The kinetics and thermodynamics of a novel efficient mixed water–1,4-dioxan solvent for the effective complexation of a neutral ruthenium complex with carbon monoxide at atmospheric pressure

Kinetic and thermodynamic investigations were performed for a mixed aqueous-organic, 1:1 (v/v) water–1,4-dioxane medium, which was found to be an efficient solvent for the interaction of a neutral dichlorotris(triphenylphosphine) ruthenium(II), RuCl₂(PPh₃)₃ complex with carbon monoxide at atmospheric pressure. During the interaction, RuCl₂(PPh₃)₃ dissociates to a neutral complex dichlorobis(triphenylphosphine) ruthenium(II), RuCl₂(PPh₃)₂, by losing a coordinated PPh₃ ligand and RuCl₂(PPh₃)₂ coordinates with CO to form an in situ carbonyl complex RuCl₂(CO)(PPh₃)₂. The in situ formed carbonyl complex RuCl₂(CO)(PPh₃)₂ was thoroughly characterized by equilibrium, spectrophotometric, IR, and electrochemical techniques. Under equilibrium conditions, the rate and dissociation constants for the dissociation of PPh₃ from RuCl₂(PPh₃)₃ were found to be favorable for the formation of the carbonyl complex RuCl₂(CO)(PPh₃)₂. The rates of complexation for the formation of RuCl₂(CO)(PPh₃)₂ were found to follow an overall second-order kinetics being first order in terms of the concentrations of both carbon monoxide and RuCl₂(PPh₃)₂. The determined activation parameters corresponding to the rate constant (ΔH^# = 35.9 ± 2.5 kJ mol⁻¹ and ΔS^# = −122 ± 6 J K⁻¹ mol⁻¹) and thermodynamic parameters corresponding to the formation constant (ΔH° = −33.5 ± 4.5 kJ mol⁻¹, ΔS° = −25 ± 8 J K⁻¹ mol⁻¹, and ΔG° = −25.7 ± 2.0 kJ mol⁻¹) were found to be highly favorable for the formation of the complex RuCl2(CO)(PPh3)2. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 359–369, 2008     

Generation of zonal magnetic fields by drift waves in a current carrying nonuniform magnetoplasma

It is shown that zonal magnetic fields (ZMFs) can be nonlinearly excited by incoherent drift waves (DWs) in a current carrying nonuniform magnetoplasma. The dynamics of incoherent DWs in the presence of ZMFs is governed by a wave-kinetic equation. The governing equation for ZMFs in the presence of nonlinear advection force of the DWs is obtained from the parallel component of the electron momentum equation and the Faraday law. Standard techniques are used to derive a nonlinear dispersion relation, which depicts instability via which ZMFs are excited in plasmas. ZMFs may inhibit the turbulent cross-field particle and energy transport in a nonuniform magnetoplasma.     

Oxidative and photooxidative degradation of poly(acrylic acid)

The oxidative degradation of poly(acrylic acid) (PAA), a water soluble polymer, was studied at various temperatures with different concentrations of persulfates, potassium persulfate (KPS), ammonium persulfate (APS) and sodium persulfate (SPS). The photodegradation of PAA was also examined with APS as oxidizer. The degraded samples were analyzed for the time evolution of molecular weight distribution by gel permeation chromatography. A theoretical model based on the continuous distribution kinetics was developed that accounted for the polymer degradation and the dissociation of persulfate. The rate coefficients for the oxidative and photooxidative degradation of PAA were determined from the parametric fit of the model with experimental data. The rate of degradation increased with increasing amount of persulfate in both oxidative and photooxidative degradation. The rate of degradation also increased with increasing temperature in the case of oxidative degradation.     

Vibrational spectroscopic investigation of poly(p‐phenylene sulfide)

Poly(p‐phenylene sulfide) (PPS) is an important polymer of engineering interest particularly useful in the electronics and automotive industries. Normal mode analysis including phonon dispersion has been performed to understand completely the vibrational spectra of this polymer. Various characteristic features of the dispersion curves have been reported. Crossing/Repulsion between various pairs of modes at certain phase values have been explained as arising due to internal symmetry in the energy momentum space. The heat capacity is calculated as a function of temperature via density‐of‐states in the range 220–360 K. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2353–2367, 2009     

High-Performance Thin-Layer Chromatography Analysis of Saccharin in Foods and Beverages

JPC – Journal of Planar Chromatography – Modern TLC - A simple, accurate, and inexpensive high-performance thin-layer chromatography (HPTLC) method has been established for analysis of...     

A quantum chemical study of reactions of DNA bases with sulphur mustard: a chemical warfare agent

Reactions of the sulphonium ion of sulphur mustard (SM⁺¹) at the N7, N3 and O6 sites of guanine, N7, N3 and N1 sites of adenine, O2 and N3 sites of cytosine and O2 and O4 sites of thymine were studied theoretically in gas phase and aqueous media employing density functional theory (DFT) and second order Møller–Plesset perturbation (MP2) theory. The B3LYP, B3PW91 and B1B95 functionals of DFT and the 6-31+G* and AUG-cc-pVDZ basis sets were used in the calculations. Basis set superposition error was treated using the counterpoise method by single point energy calculations at the B3LYP/6-31+G* level in gas phase. The present study explains the mechanism of alkylation of the DNA bases and shows that SM⁺¹ would form stable adducts at the endocyclic nitrogen sites of the DNA bases, and at the O6 site of guanine and the O2 site of cytosine. Formation of adducts at the N7 site of guanine and N3 site of adenine are found to be most favored and next most favored respectively, which agrees with experimental observations.     

Heronapyrroles A-C: farnesylated 2-nitropyrroles from an Australian marine-derived Streptomyces sp

Chemical analysis of a marine-derived Streptomyces sp. (CMB-M0423) isolated from beach sand off Heron Island, Australia, yielded three new members of the rare pyrroloterpene biosynthetic structure class. Identified by detailed spectroscopic analysis as the first reported examples of naturally occurring 2-nitropyrroles, heronapyrroles A-C (1-3) displayed promising biological activity-with low to submicromolar IC(50) activity against Gram-positive bacteria but no cytotoxicity toward mammalian cell lines.