Some chemical transformations of pummerer's ketone

The relative proportions of the epimeric alcohols obtained by reducing Pummerer's Ketone with a range of reagents have been determined, and the stereochemistries of these alcohols confirmed by europium shift studies. The reactions of Pummerer's Ketone with phenylcuprate, N,N-diethylaminopropyne, tosmic and hydrazoic acid have been investigated.     

Unsymmetrical 1-naphthyltellurium(IV) dihalides: the interplay of Te···Br,C–H···Br and C–H···π interactions in the crystal structure of (1-naphthyl)(4-methylphenyl)tellurium(IV) dibromide

The crystal structure of (1-naphthyl)(4-methyl- phenyl)tellurium(IV) dibromide, the first unsymmetrical naphthyl containing diorganotellurium(IV) dibromide, shows the formation of one-dimensional supramolecular arrays where Te···Br secondary bonds link two parallel rows of molecules in a gear-teethed fashion. The weaker C–H···Br and C–H···π hydrogen bonds play important role in the formation of three-dimensional crystal lattice by cross linking these supramolecular motifs.     

Analytical applications of copper(II) and copper(I) in acetonitrile: potentiometric and spectrophotometric determination of dithiocarbamates

The use of copper(II) perchlorate and tetra-acetonitrilocopper(I) perchlorate (in acetonitrile) for the potentiometric and spectrophotometric determination of dithiocarbamates in acetonitrile medium is described. The proposed methods are simple, accurate and reliable and show promise of wide applicability. They are recommended for routine determination of dithiocarbamates. Their advantages over the carbon disulphide evolution method, commonly employed for the determination of these compounds, are discussed.     

Secondary bonding in functionalized organotellurium compounds: preparation and structural characterization of bis(acetamido)tellurium(IV) diiodide and bis(4-methylbenzoylmethyl)tellurium(II)

Elemental tellurium inserts, under mild conditions, between C-I bond of iodoacetamide to afford bis(acetamido)tellurium(IV) diiodide (NH₂COCH₂)₂TeI₂, 1. Heating of N-bromomethylphthalimide with activated tellurium powder however, resulted in the formation of bis(phthalimido)methane, 2, instead of the expected product bis(phthalimidomethyl)tellurium(IV) dibromide. The IR spectrum of 1 is indicative of intramolecular Te?OC interaction which is also substantiated by its single-crystal structure. The compound with planar small-bite chelating organic ligands acquires butterfly shape that imparts almost perfect C_2v molecular symmetry but unlike other organotellurium(IV) iodides, the solid state structure of 1 is devoid of any intermolecular Te?I or I?I secondary interactions owing to the presence of intramolecular Te?O secondary bonds as well as intermolecular N-H?O, N-H?I and C-H?I hydrogen bonds. Bis(4-methylbenzoylmethyl)telluride (4-MeC₆H₄COCH₂)₂Te, 3b, prepared by the reduction of the corresponding dibromide, is the first structurally characterized acyclic dialkyltelluride and interestingly, does not involve intramolecular Te?OC interaction invariably present in the parent dihalides (4-YC₆H₄COCH₂)₂TeX₂ (Y = H, X = I 4a; Y = H, X = Br 5a; Y = MeO, X = Br 5c). Weak intermolecular Te?Te and C-H?O hydrogen bonds appear to be the non covalent intermolecular associative forces that dominate its crystal packing in the solid state of this Te(II) derivative. The dialkyltellurides (4-YC₆H₄COCH₂)₂Te, (Y = H, 3a, Me, 3b) undergo oxidation in presence of (SCN)₂ to give the corresponding bis(isothiocyanato)tellurium(IV) derivatives and form 2:1 adducts with Pt(II) and Pd(II) chlorides.     

A Sorption-Kinetic Model for Surfactant-Driven Spreading of Aqueous Drops on Insoluble Liquid Substrates

Spreading of aqueous drops on hydrocarbon liquids occurs only when particular surfactants are added to the droplets above a critical concentration. For surfactant solutions of didodecyl ammonium bromide (DDAB) in water spreading over mineral oil, rates of droplet expansion are much slower than those corresponding to pure liquids spreading over immiscible liquid substrates with the same initial spreading coefficients. We present a sorption-kinetic model to explain quantitatively the spreading histories for aqueous DDAB droplets on mineral oil. Due to surfactant transport limitations, spreading occurs only when enough surfactant arrives at the dilating lens surfaces to establish a slightly positive, but near-zero spreading coefficient. We solve the convective diffusion equation for a cylindrical disk-like lens under the integral constraint of a constant surfactant adsorption density corresponding to a near-zero spreading coefficient. All observed spreading behavior is correctly portrayed by the proposed sorption-kinetic model including final equilibrium lens formation and spreading rates that are sensibly independent of drop volume, but are strongly dependent on drop surfactant concentration. Quantitative agreement is found with the experimental spreading data for a surfactant diffusion coefficient of 6x10(-12) m(2)/s and an effective adsorption rate constant of 6.5x10(-7) m/s. Both values prove physically reasonable. The sorption-kinetic model provides a new mechanism for understanding slow surfactant-driven spreading. Copyright 2000 Academic Press.     

Formulation of benzoporphyrin derivatives in Pluronics

This study investigates the potential of Pluronics for the formulation of tetrapyrrole-based photosensitizers, with a particular focus on B-ring benzoporphyrin derivatives. The B-ring derivatives have a high tendency to aggregate in aqueous solutions, and this poses a significant formulation problem. Pluronics are ABA-type triblock copolymers composed of a central hydrophobic polypropylene oxide section with two hydrophilic polyethylene oxide sections of equal length at either end. Out of a range of different commercially available block copolymers studied, it was found that the longer the hydrophobic block, the better the stabilization of tetrapyrrolic drugs in monomeric form in aqueous suspensions. Of these the best performance was observed in the micelle-forming Pluronic P123. Micelle size determination by laser light scattering confirmed that particle size in stable Pluronic formulations was around 20 nm. Pluronics such as L122 formed emulsions spontaneously without the need for emulsion stabilizers; emulsions were highly stable at ambient temperatures over several days and also highly effective as potential drug delivery agents.     

Synthesis, characterization and interaction of a new chiral trinuclear complex [bis(aquodiaminotryptophanato) CuII–Sn2IV]chloride with calfthymus DNA

The new chiral trinuclear complex, [bis(aquodiaminotryptophanato)Cu^II–Sn₂^IV] chloride (1) was synthesized by employing a well-designed three-step pathway under anhydrous conditions. Interaction of the complex (1) with calf-thymus DNA was studied by spectrophotometry, cyclic voltammetry and viscosity measurements. The kinetic studies of calf-thymus DNA binding were carried out at 260 nm (λ_max of calf-thymus DNA) under pseudo-first order conditions. The rate constants, k_obs, were evaluated by the linear least squares regression method. The absorption spectra of the complex with calf-thymus DNA shows ‘hyperchromism’ which is attributed to the electrostatic interaction with calf-thymus DNA. The electrochemical behavior of complex (1) was studied in DMSO/H₂O (5:5) solution and showed a quasireversible Cu^II/Cu^I redox couple. The voltammetric studies of the complex in the absence and in the presence of DNA exhibit a shift in the formal potential E ⁰ and ratio of cathodic to anodic peak currents i_pa/i_pc indicating strong binding of the complex to calf-thymus DNA. The viscosity of DNA decreases with increasing concentration of the complex, suggesting that complex (1)binds to calf-thymus DNA by electrostatic association.     

Alkylenedithiophosphate derivatives of arsenic(III), antimony(III) and bismuth(III)

Tris(alkylenedithiophosphates) of arsenic(III), antimony(III) and bismuth(III),

have been synthesized by the reactions of alkylenedithiophosphoric acids with metal oxides and chlorides and of their ammonium salts with metal chlorides in suitable solvents. Mixed chloride alkylenedithiophosphates of arsenic(III) and antimony(III),

have been obtained by the reactions of metal chlorides with ammonium alkylenedithiophosphates at 1 : 1 and 1 : 2 molar ratios or alternatively by the co-disproportionations reactions of metal chlorides with metal tris(alkylenedithiophosphates) at different (2 : 1 and 1 : 2) molar ratios. These new compounds have been characterized by elemental analyses, molecular weight measurements and spectroscopic (IR, and ¹H and ³¹P NMR) data. Chelated structures with bidentate alkylenedithiophosphate groups have been proposed for all these derivatives.     

Optimisation of a Selective Liquid Chromatography Procedure for Hydrocortisone Acetate, Hydrocortisone Alcohol and Preservatives in a Pharmaceutical Emulsion

An accurate, reproducible and specific stability-indicating method for the high performance liquid chromatography (HPLC) assay of hydrocortisone acetate, hydrocortisone alcohol, methyl p-hydroxybenzoate and propyl p-hydroxybenzoate in a pharmaceutical suspension is described. An investigation of several column phases was undertaken and a Zorbax SB-Phenyl column gave the best selectivity and specificity due to the π-π interactions between the analytes and stationary phase. All the components were fully resolved in less than 15 min under isocratic conditions using UV detection at 254 nm with a water-methanol mobile phase. The stability-indicating method was validated over the linearity range of 25% to 150% of the nominal concentrations of each analyte. Nominal concentrations were hydrocortisone acetate (10% w/w), hydrocortisone alcohol (0.2% w/w with respect to hydrocortisone acetate), methyl p-hydroxybenzoate (0.1% w/w) and propyl p-hydroxybenzoate (0.01% w/w) respectively.     

Physico-chemical studies on samarium soaps in solid state

Summary The physico-chemical characteristics of samarium soaps (caproate and caprate) in solid state were investigated by IR, X-ray diffraction and TGA measurements. The IR results revealed that the fatty acids exist in dimeric state through hydrogen bonding and samarium soaps possess partial ionic character. The X-ray diffraction measurements were used to calculate the long spacings and the results confirmed the double layer structure of samarium soaps. The decomposition reaction was found kinetically of zero order and the values of energy of activation for the decomposition process for caproate and caprate were found to be 8.0 and 7.8 kcal mol^–1, respectively.

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Physikochemische Untersuchungen an Samariumseifen in festem Zustand

Zusammenfassung Die physikochemischen Charakteristika von Samariumseifen (Caproat und Caprat) wurden im festen Zustand mittels IR, Röntgendiffraktion und TGA-Messungen untersucht. Die IR-Ergebnisse zeigten, daß die Fettsäuren durch Wasserstoffbrücken dimer vorliegen und daß die Samariumseifen partiell ionischen Charakter besitzen. Die Röntgenuntersuchungen bestätigen die Doppelschichtstruktur der Seifen. Die Zersetzungsreaktion verlief nach nullter Ordnung, und die Aktivierungsenergien für den Zersetzungsprozeß für Caproat und Caprat waren 8.0 und 7.8 kcal mol^–1.