A novel and faster route for the synthesis of polyether-polycarbonate from carbon dioxide and epoxide through microwave irradiation

The purpose of this study was to investigate the utilization of CO₂ in order to obtain polyether-polycarbonate by the co-polymerization of epoxide with CO₂ using microwave irradiation. Double metal cyanide containing Zn with Co, Fe(II), Fe(III) and Ni has been utilized as a catalyst for the co-polymerization reaction. The effect of microwave power, catalyst amount and types of catalysts has been studied. The microwaves were found to be successful in the synthesis of polyether-polycarbonate in a shorter reaction time with higher turnover numbers than those in conventional methods.     

Zinc oxide nanoparticles-based electrochemical sensor for the detection of nitrate ions in water with a low detection limit—a chemometric approach

We report for the first time a cyclic voltammetric nitrate sensor with a low detection limit based on the immobilization of zinc oxide nanoparticles on the surface of the platinum working electrode using chitosan membrane. Cyclic voltammetric data demonstrated that zinc oxide nanoparticles can electrochemically reduce nitrate ions to ammonium ions with high conductivity. In order to estimate electroanalytical parameters for each of the nitrate concentrations, Gaussian and Lorentzian curve fitting algorithms were performed on cyclic voltammetric data. Among them, the best analytical performance results were obtained with Gaussian calibration linear model. The zinc oxide modified platinum electrode showed a linear response to nitrate ions over a concentration range from 0.1 to 2.0 mM with a low detection limit and high sensitivity of 10 nM and 39.91 μA/cm² mM, respectively. The nitrate ion concentrations in drinking water samples were determined using Gaussian calibration linear model and the predicted, added nitrate ion concentration values showed good correlation.     

Synthesis,structural characterization and catalytic activity study of Mn(II), Fe(III), Ni(II), Cu(II) and Zn(II) complexes of quinoxaline-2-carboxalidine-2-amino-5-methylphenol: Crystal structure of the nickel(II) complex

Five new transition metal complexes [MnL(OAc)]·H₂O (1), [FeLCl₂] (2), [NiL₂]·H₂O (3), [CuLCl] (4) and [ZnL₂]·2H₂O (5) have been synthesized using a tridentate Schiff base ligand, HL (quinoxaline-2-carboxalidine-2-amino-5-methylphenol) and the complexes have been characterized by physicochemical and spectroscopic techniques. The spectral analyses reveal an octahedral geometry for 3, square pyramidal structure for 2 and square planar structure for 4. Analytical and physicochemical data indicate tetrahedral structure for 1 and octahedral structure for 5. The crystallographic study reveals that [NiL₂]·H₂O shows distorted octahedral geometry with a cis arrangement of N₄O₂ donor set of the bis Schiff base and exhibits a two-dimensional polymeric structure parallel to [0 1 0] plane. The complexes were screened for catalytic phenol hydroxylation reaction. Coordinatively unsaturated manganese(II), iron(III) and copper(II) complexes were found to be active catalysts. The poor catalytic activity of the nickel(II) complex is due to coordinatively saturated octahedral nature of the complex. Maximum conversion of phenol was observed for the copper(II) complex and the major product was catechol.     

Characterization of DNA immobilized on electrochemically prepared conducting polypyrrole-polyvinyl sulfonate films

The article describes the adsorption characteristics of DNA onto electrochemically generated polypyrrole-polyvinyl sulfonate (PPY-PVS) films obtained as a function of pH. Adsorption on PPY doped with an anion proceeds by anion exchange, and since DNA possesses a fixed negative charge owing to PO ₄ ⁻ , it favors a very strong binding displacing PVS with favorable energetic interactions. Characterization of adsorbed DNA onto the PPY-PVS films was carried out by ultraviolet-visible, Fourier transform infrared spectroscopy, and cyclic voltammetric studies.     

Bioactive isoquinoline alkaloids from Cissampelos pareira†

The phytochemical and biological investigation of Cissampelos pareira leads to the isolation of one new isoquinoline alkaloid (7) along with six known isoquinoline alkaloids, namely, magnoflorine (1), magnocurarine (2), cissamine (3), curine (4), hayatinine (5) and cycleanine (6). Magnoflorine (1) and magnocurarine (2) were isolated for the first time from C. pareira. A new, rapid, simple and sensitive UPLC method was developed for simultaneous quantification of five pure compounds (1–5). Seasonal variation study revealed higher content of these compounds during the rainy season. The chloroform (CPCF) and n-butanol (CPBF) fractions showed cytotoxic efficacy against KB cells. Among pure compounds, hayatinine (5) was found to be most active against KB and A549, while, cycleanine (6) against KB cells.     

EPR and optical absorption study of Cr-doped tetramethyl ammonium cadmium chloride single crystals

EPR study of Cr³⁺-doped tetramethyl cadmium chloride (TMCC) single crystals is carried out at room temperature. The crystal field and spin-Hamiltonian parameters are evaluated from the resonance line positions of different lines observed in the EPR spectra. The g and D parameter values are found to be g=1.9741±0.0002 and D=553±2×10⁻⁴ cm⁻¹, respectively. EPR data indicate that the site symmetry of Cr³⁺ ion in the crystal is distorted octahedron. Cr³⁺ ions enter the lattice substitutionally replacing Cd²⁺ sites and bind to the neighboring extra Cd vacancies necessary for charge compensation. The optical absorption spectra are measured in 195–925 nm wavelength range at room temperature. From optical study the energy values of different orbital levels are estimated. Further, the bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed. The values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are obtained to be B=722, C=2845, Dq=2043 cm⁻¹, h=1.015 and k=0.21.     

Study of vibrational spectra of polyaniline doped with sulfuric acid and phosphoric acid

Vibrational spectra of insulator emeraldine base (EB) form of polyaniline and electrical conductive sulfuric acid-and phosphoric acid-doped emeraldine salts (ES) were studied in the region of 4000-400 cm⁻¹ at ambient temperature by Fourier transform infrared spectroscopy. Infrared transmittance spectra of EB and ES were investigated to understand the bonding behavior of different organic and inorganic groups present in the polymeric chains and their structural variations on protonation by sulfate or phosphate ion inclusion in the polymer salt network. These studies revealed the para-coupling of deformed disubstituted benzenoid (B) and quinoid (Q) rings with ends capped predominantly by (B4Q1) units. The deformation of B and Q rings was confirmed by the appearance of many weak bands, very weak bands, and satellite structures in strong transmittance peaks of polymeric chain-constituting groups. Protonation takes place at the nitrogen sites of Q rings and forms semiquinone radical ions in ES. The vibrational bands pertaining to B rings, Q rings, B4Q1 units, semiquinone segment, sulfate ions, and phosphate ions were observed and assigned from these measurements. The shift in peak position of some bands with gain or loss in intensity and appearance of some new bands were observed in sulfuric acid-and phosphoric acid-doped ES spectra. These variations are attributed to the formation of new structural groups in ES on protonation and a change in crystalline field by sulfate and phosphate ion doping for crosslinking the polymeric chains.     

The synthesis of 2- and 6-0-p-Coumaroyl and 6-0-p-hydroxybenzoyl arbutin derivatives

The Synthesis of 2 and 6-0-p-Coumaroyl and 6-0-p-hydroxybenzoyl derivatives of arbutin isolated from the leaves ofGrevillea robusta andHakea saligna is described.

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Synthese von 2- und 6-0-p-Cumaroyl- und 6-0-p-Hydroxybenzoyl-Derivaten des Arbutins

Zusammenfassung Die Synthese der im Titel genannten Derivate von Arbutin, das aus den Blättern vonGrevillea robusta undHakea saligna isoliert wurde, ist beschrieben.

     

Synthesis of 25-oxygenated D:A-friedooleananes from D:A-friedoolean-7β -ol

D:A-Friedoolean-25-ol ( ) and 25-al ( ) have been synthesised from D:A-friedoolean-7β -ol ( ). Substituted tetrahydrofuran rings are opened up on treatment with lithium in ethylene-diamine to yield the corresponding saturated alcohols.     

Kinetics and mechanism of oxidation of aliphatic alcohols by tetrabutylammonium tribromide

Oxidation of nine primary aliphatic alcohols by tetrabutylammonium tribromide (TBATB) in aqueous acetic acid leads to the formation of the corresponding aldehydes. The reaction is first order with respect to TBATB. Michaelis-Menten type kinetics is observed with respect to alcohols. The reaction failed to induce the polymerization of acrylonitrile. Tetrabutylammonium chloride has no effect on the reaction rate. The proposed reactive oxidizing species is the tribromide ion. The oxidation of [1,1-²H₂]ethanol exhibits a substantial kinetic isotope effect. The effect of solvent composition indicates that the rate increases with increase in the polarity of the solvent. The reaction is susceptible to both polar and steric effects of substituents. A mechanism involving transfer of a hydride ion in the rate-determining step has been proposed.