Importance of π-bonding in the stabilisation of ternary complexes

Summary Stability constants (K _MAL ^MA ) together with other thermodynamic parameters measuring the stabilities and the contribution of astatistical factors governing the stability of ternary complexes, MAL [M=Co^II, Ni^II, Cu^II or Zn^II; A=2, 2-dipyridylamine (A³), 5-nitro-o-phenanthroline (A⁵), 5-methyl-o-phenanthroline (A⁶); LH=benzohydroxamic acid] have been determined at 25°CC, at ionic strength 0.1 M KNO₃. The results are compared with those for the complexes containing polyaminocarboxylic acids such as iminodiacetic acid (A¹) and other heteroaromaticN-bases such as 2, 2-bipyridine (A²),o-phenanthroline (A⁴) and the stability constants are found in the sequence K_{MA^4 L}^{MA^4 } > K_{MA^2 L}^{MA^3 } = ca.K_{MA^3 L}^{MA^3 } \gg K_{MA^1 L}^{MA^1 } .$$ " align="middle" border="0"> For all heteroaromaticN-bases, the sequence K_{ML_2 }^{ML} $$ " align="middle" border="0"> has been found. The sequences are explained in terms of electrostatic interaction, change of electrophilicity of the bound metal and the -acidic character of the primary ligand.     

Kinetics and mechanism of the oxidation of hydrogen peroxide by the octacyanotungstate(V) ion in alkaline aqueous media

Summary The oxidation of H₂O₂ by [W(CN)₈]^3– has been studied in aqueous media between pH 7.87 and 12.10 using both conventional and stopped-flow spectrophotometry. The reaction proceeds without generation of free radicals. The experimental overall rate law, , strongly suggests two types of mechanisms. The first pathway, characterized by the pH-dependent rate constant k _s, given by , involves the formation of [W(CN)₈· H₂O₂]^3–, [W(CN)₈· H₂O₂·W(CN)₈]^6– and [W(CN)₈· HO]^3– intermediates in rapid pre-equilibria steps, and is followed by a one-electron transfer step involving [W(CN)₈·HO]^3– (k _a) and its conjugate base [W(CN)₈·O]^4– (k _b). At 25 °C, I = 0.20 m (NaCl), the rate constant with H _a =40±6kJmol^–1 and S _a =–151±22JK^–1mol^–1; the rate constant with H _b =36±1kJmol^–1 and S _b =–136±2JK^–1mol^–1 at 25 °C, I = 0.20 m (NaCl); the acid dissociation constant of [W(CN)₈·HO]^3–, K ₅ =(5.9±1.7)×10^–10 m, with and is the first acid dissociation constant of H₂O₂. The second pathway, with rate constant, k _f, involves the formation of [W(CN)₈· HO₂]^4– and is followed by a formal two-electron redox process with [W(CN)₈]^3–. The pH-dependent rate constant, k _f, is given by . The rate constant k ₇ =23±6m ^–1 s ^–1 with and at 25°C, I = 0.20 m (NaCl).     

Thermogravimetry. Empirical approximation for the “temperature integrals”

The temperature integrals with m=0, 1/2 and 1 are approximated using empirical formulae of the type Ax^–Be^–Cx. For estimation of the precision of these approximations, the relative errors were calculated for integral values ofx. It was established that forx < 19 the maximum relative error is 0.26%, while for 19 x<50 it is less than 0.1%. The suggested approximations allow a sensible improvement of the integral methods intended to determine the kinetic parameters of the process concerned.

---

Zusammenfassung Fürm-0, 1/2 und 1 werden Temperaturintegrale der Form du mit empirischen Formeln des TypesAx ^–B e ^–Cx näherungsweise berechnet.Zur Bestimmung der Genauigkeit dieser Näherung wurde für Integralwerte vonx der relative Fehler berechnet. Der maximale relative Fehler liegt fürx < 19 bei 0.26% und ist im Intervall 19x50 kleiner als 0.1%.Die vorgeschlagenen Näherungen erlauben eine wesentliche Verbesserung von Integriermethoden zur Bestimmung kinetischer Parameter diesbezüglicher Prozesse.

---

---

This paper was presented at the National Congress of Chemistry, Bucuresti, Sept. 11–14, 1978; in Abstracts, Pt. 1, 151 (1978).     

Trennung des Strontiums von Yttrium (90Sr/90Y) mit Anionenaustauscher-Sulfaten

Zusammenfassung Die selektive Fällungssorption von Strontium an Dowex-I-Sulfat im Säulenverfahren als SrSO₄ aus 50%ig methanolischer Lösung erlaubt die rasche Gewinnung von fremdstrahlungsfreiem Yttrium-90 aus dem Zerfallsprozeß . Die Kontrolle des Trenneffektes erfolgt durch Bestimmung der Halbwertszeit des ⁹⁰Y. Je nach Länge der Austauscherschicht kann unter Beachtung der Bildungsschnelligkeit von ⁹⁰Y dieses mehrfach entnommen werden.

---

Summary Selective precipitating Sorption of strontium as SrSO₄ on Dowex-I-sulphate in a column operation, using aqueous methanol solution (11), permits the isolation of pure ⁹⁰Y, produced by the decay process . The effect of separation may be controlled by determination of the half-life of ⁹⁰Y. Taking into account the velocity of formation ⁹⁰Y can be obtained several times according to the length of the ion-exchanger column.

     

Studies on mixed ligand complexes of cobalt(II), nickel(II), copper(II) and zinc(II) involving 8-hydroxyquinoline-5-sulphonic acid as a primary ligand and substituted catechols as secondary ligands

Summary Stability constants (K _MAL ^MA ) and other thermodynamic parameters of the MAL complexes (charges omitted) [M=Co^II, Ni^II, Cu^II or Zn^II; AH₂=8-hydroxyquinoline-5-sulphonic acid; LH₂=catechol (L¹H₂), 1,2-dihydroxybenzene-sulphonate (L²H₂), 1,2-dihydroxybenzene-3, 5-disulphonate (L³H₂), 4-nitro-1,2-dihydroxybenzene (L⁴H₂)] have been determined at 25°C and at an 0.1 M KNO₃ ionic strength by the extended Irying-Rossotti technique. The stability constants lie in the sequences: K_{MAL}^{MA} ?K_{ML_2 }^{ML} ; K_{MAL}^{MA_1 } > K_{MAL}^{MA_2 } > K_{MAL}^{MA_3 } \gg K_{MAL}^{MA_4 } $$ " align="middle" border="0"> and all follow the Irving-Williams stability order. These observations can be explained in terms of electrostatic interaction, change of electrophilicity of the bound metal and -acidic character of the primary ligand.     

The Influence of Ionic Strength on Yttrium and Rare Earth Element Complexation by Fluoride Ions in NaClO<Subscript>4</Subscript>, NaNO<Subscript>3</Subscript> and NaCl Solutions at 25 °C

Stability constants of the form _F β ₁(M)=[MF²⁺][M³⁺]⁻¹[F⁻]⁻¹ (where [MF²⁺] represents the concentration of a yttrium or a rare earth element (YREE) complex, [M³⁺] is the free YREE ion concentration, and [F⁻] is the free fluoride ion concentration) were determined by direct potentiometry in NaNO₃ and NaCl solutions. The patterns of log_{10  F} β ₁(M) in NaNO₃ and NaCl solutions very closely resemble stability constant patterns obtained previously in NaClO₄. For a given YREE, stability constants obtained in NaClO₄ were similar to, but consistently larger than _F β ₁(M) values obtained in NaNO₃ which, in turn, were larger than formation constants obtained in NaCl. Stability constants for formation of nitrate and chloride complexes ( and _Cl β ₁(M)=[MCl²⁺][M³⁺]⁻¹[Cl⁻]⁻¹) derived from _F β ₁(M) data exhibited ionic strength dependencies generally similar to those of _F β ₁(M). However, in contrast to the somewhat complex pattern obtained for _F β ₁(M) across the fifteen member YREE series, no patterns were observed for nitrate and chloride complexation constants: neither nor _Cl β ₁(M) showed discernable variations across the suite of YREEs. Nitrate and chloride formation constants at 25 °C and zero ionic strength were estimated as log₁₀  and log_{10  Cl} β ₁^o(M)=0.71±0.05. Although these constants are identical within experimental uncertainty, the distinct ionic strength dependencies of and _Cl β ₁(M) produced larger differences in the two stability constants with increasing ionic strength whereby _Cl β ₁(M) was uniformly larger than .     

Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C

The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO₃, KBr, KI, KNO₃, CaCl₂, SrCl₂, BaCl₂, Li₂SO₄, K₂SO₄, Mn(NO₃)₃)] as a function of concentration at 25°C. The solubilities, mol (kg-H₂O)^–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg^–1)

Quantum-Chemical Study of Anisole Molecule

The potential functions of internal rotation around the C -O bond in the C₆H₅OCH₃ molecule were obtained by HF/6-31G(d), MP2(f)/6-31G(d), and B3LYP/6-31(d) calculations. Hartree-Fock calculations reveal a fourfold barrier to internal rotation around the C -O bond. The MP2 and B3LYP calculations reveal a twofold barrier with a height of 7.78 and 10.70 kJ mol^{- 1}, respectively (corrected for the zero vibration energy). The molecular geometries, first Koopmans ionization potentials, and dipole moments are reported. Calculations for liquid anisole in the self-consistent reactive field (SCRF) continual model give the results that only slightly differ from the results obtained for the isolated molecule in a vacuum. Within the framework of the Natural Bond Orbitals formalism, the following parameters were determined: energy, degree of hybridization, and population of oxygen lone electron pairs and energy of their interaction with antibonding ^* orbitals of the aromatic ring.     

The Decay of Methylene Blue in Alkaline Solution

The decomposition of methylene blue in aqueous alkaline solution is described. The rate equation is of the form: , where k = 9.0 × 10^-4 mol^- [dm³s^-1 at 20°C and] = 0.5 mol dm^-3.     

Osmium liquid-phase catalysts for hydrogenolysis of saturated hydrocarbons and hydrogenation of arenes

Reduction of OsO₄ by molecular hydrogen in alkane (cycloalkane) or benzene (toluene) solution produces small-ligand clusters of osmium of composition Os_1.5–2.5. CH_0–2 with a particle size 10–40 Å and a specific surface area of 34–46 m²/g. Hydrogenation of dry catalyst produces methane. The small-ligand osmium clusters obtained effectively catalyze hydrogenolysis of alkanes and cycloalkanes at 100–150°C and =5 MPa and hydrogenation of benzene at 20°C and =0.1 MPa.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2428–2433, November, 1989.     

The gas phase ion chemistry of the acetyl cation and isomeric [C2H3O]+ ions. On the structure of the [C2H3O]+ daughter ions generated from the enol of acetone radical cation

Methods are described for the unequivocal identification of the acetyl, [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document} ?O] (a), 1-hydroxyvinyl, [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH] (b), and oxiranyl, (d), cations. They involve the careful examination of metastable peak intensities and shapes and collision induced processes at very low, high and intermediate collision gas pressures. It will be shown that each [C₂H₃O]⁺ ion produces a unique metastable peak for the fragmentation [C₂H₃O]⁺ → [CH₃]⁺+CO, each appropriately relating to different [C₂H₃O]⁺ structures. [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] ions do not interconvert with any of the other [C₂H₃O]⁺ ions prior to loss of CO, but deuterium and ¹³C labelling experiments established that [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH] (b) rearranges via a 1,2-H shift into energy-rich leading to the loss of positional identity of the carbon atoms in ions (b). Fragmentation of b to [CH₃]⁺+CO has a high activation energy, c. 400 kJ mol^?1. On the other hand, , generated at its threshold from a suitable precursor molecule, does not rearrange into [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH], but undergoes a slow isomerization into [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] via [CH₂\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}HO]. Interpretation of results rests in part upon recent ab initio calculations. The methods described in this paper permit the identification of reactions that have hitherto lain unsuspected: for example, many of the ionized molecules of type CH₃COR examined in this work produce [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH] ions in addition to [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] showing that some enolization takes place prior to fragmentation. Furthermore, ionized ethanol generates a, b and d ions. We have also applied the methods for identification of daughter ions in systems of current interest. The loss of OH^˙ from [CH₃COOD]^+˙ generates only [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OD]. Elimination of CH₃^˙ from the enol of acetone radical cation most probably generates only [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] ions, confirming the earlier proposal for non-ergodic behaviour of this system. We stress, however, that until all stable isomeric species (such as [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^{\rm + } $\end{document}?C:]) have been experimentally identified, the hypothesis of incompletely randomized energy should be used with reserve.     

Simple and rapid catalytic spectrophotometric determination of superoxide anion radical and superoxide dismutase activity in natural medical vegetables using phenol as the substrate for horseradish peroxidase

The coupling reaction of 4-aminoantipyrine (4-AAP) with phenol using the superoxide anion radical ( ) as oxidizing agent under the catalysis of horseradish peroxidase (HRP) was studied. Based on the reaction, produced by irradiating vitamin B₂ (V_B2) was spectrophotometrically determined at 510 nm. Under the optimum experimental conditions, the relationship between A ₅₁₀ and concentration was linear in the range 9.14×10^–6–1.2×10^–4 mol L^–1. The detection limit was determined to be 1.37×10^–6 mol L^–1. A possible reaction mechanism was discussed. The effect of interferences and surfactants on the determination of was also investigated. The proposed method was applied to determine superoxide dismutase activity in garlic, scallion, and onion with satisfactory results.     

Polymer crystal formation: On an analysis of the dilute solution lamellar thickness-crystallization temperature data for poly(ethylene)

Summary A detailed analysis of available crystal size-crystallization temperature data for crystallization of poly (ethylene) from dilute solutions indicates that all of the data may be represented by the semi-empirical expression: . For good solvents,T _s ⁰ =110.5 °C, _e =72.0 erg cm^–2, and . This semi-empirical expression differs from theoretical expressions,l ^*=2 _e T _s ⁰/h _f T _c +l, only in the magnitude of l predicted (5–15 Å) relative to the empirical value of . One possible origin of this difference may be a temperature dependence of _e .

---

Zusammenfassung Eine detaillierte Analyse von Daten über die Abhängigkeit der Kristallgröße von der Temperatur in der Kristallisation von Polyäthylen aus verdünnten Lösungen zeigt, daß die Engebnisse wiedergegeben werden können durch die semi-empirische Gleichung: . Für gute Lösungsmittel:T _s ⁰ =110,5 °C, _e =72.0 erg cm^–2 und . Diese semi-empirische Beziehung unterscheidet sich von den theoretischen Ausdrücken,l _*=2 _e T _s ⁰/h _f T _c +l, nur in der Größe des Verhältnisses des vorausgesagten l (5–15 Å) zu dem empirisch gefundenen Wert von . Die Temperaturabhängigkeit von _e kann möglicherweise diesem andersartigen Verhältnis zugrunde liegen.

---

---

With 4 figures and 1 table

---

Contribution number 490 from the Chemstrand Reseach Center.     

Equilibrium study of ternary complexes involving heteroaromaticN-bases and acetohydroxamic acid

Summary Stability constants (K _MAL ^MA ) and other thermodynamic parameters, including statistical factors relating to the ternary complexes (MAL) [M=Co^II, Ni^II, Cu^II or Zn^II; A=2, 2-dipyridylamine (A³), 5-nitro-o-phenanthroline (A⁵), 5-methyl-o-phenanthroline (A⁶); LH=acetohydroxamic acid] have been determined at 25° C, at ionic strength 0.1 M KNO₃. The results are compared with data on aminopolycarboxylic acids, such as iminodiacetic acid (A¹), and other unsubstituted heteroaromaticN-bases:e.g. 2, 2-bipyridine (A²),o-phenanthroline (A⁴). The resulting stability sequence is: , and for heteroaromaticN-bases: . The results have been explained in the light of electrostatic interactions, -acidities of the primary ligands (A) andcistrans equilibria for MAL.     

Synthesis of flexible ligands for assembling two metals in close proximity. Magnetic,electrochemical and spectral properties of binuclear copper (II) complexes with different exogenous bridging motifs

Binuclear Cu^II complexes having new flexible heptadentate ligands 2,6-bis{[bis(3,3-N,N-dimethylaminopropyl)amino]methyl}-4-bromophenol [HL¹], 2,6-bis(3,3-N,N-dimethylaminopropyl)amino]methyl}-4-methylphenol [HL²], and 2,6-bis{[bis(3,3-N,N-dimethylaminopropyl)amino]methyl}-4-methoxyphenol [HL³], capable of assembling two copper ions in close proximity have been synthesized. Comparisons of the charge-transfer (CT) features, observed in electronic spectra of these complexes, are correlated with the electronic effect on the aromatic ring of the ligand systems. Cyclic voltammetry has revealed the existence of two reduction couples,

Studies on ion exchange equilibria and kinetics

¹⁶⁰Tb was used as radiotracer and the equilibria and kinetics of cation exchange with zeolite-Y were studied. The ion exchange isothems and the Kielland plots at 298 and 303 K were obtained. It was found that the ion exchange rate is controlled by particle diffusion. The integral interdiffusion coefficients for the direct and reverse exchanges at 298 K and 303 K were calculated. In addition, the isotopic ion exchange was studied too.     

NMR spectra of icosahedral (Ih and I) fullerenes

By analyzing the topological structures of the three types of icosahedral fullerenes: (1) , (2) and (3) k,\;h,k = 1,2,...} \right)$$ " align="middle" border="0"> , we have obtained theoretically the ¹³C NMR spectra with natural abundance for ¹³C of all the icosahedral (I_h and I) fullerenes.     

Electrochemical study of some bromo-substituted [2.2]paracyclophanes

The potentials of electrochemical oxidation ( ) and reduction ( ) of monobromo- and isomeric di- and tribromo[2.2]paracyclophanes as well as of mono-, di-, and tribromobenzenes were measured in acetonitrile. The similarity between the properties ofpseudo-para-disubstituted cyclophanes andmeta-disubstituted benzenes, on the one hand, andpseudo-meta-disubstituted cyclophanes andpara-disubstituted benzenes, on the other hand, was confirmed by the existence of a linear relationship between of bromo-substituted [2.2]paracyclophanes and of the corresponding bromo-substituted benzenes. The results were explained in terms of the qualitative theory of molecular orbitals, taking into account a through space interaction between the -systems of the benzene rings.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 839–845, May, 1994.The authors wish to express their gratitude to Professor R. Hoffmann (Cornell University, USA) for a useful discussion and criticisms of the text of this paper.This work was financially supported by the Russian Foundation for Basic Research (Project 93-03-5246).     

Thermische Zerfallsreaktionen von Nitroverbindungen in Stosswellen. III: Dissoziation von 1-Nitropropan und 2-Nitropropan

The pyrolysis of 1- and 2-nitropropane highly diluted in Ar has been studied in shock waves at temperatures K 915 < T < 1200 K and total gas concentrations 7 · 10^?6 mol cm^?3 < [Ar] < 1.5 · 10^?4 mol cm^?3. The reactions behind the shock waves have been followed by recording light absorption-time profiles of the decomposing molecules and the produced NO₂ Under the conditions of the experiments, the primary reaction step in both cases is the C? N bond:fission: \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{rcl} {\rm 1} - {\rm C}_{\rm 3} {\rm H}_{\rm 7} {\rm NO}_{\rm 2} {\rm (} + {\rm M)} &\to & n - {\rm C}_{\rm 3} {\rm H}_{\rm 7} + {\rm NO}_{\rm 2} {\rm (} + {\rm M)\quad k} = 2.3 \cdot 10^{15} {\rm exp }(- 55{\rm kcal mol}^{ - 1} /{\rm RT}){\rm s}^{ - 1} \\ 2 - {\rm C}_{\rm 3} {\rm H}_{\rm 7} {\rm NO}_{\rm 2} {\rm (} + {\rm M)} &\to & i - {\rm C}_{\rm 3} {\rm H}_{\rm 7} + {\rm NO}_{\rm 2} {\rm (} + {\rm M)\quad k} = 2.4 \cdot 10^{15} {\rm exp }(- 54{\rm kcal mol}^{ - 1} /{\rm RT}){\rm s}^{ - 1} \\ \end{array} $\end{document} (first order rate constants k measured at concentrations of [Ar] ? 10^?4 mol cm^?3). At these concentrations the reactions are near to the high pressure limit. By varying the Ar-concentrations over one order of magnitude, only a slight pressure dependence was found. Reaction mechanisms which account for NO₂ removal are discussed.     

On the special values of monic polynomials of hypergeometric type

Special values of monic polynomials y _n (s), with leading coefficients of unity, satisfying the equation of hypergeometric type