Extraction-spectrophotometric determination of iron with 2-(2′-benzothiazolylazo)-4,6-dimethylphenol

An extraction-spectrophotometric method for the determination of trace amounts of iron based on its extraction into chloroform with 2-(2-benzothiazolylazo)-4,6-dimethylphenol (BTADMP) from a pH 6.5 medium has been developed. The extracted 12 FeBTADMP complex species allow the determination of 4–30gmg of iron (=3.92×10⁴1·mol^–1·cm^–1 at 790 nm). The method is highly selective and has been applied to the determination of iron in polymineral-polyvitamin pharmaceutical products.     

Reactions of superoxide anion radical with antioxidants and their use in voltammetry

Kinetic parameters were calculated for the electrochemical reduction of oxygen at a glassy-carbon electrode with the generation of superoxide radical anions in a 0.05 M solution of (C₂H₅)₄NI in dimethylformamide in the presence of fat-soluble antioxidants, retinol and -tocopherol. A procedure based on the protonation of the radical anion with antioxidant molecules is proposed for the voltammetric determination of antioxidants to determine milligram amounts of retinol and -tocopherol in model solutions (RSD = 1–2%). The calibration graphs for retinol and -tocopherol are linear in the concentration ranges 9.7 × 10^–5–2.3 × 10^–3 and 6.2 × 10^–4–3.1 × 10^–3 M, respectively. The detection limits for retinol and -tocopherol are 4.8 × 10^–5 and 4.1 × 10 ^–4 M, respectively. The procedure was applied to the determination of the active component (retinol and -tocopherol) in pharmaceuticals.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 56–59.Original Russian Text Copyright © 2005 by Ziyatdinova, Gilmetdinova, Budnikov.     

Investigation of electronic structure of allenyl ethers by means of photoelectron and UV spectroscopy

A study of the photoelectron spectra of alkyl allenyl ethers has demonstrated their similarity to spectra of alkyl vinyl ethers, with the exception of a band in the 10.0–10.3 eV interval due to ionization of the -orbital of the allenyl fragment C=C. According to data obtained by photoelectron spectroscopy and MNDO quantum-chemical calculations, alkyl allenyl ethers with straightchain substituents exist primarily in the s-cis conformation. The stable conformation of allenyl tert-butyl ether is the s-trans form. The long-wave absorption bands in the UV spectra of alkyl allenyl ethers at 255–275 and 208–213 nm are assigned to electronic transitions of the ^* and ^{* *} types; these are quite insensitive to s-cis/s-trans isomerism.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 81–88, January, 1990.The authors are extremely grateful to V. K. Turchaninov for assistance in interpreting the spectra.     

The effect of zinc(II) on the formation of 2,2′- and 2,3′-bipyridine complexes of [Ru2II(ttha)]2−(ttha6−=triethylenetetraminehexaacetate)

Ru2II(ttha)(H2O)2]2– (ttha6–= triethylene tetramine hexa-acetate), prepared by the reduction of the ruthenium(III) precursor, reacts with 2,2-bipyridine (2,2-bpy) in a multi-step fashion. The first 2,2-bpy equivalent (1:1) adds with bidentate chelation at one ruthenium(II) site as revealed by separate ruthenium(II)/(III) waves at 0.03 and 0.54V vs. n.h.e. A second equivalent of 2,2-bpy (1:2) is initially stored and retained as the [Zn(2,2-bpy)]2+ complex. Further addition of 2,2-bpy initiates coordination at the second ruthenium(II) site. [Ru2(ttha)-(2,2-bpy)(H2O)]2– forms a strong ion-pair with zinc(II) that is in rapid equilibrium with the Zn(H2O)62+/Zn(2,2-bpy)]2+ pool. The solubility of the ion-pair is low. The ion-pair exhibits a shifted ruthenium(II)/(III) wave at 0.60V. Higher amounts of 2,2-bpy recomplex the zinc(II), solubilizing the complex and returning the E1/2 value to 0.54V. Other ligands which either have a higher affinity for ruthenium(II) centres than for zinc(II) as bidentate donors (1,10-phenanthroline), or ligands that cannot form bidentate zinc(II) complexes [(2-methylpyrazine, 4,4-bipyridine (4,4-bpy), and 2,3-bipyridine (2,3-bpy)] do not exhibit the unusual competition by zinc(II). These ligands all add statistically to the ruthenium(II) centres forming 1:2 complexes with 1:2 stoichiometries. 1H-n.m.r. studies of the Ru(II)polyaminopolycarboxylate complexes [RuII(hedta)(H2O)]– complex, and [Ru2(ttha)(H2O)2]2– itself, reveal that substitution of 2,3-bpy at ruthenium(II) sites occurs with an initial kinetic split between the pyridyl rings of the 3- less-hindered and 2-more-hindered ring. A slower rearrangement occurs, producing the isomer of the more-hindered 2-substituted ring. A process is driven by forming a more -accepting system when ruthenium(II) binds to the 2-ring of 2,3-bpy. Understanding the unusual influence of zinc(II) on the substitution of 2,2-bpy with [Ru2(ttha)(H2O)2]2– clarifies the nature of the 1:1 complex – namely that the 2,2-bpy becomes bidentate at one ruthenium(II) centre rather than serving as a trans-bridging ligand between both ruthenium(II) centres within one [Ru2(ttha)]2– unit.     

Formation of N-butane in the pyrolysis of ethylene [1]

Yields of n-C₄H₁₀ have been measured from the flow pyrolysis of C₂H₄ at 897 (±7) K. From 77 to 720 Torr the order of n-C₄H₁₀ formation was found to be 2.0±0.3 The rate constant for the reaction, was estimated to be 2.4(±0.6)×10^–4l mol^–1s^–1.

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-C₄H₁₀ C₂H₄ 897 (±7) . -C₄H₁₀ 77 720 2.0±0.3. 2C₂H₄C₂H₃+C₂H₅ 2,4 (±0,6)×10^{–4 –1–1}.

     

INAA of Minoan ceramics from Kommos,Crete

A recent study concerning the deviation of the E^–(1+) epithermal neutron flux distribution from the E^–1 law, developed by F. DE CORTE et al. is applied to -determination in different channels of the CRN reactor (Strasbourg). It is found that the coefficient is positive inside the reactor core and negative outside. The accuracy of the neutron activation analysis using the corrected resonance integral I() is tested.     

Die Schwingungsspektren von Trimethylsilyl-alkyl-bzw.-phenyl-aminen

Zusammenfassung Die Infrarot- und die Raman-Spektren der Silylamine (CH₃)₃Si–NH–R (R=CH₃, C₂H₅ und C₆H₅) sowie der analogen N-deuterierten Verbindungen werden mitgeteilt und analysiert. Starke Kopplungen führen zu einer Mischung vonv SiN bei etwa 700 cm^–1 mit anderen Schwingungen des C₃Si–NHR-Skelettes.

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The Infrared and Raman spectra of the silylamino compounds (CH₃)₃Si–NH–R (R=CH₃, C₂H₅, and C₆H₅) and the analogous N-deuterated species are reported and assigned. The SiN stretching mode at about 700 cm^–1 is strongly coupled with other vibrations of the molecules.

     

Theoretical study of the6Σ+,6Π, and4Σ+ van der Waals states of NO

Summary Potential energy curves for the weakly bound⁶⁺,⁶, and⁴⁺ states of NO are presented at various levels of correlation treatment. The binding energies for the van der Waals minima vary from about 30 cm^–1 for the⁶⁺ state to about 20 cm^–1 for the⁴⁺ and⁶ states. We investigate the importance of constraining the wave function to dissociate to a spherically symmetric O atom where the oxygen 2p orbitals are equivalent. For high levels of correlation treatment, we find that these restrictions have little effect on the potential, while greatly increasing the length of the CI expansion.     

Chromium(VI), chromium(V) and chromium(IV) oxidation of 12-tungstocobaltate(II)

The reaction between Cr^VI and 12-tungstocobaltate(II) was carried out in 2.0 mol dm^–3 HCl and followed a simple second order rate law. The reaction was catalysed by hydrogen ion due to the formation of active H₂CrO₄ and was inhibited by chloride ion as, in its presence, conversion of the active species into inactive chlorochromate occurs. Chromium(V) and chromium(IV) were generated in situ by the use of Cr^VI—V^IV or Cr^VI—2-ethyl-2-hydroxybutyric acid and Cr^VI—i-PrOH reactions respectively, and the oxidation of 12-tungstocobaltate(II) by these atypical oxidation states, was also studied. The rate constants for the oxidation of 12-tungstocobaltate(II) by Cr^VI, Cr^V and Cr^IV were found to be in the ratio 1:1.2:5.2 respectively. The ionic strength did not affect the reaction, while decrease in the solvent polarity increased the rate of the reaction. The activation parameters were also determined and the values H , G and S were found to be 52.4 ± 6 kJ mol^–1, 100.8 ± 7 kJ mol^–1, –151.7 ± 10 J K^–1 mol^–1 respectively, supporting the mechanism proposed.     

Steroid compounds of marine sponges. VII. Preparation of derivatives of sokotrasterol and halistanol sulfates and structure-activity interrelationships among these compounds

Five new sulfated derivatives of sokotrasterol and halistanol have been obtained: 24-nor-5-cholane-2,3,6,23-tetraol 2,3,6-tri(sodium sulfate); 24-nor-5-cholane-2,3,6,23-tetraol 2,3,6-tri(sodium sulfate) 23-palmitate; 24,25-dimethyl-5-cholestane-2,3,6-triol 3-(sodium sulfate); 24,25-dimethyl-5-cholestane-2,3,6-triol 6-(sodium sulfate); and 24,25-dimethyl-5-cholestane-2,3,6-triol 2,6-di(sodium sulfate). The inhibiting and membranolytic properties of the polysulfated steroids from sponges and their derivatives have been studied. It has been shown that physiological activity in this series of compounds depends on biphilicity.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 441–445, July–August, 1986.     

Electric properties of the chloride ion

The dipole (), quadrupole (C), and dipole-quadrupole (B) polarizabilities and the dipole hyperpolarizability () of the chloride ion have been calculated by using the many-body perturbation theory approach and a series of large polarized GTO/CGTO basis sets. The complete fourth-order treatment of the electron correlation effects with a basis set comprising the s, p, d, f, and g functions gives: =38.01 a.u., C=211.5 a.u., B=–5.14×10³ a.u., and =128. 5×10³ a.u. as compared to the corresponding SCF values (=31.49 a.u., C=158.9 a.u., B=–2.92×10³ a.u., =57.7×10³ a.u.). The quenching of polarizabilities of the Cl^– ion in solutions and ionic crystals is discussed.     

Investigation of furan acetal compounds

New 1,3-dioxanes, which are derivatives of 2-nitro-2-ethylpropane-1,3-diol and aldehydes of the furan series, were synthesized. The nitrodioxanes were reduced by means of sodium amalgam to the corresponding amines. The kinetics of the formation of the nitrodioxanes was studied. The accelerating action of the electron-acceptor diol substituent on the reaction rate was established. The rate constants in the aldehyde series increase on passing from-methylfurfural to-nitrofurfural, and they correlate satisfactorily with Brown's _p ⁺ constants.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1159–1162, September, 1972     

Heterogeneous reactions of solid nickel(II) complexes

The influence of different modes of preparation on the stoichiometry of thermal decomposition of isothiocyanatonickel(II) complexes with ammonia was studied. It was found that the complex Ni(NCS)₂(NH₃)₄ (I) prepared by heterogeneous reaction undergoes decomposition in two steps (–2 NH₃, –2 NH₃), while for complex II, of the same composition but prepared by homogeneous reaction from solution, the decomposition proceeds in three steps (–1 NH₃, –1 NH₃, –2NH₃). Electronic and infrared absorption spectra were used for the study of the spectral properties of the starting complex. It was found that the different stoichiometries of thermal decompositions of complexes I and II do not cause differences in the bonding strength of the ammonia molecules (chemical factor); this effect is rather brought about by physical factors such as different imperfections of the crystal lattice.

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Zusammenfassung Der Einfluß der Herstellung auf die Stöchiometrie der thermischen Zersetzung von Amin-Komplexen des Isothiocyanatonickels wurde studiert. Der Zerfall des Komplexes Ni(NCS)₂(NH₃)₄ (I), hergestellt durch heterogene Reaktion, verlief in zwei Etappen (–2 NH₃, –2 NH₃). Beim selben Komplex (II), hergestellt durch homogene Reaktion in Lösung, wurden jedoch drei Etappen beobachtet (–1 NH₃, –1 NH₃, –2 NH₃). Die Eigenschaften des Ausgangsproduktes wurden durch Elektronen- und IR-Spektroskopie untersucht. Das unterschiedliche thermische Verhalten ist nicht auf eine verschiedene Bindungsstärke der NH₃ Moleküle, sondern auf physikalische Ursachen, wie z. B. Unregelmässigkeiten im Kristallgitter zurückzuführen.

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Résumé On a étudié l'influence des diverses méthodes de préparation sur la stoechiométrie de la réaction de décomposition thermique des complexes de l'isothiocyanate de nickel(II) avec l'ammoniac. On a établi que le complexe Ni(SCN)₂(NH₃)₄, (I), préparé rar réaction hétérogène, subit une décomposition en deux étapes (–2NH₃, –2NH₃), tandis que le complexe (II), de même composition, mais préparé par réaction homogène, à partir de solutions, se décompose en trois étapes (–1NH₃,–1NH₃, –2NH₃). Les propriétés spectrales du complexe initial ont été étudiées par absorption électronique et infrarouge. On a trouvé que les différences de stoechiométrie des réactions de décomposition thermique des complexes (I) et (II) n'apportaient pas de différences entre les énergies de liaison des molécules d'ammoniac (facteur chimique). C'est plutôt à des facteurs physiques, comme les différentes imperfections du réseau cristallin, que cet effet serait dû.

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(II) . , Ni(NCS)₂(NH₃)₄ (I), , (–2NH₃,–2NH₃). , II , , (–1 NH₃,–1 NH₃ –2NH₃). . , I II ( ), , .

     

SIMS studies of water vapor adsorption on polycrystalline rhodium

Studies of water vapor adsorption on polycrystalline Rh at T>315 K and P=(2–4)×10^–2 Pa indicate that water is adsorbed dissociatively to O_ads and O_ads through a molecularly adsorbed species. Desorption activation energy is 46 and 69 kJ/mol for molecular and dissociative species, respectively.

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Rh (2–4)·10^–2 . , O OH - . 46 /, -69 /.

     

Effect of CO2 on O2 photo-adsorption on anatase

The presence of CO₂ on TiO₂ affects the process of oxygen photo-adsorption depending on the hydroxylation state of the surface. In dehydroxylated samples CO₂ blocks the formation of O ₃ ^– and O ₂ ^– . On H₂O₂/TiO₂ samples pretreated in the range of 150–200°C it leads to CO₂–O ₂ ^– species.

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, Cu(II). . .

     

Synthesis of 10-(N′-phenyl)imidoyl derivatives of phenothiazine,and their reactions with o,o-dialkylthio- and dithiophosphates

Condensation of phenothiazine with phenyl isocyanide dichloride has given 10(N-phenylchloroformimidoyl)phenothiazine, exchange reactions of which with salts of diakylthio- and dithiophosphoric acids result in rearrangement of the initially formed 10-[N-phenyldialkoxy(thio)phosphorylthioformimidoyl]phenothiazines to 10-{N-phenyl-N-[dialkoxy(thio)phosphoryl]thiocarbamoyl}phenothiazines, while reaction with diisopropyl dithiophosphoric acid affords diisopropyl chlorothiophosphate, phenyl isothiocyanate, and phenothiazine. 10-(N-Phenylethoxyformimidoyl)phenothiazine alkylates dithiophosphoric acid to give 10-(N-phenylcarbamoyl)phenothiazine, while N²-phenyl-N¹,N¹-diethyl-(10-phenothiazinyl)formamidine reacts with diisopropyl dithiophosphoric acid, affording the salt N²-phenyl-N¹,N¹-diethyl-(10-phenothiazinyl)formamidinium O,O-diisopropyl dithiophosphate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2596–2601, November, 1989.     

Gamma radiolysis of Methyl Red solution and reaction induced by γ-irradiated NaCl in Methyl Red

The -radiolysis of Methyl Red solution in HCl medium at pH=2 has been studied along with energy transfer reaction brought about byF and hole centers of -irradiated NaCl. The G-values for degradation of the azo dye indicator by radiolysis and -irradiated salt were determined as 9·10^–1 and 4.8·10^–3, respectively. The kinetic rate constants (k) of degradation are evaluated as 2·10^–5 rad^–1 in the case of direct radiolysis, while for the irradiated salt it is 2·10^–7 rad^–1. The extent of degradation by direct -radiolysis is 100–200 times greater as compared to that by the -irradiated salt. The same mechanism is proposed for radiolysis as well as the reaction induced by -irradiated sodium chloride.     

Kinetics of heterogeneous catalytic hydroformylation of propylene on rhodium-cobalt catalysts. Reaction mechanism

Steady-state kinetics of combined heterogeneous catalytic hydrogenation and hydroformylation of propylene on Rh–Co-containing catalysts has been studied at atmospheric pressure and T=140–170 °C. A reaction mechanism is suggested. The kinetic model adequately describes all observations.

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- Rh–Co- 140–170 °C. . , .

     

Kinetics and mechanism of the permanganate oxidation of trans-crotonic acid

The kinetics and intermediates of the permanganate oxidation of trans-crotonic acid have been investigated in the pH range of 0.5–5.0 using the stoppedflow technique. The formation of manganese(III) as a short-lived intermediate has been established. The reaction is first order with respect to both MnO ₄ ^– and crotonic acid (crotonate). The resolved rate constants at 25°C are 730 and 410 M^–1 sec^–1 for the acid and the anion, respectively. The reaction mechanism is discussed.

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pH=0,5–5,0, . (III) . MnO ₄ ^– , (). 25°C 730 410 M^{–1 –1} , . .

     

Photometric detection of cyclodextrins in liquid chromatography by using iodine generated electrochemically in-situ

A method has been developed for photometric detection of cyclodextrins (CD) in liquid chromatography using iodine (I₂) generated electrochemically in-situ. Iodide ion in the mobile phase was electrochemically oxidized to I₂ which was subsequently reacted with I^–, in an electrochemical flow cell, forming I₃^–. The absorbance of I₃^– was found to be greatly enhanced when CD were present in the mobile phase. The absorbance enhancement was caused by the change in the mole fraction of I₃^–, because of the inclusion reaction of I₃^– with CD. On the basis of this phenomenon, CD were detected by means of a photodiode-array UV–visible detector positioned downstream of the electrochemical flow cell. The signals were found to be linearly dependent on CD concentration. Because the formation constants of I₃^– with CD decrease in the order -CD>-CD>-CD, -CD was most detectable by the method. Detection limits were 1.0 mol L^–1 for -CD, 65 mol L^–1 for monoG1--CD, 100 mol L^–1 for -CD, and 200 mol L^–1 for -CD.