Palladium(O) and rhodium(I) catalysis of the carbonylation of unactivated bromides

Alkyl, vinyl, and aromatic bromides react with organoborates and carbon monoxide, in the presence of catalytic quantities of 1,5-hexadienerhodium(I) chloride dimer and tetrakis(triphenylphosphine)palladium(O),to give carboxylic esters in good yields.     

Characterization of new fluorescent peroxidase substrates

The reagents Lumigen PS-1 and Lumigen PS-3 were originally developed as chemiluminescent substrates for ultrasensitive detection of horseradish peroxidase (HRP) in homogeneous solution and membrane blotting assays. However, an additional unique feature of these acridan-based reagents is the generation of a fluorescent species on reaction with peroxidase, a property which has been termed as chemifluorescence. These reagents, therefore, represent the first dual-use substrates enabling both chemiluminescent and fluorescent detection. We have developed several additional acridan-based substrates for fluorescent detection of HRP which are capable of subattomole detection sensitivity. By varying several structural parameters within the class of compounds we have produced substrates which either produce fluorescence alone or both chemiluminescence and fluorescence.     

Spectrophotometric determination of acidity constants of some anthraquinones and anthrones in methanol-water mixtures

The acidity constants of some synthetic derivatives of 9,10-anthraquinone and 9-anthrone in methanol-water mixtures at 25 degrees have been determined spectrophotometrically. A linear reverse relationship is observed between pK(a1) of all acids and the mole fraction of methanol. The influence of substituents in the molecular structure on the ionization constants is discussed.     

Spectrofluorometric study of complexation of some amino derivatives of 9,10-anthraquinone with beta-cyclodextrin

Complexation reactions between 1-amino-9,10-anthraquinone (AA1), 1-amino-2-methyl-9,10-anthraquinone (AA2), 1-amino-2,4-dimethyl-9,10-anthraquinone (AA3) and 1-amino-2-ethyl-9,10-anthraquinone (AA4) and beta-cyclodextrin were studied spectrofluorometrically, under optimized experimental conditions. The formation constants of the resulting 1:1 beta-cyclodextrin complexes were evaluated and found to decrease in the order AA4>AA1>AA3>AA2. Possible reasons for the observed stability sequence are discussed based on the structures proposed for the resulting inclusion complexes.     

Solution equilibria and stability of the complexes of pyridinecarboxylic acids: Complexation reaction of mercury(II) with 2-hydroxynicotinic acid

Summary The solution equilibria of 2-hydroxynicotinic acid (hyna) complexes with mercury(II) have been studied spectrophotometrically in 50% (v/v) ethanol at 20°C and an ionic strength of 0.1mol dm^–3 (NaClO₄). Three mercuric complexes are formed in solution in dependence on the acidity of the medium. The basic characteristics of the different complexes are determined and the analytical aspects of the complexation reaction are demonstrated. A critical investigation has also been presented of the solution equilibria and stability of the mixed complex of mercury(II) withhyna and thiosalicylic acid (tsa). The various complex transitions leading to the formation of the 1 : 1 : 1 Hg(tsa)(hyna) ternary complex in solution are investigated. The non-charged mono-ligand complex Hg(hyna) is used for UV-spectrophotometric determination of mercury atpH 4.5–5 (_max=325nm, =0.8·10⁴lmol^–1cm^–1). The system obeyed Beer's law up to 36.1 µg ml^–1 of Hg(II). The optimum concentration range (Ringbom) is between 6 and 28.5µg ml^–1. Interference caused by a number of ions was masked by the addition of fluoride ions.

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Lösungsgleichgewichte und Stabilitätskonstanten von Komplexen der Pyridincarbonsäuren: Die Komplexierungsreaktion von Quecksilber(II) mit 2-Hydroxynikotinsäure

Zusammenfassung Die Lösungsgleichgewichte von 2-Hydroxynikotinsäure (hyna) mit Hg(II) wurde spektrophotometrisch in 50% (v/v) Ethanol bei 20°C und einer Ionenstärke von 0.1 mol dm^–3 (NaClO₄) untersucht. In Abhängigkeit von der Acidität des Mediums werden drei Quecksilberkomplexe gebildet. Die grundlegenden Charakteristika der Komplexe wurden bestimmt und die analytischen Aspekte aufgezeigt. Die gemischten Komplexe von Hg(II) mithyna und Thiosalicylsäure (tsa), insbesondere die verschiedenen Komplexübergänge zum ternären 1 : 1 : 1 Hg(tsa)(hyna)-Komplex, wurden ebenfalls untersucht. Der ungeladene Monoligandenkomplex Hg(hyna) kann beipH 4.5–5 zur UV-spektroskopischen Quecksilberbestimmung eingesetzt werden (_max=325nm, =0.8·10⁴lmol^–1cm^–1). Das System gehorcht bis zu einer Hg(II)-Konzentration von 36.1µgml^–1 dem Beerschen Gesetz. Der optimale Konzentrationsbereich (Ringbom) liegt zwischen 6 und 28.5µgml^–1. Interferenzen mit einer Reihe anderer Ionen konnten durch Maskierung mit Fluoridionen umgangen werden.

     

Complexation equilibria and spectrophotometric determination of iron(III) with resorcylic acid

The complexation equilibria of Fe(III) with resorcylic acid (2,4-dihydroxybenzoic acid, DHB) were studied spectrophotometrically in ethanol-water (4 + 6, v/v) at an ionic strength of 0.1 M NaClO4. The complexation reactions were demonstrated and characterized. A simple, rapid, and sensitive method based on the formation of the Fe(III)-DHB complex at pH 2.5 (lambdamax = 520 nm, epsilon = 0.8 x 10(4) L/mol x cm) was developed for the spectrophotometric determination of Fe(III). The effect of diverse ions on the sensitivity of the proposed method was studied. The Fe-DHB complex was isolated and characterized by both elemental analysis and infrared spectroscopy. The thermal behavior of the complex in dynamic nitrogen gas was studied by thermogravimetric and differential thermogravimetric analysis. Thermal events encountered throughout the course of decomposition were monitored. A computer program was used for regression analysis and for determination of kinetic and thermodynamic parameters from experimental nonisothermal thermogravimetric data. The proposed method was tested by determinations of iron in various synthetic samples and Portland cement materials.