Synthesis and characterization of a novel chiral azomethine diselenide

The first chiral diselenide 9 having an ortho-azomethine functional group has been synthesized by the reaction of bis(o-formylphenyl) diselenide with the chiral amine R(+)-(1-phenylethylamine). The chiral diselenide 9 was further characterized by derivatizing it into the corresponding selenenyl halides. The derivatives are characterized by single crystal X-ray diffraction studies. In the solid state, the bromide derivative 11 shows the strongest Se?N intramolecular interaction. The chiral azomethine diselenide 9 has been further reduced to afford the diselenide 13. The monoselenide analogues of 9 and 13 have also been synthesized.     

Discrete breathers: exact solutions in piecewise linear models

Exact breather solutions are constructed in piecewise linear (PWL) versions of the discrete nonlinear Schrodinger and Klein-Gordon equations. These solutions correspond to intersections of stable and unstable manifolds of relevant fixed points in associated 2D mappings, an exact construction of which is possible due to the PWL nature of the models. Such exact solutions give us insight into several aspects of breather properties. The problem of dynamical stability of the breathers is mentioned as an instance, detailed results on which will be presented in a future paper.     

Thermal analysis of spurrite from a rotary cement kiln

A number of samples from the pre-burning zone of a wet-process cement rotary kiln were examined by combined DTA/TG and XRD for estimation of spurrite (2Ca₂SiO₄·CaCO₃). It was found that decarbonation temperatures of spurrite range from 1130 to 1190 K and they are 45 to 75 K higher than that of calcite occurring in the same sample. In the TG curves calcite and spurrite can be easily distinguished and accordingly both can be estimated from the same TG scan. Combined DTA/TG, supplemented by XRD, is a very effective method for qualitative and quantitative estimation of spurrite in cement rotary kiln materials.

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Zusammenfassung Unter kombinierter Anwendung von DTA/TG und Röntgendiffraktionsverfahren wurde eine Anzahl Proben aus einem Vorkalzinator eines Drehrohrofens zur Zementherstellung nach dem Naßverfahren auf Spurrit (2Ca₂SiO₄·CaCO₃) untersucht. Es wurde festgestellt, daß die Temperatur für das Austreiben von CO₂ bei Spurrit zwischen 1130 und 1190 K und somit um 45–75 °C höher als bei in derselben Probe vorliegenden Kalzit liegt. Aufgrund der TG-Kurven können Kalzit und Spurrit leicht voneinander unterschieden und demzufolge mit einem einzigen TG-Scan bestimmt werden. Kombinierte DTA/TG, ergänzt durch Röntgendiffraktionsverfahren ist eine sehr leistungsstarke Methode zur qualitativen und quantitativen Bestimmung von Spurrit in Stoffen aus Zementdrehrohröfen.

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(2Ca₂SiO₄ · CaCO₃), / , , . , 1130– 1190 , 46–75 , . . /, , .

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The authors are very grateful to Mr. A. H. Dalmia, president, M/s. Orissa Cement Limited, Rajgangpur for allowing to collect the samples during the stoppage of the kiln and also for his permission to publish the paper.     

On non-binary social choice

In a recent paper Grether and Plott (1982) have extended Arrow's General Possibility Theorem to the case where choice over small (in particular ‘two-element’) sets may not be possible. This obviously raises the question whether the counterparts of other existing impossibility results will go through in the same framework. This note settles the question for the counterpart of the well-known impossibility theorem of Gibbard. By weakening the collective rationality condition of Arrow we show that all the social choice functions will be ‘oligarchical’ in Gibbard's sense, in the Grether and Plott (1982) framework.     

Studies in nickel(IV) chemistry. Part 6. Kinetics of electron transfer from phenylhydrazine to tris-(dimethylglyoximato) nickelate(IV) in aqueous medium

The kinetics of electron transfer from phenylhydrazine(S) to tris-(dimethylglyoximato) nickelate(IV), Ni(dmg) (dmg^2? = dimethylglyoximate dianion), have been studied in aqueous medium in the range of 6.21 ? pH ? 12.2. The kinetics exhibit a pseudo-first-order disappearance of Ni(dmg) when excess S is present. The pseudo-first-order rate constants k_obs are almost linearly dependent on [S]₀ for varying concentrations of the reductant. At constant [S]₀, the k_obs?pH profile is U shaped. The k_obs values register a decrease as the [H⁺] is increased in the pH range of ∽12.2–9.5, remain almost constant (minimum) in the range of ∽9–8, and then again linearly increase as [H⁺] is increased in the pH range of ∽7–6.21. Results are interpreted in terms of a probable mechanism involving outer-sphere electron transfer from the phenylhydrazine and phenylhydrazinium cation species to the unprotonated and one-protonated species of the Ni(IV) complex. The reduction rate appears to be dependent on the nature of the species (unprotonated and one-protonated) of the oxidant Ni(IV) complex. The phenylhydrazinium cation reduces the Ni(IV) complex at least one order of magnitude faster than does the neutral reductant species. The major product of the oxidation of phenylhydrazine by the Ni(IV) complex is 4-hydroxyazobenzene with a small amount of phenol.     

Studies in nickel(IV) chemistry. Kinetics of the Cu(II) ion-mediated acid decomposition of tris(dimethylglyoximato) nickelate(IV) in aqueous acidic medium

Kinetics of the Cu(II) ion-mediated acid decomposition of tris (dimethylglyoximato)nickelate(IV), Ni(dmg)₃^2? (dmg^2? = dimethylglyoximate dianion), are reported in aqueous medium in the range of 3.6 ? pH ? 6.6 at 35°C and μ = 0.57 M. The pseudo-first-order rate constants of the disappearance of Ni(IV) k_obs(M) satisfy the equation where k_ad refers to the pseudo-first-order rate constants for the proton-assisted decomposition of the Ni(IV) complex determined independently and is a function of [H⁺], and k_dec(M) to that for the Cu(II) ion-mediated route and is a function of [H⁺] and [Cu²⁺]. Both k_obs(M) and k_dec(M) are found to increase with increasing [Cu(II)]₀, tending to attain limiting values at higher relative [Cu(II)]₀. At low [Cu(II)]₀ the k_dec(M) is found to register a decrease with increasing pH in the pH range of 3.6–4.4, then an increase in the range of 4.4–5.76, and again a decrease in the range of 5.76–6.6. Results on the Cu(II) ion-mediated acid decomposition are interpreted in terms of a probable mechanism involving pH-dependent adduct formation equilibria involving the one-protonated and the two-protonated species of Ni(IV) and the various species of Cu(II) ion in the media, followed by rate-determining acid decomposition of the adduct(s) to give Ni(II) aq. and Cu(dmgH)₂. While the two-protonated Ni(IV) complex apparently reacts about five orders of magnitude faster than the one-protonated species, the aquacopper(II) reacts about two orders of magnitude slower than the hydroxoaquacopper(II).     

Kinetics and mechanism of OsO4 catalyzed oxidation of maleic, fumaric, cinnamic and acrylic acids by acid bromate

The title reactions are zero order in bromate, first order in both substrate and catalyst. The order of reactivity is cinnamic acid>acrylic acid>fumaric acid>maleic acid. A plausible mechanism is discussed.

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Magnetic and structural behaviours of nanocrystalline Fe 70.8 Nb 3.7 Cu 1 Al 2.7 Mn 0.7 Si 13.5 B 7.6 alloy

The crystallization behaviour of Fe 70.8 Nb 3.7 Cu 1 Al 2.7 Mn 0.7 Si 13.5 B 7.6 alloy prepared in the form of amorphous ribbons by melt-spinning technique was studied using differential scanning calorimetry and the temperature variation in resistivity. An X-ray diffaction and transmission electron microscopy study showed the formation of f-Fe(Si, Al) and/or Fe 3 (Si, Al) nanoparticles after the first stage of crystallization. The activation energy for this nanophase formation was 68 kcal mol m1 . The brittleness of the alloy increased with the formation of nanoparticles after heat treatment. Superior soft magnetic properties were achieved when the material was heat treated at 790 K for 15 min. The particle size at the optimum heat treatment condition for superior soft magnetic properties was found to be 6.0 -0.5 nm which was less compared than for the Fe-Nb-Cu-Si-B system. The observed coercivity value at the optimum heat treatment condition was found to be 0.32 A m m1 (approximately 4 mOe). The presence of Al in the alloy reduced the particle size and the magnetic anisotropy energy of the system, which resulted in superior soft magnetic properties of the heat-treated materials.