Chemometric analysis of groundwater quality data of alluvial aquifer of Gangetic plain, North India

Water quality data set from the alluvial region in the Gangetic plain in northern India, which is known for high fluoride levels in soil and groundwater, has been analysed by chemometric techniques, such as principal component analysis (PCA), discriminant analysis (DA) and partial least squares (PLS) in order to investigate the compositional differences between surface and groundwater samples, spatial variations in groundwater composition and influence of natural and anthropogenic factors. Trilinear plots of major ions showed that the groundwater in this region is mainly of Na/K-bicarbonate type. PCA performed on complete data matrix yielded six significant PCs explaining 65% of the data variance. Although, PCA rendered considerable data reduction, it could not clearly group and distinguish the sample types (dug well, hand-pump and surface water). However, a visible differentiation between the water samples pertaining to two watersheds (Khar and Loni) was obtained. DA identified six discriminating variables between surface and groundwater and also between different types of samples (dug well, hand pump and surface water). Distinct grouping of the surface and groundwater samples was achieved using the PLS technique. It further showed that the groundwater samples are dominated by variables having origin both in natural and anthropogenic sources in the region, whereas, variables of industrial origin dominate the surface water samples. It also suggested that the groundwater sources are contaminated with various industrial contaminants in the region.     

Conductance studies in amide-water mixtures. II. Sodium salts inN,N-dimethylformamide-water mixtures at 35°C

Conductance data for sodium nitrite, chloride, and acetate in water andN,N-dimethylformamide (DMF)-water mixtures (74.82D42.48) for the concentration range 0.001–0.04N, as well as the densities, viscosities, and dielectric constants of the solvent mixtures at 35°C, are reported. The data have been analyzed by the Fuoss (1975) equation. The existence of a maximum in the viscosity at a 13 mole ratio of DMF and water is indicated. The Walden products for all the three salts pass through a maximum while the equivalent conductances show a minimum with increasing DMF content. The maxima in the Walden product are attributed to the dehydration of ions by the cosolvent (DMF).Part I:Indian J. Chem. 14A, 1015 (1976).Deceased.     

Palladium-catalysed 5-endo-trig allylic (hetero)arylation

A palladium-catalysed intramolecular allylic (hetero)arylation strategy for the synthesis of fused cyclopentenes incorporated with all-carbon quaternary and spiro centres is described. The method is straightforward, shows broad scope, proceeds in synthetically useful yields, and provides a rare means to construct complex cyclopentanoids. The reaction is believed to involve a kinetically unfavourable 5-endo-trig carbocyclisation of the tethered (π-allyl)palladium system. Further, this method was successfully applied as the key step in the total synthesis of diterpene natural products taiwaniaquinone H and dichroanone.

A palladium-catalysed intramolecular allylic (hetero)arylation strategy for the synthesis of fused cyclopentenes incorporated with all-carbon quaternary and spiro centres is described.     

In situ assembled ZIF superstructures via an emulsion-free soft-templating approach

Assembling well-defined MOF superstructures remains challenging as it requires easily removable hard templates or readily available immiscible solutions for an emulsion-based soft-template approach. In this work, a single-step emulsion-free soft templating approach is reported to spontaneously prepare hollow ZIF-8 and ZIF-67 colloidosomes with no further purification. These superstructures can load different enzymes regardless of the size and charge with a high encapsulation efficiency of 99%. We envisage that this work will expand the repertoires of MOF superstructures by the judicious selection of precursors and the reaction medium.

An emulsion-free approach for the preparation of hollow ZIF-8 superstructures in a single step is established based on metal sulfate hydrates in methanol.     

First systematic investigation of C-H...Cl hydrogen bonding using inorganic supramolecular synthons: lamellar, stitched stair-case, linked-ladder, and helical structures

Using a group of six neutral M(II)Cl(2)-containing coordination compounds as building blocks, the first systematic investigation of C-H...Cl hydrogen-bonding interactions was performed. Single-crystal X-ray structural analyses of four new compounds (pseudo-tetrahedral Co(II) and Zn(II); distorted trigonal bipyramidal Zn(II)) authenticate the metal coordination geometry. To provide a unified view of the presence of noncovalent interactions in this class of compounds, we have re-examined the packing diagram of two previously reported compounds (a distorted square-pyramidal Cu(II) complex and a trans-octahedral Co(II) complex). The organic ligands of our choice comprise bidentate/tridentate pyrazolylmethylpyridines and an unsymmetrical tridentate pyridylalkylamine. This systematic investigation has allowed us to demonstrate the existence of versatile C-H...Cl(2)M interactions and to report the successful application of such units as inorganic supramolecular synthons. Additional noncovalent interactions such as C-H...O and O-H...Cl hydrogen bonding and pi-pi stacking interactions have also been identified. Formation of novel supramolecular architectures has been revealed: 2D lamellar (p-cyclophane) and 3D lamellar, 3D "stitched staircase" (due to additional hydrogen-bonding interactions by water tetramers, with an average O-O bond length in the tetramer unit of 2.926 A, acting as "molecular clips" between staircases), 3D linked ladder, and single-stranded 1D helix.     

Ammonium 2-(2'-lepidylazo)-1-naphthol-4-sulphonate as indicator in mercurimetric determination of halides

The use of ammonium 2-(2'-lepidylazo)-1-naphthol-4-sulphonate as indicator in titrimetric estimation of chloride, bromide and iodide with mercury(II) has been examined. The precision, accuracy and applicability of the procedures have been evaluated.     

Diphenylcarbazone as a sensitive reagent for the spectrophotometric determination of iridium(IV)

Summary The blue iridium(IV)-diphenylcarbazone complex, formed by heating the solutions in boiling water bath for 45 minutes, having an absorption maximum at 550 nm with maximum molar absorptivity of 1.90·10⁴l·cm^–1·mole^–1 (within 1.5 %) is recommended for the spectrophotometric determination of 40–240g iridium(IV) in 25–60 % ethanol medium. The complex formed in solutions at pH 3.5–7.0, after formation, is stable within the pH range 2.5 to 9.2. The effect of foreign ions has been investigated.

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Zusammenfassung Der blaue Iridium(IV)-diphenylcarbazon-Komplex entsteht beim Erwärmen der beiden Lösungen im siedenden Wasserbad für 45 Min. Er hat ein Absorptionsmaximum bei 550 nm und eine molare Extinktion von 1,90 × 10⁴ l·cm^–1·mole^–1. Diese Farbreaktion wird zur spektrophotometrischen Bestimmung von 40–240g Ir(IV) in 25-bis 60%igem Äthanol empfohlen. Der bei pH 3,5–7,0 entstandene Komplex ist zwischen pH 2,5 und 9,2 beständig. Der Einfluß von Fremdionen wurde untersucht.

     

Generalized mean-square amplitudes of vibration in some XY4 type ions (II)

The generalized mean-square amplitudes of vibration and mean amplitudes of vibration have been computed for CrO^3-₄, Mn¹⁸O^-₄, MoSe^2-₄ and WSe^2-₄ ions at three temperatures, T = 0°K, T = 298°K, T = 500°K, employing Cyvin's method. The results have been discussed in the light of atomic weight and electronegativity of the atom in the ionic system.     

Superconvergence error estimates of discontinuous Galerkin time stepping for singularly perturbed parabolic problems

Numerical Algorithms - A parabolic convection-diffusion-reaction problem is discretized by the non-symmetric interior penalty Galerkin (NIPG) method in space and discontinuous Galerkin (DG) method...