v = 4 and v = 5 have been identified in the range 23 GHz–39 GHz of the microwave spectrum of 1,3-dioxolane (C₃H₆O₂); their frequencies have been measured. Spectrum analysis was performed using numerical diagonalization of the effective rotational Hamiltonian for three states: v = 4, 5, and 6 of hindered pseudorotation, and it gave the intervals ΔE ₄₅ = 331,023 MHz and ΔE ₅₆ = 298,771 MHz. The potential function of hindered pseudorotation was determined from the values of ΔE ₄₅ and Δ E ₅₆ and from the values of ΔE ₀₁, ΔE ₁₂, ΔE ₂₃, and ΔE ₇₈ found previously for the molecule; the molecular conformation has been established.Original Russian Text Copyright © 2004 by A. Kh. Mamleev, L. N. Gunderova, R. V. Galeev, and A. A. Shapkin__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1008–1012, November–December, 2004.     

Characteristics of the 5S rRNA from cotton seeds

The individuality of the 5S rRNA from cotton seeds has been determined by the production of a single narrow band on gel electrophoresis and by the characteristic UV spectrum with values of the ratios E₂₆₀/E₂₃₀ and E₂₆₀/E₂₈₀ of 2.03–2.1 and 2.08–2.14, respectively. The melting curve of the 5S rRNA has been obtained and a total hyperchromic effect of 25% has been calculated. The nucleotide composition of the 5S rRNA has been established by determining the amount of nucleotides in an alkaline hydrolysate (22.6% of AMP; 30.2% of GMP; 22.6% of UMP; and 24.6% of CMP). The nucleotides were identified from the position of their appearance in the elution profile, from their UV spectra in 0.1 N HC1 and 0.1 KOH, and also by one- and two-dimensional chromatography of the nucleotides obtained, in the presence of markers.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 817–821, November–December, 1980.     

Thermodynamic parameters of liquid ternary Fe1−x(Ni5/6Cr1/6)x alloys

Summary Computer-aidedKnudsen cell mass spectrometry is used for thermodynamic investigations on liquid ternary Fe_1–x(Ni_5/6Cr_1/6)_x alloys. The thermodynamic excess properties have been determined by means of the Digital Intensity-Ratio (DIR) method. Liquid ternary Fe_1–x(Ni_5/6Cr_1/6)_x alloys are characterized by exothermic molar heats of mixingH ^E, negative molar excessGibbs energiesG ^E, and negative molar excess entropiesS ^E. At 1850 K, the minimumH ^E value is –3120 J/mol (42.3 at.% Fe), the minimumG ^E value is –2540 J/mol (30 at.% Fe), and the minimumS ^E value is –0.44 J/(mol K) (60 at.% Fe). At 1850 K, the thermodynamic activities of Fe show slight negative deviations from the ideal behaviour for alloys with a Fe-content of less than 75 at.%, and ideal behaviour for the Fe-rich alloys (x _Fe>0.75).

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Thermodynamische Parameter flüssiger ternärer Fe_1–x(Ni_5/6Cr_1/6)_x-Legierungen

Zusammenfassung Die Thermodynamik flüssiger ternärer Fe_1–x(Ni_5/6Cr_1/6)_x-Legierungen wurde mit Hilfe der computerunterstützten Knudsenzellen-Massenspektrometrie studiert. Die thermodynamische Auswertung der experimentellen Untersuchungen erfolgte nach der digitalen Intensitätsverhältnismethode (DIR). Flüssige ternäre Fe_1–x(Ni_5/6Cr_1/6)_x-Legierungen zeigen exotherme molare MischungswärmenH ^E, negative molareGibbssche ZusatzenergienG ^E, und negative molare ZusatzentropienS ^E. Bei 1850 K sind die Minimumswerte fürH ^E –3120 J/mol (42.3 At.% Fe), fürG ^E –2540 J/mol (30 At.% Fe) und fürS ^E –0.44 J/(mol K) (60 At.% Fe). Bei 1850 K zeigen die thermodynamischen Aktivitäten von Fe bei Legierungen mit einem Fe-Gehalt von höchstens 75 At.% leichte negative Abweichungen vom idealen Verhalten, die Fe-reichsten Legierungen (x _Fe>0.75) verhalten sich hingegen nahezu ideal.

     

First example of the formation of highly ordered supermolecular structures in a series of gibberellin derivatives

The 3-O-palmitate and 3-O-tridecanoate of gibberellin A₃ have been synthesized and monomolecular Langmuir-Blodgett films have been obtained from them.Novosibirsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 793–795, November–December, 1994.     

Thermodynamic properties of binary mixtures: Hexamethylphosphoric triamide + a polar liquid at 25°C

Excess enthalpies H _m ^E excess isobaric heat capacities C _p,m ^E , densities, and speeds of sound of hexamethylphosphoric triamide (HMPA)+acetonitrile (AN), + N,N-dimethylformamide (DMF), and + dimethylsulfoxide (DMSO) were measured at 25degrC. H _m ^E =–1200 J-mol^–1 for HMPA + AN, –180 J-mol^–1 for HMPA + DMF, and 75 J-mol^–1 for HMPA + DMSO C _p,m ^E is positive and considerably larger than C _v,m ^E . V _m ^E for HMPA + DMSO was small and changed sign from negative to positive around HMPA mole fraction x=0.6. V _m ^E for the other two mixtures were negative. The excess compressibilities, K _m ^E for the other two mixtures were negative. The excess compressibilities, K _S ^E and K _T ^E were similar to V _m ^E Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30-June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

Extractive substances of the bark of Picea obovata

The chemical composition of a petroleum ether extract of the bark of the Siberian spruce has been studied. Extracts included saturated aliphatic alcohols and C₁₆-C₂₄ acids — abietic, dehydroabietic, isopimaric, oleic, lineolic, and linolenic — alkyl ferulates, ketones, and alcohols of the serratene type, and also ⁴-stigmasten-3-one. Onoceradienedione and onoceradienediol — precursors of the serratene triterpenoids — and also a saturated vicinal diol — triacontane-10,11-diol — have been isolated from the extractive substances of conifer in the native form for the first time.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 654–662, November–December, 1992.     

Surface and Subsurface Oxygen on Platinum in a 0.5 M H2SO4 + 0.01 M CuSO4 Solution

The formation of a copper adatom layer on polycrystalline platinum in a copper sulfate solution is studied by cyclic voltammetry in different cycling ranges at 0.1 V s^–1. The copper adatom deposition kinetics is controlled by the following factors. The substrate's top layer structure during the oxygen exit onto the surface may be unstable at anodic limits E _a = 0.90–1.35 V. The concentration of copper oxides (active centers) may be higher at E _a = 0.8–0.95 V. The balance between different adsorption sites differs in different cycling conditions. Of importance is the number of complexes O_ss–Pt _n –SO₄ and O_ss–Pt _n –O_c, where O_ss is subsurface oxygen and O_c is chemisorbed oxygen.     

Polarographic properties of ubiquinones with isoprenoid chains of different lengths

It has been shown that in aqueous ethanolic solutions the polarographic potentials E₁/₂ for ubiquinones with isoprenoid chains with different lengths are the same, –0.235 V (relative to a normal calomel electrode) at pH 7.9, and correspond to quasi-irreversible reduction with the addition of 2e^–/2H⁺. It has been found that the potential E₁/₂ for the ubiquinone UQ-O having no isoprenoid chain is more positive by 57 mV relative to the potentials of the other ubiquinones.Institute of Soil Science and Photosynthesis, USSR Academy of Sciences, Pushchino. Moscow Oblast. Translated from Khimiya Prirodnykh Soedinemii, No. 5, pp. 703–707, September–October, 1988.     

Voltamperometric determination of uranium and plutonium in alkaline solutions

The simultaneous determination of U(VI), Pu(VI), Pu(V) in 0.5–4.0 M NaOH has been elaborated by means of classical and differential pulse voltamperometry. U(VI) is determined with a dropping mercury electrode (DME) at the half-wave potential of E_1/2=–0.89 V vs. Ag/AgCl reference electrode due to reduction to U(V). The limiting current or peak heights are proportional to uranium(VI) concentration in the range of 1.3.10^–7–3·10^–4 M U(VI). Deviation from proportionality is observed for higher concentrations due to polymerization of uranates. Pu(VI) and Pu(V) are determined with a platinum rotating electrode at E_1/2=–0.02 V due to the reaction Pu(VI)+e^–»Pu(V) and with DME at E_1/2=–1.1 V due to the reduction to Pu(III). The limiting currents of both Pu(VI) and Pu(V) are proportional to their concentrations in the range of 4·10^–6–1.2·10^–3 M Pu. The determination of U(VI), Pu(VI), Pu(V) is not interfered by the presence of the following salts: 2M NaNO₃, 2M NaNO₂, 1.5M NaAlO₂, 0.5M NaF and ions of Mo(VI), W(VI), V(V), Cu(II). The presence of CrO ₄ ^2– and FeO ₂ ^– ions disturbs the determination of U(VI) in 1–4M NaOH, however, contribution of the reaction Fe(III)+e^–»Fe(II) to uranium reduction peak can be calculated from the height of the second peak Fe(II)+2 e^–»Fe(0).     

Instantaneous strain recovery elasticity and endothermic heat change in nylon-6 monofilaments and silicone rubbers

The instantaneous elastic moduli for a nylon-6 monofilament were derived on strain recoveries right after creep, stress relaxation, and rapid elongation,E _c ,E _s andE _e , respectively. It was found that during strain recoveryE _s (>E _e ) andE _e increase monotonically with increasing load,m ₁, on the sample. The extrapolated value of E_s atm ₁=0 g is almost equal to Young's modulus, 4.06 GPa. The value ofE _c also increased with increasingm ₁, and atm ₁=600 g (1.93 t cm^–2) reached about 14 GPa. The endothermic heat change right after creep, stress relaxation or rapid elongation,Q, was negligibly small. For comparison,E _s ,E _c andQ were also investigated for silicone rubber. It was found thatE _s (53.8 M Pa at the draw ratioD=1.2) decreased abruptly atD=1.3. In the range ofD=1.4–1.9,E _s was only 22.6 MPa. In the case of stress relaxation,Q increased with increasingD from 4 J mol^–1 (atD=1.2) to 56 J mol^–1 (atD=1.9). FurthermoreE _c (5.58 MPa atm ₁=133.8 g (429.4 kg cm^–2)) increased gradually with increasing m₁ and attained 16.6 MPa atm ₁=548.4 g (1.76 t cm^–2). In the case of creep,Q was in the range of 0–11.5 J mol^–1 and larger when larger loads,m ₂ were removed during the later stages of creep.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayThe author wishes to thank Mr. Keizi Igarashi and Mr. Tetsuya Yasui for helping in the experiments.     

Investigations of TsVM zeolite acidities with different degrees of exchange of Na+ by H+

The method of programmed thermal desorption of ammonia has been used to establish that on the surface of the sodium form of type TsVM zeolite having a modulus SiO₂/Al₂O₃= 34.5 there are two types of acidic centers having ammonia desorption activation energies E_d equal to 40–45 and 80–100 kJ/mole. Replacement of Na⁺ by H⁺ leads to the appearance of a third type of center with a value E_D=130–150 kJ/mole. In this case in the IR spectra of specimens saturated with ammonia a band appears at 1410 cm_–1, which is evidence for the presence of NH ₄ ⁺ ions. Increasing the degree of Na⁺ replacement by H⁺ leads to a nonproportional rapid increase in the concentration of highly energetic centers, which may be explained by the partial transfer of aluminum into cationic positions with the formation of additional acidic centers.Translated from Teoreticheskie i Éksperimental'naya Khimiya, Vol. 22, No. 6, pp. 752–755, November–December, 1986.     

Surface and Subsurface Oxygen on Platinum in a 0.5 M H2SO4 Solution

The oxidation of polycrystalline platinum in 0.5 M H₂SO₄ is studied by cyclic voltammetry at potential scan rates of 5–500 mV s^–1 while varying the potential cycling range. The scheme, which is proposed for explaining the observed acceleration and deceleration of oxygen sorption at 0.75–1.0 V, accounts for the presence of oxygen in the subsurface layers of platinum (O_ss) and the formation of a barrier layer comprising complexes O_ss–Pt _n –SO₄. Cycling platinum secures certain steady-state contents of O_ss at 0.01–1.35 V. In an anodic scan, O_ss accumulates at E > 0.85 V (slow post-electrochemical stage) due to exchange of platinum and oxygen atom sites. In a cathodic scan, the desorption of most oxygen gives way to the adsorption of anions, which prevent residual O_ss from appearing on the surface. The residual O_ss disappears at E < 0.1 V after a sufficiently complete desorption of anions and the destruction of stable complexes O_ss–Pt _n –SO₄. Varying the potential cyclic limit leads, after a delay, to other steady-state O_ss contents.     

Energy of the ground state of Be

The contributions from the diagrams of the first two orders are calculated for the energy of the ground state of Be. The result is E₂= =–1.25 Z²+1.55927422 Z–0.8775, with E ₂ ^corr =–0.01172683 Z –0.0720. Perturbation theories for the ground-state energy of Be are compared for Hartree-Fock and hydrogen-type functions.     

X-Ray diffraction study of solid-state photoisomerization products [Co(NY3)5NO2]XY (X,Y = Cl,Br, I,NO3)

Complexes [Co(NH₃)₅NO₂]XY and [Co(NH₃)₅ONO]XY (X,Y=Cl, Br, I, NO₃) have been studied by the X-ray diffraction method. The unit cell parameters were refined for the nitro isomers and determined for the nitrito isomers. We have analyzed changes in the latter arising during the nitro-nitrito photoisomerization and the reverse nitrito-nitro thermal isomerization. The topotaxial character of the structural rearrangement has been shown. The X-ray diffraction data obtained were compared with IR and kinetic data.Institute of Solid State Chemistry and Processing of Mineral Raw Materials, Siberian Branch, Russian Academy of Sciences. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Novosibirsk State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 128–140., July–August, 1993.Translated by T. Yudanova     

Thermodynamic study of perfluorohexane + ether mixtures: VLE, LLE, and H

Vapour–liquid equilibria (VLE), liquid–liquid equilibria (LLE), and excess enthalpies (H^E) of binary mixtures of perfluoro-n-hexane plus an ether (diethyl, dipropyl, dibutyl, butyl methyl, and butyl ethyl ether), have been determined using a head-space gas-chromatographic technique, a turbidimetric apparatus, and a heat-flow calorimeter, respectively. A recently designed titration technique and calculation procedure have been used to obtain H^E from heats of solution. The observed liquid–liquid coexistence curves have been compared with those predicted by the activity coefficients γ_i and their temperature dependence. All mixtures are strongly endothermic (H^E > 0) and show large positive deviations from ideality (G^E > 0), which increase with the size of the ether. Molecular interactions have been examined by calculating and discussing solvation functions and Kirkwood–Buff (KB) integrals. Perfluorohexane proved to be an inert molecule that interacts with ethers more weakly than hexane.     

Differential pulse voltammetric determination of arsenic(III,V) and antimony (III,V) in glasses

Summary Analytical methods based on differential pulse voltammetry (DPV) have been described for the determination of total As, As(III), As(V), total Sb and Sb(III) as trace to minor constituents in complex glasses. For total As, the sample is decomposed with HF-H₂SO₄-KMnO₄. The As(V) is chemically reduced to As (III) by hypophosphite and a DPV scan is carried out at the dropping mercury electrode from –0.2 to –0.7 Vvs. SCE (E _p –0.41V). As(V) is determined by decomposing the sample in HF-H₂SO₄ and volatilizing the As(III) as AsF₃. The chemical reduction of As(V) and the DPV scan are then applied. If the glass can be decomposed with cold HF, the As(III) present in the glass can be determined by applying the DPV scan after cold sample-dissolution. For Sb(III), the sample is decomposed with HF-H₂SO₄, diluted, and adjusted to 1M in HCl. A DPV scan is conducted from –0.03 to –0.5 V (E _p –0.15 V). Sb(V) is not reduced in the 1M HCl supporting electrolyte. Total Sb is determined by using an aliquot of the sample solution adjusted to 6M in HCl. The DPV sweep is carried out from –0.5 to –0.1 V [E _p for Sb(V) and Sb(III) is –0.30 V]. The methods have been applied to a wide range of glass compositions and the results compared with values obtained by spectrophotometry and coulometric titration.

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Bestimmung von Arsen(III, V) und Antimon(III, V) in Gläsern mit Hilfe der Differential-Puls-Voltammetrie

Zusammenfassung Analytische Methoden auf der Grundlage der Differential-Puls-Voltammetrie (DPV) für die Bestimmung des gesamten Arsens, As(III), As(V), des gesamten Antimons und Sb(III) als Spuren in komplexen Gläsern wurden beschrieben. Zwecks Bestimmung des Gesamt-As wird die Probe mit Flußsäure +Schwefelsäure + Permanganat aufgeschlossen. As(V) wird mit Hypophosphit reduziert und die DPV wird an einer Quecksilber-Tropfelektrode zwischen –0,2 und –0,7V gegen eine ges. Kalomelelektrode (E _p =–0,41V) durchgeführt. Zur Bestimmung von As(V) wird die Probe mit HF-H₂SO₄ unter Verflüchtigung des As(III) als AsF₃ aufgeschlossen. Dann erfolgt die Reduktion des As(V) und die DPV. Wenn sich das Glas mit kalter HF lösen läßt, wird anwesendes As(III) mittels DPV in dieser Lösung bestimmt. Zur Bestimmung des Sb(III) wird die Probe mit HF-H₂SO₄ zersetzt, verdünnt und bis zur 1-Molarität mit HCl versetzt. Dann wird mit DPV zwischen –0,03 und –0,5V gemessen (E _p =–0,15V). Sb(V) wird in 1M salzsaurer Lösung nicht reduziert. Das Gesamt-Sb wird in einem Aliquot der Probelösung bestimmt, das dazu mit HCl bis zur 6fachen Molarität versetzt wird. Der DPV-Bereich wird von –0,5 bis –0,1 V ausgenützt (E _p f:ur Sb(V) und Sb(III) ist –0,30 V). Das Verfahren wurde für Gläser verschiedenster Zusammensetzung angewendet. Die Ergebnisse wurden mit den Resultaten der Spektrophotometrie und der coulometrischen Titration verglichen.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Electrochemical Behavior of Platinum-Modified Polyaniline Films in Sulfuric Acid Solutions of Carbon Monoxide

On the Pt–PAN–GC and PAN–Pt electrodes in H₂SO₄solutions that are first saturated with CO and then rid of it, during anodic scans of E _r, oxidation peaks are observed at 0.85–0.95 V, which disappear only after repeatedly cycling E _rin the interval 0.65 to 1.1 V. The effect is attributed to the capability of a PAN film to sorb considerable CO amounts. The sorption interaction is of a chemical nature. The electrooxidation of CO in the film is closely related to the PAN oxidation, which results in its destruction.     

Surface and Subsurface Oxygen on Platinum in a Copper Perchlorate Solution

The formation of an adatom layer on polycrystalline platinum and the three-dimensional nucleation of copper in a copper perchlorate solution are studied by cyclic voltammetry at 0.1 V s^–1 while varying potential ranges and by recording potentiostatic current transients. About 0.6 monolayers of copper adatoms are deposited when cycling with anodic limit E _a = 1.35 V, the process is slower than that in an acid sulfate solution. Decreasing E _a accelerates the process (nearly one monolayer forms for E _a = 0.80–0.95 V in a cathodic scan) due to an increased number of active centers (metastable copper oxides) and, probably, to a change in the platinum surface microstructure. Oxygen for copper oxides is presumably supplied by water molecules adsorbed on a monolayer of copper adsorbed atoms and by subsurface oxygen (O_ss), which appears on the platinum surface after the destruction of complexes O_ss–Pt _n –ClO₄. Both the copper nucleation and the deposit growth accelerate at higher concentrations of copper oxides, which form at low E _a. High cathodic overvoltages decrease the number of active crystallization centers due to reduction or removal of copper oxides.     

Thermocatalytic transformations of wood and cellulose in the presence of HCl, HBr, and H2SO4

The compositions of the liquid organic products formed from aspen wood and cellulose at 150, 200, and 250° C in the presence of 1, 3, and 5% of HCl, HBr, and H₂SO₄ have been studied. The yield of levulinic acid from wood reached 13.0–15.5%, and from cellulose 28.8%.Institute of the Chemistry of Natural Organic Raw Material, Siberian Division of the Russian Academy of Sciences, Krasnoyarsk, fax (3912) 43 93 42. Translated from Khimiya Prirodnykh Soedinenii, Vol. 33, No. 1, pp. 107–112, January–February, 1997.     

Exchange parameters of five-spin clusters of Cu(II) coordination compounds with imidazoline nitroxide radicals

The exchange Heisenberg interaction parameters have been determined from theoretical analysis of the temperature dependence of magnetic susceptibility of coordination cluster compounds [Cu(hfacac)₂]₃(Li⁽ⁱ⁾)₂ (hfacac is hexafluoroacetylacetonate, L⁽ⁱ⁾ are 3-imidazoline nitroxides). Upon coordination of both N O oxygens and heterocycle N(3) atoms by Cu²⁺ ions, the interactions are ferromagnetic in nature and have the same order of magnitude. The minor intercluster interactions are antiferromagnetic.Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences. International Tomography Center. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 3, pp. 70–74, May–June 1993.Translated by L. Smolina