Ag+ ion transport studies in a polyvinyl alcohol-based polymer electrolyte system

Thick films of pure polyvinyl alcohol and polyvinyl alcohol doped with silver nitrate with different compositions have been prepared by solution cast technique. The FT-IR spectrum confirms the complexation process. The conductivity of the pure polyvinyl alcohol is of the order of 10⁻⁷ Sm⁻¹ at 90 °C, and its value increases by two orders of magnitude when doped with 20 wt% of AgNO₃. The activation energy, calculated from the Arrhenius plot for all compositions of the poly vinyl alcohol doped with silver nitrate, is between 0.24 and 0.35 eV. The migration energy for the ion in polymer electrolyte has been calculated from the modulus spectrum, and is in good agreement with the activation energy calculated from the Arrhenius plot. The modulus spectra indicate the non-Debye nature of the material.     

Spectrophotometric determination of mercury(II) as the ternary complex with rhodamine 6g and iodide

The formation of a pink-coloured product when rhodamine 6G is treated with tetraiodomercurate(II) is used to determine mercury (5–25 μg) in a final volume of 25 ml. The reaction occurs immediately over the pH range 1–7 and, when the system is stabilized with gelatin, the absorbance remains unchanged at 575 nm for at least 24 h. The few interfering ions can be masked by the addition of appropriate reagent solutions. The method is simple and reliable and provides a molar absorptivity of 7.0·10⁴ l mole^-1 cm^-1.     

Synthesis of novel 3-carboethoxy-6-methyl-4-oxo-4H-pyrimido[1′,2′:5,6]-[1,3,5]triazino[1,2-a]benzimidazoles

Reaction of 4-amino-2-methylbenzimidazo[1,2-a][1,3,5]triazines 2 with diethyl ethoxymethylenemalonate afforded 3-carboethoxy-6-methyl-4-oxo-4H-pyrimido[1′,2′:5,6][1,3,5]triazino[1,2-a]benzimidazoles 3 , a new ring system.     

Polyimides containing oxyethylene units

Four aromatic dinitro compounds containing oxyethylene units 1,2-bis(4-nitrophenoxy)ethane, bis(2)-(4-nitrophenoxy)ethyl ether, 1,2-bis(2)-(4-nitrophenoxy)ethoxy)ethane, and bis(2-(2-(4-nitrophenoxy)ethoxy)ethyl) ether were prepared by an aromatic nucleophilic substitution reaction that involved 1-fluoro-4-nitrobenzene and the appropriate oxyethylene glycol. Each of the dinitro compounds could be reduced chemically or catalytically to produce the diamines 1,2-bis(4-aminophenoxy)ethane, bis(2-(4-amino-phenoxy)ethyl ether, 1,2-bis(2-(4-aminophenoxy)ethoxy)ethane, and bis(2-(2-(4-aminophenoxy)ethoxy)ethyl) ether. Polymerization of the diamines was carried out in m-cresol with toluene as an azeotroping agent. Polymides derived from 5,5′-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis-1,3-isobenzofuradione exhibited good solubility in chlorinated solvents, glass transition temperatures as low as 140°C, as evidenced by viscous flow, and good thermal stability; a 5% weight loss generally occured at greater than 450°C. Isothermal aging studies conducted at 600°F(315°C) for 200 h indicated that weight loss is directly related to oxyalkylene chain length–10% for the shortest and 50% for the longest chain.     

Some aspects of tailoring flame retardancy in HET-acid-based flame retardants

HET acid was condensed with either ethylene glycol or 1,4-butanediol to yield the respective oligoesters. These oligoesters were characterized by molecular weight, measured by vapor-pressure osmometry. The degradation mechanism of oligoesters of HET acid with either ethylene glycol or 1,4-butanediol was elucidated. The thermal properties of these polyesters were studied using differential thermal analysis and thermal volatilization analysis. The mechanism of degradation was proposed on the basis of pyrolysis–gas chromatography studies, the degradation products being subsequently identified by mass spectrometry. It turned out that in the course of decomposition, hexachlorocyclopentadiene was formed, which is believed to be the active substance for flame retardance in these systems. The aspect of tailoring flame retardancy by changing the chemical environment, i.e., by using different diols, is discussed.     

(E)‐3‐(Benzo[b]thiophen‐2‐yl)‐2‐(3,4,5‐trimethoxyphenyl)acrylonitrile and (Z)‐3‐(benzo[b]thiophen‐2‐yl)‐2‐(3,4‐dimethoxyphenyl)acrylonitrile

The title compounds, C₂₀H₁₇NO₃S, (I), and C₁₉H₁₅NO₂S, (II), were prepared by the reaction of benzo[b]thiophene‐2‐carbaldehyde with (3,4,5‐trimethoxyphenyl)acetonitrile and (3,4‐dimethoxyphenyl)acetonitrile, respectively, in the presence of methanolic potassium hydroxide. In (I), the C=C bond linking the benzo[b]thiophene and the 3,4,5‐trimethoxyphenyl units has E geometry, with dihedral angles between the plane of the bridging unit and the planes of the two adjacent ring systems of 5.2 (3) and 13.1 (2)°, respectively. However, in (II), the C=C bond has Z geometry, with dihedral angles between the plane of the bridging unit and the planes of the adjacent benzo[b]thiophene and 3,4‐dimethoxyphenyl units of 4.84 (17) and 76.09 (7)°, respectively. There are no significant intermolecular hydrogen‐bonding interactions in the packing of (I) and (II). The packing is essentially stabilized via van der Waals forces.     

Magnetic properties of carbon nanosheets

Two-dimensional carbon nanosheets have been fabricated using inductively coupled radio frequency plasma-enhanced chemical vapour deposition. The structural properties of the nanosheets have been characterised using atomic force microscopy, scanning electron microscopy and X-ray diffractometer. The magnetisation of the samples was studied using vibrating sample magnetometer. The magnetisation of the nanosheets was found to be diamagnetic for fast synthesis processes (30 and 60 min). On the other hand, the nanosheets exhibited a weak ferromagnetic response for the slow (120 min) synthesis process. Energy dispersive spectrometry and atomic absorption spectroscopy confirmed that the magnetisation exhibited by the carbon nanosheets was an intrinsic property and that it was not due to contamination from the substrate. Raman spectroscopy studies revealed that the ferromagnetic carbon nanosheets have a higher ratio (1.20) of graphite peak (I _G) to disordered peak (I _D) than normally expected (0.75–0.90). Available data indicated that the magnetisation was due to the presence of structural disorders.     

Theoretical Studies on the Mechanistic Insertions of Singlet Methylene and Halomethylene into Polar S‒H Bonds of Methanethiol,Ethanethiol, 1-Propanethiol and 2-Propanethiol

Abstract

The insertion of ¹CH₂, ¹CHF, ¹CF₂,¹CHCl, and ¹CCl₂ into primary and secondary polar S?H bonds of methanethiol, ethanethiol, 1-propanethiol, and 2-propanethiol have been investigated at HF (Hartree–Fock), MP2 (Møller–Plesset Perturbation Theory), and DFT (density functional theory) levels using 6-31G (d, p) basis set. The insertions follow a two-step mechanism. The potential energy surface exploration identifies ylide-like structures undergoing the 1,2-sigmatropic hydrogen shift concertedly giving the thioether product. But ¹CF₂ forms weak complexes involving 1,2-hydrogen shift. The barrier height in the concerted mechanism varies with the type of carbene moiety and S?H bond. The initial interaction seems to be a function of HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies of thiols and carbenes, respectively. The natural bond orbital charge analysis showing a net charge flow from the substrate thiol to the reagent carbene at the transition states corroborates this fact.