Thermodynamics of the extraction of Eu3+ with thenoyltrifluoroacetone,triphenylarsine oxide and other phosphine oxides

Extraction of Eu³⁺ from 0.1M aqueous perchlorate medium by thenoyltrifluoroacetone (HTTA) and by mixtures of HTTA and tributylphosphate (TBP), HTTA and triphenylphosphine oxide (TPPO), HTTA and trioctylphosphine oxide (TOPO) and HTTA and triphenylarsine oxide (TPAsO) has been studied at various temperatures allowing for the elucidation of the mechanism of extraction in each case and a comparison between the various bases.     

Origin of the oxygen in the oxidation of triphenylphosphine by potassium persulfate—application of the 18O isotope effect in 31P NMR

Potassium persulfate oxidizes triphenylphosphine to triphenylphosphine oxide in 60% aqueous acetonitrile. It has been suggested that the oxygen of the product, triphenylphosphine oxide, might originate from solvent water, following nucleophilic attack on an intermediate phosphonium ion. We have investigated the origin of the oxygen in the oxidation of triphenylphosphine by potassium persulfate in 60% aqueous acetonitrile containing 20% [¹⁸O]water. The product was analyzed by using the ¹⁸O isotope effect in ³¹P NMR spectroscopy. The magnitude of the ¹⁸O isotope-induced shift was determined by synthesizing triphenylphosphine [¹⁸O]oxide and was found to be 0.038 ppm upfield. The product of the oxidation reaction in 20% [¹⁸O]water displayed no ¹⁸O isotope effect. The origin of the oxygen in the oxidation reaction is the persulfate ion, consistent with an alternative mechanism involving nucleophilic attack by water at the sulfur atom of a phosphonium peroxysulfate intermediate.     

Reaction of polyperoxides with triphenylphosphine

The triphenylphosphine deoxygenation of the polyperoxides, poly(styrene peroxide), poly(methyl methacrylate peroxide), and poly(α-methylstyrene peroxide) proceed via the phosphorane intermediates, which in the presence of moisture hydrolyze to give the respective diols. At higher temperatures and under dry conditions the phosphorane decomposes into epoxide and triphenylphosphine oxide. The reaction has been studied by ¹H-, ¹³C-, and ³¹P-NMR spectroscopy. The results obtained are consistent with a concerted insertion of the biphile, triphenylphosphine, into the peroxy bond and this reaction pathway seems to be new as far as the chemistry of polyperoxides is concerned. Though the aim of this investigation was to test the selective deoxygenation of polyperoxide by triphenylphosphine as a method of preparing polyethers, it turned out to be a fruitful method of synthesis of stereospecific diols. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1167–1172, 1997     

Phosphine oxides as stabilizing ligands for the palladium-catalyzed cross-coupling of potassium aryldimethylsilanolates

The palladium-catalyzed cross-coupling reaction of potassium (4-methoxyphenyl)dimethylsilanolate (K⁺1⁻) with aryl bromides has been demonstrated using triphenylphosphine oxide as a stabilizing ligand. Unsymmetrical biaryls can be prepared from a variety of aryl bromides in good yield with short reaction times. Qualitative kinetic studies compared effects of different phosphine oxides on the rate of cross-coupling and established the beneficial effect of these ligands in the reaction of electron-rich arylsilanolates. The improved yield and reproducibility of the cross-coupling of several bromides was demonstrated by direct comparison of reactions performed with and without triphenylphosphine oxide under non-rigorous exclusion of oxygen.     

Thermal behaviour of chromium (III) perchlorate hexahydrate

Thermal behaviour of intimate mixtures of chromium(III) oxide and lithium¹, potassium², rubidium³, cesium³ and thallium(I)⁴ perchlorates revealed that chromium(III) oxide not only catalyses the decomposition by lowering the decomposition temperatures of the pure metal perchlorates but also chemically interacts resulting in the formation of metal dichromate. The oxidation of chromium(III) into the hexavalent state is attributed to the abstraction of oxygen from the perchlorate moiety during the decomposition. In this context, it was thought interesting to study the thermal behaviour of chromium(III) perchlorate and to identify the decomposition products in order to find out whether chromium(III) is oxidized into chromium(VI) by the perchlorate group. Except for a report⁵ on the preparation of chromium(III) perchlorate with different molecules of water of hydration no work seems to have been carried out on the thermal decomposition of this compound. In the present study, the decomposition characteristics are followed by TG and DTA techniques and the decomposition products have been examined by chemical analysis, X-ray powder diffraction patterns and infrared spectral measurements.     

The Simultaneous Determination of Phenylephrine Hydrochloride,Paracetamol, Chlorpheniramine Maleate and Dextromethorphan Hydrobromide in Pharmaceutical Preparations

A new rapid and sensitive method has been developed and validated for the simultaneous determination of phenylephrine hydrochloride, paracetamol, chlorpheniramine maleate and dextromethorphan hydrobromide in pharmaceutical preparations. The separation was achieved on a C18 column using a gradient mobile phase of acetonitrile–sodium perchlorate (pH 3, 0.01 M) at a flow rate of 1.4 mL min⁻¹. Detection was at 204 nm. Pseudoephedrine hydrochloride was selected as internal standard. The recovery of the drugs ranged from 97.8 to 100.9%. Central composite design was used during validation to calculate method robustness and the percentage of sodium perchlorate, temperature and flow rate were investigated as factors. The method was found to be applicable for the determination of the four compounds in sugar-coated tablets.

     

Mechanochemical Preparations of Anion Coordinated Architectures Based on 3-Iodoethynylpyridine and 3-Iodoethynylbenzoic Acid

The halogen bond has previously been explored as a versatile tool in crystal engineering and anion coordination chemistry, with mechanochemical synthetic techniques having been shown to provide convenient routes towards cocrystals. In an effort to expand our knowledge on the role of halogen bonding in anion coordination, here we explore a series of cocrystals formed between 3-iodoethynylpyridine and 3-iodoethynylbenzoic acid with halide salts. In total, we report the single-crystal X-ray structures of six new cocrystals prepared by mechanochemical ball milling, with all structures exhibiting C≡C−I⋅⋅⋅X⁻ (X=Cl, Br) halogen bonds. Whereas cocrystals featuring a pyridine group favoured the formation of discrete entities, cocrystals featuring a benzoic acid group yielded an alternation of halogen and hydrogen bonds. The compounds studied herein were further characterized by ¹³C and ³¹P solid-state nuclear magnetic resonance, with the chemical shifts offering a clear and convenient method of identifying the occurrence of halogen bonding, using the crude product obtained directly from the mechanochemical ball milling. Whereas the ³¹P chemical shifts were quickly able to identify the occurrence of cocrystallization, ¹³C solid-state NMR was diagnostic of both the occurrence of halogen bonding and of hydrogen bonding.     

Mixed ligand extraction of cobalt(II) by thenoyltrifluoroacetone and triphenylphosphine or triphenylarsine oxides in chloroform

Extraction of Co(II) from perchlorate aqueous media by mixtures of thenoyltrifluoroacetone and triphenylarsine oxide or triphenylphosphine oxide in chloroform has been studied. It is found that the presence of these oxides enhances the extraction of Co(II). Synergic factors and formation constants were calculated and interpreted in the light of the electron donating properties of these oxides.     

Voltammetric Study of Some Synthetic Antioxidants on Platinum Microelectrodes in Acetic Acid Medium

The electrochemical oxidation of the antioxidants tert‐butylhydroquinone (BHQ), tert‐butyl‐4‐hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) has been investigated by voltammetry at platinum microelectrodes in glacial acetic acid containing sodium perchlorate or sodium acetate as a background electrolyte. BHQ, a compound with para‐diphenyl groups, was typically found to have lower oxidation potential than isolated phenols BHA and BHT. Particular attention has been devoted to the mechanism of the electrode processes. Linear scan voltammograms recorded under steady‐state conditions showed well‐defined oxidation waves of the compounds studied even at relatively high concentrations (2 mM), due to a low proclivity for adsorption of the oxidation products on the electrode surface in acetic acid. The optimal conditions for the voltammetric determination of BHQ, BHA and BHT have also been studied. The results reveal that sensitive response for all the oxidants studied can be obtained in solution containing 0.1 M NaClO₄ and 0.1 M CH₃COONa by using the differential pulse voltammetry and square‐wave voltammetry. Peak currents were found to vary linearly with the antioxidant concentration over the range 3×10^?5?1×10^?3 M.     

Double-layer effects on simple electrode reactions I. The reduction of Eu3+ and Cr3+ in the absence of specific adsorption of the supporting electrolyte

The kinetics of the reduction of Eu³⁺ and Cr³⁺ at mercury electrodes in various sodium and lanthanum perchlorate supporting electrolytes have been studied over as large a potential range as possible by using both chronocoulometry and d.c. polarography. The objective was to determine the effect of the diffuse double layer upon the reduction rates of these members of the simplest class of electrode reactions in the absence of specific adsorption. Possible additional influences from perchlorate specific adsorption, ion-pairing, and ionic strength-dependent formal potentials, and differences between the site of reaction and the o.H.p. were also considered. The effects of specific adsorption of an uncharged molecule were assessed by noting the changes in the reduction kinetics of Eu³⁺ caused by the adsorption of thiourea.The classical Gouy-Chapman-Stern model of the double layer was found to give an adequate account of the behavior in relatively dilute lanthanum perchlorate solutions, but it failed badly in more concentrated sodium perchlorate media. Better agreement resulted if the statistical theory due to Krylov and Levich was employed but some discrepancies remained. The diffuse-layer properties evaluated here represent a useful basis for comparisons with systems where specific ionic adsorption of components of the supporting electrolyte adds a second component to the electrode surface charge density which determines the diffuse-layer potential.     

The Determination of Polycyclic Aromatic Hydrocarbons in Indigenous and Transplanted Mussels (Mytilys Edulis L.) Along the Dutch Coast

Abstract

A method, originally developed to investigate the pollution of Dutch coastal water with metals and PCBs,¹ was modified for the determination of the pollution with polycyclic aromatic hydrocarbons (PAH).

The method is based on active biological monitoring with mussels (Mytilus edulis L.). Its usefulness has already been demonstrated.² In the present study a method for the determination of PAH in mussels has been developed. The method is based on the hydrolysis of tissue with 4 M sodium hydroxide, extraction with hexane, clean-up with 10% deactivated aluminium oxide and quantitative determination with Reversed Phase High Performance Liquid Chromatography (RP-HPLC) and fluorescence detection.

The accumulation plateau of most of the PAH studied has not been reached after 60 days. Gradients of pollution were found, and at least one significant source near IJmuiden was detected.     

Electroreduction of tetra-coordinate phosphonium derivatives; one-pot transformation of triphenylphosphine oxide into triphenylphosphine

Electroreduction of triphenylphosphine dichloride in acetonitrile was performed successfully in an undivided cell fitted with an aluminium sacrificial anode and a platinum cathode, wherein Al³⁺, which was electrogenerated at the anode would react as a Lewis acid with triphenylphosphine dichloride to afford tetra-coordinate chlorotriphenylphosphonium species and subsequent two-electron reduction at the cathode would give triphenylphosphine. One-pot transformation of triphenylphosphine oxide to triphenylphosphine was achieved successfully by the treatment of triphenylphosphine oxide with oxalyl chloride and subsequent electroreduction. In a similar manner, some tetra-coordinate triphenylphosphonium species derived from triphenylphosphine oxide were reduced electrochemically to triphenylphosphine in moderate yields.     

Protonation and alkylation of organophosphorus compounds with trifluoromethanesulfonic acid derivatives

Protonation (alkylation) of triphenylphosphine, triethylphosphite, triphenylphosphine oxide, triethylphosphate, hexamethylphosporamide, and dimethylphosphite with trifluoromethanesulfonic acid, its bisimide, and methyl ester was studied and the corresponding ¹H, ¹³C, ¹⁹F, ³¹P NMR spectra were analyzed.     

Conductometric study of cationic and anionic complexes in propylene carbonate

Conductivity data are used to determine thermodynamic complex formation constants for cases in which both the initial electrolyte and the complexed electrolyte form ion pairs. Using the method described in the text, the complex formation constants of Li⁺, Na⁺ and K⁺ with the crown ether 18-crown-6 and of Li⁺ with the ligand triphenylphosphine oxide in propylene carbonate have been evaluated from conductance data. The complexation of AgBr in propylene carbonate solutions of n-etrabutylammonium bromide has also been studied by the measurement of molar conductivities. The results of these studies indicate that ion pairing should not be neglected, even in high permittivity solvents such as propylene carbonate, and that the ion pair association constants correlate well with structural studies on cation-crown ether molecular conformations.     

The EPR Spectra of Tetradentate Schiff-Base Complexes of Copper II V. N,N′-bis(1,1,1-trifluoro 2,4-hexanedione)1,2-propanediimine

Abstract

Complex formation between lead(II) ions and some N-substituted iminodiacetic acids has been studied at 25° in aqueous sodium perchlorate with ionic strength 0.50 M. Measurements have been carried out with glass and lead amalgam electrodes. For all the ligands 1:1 mononuclear complexes form, one of which monoprotonated. The stability constants have been evaluated.     

Détermination, à 25°C,du produit ionique des solvants mixtes acétone+eau+perchlorate de sodium

The ionic products of different mixed solvents acetone+water with sodium perchlorate have been determined by a method of standardisation using solutions of “strong” acids and bases.The evolution of pk_i is plotted in function of molar fraction of acetone and concentration of sodium perchlorate.The approximate values of the ionic product of acetone and acetone+sodium perchlorate media (0.5 M, 1 M, 2 M, 3 M) have been achieved easily by graphical extrapolation.     

Poly (Vinyl Chloride) Matrix Membrane Electrodes Responsive to Thiocyanate,Perchlorate and Periodate

Abstract

Three types of PVC matrix membrane ion-selective electrodes (ISEs) are described. These are based on membranes containing nitron thiocyanate with 2-nitro-phenyl phenyl ether, 2-nitrophenyl phenyl ether alone and tetraphenylarsonium thiocyanate with 2-nitrophenyl octyl ether. Each type is conditioned and stored in 0.1M sodium thiocyanate. The first two electrodes have been evaluated for thiocyanate and perchlorate response and the best linear long range (linear range down to 2.5×10^?5M) response was obtained for perchlorate. The third electrode is suitable as a periodate ISE with linear calibration range down to 2×10^?4M. The plasticized (2-nitrophenyl phenyl ether) PVC electrode for thiocyanate and perchlorate had a much longer pH interference free range (1.5–12.5) than either of the other electrodes.     

Kinetics and mechanism of the cerium (IV) oxidation of α-Hydroxycycloalkanecarboxylic acids and cyclic alcohols in acidic perchlorate media

The Ce(IV) oxidation of the five-, six-, and seven-membered ring α-hydroxycycloalkanecarboxylic (C5, C6, and C7) acids to the corresponding cyclic ketones has been studied in acidic perchlorate media. The data may be interpreted in terms of a mechanism which involves fast preequilibrium complexation steps between Ce(IV) and the hydroxy acids, yielding two complexes which differ only by a proton. Complexation is followed by rate-determining decarboxylation to an intermediate (free radical?), which reacts quickly with another Ce(IV) to give products. Of the two proposed complexes, the protonated one is virtually unreactive. The C7 ring acid is oxidized more rapidly than the C6 acid, which, in turn, is oxidized faster than the C5 acid. For comparison, the oxidation of the five-, six-, and seven-membered ring cyclic alcohols to the corresponding cyclic ketones by Ce(IV) in acidic perchlorate was also studied. The order of reactivity is cyclopentanol > cycloheptanol > cyclohexanol. The differences in observed reactivities between the hydroxy acids and the cyclic alcohols are explained in terms of differences in transition state structure. The stepwise hydrolysis constants of Ce(IV) leading to Ce(OH)^3Plus; and Ce(OH)₂²⁺ were determined. In the case of the hydroxy acids, evidence is in favor of Ce(OH)³⁺ as the reactive ceric species in aqueous acidic perchlorate media.     

Cathodic and Adsorptive Stripping Votammetry of Naftazone

Abstract

Naftazone (1,2-naphthoquinone-2-semicarbazone) undergoes a reversible two-electron transfer in both acidic and alkaline solutions and also gives rise at pH > 7 to an anodic wave attributed to the formation of a mercury derivative. Cathodic stripping voltammetry is proposed to determine the compound down to 5 × 10^?9 M after accumulation of its mercury salt formed at -0.05V in a 0.05M sodium hydroxide solution. These results have been compared with those obtained by performing an adsorptive collection of the drug in a pH 3 sodium perchlorate solution. Concentrations ranging from 1 × 10^?7 to 2 × 10^?7M can be easily investigated, the detection limit being 7 × 10^?11M. The influence of several operational parameters has also been considered.     

Preparation and properties of the MIIIU2O7.5 polyuranates (MIII = Y,Tb, Dy,Ho, Er,Tm, Yb,or Lu)

The novel compounds of the M^IIIU₂O_7.5 type (with M^III being yttrium or lanthanides from terbium to lutetium) have been prepared via hydrothermal synthesis from hydrated uranium(VI) oxide and aqueous solutions of M(III) nitrates at 200°C. Composition and structure of the products have been studied by means of elemental analysis, high-temperature X-ray diffraction, and IR spectroscopy; the products thermal stability has been estimated.