Synthesis and analytical properties of a chelating resin functionalised with bis-(N,N'-salicylidene)1,3-propanediamine ligands

A polystyrenedivinylbenzene-based macroreticular resin was functionalised with bis-(N,N'-salicylidene)1,3-propanediamine ligands and its analytical properties have been investigated. The pH dependence of metal resin chelation has been determined for Cu(II), Ni(II), Co(II), Zn(II), Fe(II), Mn(II), Pb(II), Cd(II) and Cr(III). Trace amounts of these metal ions were quantitatively retained on the resin at neutral pH and easily recovered by elution with 1 N hydrochloric acid. The resin exhibits good chemical stability and fast equilibration with the metal ion making it useful for rapid concentration of trace amounts of metal ions on the resin columns.     

Synthesis,Characterization and Properties of Single-Walled Carbon Nanohorns

Single-walled nanohorns (SWNHs) have been prepared by sub-merged arc discharge of graphite electrodes in liquid nitrogen. The samples were examined by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Nitrogen and boron doped SWNHs have been prepared by the sub-merged arc discharge method using melamine and elemental boron as precursors. Intensification of Raman D-band and stiffening of G-band has been observed in the doped samples. The electrical resistance of the SWNHs varies in opposite directions with nitrogen and boron doping. Functionalization of SWNHs through amidation has been carried out for solubilizing them in non-polar solvents. Water-soluble SWNHs have been produced by acid treatment and non-covalent functionalization with a coronene salt. SWNHs have been decorated with nanoparticles of Au, Ag and Pt. Interaction of electron donor (tetrathiafulvalene, TTF) and acceptor molecules (tetracyanoethylene, TCNE) with SWNHs has been investigated by Raman spectroscopy. Progressive softening and stiffening of Raman G-band has been observed respectively with increase in the concentration of TTF and TCNE.     

Numerical simulation of rapid pressurization and depressurization of a zeolite column using nitrogen

The required durations of pressurization and depressurization steps of a rapid pressure swing adsorption process are primarily governed by adsorbent particle size, adsorption kinetics, column pressure drop, column length to diameter ratio, and the valve constant of the gas inlet and outlet control valve attached to the adsorbent column. A numerical model study of the influence of these variables for an adiabatic LiX zeolite column is presented using pure N₂ as an adsorbate gas. An adsorbent particle size range of 200–350 μm was found to minimize (<1 s) the times required for the pressurization and depressurization steps.     

Complexometric determination of thallium(III) in pure solution,alloys, and complexes using semicarbazide hydrochloride as a releasing agent

A simple and accurate complexometric method is proposed for the determination of Tl(III) using semicarbazide hydrochloride as a releasing agent. In the presence of diverse metal ions, thallium is complexed first with a known excess of EDTA, and the surplus EDTA is then titrated with standard zinc sulfate at pH 5.0–6.0 (hexamine) using xylenol orange indicator. An excess of 5% aqueous neutral solution of semicarbazide hydrochloride is then added and the released EDTA is titrated against standard zinc sulfate solution. The method works well in the range 2–50 mg of Tl(III) with relative errors < 0.5%, standard deviations 0.05mg and coefficient of variation 0.4%. The method is applied for the determination of thallium content in complexes and alloy compositions     

Aromatics to polyquinanes: A general method for the construction of tricyclo[6.3.0.0]-and tricyclo[6.3.0.0]undecanes

The conversion of aromatic compounds to linear and angular triquinanes is described and involves a 5-exo-trig-allyl radical cyclization as the key reaction for constructing the strained ketones 9 and 18, which are then transformed into the quinanes 12 and 23, respectively.     

EPR/ENDOR study of an X-irradiated single crystal of: 1-triphenylphosphoranylidene-2-propanone: The role of hydrogen bonds in the trapping of radiogenic radicals

As shown from the crystal structure, the oxygen atom of Ph₃P=CH---C(O)CH₃ forms both intra and intermolecular hydrogen bonds. X-irradiation of this compounds produces a room-temperature-stable radical which was studied by single crystal EPR/ENDOR spectroscopy. Comparison of the experimental hyperfine couplings with those obtained from ab initio calculations shows that the radical cation Ph₃P⁺---CH=C(OH)CH₂ is formed under radiolysis. The principal directions of the hyperfine tensors indicate that, in this process, some of the hydrogen bonds are broken and that the radical undergoes a drastic reorientation around the Ph₃P---C bond.     

Oxidation of 2,6-di-tert-butylphenol with polymer anchored molybdenyl and vanadyl complexes

The oxidation of 2,6-di-tert-butylphenol with tert-butylhydroperoxide (Bu^tO₂H) has been studied using polymer (XAD₄) anchored salicylaldoxime, 1,3-propylene-bis-salicylaldimine and o-phenylene-bis-salicylaldimine complexes of molybdenum and vanadium in acetonitrile. The predominant products formed in the oxidation reactions were 2,6-di-tert-butylbenzoquinone (BQ) and 3,3′-5,5′-tetra-tert-butyldiphenoquinone (dPQ), whereas with some only 2,6-di-tert-butylbenzoquinone was formed. This is the first reported use of polymer anchored molybdenyl and vanadyl complexes in selective oxidation of 2,6-di-tert-butylphenol. Solvent plays an important role in this reaction. The effects of varying the ligand, metal and the support on the catalytic activity in the oxidation of 2,6-di-tert-butylphenol have been studied. With polymer anchored MoO₂(salpen), 81% of 2,6-di-tert-butylbenzoquinone was formed from 2,6-di-tert-butylphenol.     

Some novel photosensitive diacetylene diurethanes and their mixtures in common polymers

Some new octa-3,5-diynylene diurethanes were prepared using 3-butyn-1-ol, and all were found to be highly light-sensitive and to undergo topochemical polymerization on exposure to irradiation. The di-n-octyldiurethane was mixed with vinyl polymers such as poly(vinyl acetate) and poly(N,N-dimethylamino-ethyl methacrylate) and the mixtures were made into thin films by spin coating. The films were then irradiated by an electron beam to polymerize the diacetylene. The purple films thus obtained showed third-order nonlinear susceptibility, χ⁽³⁾, of the order of 10⁻¹⁰–10⁻¹¹ e.s.u.