Synthesis of cetyltrimethylammonium tribromide (CTMATB) and its application in the selective oxidation of sulfides to sulfoxides

The bright yellow crystalline cetyltrimethylammonium tribromide (CTMATB) reagent has been synthesized from the reaction of CTMAB and KBr with H₂MoO₄·H₂O, H₂O₂ and H₂SO₄ in the molar ratio 1:2:0.01:4:0.93. CTMATB selectively oxidizes a variety of dialkyl and alkyl aryl sulfides to the corresponding sulfoxides in high yields under mild conditions.     

A novel synthetic approach towards N-phenylsuccinimides from γ-lactam-2-carboxylic acid derivatives by reaction with CAN-NaBrO3

N-Arylsuccinimides have been synthesized by decarboxylative oxidation of N-aryl-γ-lactam-2-carboxylic acids with the dual oxidant CAN/NaBrO₃ in refluxing acetonitrile-water.     

Prospects for studying chemisorption kinetics using current fluctuations

The rates of surface catalytic reactions are, in principle, reflected in the frequency spectrum of adsorbate density fluctuations. These fluctuations change the incremental current (i.e., increment over the average current corresponding to the average surface coverage) noise due to electron transfer between the adsorbate and the substrate and to the scattering of the substrate electrons from the adsorbates. In an adiabatic limit, the incremental current noise is proportional to the conductivity modulation induced by the adsorbate density fluctuations and to the square of the applied voltage. Thus, the noise in the substrate current provides information about the surface reaction kinetics. This reaction may proceed either in equilibrium or in nonequilibrium. The adsorbate density spectrum has been calculated both in and out of equilibrium for two specific reactions. No major difference is found between the in and out of equilibrium cases. When these involve two-step processes, the adsorbate density correlation function is the sum of two decaying exponentials and the spectrum is the sum of two Lorentzians.     

Hydrolysis of schiff bases, 1: Kinetics and mechanism of spontaneous,acid, and base hydrolysis of N-(2/4-hydroxybenzylidene)-2-aminobenzothiazoles

The rate of hydrolysis of title schiff bases was studied in the pH range 4–13 in 10% dioxanewater system, CTAB, NaLS micellar solutions. The hydrolysis was found to be due to ‘water’ and ‘hydroxide’ reactions and hence the rate constants in different pH were computed and analyzed with an intermediate involving a water molecule being positioned with the help of 2-OH group and the thiazolyl C–N pi bond. The ‘hydroxide’ reaction was due to a direct nucleophilic attack of hydroxide ion at the aldimine linkage of the reactant. The influence of cationic and anionic micelles supports the mechanistic picture in the entire pH range.     

Chiral Salarg and its metal complex: unique extrinsic fluorophores

We present a fluorescence spectroscopic study of a chiral amino acid Schiff base ligand Salarg and its metal complex Mn-Salarg. This study reveals that the Salarg ligand and its metal complex have the properties of a typical extrinsic fluorophore. A detailed comparison has been made with the fluorescence spectroscopic properties of various other extrinsic and intrinsic fluorophores. It is suggested that Salarg and Mn-Salarg, which are economic, efficient, easy to synthesize and environment-friendly extrinsic fluorophores, might be used to label DNA and lipids respectively.     

Ge/Si photodetectors and group IV alloy based photodetector materials

Photodetectors using Si, Ge and their alloys with other group IV elements are of current interest for application in telecommunication as well as in optical interconnects. We have presented in this paper our work on resonant cavity enhanced Si/SiGe multiple Quantum Well and Ge Schottky photodetectors. Calculated values of external quantum efficiency for GeSiC based photodetectors are also reported. Tensile strained Ge layers grown with suitable barriers show direct gap type I band alignment. Predicted performance of photodetectors using strong Quantum Confined Stark Effect and Franz-Keldysh Effect in these structures and properties related to photodetection using these new materials are also described.     

Exposure to underground radon in and around Kolkata Municipal Corporation area: an exhaustive study

Air radon survey was carried out at different underground locations at Kolkata using radon monitor. Average radon concentration for basements was found to be 22.70 ± 1.12 Bq/m³ with maximum 59.00 ± 7.18 Bq/m³ and minimum 8.50 ± 3.14 Bq/m³. Average level for sub-ways was 23.05 ± 2.59 Bq/m³ fluctuating between maximum 39.00 ± 1.24 Bq/m³ and minimum 13.50 ± 1.78 Bq/m³. In comparison, open air background at basement entrance was 19.44 ± 1.06 Bq/m³ and subway entrance was 18.58 ± 1.14 Bq/m³. Annual effective dose was calculated to assess probable health risk. Radon concentration level and annual effective dose were found well below safe levels recommended by International Agencies WHO and UNSCEAR.

     

NaBH4‐I2 mediated chemoselective reduction of γ‐lactam and thio‐γ‐lactam in presence of gem‐dicarboxylates: An easy access to 1,3‐diaryl pyrrolidines

Substituted pyrrolidine derivatives were synthesized in high yield by NaBH₄/I₂ mediated chemoselective reduction of N‐aryl‐γ‐lactam and N‐aryl‐thio‐γ‐lactam‐2,2‐dicarboxylate. With excess NaBH₄/I₂, carbonyl functionality of the ester groups remained unchanged. J. Heterocyclic Chem., (2011).     

A novel access to bisformylated pyrroles via decarboxylation of N-aryl-γ-lactam-carboxylic acids under Vilsmeier reaction conditions

A simple methodology for the conversion of substituted N-aryl-γ-lactam 2/3-carboxylic acids to substituted N-aryl-diformylated pyrroles has been developed. Several γ-lactam 2/3-carboxylic acids were subjected to Vilsmeier reagent and substituted diformylated pyrroles are isolated in one-step process.