Status report on the folded tandem ion accelerator at BARC

The folded tandem ion accelerator (FOTIA) facility set up at BARC has become operational. At present, it is used for elemental analysis studies using the Rutherford backscattering technique. The beams of¹H, ⁷Li, ¹²C, ¹⁶O and ¹⁹F have been accelerated up to terminal voltages of about 3 MV and are available for experiments. The terminal voltage is stable within ±2 kV. In this paper, present status of the FOTIA and future plans are discussed.     

Visible-light assisted one-pot preparation of aryl glyoxals from acetoarylones via in-situ arylacyl bromides formation: Selenium-free approach to acetoarylones oxidation

A novel visible-light (blue LEDs: hν = 425 ± 15 nm) photocatalyzed one-pot method for the synthesis of electronically diverse aryl glyoxals in good to excellent yields from acetoarylones and green regents such as air, vitamin C and dioxane dibromide has been described. In addition, an application of the current methodology has been demonstrated for the oxidation of monoamine oxidase-B inhibitors, i.e., 1-(4-((4-fluorobenzyl)oxy)phenyl)ethanone and 1-(3-((4-chlorobenzyl)oxy)phenyl)ethanone. This finding may serves as a valuable alternative to the traditional acetoarylones oxidation reactions conducted using selenium dioxide a harmful and unselective reagent known to simultaneously oxidize allylic, benzylic, CH₃ and so on.     

Synthesis, characterization and theoretical interpretation of vibrational spectra of poly(2-methylbut-2-enyl thiophene-3-carboxylate)

Electroactive thiophene substituted polyacetylene derivative, namely poly(2-methylbut-2-enyl thiophene-3-carboxylate) (PMT) was synthesized. First, novel acetylene monomer was synthesized by the reaction of 3-thiophenecarboxylic acid with propargyl bromide and then polymerized with a Rh catalyst to give the corresponding polymer. FTIR and FT-Raman spectra were recorded experimentally and used for complete normal mode analysis using Wilson’s GF matrix method and Phonon dispersion of poly(2-methylbut-2-enyl thiophene-3-carboxylate). The simple non-redundant set of internal coordinates and a simplified Urey-Bradley force-field approximation was employed in normal coordinate analysis and to calculate the potential energy distribution (PED) for each fundamental vibration. The PED contribution corresponding to each of the observed frequencies shows the reliability and accuracy of the spectral analysis. Apart from detailed assignments of modes, various characteristic features of dispersion curves have also been explained as arising due to internal symmetry in energy momentum space. Predicted values of intramolecular contribution to the heat capacity of this polymer calculated by density-of-states are also being reported.     

Structure–property correlations in lead silicate glasses and crystalline phases

Lead silicate glasses containing 40–65?mol% of PbO were prepared at two melt-quenching rates and characterized by X-ray diffraction, UV-Visible absorption spectroscopy, density, microhardness, thermo-mechanical analysis, differential scanning calorimetry and Raman scattering studies. On increasing the PbO concentration, density increases, glass transition temperature decreases and the optical absorption edge shifts towards longer wavelength. An intense optical absorption band was observed just below the absorption edge in glasses with 55?mol% and higher concentration of PbO. Dilatometric measurements show an unusual property that glasses do not show any abrupt increase in volume near the glass transition temperature but transform directly into the liquid state. Raman spectroscopy confirmed that the concentration of SiO₄ tetrahedra containing one or more NBOs increase with PbO mol%. Devitrification studies on lead silicate glasses found that samples with 40–45?mol% of PbO do not crystallize, whereas samples with higher PbO concentration produce multiple crystalline phases like PbSiO₃, Pb₃₃Si₂₄O₈₁, Pb₂SiO₄ and Pb₃Si₂O₇ on heat treatment.     

Kinetics and mechanism of osmium(VIII)-catalyzed oxidation of hypophosphite by hexacyanoferrate(III) in aqueous alkali

The kinetics of osmium(VIII)-catalyzed oxidation of hypophosphite with hexacyanoferrate(III) in alkaline medium has been studied. The rate is independent of the concentration of the oxidant. The order with respect to hydroxide ion is variable. Rate law (1) conforms with the experimental observations.