A new class of isoquinoline alkaloids: The indenobenzazepines

The dark yellow indenobenzazepine alkaloids lahorine ($\text{1}$) and lahoramine ($\text{2}$) have been found in $\text{Fumaria}$$\text{parviflora}$ Lam. (Fumariaceae). In a transformation with biogenetic implications, treatment of the spirobenzylisoquinolines dihydrofumariline ($\text{4}$) and dihydroparfumidine ($\text{7}$) with methanesulfonyl chloride and triethylamine in dry THF, followed by iodine oxidation, provided $\text{1}$ and $\text{2}$, respectively.     

The role of various binding materials for trace elemental analysis of powder samples using laser-induced breakdown spectroscopy

Study of various binding materials like potassium bromide, poly(vinyl alcohol), starch, silver and aluminum has been carried out using laser-induced breakdown spectroscopy (LIBS). The role of matrix effects using these five binders on LIBS signal intensity was investigated for better performance of LIBS technique as a quantitative analytical tool. For comparative study of different binders, the signal intensity of different Mg lines at 518.3, 517.2, 383.8 and 279.5 nm wavelengths were recorded for pellets prepared with known concentrations of Mg in these binders. The influence of laser energy on ablated mass under different binding materials and its correlation with LIBS signal intensity has been explored. Optical scanning microscopy images of the ablated crater were studied to understand the laser ablation process. The study revealed that the binding material plays an important role in the generation of LIBS signal. The relative signal intensity measured for a standard Mg line (at 518.3 nm) were 735, 538, 387, 227 and 130 for potassium bromide, starch, poly(vinyl alcohol), silver and aluminum as binders, respectively. This indicates clearly that potassium bromide is better as a binder for LIBS studies of powder samples.     

Asymmetric alkylation of diarylmethane derivatives. Improved results using methoxyethoxy substituent

Alkylation of 2-methoxyethoxyphenyl phenyl methane using sec-BuLi and (−)-sparteine has been carried out in excellent yields and up to 94% ee. The best results were obtained in allylation reactions but methylation, ethylation, benzylation and trimethylsilylation have all been carried out with acceptable ee.     

Studies on thermal oxidation of chalcopyrite from Chitradurga,Karnataka State,India

When chalcopyrite is heated in air, up to 350? there is no marked change. Between 350 and 440?, surface material is oxidised to iron sulphate, CuSO₄ and Fe₂O₃, while in regions not accessible to oxygen the formation of Cu₅FeS₄, FeS and S takes place. From 440 to 500? oxidation and sulphation phenomena occur. Stable compounds between 500 and 650? are iron sulphate, CuSO₄ and Fe₄O₃, with a minor amount of 6CuO.Cu₂O indicated at 650?. After the decomposition of iron sulphate, CuSO₄ decomposes, first to CuO.CuSO₄ and then to CuO. By 750? the sulphur has been totally lost from all compounds, while the oxides of copper and iron partly react to form CuFe₂O₄. Final products of oxidation between 800 and 850? are CuO, CuFe₂O₄ and Fe₃O₄.     

Development of novel antioxidants: design,synthesis, and reactivity

We are attempting to develop novel synthetic antioxidants aimed at retarding the effects of free-radical induced cell damage. In this paper we discuss the design strategy and report the synthesis of seven novel antioxidants, including six catechols and a benzylic phenol. The bond dissociation enthalpy (BDE) for the most active (weakest) OH bond in each molecule was calculated by theoretical methods, as well as the BDE for the semiquinone radical. Reaction rates with the nitrogen-centered free radical DPPH(*) were measured in ethyl acetate. The log of k(DPPH) for bimolecular reaction correlated well with the primary BDE. The correlation between rate constants and calculated BDEs shows that the BDE is a good predictor of antioxidant activity with DPPH(*), suggesting that our design criteria are useful and that these compounds should undergo further testing in cell cultures and in animal models.     

N-Methylethylxanthocarbamate as an Analytical Reagent: Differential Pulse Polarographic Determination of Cadmium in Standard Alloys, Biological and Environmental Samples after Adsorption of its Complex on Microcrystalline Naphthalene

N-methylethylxanthocarbamate has been used as an analytical reagent for the determination of trace amounts of cadmium in standard alloys, biological, and environmental samples. The reagent has been found to form a water insoluble complex with cadmium. It is quantitatively adsorbed over microcrystalline naphthalene in the pH range 2.5 to 12.0. The metal complex is desorbed with HCl and cadmium determined with a differential pulse polarograph. The detection limit is 0.05 ppm (signal-to-noise ratio = 2) and the linearity is maintained in the concentration range 0.2–25 g/ml, with correlation coefficient of 0.9995 and a relative standard deviation of ±0.81%. Characterization of the electroactive process includes an examination of the degree of reversibility. Various parameters, such as the effect of pH, reagent concentration, amount of naphthalene, volume of aqueous phase, and the interference of a large number of metal ions on the determination of cadmium, have been studied in detail to optimize the conditions for its determination in various complex materials.     

Spectrophotometric studies on the complexation equilibria of Ni and Pb with 2-carboxy-2-hydroxy-5'-sulfo-formazylbenzene. Simultaneous determination of trace amounts of Ni and Pb

Spectrophotometric studies have been made to investigate the reaction of Nickel and Lead with 2-carboxy-2'-hydroxy-5'-sulfoformazyl-benzene (zincon) in 50%(v/v) ethanol-water at 25 degrees C and an ionic strength of 0.1 M NaClO4. A complete picture of the complexation equilibria in the pH range (4.2-12.0) for nickel and (1.9-11.5) for lead are presented. Simple, rapid, selective and sensitive methods for the spectro-photometric determination of nickel and lead has been developed based on the color reaction of their complexes with zincon. The methods allow the determination of 4.69 microg mL(-1) of nickel at pH = 6.3 (lambdamax = 665 nm) and 10.3 microg ml(-1) of lead at pH = 5.6 (lambdamax = 610 nm). The apparent molar absorptivities were epsilon = 1.3 x 10(4) L mol(-1) cm(-1) for nickel and epsilon = 0.6 x 10(4) L mol(-1) cm(-1) for lead. The interference of a large number of foreign ions and complexing agents has been studied. Thiosulphate, as masking agent allows the simultaneous determination of nickel and lead in the presence of high concentrations of copper. Ascorbic acid, sodium cyanide and or sodium fluoride provide the elimination of many other interferences. The methods have been applied successfully to the simultaneous determination of nickel and lead in an aluminium and non-ferrous alloy.     

One-Pot Convenient and High Yielding Synthesis of Dithiocarbamates

Summary. A convenient and high yielding method for the synthesis of diverse dithiocarbamates having various substituents including alkyl, aryl, heteroaryl, and alkylaryl at the thiol chain or at the amine chain or at both thiol and amine chains were developed by the one-pot reaction of mercaptans, amines, and bis(benzotriazolyl)methanethione in presence of amidine base under mild reaction conditions.     

Preparation and Properties of Aramid-Silica Hybrids with Inter-Phase Bonding Through (3-glycidoxypropyl)-trimethoxysilane

Nano-composites from aramid-silica system have been prepared via sol-gel process. Poly (phenyleneterephthalamide) copolymer chains were prepared by reacting a mixture of p- and m-phenylenediamines with terephthaloyl chloride in dimethylacetamide used as solvent. The sol-gel process in the polymer matrix was carried out through hydrolysis and condensation of a mixture of tetraethoxysilane and (3-glycidoxypropyl) trimethoxysilane. The latter was used to develop linkage, on one hand with silica network structure using alkoxy groups and on the other hand with aramid chains at its secondary amine groups through glycidal groups of silane. Mutual interaction between the two disparate phases aramid and silica network was thus created. Thin films of the composites containing different proportions of silica ranging from 5.0 to 25.0-wt% were cast by the solvent elution technique. The α-relaxation temperature associated with the glass transition was measured by the dynamic mechanical thermal analysis. The results showed an increase in the glass transition temperature from 328°C for the pure aramid to 352°C for the hybrid materials containing 25-wt% silica, an indicative of the increased interfacial interaction between the two phases. Films having relatively low silica content were flexible and transparent, but those with high silica content were opaque and brittle. These films were tested for their tensile strength, modulus and toughness. The mechanical strength of the composites as compared to the pure aramid increased initially but with further addition of silica the strength decreased. The initial increase can be explained due to increased interfacial interaction between the two phases, however agglomeration of silica particles was responsible for decreasing strength at higher silica contents.     

A comparative kinetic and mechanistic study of glutamic acid oxidation by acid permanganate in the absence and presence of sodium dodecyl sulphate

The kinetics and mechanism of glutamic acid (GCO₂H) oxidation by acid permanganate has been carried out in the absence and presence of sodium dodecyl sulphate (SDS). The surfactant enhances the reaction rate without changing the reaction mechanism. The overall rate expression for the reduction of Mn^VII may be written: