Gravimetric determination and radiochemical separation of palladium(II) with ethyl-α-isonitrosoacetoacetate

The use of ethyl-ga-isonitrosoacetoacetate (HEINA) for determination of palladium is reported. Pd can be estimated quantitatively from 0.5M to 2M HCl solution. Accurate results are obtained in 1M solution with an accuracy better than 1%. Decontamination values against platinum metals and other metals usually associated with Pd are greater than 10⁵. The time required for gravimetric determination is about an hour, for radiochemical separation about 25 min and the recovery is better than 90%.     

Modified pyrohydrolysis apparatus for the separation of fluorine and chlorine trace impurities from nuclear fuel samples for quality control analysis

A quartz pyrohydrolysis apparatus designed for the safe handling of pyrophoric carbide nuclear fuel samples while separating C1 and F trace impurities for quality control analysis is described. It has several advantages over the commonly used pyrohydrolysis apparatus. Performance of the apparatus during routine analysis of a large number of nuclear fuel samples has been found to be quite satisfactory.     

Chemoselective anti-Markovnikov hydroamination of α,β-ethylenic compounds with amines using montmorillonite clay

The catalytic activity of montmorillonite clays as a catalyst for the hydroamination of α,β-ethylenic compounds with amines was tested. Aniline and substituted anilines reacted with α,β-ethylenic compounds in the presence of catalytic amount of commercially available clay to afford exclusively anti-Markovnikov adduct in excellent yields. Aniline reacted with ethyl acrylate to yield only anti-Markovnikov adduct N-[2-(ethoxycarbonyl)ethyl]aniline (mono-addition product). No Markovnikov adduct (N-[1-(ethoxycarbonyl)ethyl]aniline and double addition product N,N-bis[2-(ethoxycarbonyl)ethyl]aniline were formed under selected reaction conditions. For a better exploitation of the catalytic activity in terms of increased activity and improved selectivity for the mono-addition product, the reaction parameters were optimized in terms of temperature, solvent, reactant mole ratio. Under optimized reaction conditions, montmorillonite clay K-10 showed a superior catalytic performance in the hydroamination of ethyl acrylate with aniline with a conversion of aniline to mono-addition product (almost 100% chemoselectivity) with a high rate constant 0.3414 min⁻¹ compared to the reported protocols. The dependence of conversion of aniline over different types of montmorillonite clays (K-10, K-20, K-30, Al-Pillared clay and untreated clay) has also been discussed. The activities of clay for the hydroamination of different aromatic and aliphatic amines have also been investigated. Under harsh reaction conditions (increased temperature and long reaction time) small amounts of di-addition products were observed. The kinetics data has been interpreted using the initial rate approach model.     

Track etching characteristics of polyester track detector and its application to uranium estimation in seawater samples

Garware Polyester Film, an indigenously available material has been evaluated systematically as a nuclear track detector for the detection of fission fragments. The relative fission track detection efficiency of this film was found to be (86.0±4.0)%. The bulk etch rate, determined by the gravimetric method, was found to be 0.75±0.05 μm/h. The track etch rate was determined as 15.0±1.5 μm/h. This detector was employed for the estimation of uranium in seawater samples and the results obtained were compared with the results obtained by using the commonly used Lexan detector. Uranium fractions after chemical separation from seawater samples were also analyzed by alpha-spectrometry and neutron activation analysis techniques and the results were compared with that obtained by the fission track method. Fission track method has the advantage, as it does not require any chemical separation. The indigenously available polyester film (polyethylene terphthalate) appears to be a good substitute of Lexan as nuclear track detector.     

Densities, viscosities, and ultrasonic velocity studies of binary mixtures of trichloromethane with methanol, ethanol, propan-1-ol, and butan-1-ol at T = (298.15 and 308.15) K

Densities, viscosities, and ultrasonic velocities of binary mixtures of trichloromethane with methanol, ethanol, propan-1-ol, and butan-1-ol have been measured over the entire range of composition, at (298.15 and 308.15) K and at atmospheric pressure. From the experimental values of density, viscosity, and ultrasonic velocity, the excess molar volumes (V^E), deviations in viscosity (Δη), and deviations in isentropic compressibility (Δκ_s) have been calculated. The excess molar volumes, deviations in viscosity and deviations in isentropic compressibility have been fitted to the Redlich-Kister polynomial equation. The Jouyban-Acree model is used to correlate the experimental values of density, viscosity, and ultrasonic velocity.     

Synthesis of the C17-C25 subunit of lasonolide A utilizing a Tsuchihashi-Yamamoto type rearrangement

An efficient synthesis of the C₁₇-C₂₅ subunit resident in (−)-lasonolide A is reported herein. The key reaction features that were utilized include a Tsuchihashi-Yamamoto type rearrangement and Molander-Reformatsky SmI₂ mediated intramolecular aldol reaction sequence. Lastly, a diastereoselective target oriented β-C-glycoside formation sequence via an oxocarbenium reduction completed the stereochemistry required for the completion of the C₁₇-C₂₅ segment of (−)-lasonolide A.     

Polyaniline nanoparticles prepared in rodlike micelles

The effect of aniline hydrochloride (AHC) on the size and shape of sodium dodecyl sulfate (SDS) micelles has been investigated by dynamic light scattering. A monotonic decrease in the diffusion coefficient of the micelles was observed with an increase in AHC at fixed SDS concentration. This was ascribed to prolate ellipsoidal growth of the micelles due to decrease of the effective headgroup area/molecule by adsorption of AHC on SDS micelles. The length of the micelles can be tuned by controlling the ratio of concentrations of AHC to SDS. Polymerization of aniline in micelles of different sizes leads to the formation of colloidal polyaniline with variable sizes. A direct correlation between size ofmicelles and size ofpolyaniline particles was observed. Combination of static and dynamic light scattering experiments reveal that the conformations of the polymer do not change significantly with size of the colloid.     

Heteropoly acid encapsulated SBA-15/TiO2 nanocomposites and their unusual performance in acid-catalysed organic transformations

The preparation of SBA-15/TiO(2) nanocomposites with different loadings of Keggin-type 12-tungstophosphoric acid (TPA) nanocrystals in their mesochannels through a simple and effective vacuum impregnation method is reported for the first time. The catalysts have been characterised by various sophisticated techniques, including XRD, HRSEM, and TEM. It has been found that the acidity and the textural parameters of the nanocomposites can be controlled by simply changing the loadings of TPA and TiO(2) or the calcination temperature. TPA and TiO(2) loadings of 15 and 22.4 wt %, respectively, and a calcination temperature of 1123 K have proved to be optimal for obtaining mesoporous nanocomposite materials with the highest acidity. Moreover, the activities of these catalysts in promoting hydroamination as well as Mannich and Claisen rearrangement reactions have been extensively investigated. The results show that the amount of TPA has a great influence on the activity of the nanocomposites in all of the reactions studied. The effects of other reaction parameters, such as temperature and reaction time, on the conversion and product selectivity have also been studied in detail. A kinetic analysis of the formation of the products under various reaction conditions is presented. It has been found that the activity of the nanocomposite composed of 15 wt % TPA deposited on 22.4 wt of TiO(2) on SBA-15 in promoting the studied reaction is remarkably higher than the catalytic activities shown by pure TPA, TiO(2)-loaded SBA-15, or TPA-loaded SBA-15. The results obtained have indicated that the acidity and the structural control of the nanocomposite materials are highly critical for obtaining excellent catalytic activity, and the presented highly acidic nanocomposites are considered to show great potential for use as catalysts in promoting many acid-catalysed organic transformations.     

Triphenyl borate catalyzed synthesis of amides from carboxylic acids and amines

Herein we report triphenyl borate as a new catalyst for synthesis of amides by catalytic condensation of carboxylic acids and amines. Our protocol is applicable for synthesis of wide range of amides furnishing excellent yields up to 92%. In addition developed method requires low catalyst loading, short time, less amount of solvent, works under air atmosphere and notably no need of azeotropic reflux using special Dean Stark apparatus or molecular sieves.     

Potentiometric studies on aqueous fluoride complexes of actinides: Stability constants of Th(IV)-, U(IV)-, Np(IV)- and Pu(IV)-fluorides

The extraction behaviour of Th(IV) and U(VI) in extraction chromatography has been investigated on the basis of partition and infrared studies. The stationary phase was purified undiluted TBP supported on Amberlite XAD-4 and the mobile phase was nitric acid. The results have shown that the equilibria for the extraction of Th(IV) and U(VI) by the TBP/XAD-4 resin agreed very closely with those in solvent extraction.