Thermal Studies of Cobalt(II), Nickel(II) and Copper(II) Complexes of 4-(Sulfonylazido Phenylazo) Pyrazolones

The thermal decompositions of cobalt(II), nickel(II) and copper(II) complexes of4-(3'-sulfonylazido-6'-methoxyphenylazo)-1-phenyl-3-methyl-2-pyrazolin-5-one H(D¹–SO₂N₃) and 4-(4'-sulfonylazido phenylazo)-3-phenyl-3-methyl-2-pyrazolin-5-one H(D²–SO₂N₃) were studied by thermogravimetry. The decomposition in all cases takes place along two stages. The first stage is due to the elimination of water and nitrogen molecules with the formation of tetracoordinate complexes containing nitrene reactive species[M(DSO₂N:)₂]. The second stage represents the decomposition of the material to the metal oxide. The kinetics of the decomposition were examined by using Coats–Redfern, the decomposition in all complexes was found to be first order for the first and second stages. The activation energies and other activation parameters (H^* and S^* and G^*) were computed and related to the bonding and stereochemistry of the complexes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Quadrivalent uranium as a reducing agent in potentiometric titrations: Estimation of dichromate,permanganate, bromate and tellurate

Quadrivalent uranium can further be used for the estimation of K₂Cr₂O₇ KmnO₄ (in acid or alkali), H₂TeO₄ and KbrO₃ either alone or in conjunction with Fe⁺³, Ce⁺⁴ and V⁺⁵ The reaction proceeds rapidly in dilute acid solutions and especially when Fe⁺³ iron is used as a catalyst. Reduction of aqueous KmnO₄ gives MnO₂ which then dissolves in the acid of the reagent and undergoes reduction to Mn⁺². In acid solutions no MnO₂ separates. In alkaline medium (1.5–3N NaOH) KmnO₄ is reduced absolutely to MnO₂.     

Doubly-Colored Graphs as Graphical Models for Subductions of Coset Representations, Double Cosets, and Unit Subduced Cycle Indices

The concept of doubly-colored graphs is proposed to model subductions of coset representations, double cosets, and unit subduced cycle indices, which have been mathematically formulated in coset algebraic theory developed by Fujita (Symmetry and Combinatorial Enumeration in Chemistry, Springer-Verlag, Berlin, 1991).     

Reactions with heterocyclic amidines 1. Cyanoethylation of cyclic amidines

2-Amino-5-phenyl-1,3,4-oxadiazole ( 1a ) and 2-amino-1,3,4-thiadiazole ( 1b ) reacted with acrylonitrile to yield β-cyanoethylamino derivatives. On the other hand, 2-amino-4-phenylthiazole ( 2 ) reacted with acrylonitrile under the same experimental conditions to yield a di-β-cyanoethylaminothiazole derivative. 3-Phenyl-Δ²-1,2,4-triazoline-5-thione reacted with acrylonitrile to yield the corresponding adduct. The structure of the adduct was established by its conversion into the acid 13 which could be synthesised via another independent route.     

Syntheses with heterocyclic β-enaminonitriles: A facile preparation of polyfunctionally substituted thiophene,thieno[3,2-b]pyridine and thieno[3,2-d]pyrimidine derivatives

Summary A convenientGewald synthesis of 3,5-diaminothiophene-2-carbonitrile derivatives (2) is reported. The synthetic potential of the -enaminonitrile moiety in2 has been explored; it proved to be a promising candidate for the synthesis of polyfunctionally substituted thieno[3,2-b]pyridines and thieno[3,2-d]pyrimidines.

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Synthesen mit heterocyclischen -Enaminonitrilen: Eine einfache Methode zur Herstellung polyfunktionell substituierter Thiophen-, Thieno[3,2-b]pyridin- und Thieno[3,2-d]pyrimidinderivate

Zusammenfassung Eine bequeme Methode zur Herstellung von 3,5-Diaminothiophen-2-carbonitril-Derivaten (2) nachGewald wird vorgestellt. Das synthetische Potential der -Enaminonitrilfunktion von2 wurde untersucht.2 ist ein geeignetes Ausgangsmaterial für die Synthese polyfunktionell substituierter Thieno[3,2-b]pyridine und Thieno[3,2-d]pyrimidine.

     

Simple depolarizers for spectrophotometric measurements of anisotropic samples

Spectrophotometric measurements on optically anisotropic samples are considerably affected by the partial polarization of light in the instrument. It is shown that by depolarizing the incident beam, more realistic results are obtained even for strong directional anisotropic materials. Two types of depolarizers were investigated.     

Effect of detector noise in incoherent hybrid imaging systems

Hybrid imaging systems involve the joint design of an optical image-gathering module and digital processing algorithms to obtain a required final image. They have the potential to achieve imaging performance hitherto unobtainable by conventional imaging techniques. A reduction in the signal-to-noise ratio of the final image is one of their main disadvantages when one is considering linear signal processing. We analyze the effect of additive white noise at the detector on the performance of hybrid imaging systems under quasi-monochromatic incoherent illumination. We also show numerical results and computer-simulated images for an extended depth-of-field hybrid system.     

The proton affinities of styrene,trsns-β-methylstyrene,and indene

We report experimental and theoretical AM1 proton affinities of styrene,-methylstyrenes, and indene. The computed AM1 proton affinities for the species of interest were in good agreement with the experimental values.trans--Methylstyrene was found to have a proton affinity slightly lower than that of styrene. This is an unusual result since methyl substitution in most classes of compounds increases the proton affinity by 2–4 kcal mol^–1. The lower basicity oftrans--methylstyrene compared to styrene is due to the greater stabilizing effect of the methyl group in the neutral species compared to the cation.     

Studies on triazolo- and imidazo- [4.5-f]Quinolines

Oxidation of 5-arylazo-6-aminoquinoline with copper sulphate in pyridine gives the corresponding 2-aryltriazolo[4.5-f]quinolines. Condensation of halogenated nitrobenzenes with triazolo- [4.5-f]quinoline yields the corresponding 2- and 3-derivatives. Imidazo[4.5-f]quinoline behaves similarly and furnishes the 3-derivative. NMR, IR and UV spectra of several of the products are discussed.     

Quadrivalent uranium as a reducing agent in potentiometric titrations: Estimation of ferric and ceric salts

Quadrivalent uranium is found to be a suitable reducing agent in potentiometric titrations, for the estimation of ferric and ceric salts. The stability of the reagent increases by raising the acidity and becomes considerable in the presence of HCl. The stability is not seriously affected by H₃PO₄ although Zn⁺² and Co⁺² ions enhance its oxidation. Light affects the stability of the reagent only in the presence of air.The redox potential varies with l'acidity, being 0.3 volt at 0.1N HCl or H₂SO₄ rising to 0.53 or 0.61 in 1-7 N HCl or 1–9.N H₂SO₄ and increasing thereafter to ~ 1 volt.