Volumetric Properties of Sodium Nitrobenzoate in <Emphasis Type="Italic">N</Emphasis>, <Emphasis Type="Italic">N</Emphasis>-Dimethylformamide–Water Mixtures at 298.15 K

Densities of sodium nitrobenzoate (o-, m-, p-) have been measured in dimethylformamide (DMF)–water mixtures at 298.15 K with an oscillating-tube densimeter. From these densities, apparent molar volumes of sodium nitrobenzoate in DMF–H₂O-mixtures have been calculated and partial molar volumes at infinite dilution have been evaluated. Substituent and solvent effects on the transfer volumes of each isomer from water to DMF–H₂O-mixed solvents have also been obtained. The results are explained in terms of solvent–solvent and solute–solvent interactions.     

Zum Aufbau der Systeme V—(Fe,Co, Ni)—N

The constitution of the ternary systems V–Fe–N, V–Co–N, and V–Ni–N has been investigated by X-raymethods, metallographically and partly by microprobe analysis. Isothermal sections are presented for 1100°C and 1200°C respectively. Ternary complex nitrides have been observed in the systems V–Co–N and V–Ni–N. The compounds with formula V₄Co₂N (a=10.88–10.83±0.01 Å) and V₄Ni₂N (a=10.88–10.86±0.01 Å) crystallize with the partly filled Ti₂Ni-structure.

---

---

Mit 6 Abbildungen     

Buffer Standards for the Physiological pH of Zwitterionic Compounds,MOBS and TABS from 5 to 55°C

The values of the second dissociation constant, pK₂, and related thermodynamic quantities of 4-(N-morpholino)butanesulfonic acid (MOBS) and N-tris(hydroxymethyl)-4-aminobutanesulfonic acid (TABS) have already been reported over the temperature range 5–55°C including 37{°}C. This paper reports the pH values of twelve equimolal buffer solutions at designated pH (s) with the following compositions: (a) mixtures of MOBS (0.05 mol-kg^–1) + NaMOBS (0.05 mol-kg^–1); (b) MOBS (0.08 mol-kg^–1) + NaMOBS (0.08 mol-kg^–1); (c) MOBS (0.08 mol-kg^–1) + NaMOBS (0.08 mol-kg^–1) + NaCl (0.08 mol-kg^–1); (d) TABS (0.05 mol-kg^–1) + NaTABS (0.05 mol-kg^–1); and (e) TABS (0.08 mol-kg^–1) + NaTABS (0.08 mol-kg^–1); and (f) TABS (0.08 mol-kg^–1) + NaTABS (0.08 mol-kg^–1) + NaCl (0.08 mol-kg^–1). Two buffer solutions have ionic strengths I= 0.05 mol-kg^–1, another two have I=0.08 mol-kg^–1, and the remaining two buffer solutions have I= 0.16 mol-kg^–1, which is close to that of the clinical fluids (blood serum). These buffers have been recommended as a useful pH standard for the measurements of physiological solutions. Conventional pH values of all six buffer solutions from 5–55°C, as well as those obtained from the liquid junction potential correction at 25 and 37{°}C have been calculated. The flowing-junction calomel cell has been utilized to measure E_j, the liquid junction potential.     

Study and prediction of alkylbenzenes’ vapour pressures

Vapour pressures of 1,4-di-tert-butylbenzene (379–1647 Pa), 1,3,5-tri-tert-butylbenzene (203.9–241 Pa), 1-methyl-3,5-di-tert-butylbenzene (16.7–435.8 and 1318–103,880 Pa), and 1,2,2-trimethylpropybenzene (36.3–287.4 Pa) have been measured using a transpiration method and an ebuliometric method. Based on the literature and obtained by the authors experimental data a comparative study of prediction capabilities of the following methods has been carried out: Ambrose–Walton's, Lee–Kesler's, Riedel's and the modification of Riedel's method made by Vetere.     

Quantum Chemical Calculation of Conformations and Rotation Barriers of Functional Groups in Arylsulfonyl Halides

The semiempirical PM3 method is used to calculate the potential functions of internal rotation of the functional groups –SO₂Cl, –NO₂, –CH₃, –OCH₃, and –NH₂ of benzenesulfonyl halide molecules (PhSO₂Hal, Hal = F, Cl, Br, I) and twelve substituted derivatives of benzenesulfonyl chloride. Molecular conformations have been determined and internal rotation barriers of the functional groups have been calculated. For meta- and para-substituted benzenesulfonyl chlorides, the projection of the S–Hal bond is perpendicular to the plane of the benzene ring. The rotation barriers of the –SO₂Hal group of benzenesulfonyl halides increase in the series Hal = F, Cl, Br, I. The rotation barriers of the –SO₂Cl group of benzenesulfonyl chloride with meta- and para-substituents slightly increase with the electron-donor properties of the substituent. The rotation barriers of the functional groups of ortho-substituted benzenesulfonyl chlorides are 3 or 4 times as high as those of the meta- and para-isomers. For para-substituted benzenesulfonyl chlorides, the rotation barriers of the functional groups increase in the order –CH₃, –NO₂, –SO₂Cl, –OCH₃, –NH₂.     

Preparation and Characterization of Ultrafine Rare Earth Molybdenum Complex Oxide Particles

Ultrafine rare earth molybdenum (La–Mo and Ce–Mo) complex oxide particles have been synthesized by the sol–gel process using citric acid as complexing agent. The influence of preparation conditions such as thermal treatment temperature (T), molar ratio of citric acid to metallic ions (L/M), and pH value of the starting solution on the oxide particle size has been studied. The formation of La₂Mo₂O₉and Ce₂Mo₃O₁₂has been investigated using XRD, DTA–TG, FT-IR, TEM, and BET surface area measurements. It is shown that the morphology and structure of the oxide particles are significantly dependent on the preparation conditions. The influence of different preparation methods on the particle size of La–Mo and Ce–Mo oxides is also discussed.     

Infrared and Raman Spectra,Conformational Stability,Ab Initio Calculations,and Vibrational Assignments for Cyclopropyldifluorosilane

The infrared (3200–30 cm^–1) spectra of gaseous and solid Cyclopropyldifluorosilane, c-C₃H₅SiF₂H, and the Raman spectra (3200–20 cm^–1) of the liquid with quantitative depolarization values and the solid have been recorded. Both the syn (cis) and skew (gauche) conformers have been identified in the fluid phases, but only the syn conformer remains in the solid. Variable temperature (–55 to –100°C) studies of the infrared spectra of the sample dissolved in liquid xenon have been carried out. From these data, the enthalpy difference has been determined to be 73 ± 10 cm^–1 (209 ± 29 cal mol^–1), with the syn conformer being the more stable rotamer, which is at variance with the predictions from ab initio calculations. A complete vibrational assignment is proposed for both conformers based on infared band contours, relative intensities, depolarization values, and group frequencies. The vibrational assignments are supported by normal coordinate calculations utilizing the force constants from ab initio MP2/6-31G* calculations. Utilizing the frequencies of the silicon–hydrogen sketch, the rm Si—H bond distances of 1.474 and 1.472 Å have been obtained for the syn and skew conformers, respectively. Complete equilibrium geometries have been determined for both rotamers by ab initio calculations employing the 6-31G* and 6-311 +G** basis sets at levels of restricted Hartree-Fock (RHF) and/or Moller–Plesset (MP) to second order. The potential energy terms for the conformer interconversion have been obtained from the MP2/6-31G* calculation. The results are discussed and compared to those obtained for some similar molecules.     

Polarographic behaviour of 2-benzilidenimino-benzohydroxamic acid (2-BIBH) and 2-BIBH-Mo(VI) system

The polarographic behaviour of 2-benzilideniminobenzohydroxamic acid (2-BIBH) solutions and of 2-BIBH solutions in the presence of Mo(VI) have been studied by using differential pulse polarography and cyclic voltammetry. The polarographic characteristics of the resulting waves have been studied and possible mechanisms of the processes involved have been proposed. A linear relationship has been observed betweenI _p and Mo(VI) concentration in the range 2×10^–6 to 1.6×10^–5 M when using 3×10^–4 M 2-BIBH. Standard deviations of 5.6×10^–8 and 1.2×10^–8 M were found for 3×10^–6 and 8 × 10^–6 M Mo(VI), respectively.     

Optimal Kinoshita wave functions for heliumlike atoms

An extensive optimization has been performed for the composition ofN terms, as well as the exponent and the mixing coefficients, of Kinoshita wave functions for heliumlike atoms with atomic numberZ. The optimalN-term Kinoshita functions have been constructed forN=1–10, 20, 30, 40, 50, 100 andZ=1(H^–)–10(Ne⁸⁺). The present results demonstrate that the optimal term selection dramatically improves the accuracy of the Kinoshita function: In the case of He, for example, the optimal 100-term Kinoshita function gives – 2.903 724 376 95 hartrees, which is only 8×10^–11 hartrees higher than the most accurate literature value.     

Apparent Molar Volumes of Sodium Methylbenzoates in N, N-Dimethyl Formamide–Water Mixtures at 298.15 K

Densities of sodium methylbenzoate (o-, m-, p-) have been measured in dimethyl formamide (DMF)–water mixtures at 298.15 K with an oscillating-tube densimeter. From these densities, apparent molar volumes of sodium methylbenzoates in DMF–H₂O mixtures have been calculated and partial molar volumes at infinite dilution have been evaluated. Substituent and solvent effects on the transfer volumes of each isomer from water to DMF–H₂O mixed solvents have also been obtained. The results are explained in terms of solvent–solvent and solute–solvent interactions.     

Polarographic behaviour and determination of azintamide

Azintamide was found to be reduced at the dropping mercury electrode over the pH range 1.8–9.4 in Britton Robinson buffers containing 20% methanol. At pH 7.42 a well defined diffusion-controlled cathodic wave was produced. The limiting current versus concentration plot was linear over the range 0.025–1.0 mM and 0.005–1.0 mM in the DC_t and DPP modes, respectively, with a lower detection limit of 1 × 10^–7 M by the latter technique. A mechanism for the electrode reaction has been proposed. The method has been applied to the determination of azintamide in tablets, and the results obtained were in agreement with those obtained by a reference method.AvH Scholar 1989–1991.     

Formation of Platinum–Tin Bond by Tin(II)Chloride Insertion

The first ¹¹⁹Sn NMR evidence for the presence of direct platinum–tin bond in solution has been obtained for PtCl(SnCl₃)(bdpp) complex (bdpp = (2S,4S)-2,4-bis(diphenylphosphino)pentane). Various PtCl₂(L₂) complexes (L₂ = heterobidentate P–P, P–O, P–N, P–S chelating ligands) have been reacted with tin(II)chloride resulting in the formation of the corresponding PtCl(SnCl₃)(L₂) derivatives. Tin(II)chloride has been inserted into the Pt–Cl bond transto the harder donor atom of the L₂ ligand.     

The Complexes of Holmium with Methylenediphosphonate and 1-Hydroxyethylidenephosphonate

The composition and stability of holmium methylenediphosphonate (MDP) and 1-hydroxyethylidenephosphonate (HEDP) complexes were studied by potentiometric titration methods in 0.1M NaCl at 25 °C. It was found that besides L^4– anions the protonated H _n L^(4–n)– species (n = 1–3 for MDP and n = 1–4 for HEDP) are present in the pH region 3 to 10. The presence of the undissociated acids (H₄L) has not been unambiguously proved for MDP. The complexes of the composition HoH _n L (n varies from 1 to –2 for MDP and from 1 to –1 for HEDP) have been found if the concentration of the ligand is higher than the concentration of holmium. The protonation constants of both acids and the stability constants of the complexes discussed were determined and the comparison with literature data of analogical complexes of other lanthanides was performed.     

Electroanalytical properties of cytochrome c by direct electrochemistry on multi-walled carbon nanotubes incorporated with DNA biocomposite film

A novel conductive biocomposite film (MWCNTs–DNA–cyt c) which contains multi-walled carbon nanotubes (MWCNTs) along with the incorporation of DNA and cytochrome c (cyt c) has been synthesized on glassy carbon electrode (GCE), gold (Au), indium tin oxide (ITO) and screen printed carbon electrode (SPCE) by potentiostatic methods. The presence of both MWCNTs and DNA in the biocomposite film enhances the surface coverage concentration (Γ), increases the electron transfer rate constant (K_s) up to 21% and decreases the degradation of cyt c during the cycling. The biocomposite film also exhibits a promising enhanced electrocatalytic activity towards the reduction of halogen oxyanions and oxidation of biochemical compounds such as ascorbic acid and l-cysteine. The cyclic voltammetry has been used for the measurement of electroanalytical properties of analytes by means of biocomposite film modified GCEs. The sensitivity of MWCNTs–DNA–cyt c modified GCE possess higher values than the values obtained for DNA–cyt c film modified GCE. Further, the reduction potentials of halogen oxyanions E_pc, clearly shows that the activity of the biocomposite is dependent on the electronegativity of halogen oxyanions. Electrochemical quartz crystal microbalance studies revealed the enhancements in the functional properties of MWCNTs, DNA and cyt c. We have studied the surface morphology of the biocomposite films using scanning electron microscopy and atomic force microscopy, which revealed that DNA and cyt c have been incorporated on MWCNTs. Finally, the flow injection analysis has been used for the amperometric detection of analytes at MWCNTs–DNA–cyt c film modified SPCE.     

Blue-shifted hydrogen-bonded complexes. II. CH3F(HF)1 n 3 and CH2F2(HF)1 n 3

The equilibrium structures, binding energies, and vibrational spectra of the clusters CH₃F(HF)_{1 n 3} and CH₂F₂(HF)_{1 n 3} have been investigated with the aid of large-scale ab initio calculations performed at the Møller–Plesset second-order level. In all complexes, a strong C–FH–F halogen–hydrogen bond is formed. For the cases n = 2 and n = 3, blue-shifting C–HF–H hydrogen bonds are formed additionally. Blue shifts are, however, encountered for all C–H stretching vibrations of the fluoromethanes in all complexes, whether they take part in a hydrogen bond or not, in particular also for n = 1. For the case n = 3, blue shifts of the ν(C–H) stretching vibrational modes larger than 50 cm⁻¹ are predicted. As with the previously treated case of CHF₃(HF)_{1 n 3} complexes (A. Karpfen, E. S. Kryachko, J. Phys. Chem. A 107 (2003) 9724), the typical blue-shifting properties are to a large degree determined by the presence of a strong C–FH–F halogen–hydrogen bond. Therefore, the term blue-shifted appears more appropriate for this class of complexes. Stretching the C–F bond of a fluoromethane by forming a halogen–hydrogen bond causes a shortening of all C–H bonds. The shortening of the C–H bonds is proportional to the stretching of the C–F bond.     

Alkaloids of a new type fromSophora alopecuroides L.

Summary The structures of aloperine and allylaloperine (fromSophora alopecuroides L.) — alkaloids of a new structural type for the genusSophora — have been established by chemical and spectral methods. A number of parameters, NMR spectra, and mass spectra characterizing this class of compounds has been obtained. The partial synthesis of allylaloperine has been performed.All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 30–37, January–February, 1975.     

Unsymmetrical bis-Schiff bases derived from ethylenediamine,dehydroacetic acid and another aldehyde/ketone and the preparation and characterisation of their copper(II) and nickel(II) complexes

Summary Partial displacement of the symmetrical bis-Schiff bases (1)–(4) of ethylenediamine and salicyladehyde, o-hydroxyacetophenone, acetylacetone or benzoylacetone by dehydroacetic acid have led to the formation and isolation of the unsymmetrical bis-Schiff base ligands (6)–(9). Attempted partial displacements of the symmetrical bis-Schiff base (5) of dehydroacetic acid or (1)–(4) by each of the other four carbonyl compounds have been unsuccessful. The Ni^(II) and Cu^(II) complexes of (6)–(9) have been prepared and characterized.     

Far-infrared spectrum,barrier to internal rotation,ro structure,and ab initio calculations for acetylacetylene

The far-infrared spectrum has been recorded from 50 to 360 cm^–1 at a resolution of 0.10 cm^–1 for acetyiacetylene (1-butyne-3-one], CH₃C(O)CCH. The fundamental methyl torsion has been observed at 117.94 cm^–1, from which a periodic barrier to internal rotation has been calculated to be 346 cm^–1 (989 cal mol^–1]. Infrared spectra (3500-50 cm^–1] of the gas and solid and the Raman spectra (3500-100 cm^–1) of the gas, liquid, and solid are reported. Utilizing previously reported rotational constants for three isotopic species,r _o structural parameters have been determined for the heavy-atom skeleton. The fundamental vibrational frequencies, barrier to internal rotation, and structural parameters that have been obtained experimentally are compared to those obtained from ab initio Hartree-Fock calculations employing 3-21G, 6-31G, and DZ basis sets and to the corresponding quantities for some similar molecules.     

Über die Synthese eines im Gift von Bombina variegata vorkommenden hexapeptid-diamids

Zusammenfassung Mittels der p-Nitrophenylestermethode wurde das Hexapeptiddiamid der Sequenz Ala–Glu–His–Phe–Ala–Asp(NH₂)₂, durchwegsl-Aminosäure, stufenweise aufgebaut. Das synthetische Produkt war mit einem aus Unkengift (Bombina variegata) isolierten Peptid strukturell identisch.

---

Using the p-nitrophenylester method the hexapeptide diamide Ala–Glu–His–Phe–Ala–Asp(NH₂)₂ was synthesized froml-amino acids. This product was identical with a natural peptide, which had previously been isolated from the venom ofBombina variegata.

     

The pure rotational spectrum of NaCH3 ( )

The pure rotational spectrum of NaCH₃ and NaCD₃ in their states has been recorded using millimeter/sub-mm direct absorption techniques in the 300–510 GHz range. This work is the first gas-phase detection of sodium monomethyl, which was created by the reaction of sodium vapor with tetramethyl tin. Ten rotational transitions were measured for NaCH₃ for the K=0 through K=5 components and, in select cases, up to K=10, and four transitions (K=0–7) for NaCD₃. Rotational constants have been accurately determined for both isotopomers, suggesting a sodium–carbon bond length of 2.30 Å and an H–C–H bond angle of 107.3°.