On the Reactivity of Metal and Organometallic Halides and Pseudohalides Towards Stannosiloxane (Ph3Sn-O-SiPh3)

Abstract

Interactions of HgX₂ (X = Cl, Br, I, SCN, CN, NCO), SbCl₃, TeCl₄, and PhTeCl₃ with Ph₃Sn-O-SiPh₃ at room temperature have been found to proceed with the simultaneous cleavage of Sn-O and Si-O bonds, invariably yielding Ph₂SnO, Ph₃SiX, and the corresponding organo-mercury, -antimony, and -tellurium derivatives. The course of the reactions suggests the instability of the Sn-O-M (M = Hg, Sb, Te) system.

GRAPHICAL ABSTRACT      

Separation and Analysis of Nucleic Acids and Their Constituents by Ion-Exclusion and Ion-Exchange Column Chromatography

The recent commercial development of high pressure liquid chromatographic instruments, and the availability of small and uniformly sized resin beads has enhanced the role of column chromatography for the rapid assay of nucleic acid components. A major advancement in the purification and analysis has been due to the recent demonstration that the ion exclusion is more or equally effective than the ion exchange as a separation principle for the resolution of purine and pyrimidine bases, nucleosides, deoxynucleosides and nucleotides^1–3. This article deals with the recent applications of separation principles that have been employed for the separation of nucleic acid constituents. The reader is referred to two review articles of Cohn for the earlier works on this subject^{4, 5}. Separations by chromatography and electrophoresis on paper and thin layers are not described here; several monographs and review articles are available in the literature^6–12.The reader is also referred to a recent methodological study for the base analysis of ribopolynucleotides by chemical tritium labeling which utilizes two dimensional chromatography on thin layers of cellulose as a separation means^{13, 14}.     

Mild Organic Ammonium Tribromide–Mediated Regioselective Ring Opening of Epoxides with Alcohols,Water, Acetic Anhydride,and Amines Under Solvent-Free Reaction Conditions

Organic ammonium tribromide (OATB), N-methylpyrrolidine-2-one hydrotribromide (MPHT) was found to be an efficient catalyst for the regioselective ring opening of epoxides with various nucleophiles under solvent free conditions. This procedure occurs under neutral and mild reaction conditions with out adding any additive and afforded high yields of products.

Use of ultra-filtration in organic-rich groundwater for the physical separation of thorium

During this work, size fractionation technique “ultra filtration” is used in physical speciation of thorium in organic rich groundwater. Laboratory simulated experiments were carried out to study the physical speciation of thorium in aquatic environment having elevated level of dissolved humus material classified as dissolved organic carbon (DOC). Samples were collected from organic rich environment having DOC in the range of 50–60 µg mL^?1. Th(IV) ions are extremely particle reactive having K _d value of the order of 10^5–6, hence to avoid adsorption on suspended particulate matter, spiking of the solution with Th(NO₃)₄ was carried out in ground water samples after filtering through 450 nm pore size using suction filtration. Particles in dissolved state (colloids) ranging between <450 and >220 nm were separated using suction filtration assembly having a membrane with a pore diameter of 220 nm. Thereafter, solution was sequentially passed through the ultra-filtration membranes having pore diameters of 14 nm [300 k NMWL (nominal molecular weight limit)], 3.1 nm (50 k NMWL), 2.2 nm (30 k NMWL), 1.6 nm (10 k NMWL) and 1.1 nm (0.5 k NMWL) by using “Stirred Ultra-filtration Cells”, operating in concentration mode. Thorium has only one stable oxidation state i.e. IV, under all redox conditions in natural waters and therefore, its speciation is dominated by its interaction with various fractions of DOC. Experimental results show 50–60 % of the spiked Th is in association with fraction enriched with particles of 10 k NMWL (1.6 nm) followed by fraction enriched with particle of 0.5 k NMWL and <220 nm.     

Trash GGBFS-based geopolymer as a novel sunlight-responsive photocatalyst for dye discolouration

In this study, we report a waste material-ground granulated blast furnace slag (GGBFS) as a low cost geopolymer, hybridised with ZnO to form a novel and efficient photocatalyst capable of discolouring textile wastewater. GGBFS is a waste material in an iron industry. Methylene blue was used as the probe dye and natural sunlight was used for activation of the photocatalyst. It was observed that under the experimental conditions, ZnGP-40 exhibited twice the discoloration efficiency than conventionally used ZnO or TiO₂. This enhanced performance is majorly attributed to increased surface area of ZnO when strewn in the GGBFS matrix. The photocatalysts were characterized by SEM, TEM, PSA, TGA, BET and UV–Vis/NIR. The effect of photocatalyst loading, speed of agitation and solar insolation has also been studied. Since this study has been performed in direct sunlight, it exhibits a realizable application of solar energy in the treatment of wastewater.     

Kaolin-catalysed one-pot synthesis of thiophene containing aminonaphthols under solvent-free condition and their in vitro anticancer and antioxidant activity

Research on Chemical Intermediates - An efficient and eco-friendly synthetic protocol via a one-pot three-component reaction to yield thiophene containing aminonaphthols (Betti bases) is reported....     

Preparation and characterization of nanosize nickel-substituted cobalt ferrites (Co1−xNixFe2O4)

Nanosize nickel-substituted cobalt ferrites were prepared using aerosol route and characterized by TEM, XRD, magnetic and Mössbauer spectroscopy. The particle size of as obtained samples was found to be ∼10 nm which increases upto ∼80 nm on annealing at 1200 °C. The unit cell parameter ‘a’ decreases linearly with the nickel concentration due to smaller ionic radius of nickel. The saturation magnetization for all the samples after annealing at 1200 °C lies in the range 47.6-84.5 emu/g. Room temperature Mössbauer spectra of as obtained samples exhibit a broad doublet, suggesting super paramagnetic nature of the sample. The broad doublet is further resolved into two doublets corresponding to the iron atoms residing at the surface and internal regions of the particle. The samples annealed at 1200 °C showed broad sextet, which is resolved into two sextets, corresponding to tetrahedrally and octahedrally coordinated Fe cations. Cation distribution calculated using XRD and Mössbauer data indicates a decrease in Fe³⁺(oct.)/Fe³⁺(tet.) ratio with increasing nickel concentration.     

Comment on “Effect of annealing temperature on structure, magnetic properties and optical characteristics in Zn0.97Cr0.03O nanoparticles” by Liu et al., [Appl. Surf. Sci. 256 (2010) 3559]

The authors of a recent paper (Appl. Surf. Sci. 256 (2010) 3559) studied the effect of annealing temperature on structural, magnetic and optical properties in Cr-doped zinc oxide (Zn_0.97Cr_0.03O) nanoparticles synthesized by sol-gel method. The authors have verified that Cr ions, in 3+ valence state, substitute the Zn ions in the ZnO lattice. They concluded that the ferromagnetism observed in the samples is an intrinsic property of the Cr-doped ZnO. However, we noticed an unusual point in this article. The Cr 2p XPS spectrum shown by them is against the general trend of the 2p XPS spectra of the transition metals. In this light, we re-measured the high-resolution 2p XPS spectrum of Cr for a 3% Cr-doped ZnO sample that is entirely different than theirs. The spectrum presented by them therefore demands proper interpretations or it might mislead the researchers in this developing field.     

Using path sampling to build better Markovian state models: predicting the folding rate and mechanism of a tryptophan zipper beta hairpin

We propose an efficient method for the prediction of protein folding rate constants and mechanisms. We use molecular dynamics simulation data to build Markovian state models (MSMs), discrete representations of the pathways sampled. Using these MSMs, we can quickly calculate the folding probability (P(fold)) and mean first passage time of all the sampled points. In addition, we provide techniques for evaluating these values under perturbed conditions without expensive recomputations. To demonstrate this method on a challenging system, we apply these techniques to a two-dimensional model energy landscape and the folding of a tryptophan zipper beta hairpin.     

An expedient protocol for conversion of olefins to α-bromo/iodoketones using IBX and NBS/NIS

A variety of olefins have been shown to undergo conversion to the corresponding α-bromo/iodoketones when reacted with NBS/NIS and IBX in DMSO at room temperature. While the reaction is found to occur rapidly with e-rich arylolefins leading to the corresponding haloketones in 65-95% yields in 0.3-3.0 h, those containing e-withdrawing groups are found to yield diketones concomitantly, such that the latter are the exclusive products over extended duration of the reactions.