Fe(0)-mediated synthesis of tri- and tetra-substituted olefins from carbonyls: an environmentally friendly alternative to Cr(II)

Fe(0) was investigated as a cost-effective, environmentally friendly alternative to Cr(II) for the olefination of carbonyls by activated polyhalides. In many instances, Fe(0) was equivalent or superior to Cr(II). Notably, Fe(0), but not Cr(II), proved compatible with a wide range of functionality, inter alia, unprotected phenol, aryl nitro, carboxylic acid, and alkyl nitrile. A surprising reversal of stereoselectivity for aldehydes versus ketones was observed using both metals. The resultant alpha-halo-alpha,beta-unsaturated or alpha,beta-unsaturated carboxylic acids, esters, and nitriles are common structural elements in numerous compounds of interest as well as key intermediates in the preparation of other functionality.     

Spectrophotometric Determination of Rhenium(IV) with Thiocyanate,TX-100 and N,N′-Diphenylbenzamidine

A spectrophotometric method to determine rhenium(IV) at trace level is based on the extraction of Re(IV)-SCN^? complex in sulphuric acid media with N,N′-diphenylbenzamidine(DPBA) in presence of a non-ionic surfactant triton X-100 (TX-100) in chloroform. The complex shows maximum absorbance at 435 nm with amolar absorptivity value of 4.24 × 10⁴ L mol^?1 cm^?1 at an acidity range 3.5-6.5 M H₂SO₄. The method followed Beer's Law for the system Re(IV)-SCN^?(TX-100)-DPBA upto 4.0 μg Re(IV) mL^?1. The detection limit of the method is 5 ppb. None of the tested foreign ions, except molybdenum(VI), interfere with the determination of rhenium. The interference due to molybdenum could effectively be removed by prior precipitation with oxine. The effect of various analytical parameters on the extraction of the metal are discussed.     

Asymmetric stochastic localization in geometry controlled kinetics

We consider the motion of Brownian particles confined in a two-dimensional symmetric bilobal enclosure with uneven cross section. Varying cross section of the confinement results in an effective entropic potential in reduced dimension. By employing two external noise forces, one additive and another multiplicative along x direction, we demonstrate that a correlation between them causes a symmetry breaking of entropic stability, i.e., a difference in relative stability of two lobes. This leads to an asymmetric localization of population in the stationary state. A two-state model is proposed to explain the asymmetric localization of population due to entropic diffusion.     

Simple Chemical Route Synthesis of Fe2O3 Nanoparticles and its Application for Adsorptive Removal of Congo Red from Aqueous Media: Artificial Neural Network Modeling

Nanocrystalline Fe₂O₃ powder was synthesized by a simple chemical route involving FeCl₃ and NaOH. The Fe₂O₃ powder thus prepared was characterized using x-ray diffraction study, scanning electron microscopy, and Fourier transform infrared spectroscopy. The adsorption properties of crystalline Fe₂O₃ powder have been investigated with an aim to explore a possible low cost and efficient way to remove Congo red (CR) from waste water. Fe₂O₃ powder was found as an excellent adsorbent for CR from aqueous medium. Adsorption capacity as much as 203.66 mg g^?1 is reported at room temperature. Effect of different experimental parameters such as reaction pH, initial CR dye concentration, adsorbent dose, and reaction temperature were studied on adsorption capacity of Fe₂O₃ powder and modeled by artificial neural network (ANN). Optimal ANN structure (4–5–1) shows minimum mean squared error (MSE) of 0.00235 and determination coefficient (R²) of 0.991 with Levenberg–Marquardt algorithm. Isotherm analysis of experimental data exhibited better fit to the Langmuir isotherm. The adsorption process was found to follow second-order kinetics as depicted by the analysis of experimental results. Thermodynamic study shows that the adsorption process is endothermic, spontaneous, and thermodynamically favorable in the temperature range of 27°C to 60°C.     

Dynamics of electronic motion in hydrogen atom under parallel strong oscillating magnetic field and intense laser fields

The mechanism of ionization of an H atom interacting with intense laser electric fields is altered when a strong, oscillating magnetic field is applied along a direction parallel to the laser field. In this first study, these two strongly nonperturbative situations have been combined together and the corresponding time‐dependent (TD) Schrödinger equation has been numerically solved without using any basis set. The electric field arising out of the magnetic field and the magnetic field arising out of the laser electric field are found to be negligibly small, thereby not affecting the results. There are two main, apparently counter‐intuitive results from this study of parallel fields of the same frequency but different field strengths: (1) In presence of an oscillating magnetic field, the ionization rate due to the laser field diminishes, and (2) increasing the laser intensity, keeping the magnetic field strength the same, makes the electron density ionize with a lesser rate, in contrast to the situation with intense lasers in the absence of a strong TD magnetic field. © 2015 Wiley Periodicals, Inc.     

Langmuir-Blodgett films of 9-phenyl anthracene molecules incorporated into different matrices

This communication reports the surface pressure (pi) versus area per molecule (A) isotherm characteristics of the mixed films of 9-phenyl anthracene (PA) in stearic acid (SA) and polymethyl methacrylate (PMMA) matrices, at the air-water interface. The mixed Langmuir films at the air-water interface have been observed to be easily transferred onto solid substrates to form uniform Langmuir-Blodgett films. By changing various parameters, namely molefraction, surface pressure of lifting and number of layers, the mixed Langmuir-Blodgett (LB) films of various types have been fabricated successfully and their spectroscopic characteristics have been reported. From the isotherm characteristics and the area per molecule versus molefraction plot, it is evident that the PA molecules are successfully incorporated into mixed Langmuir-Blodgett films. UV-vis absorption spectroscopic study of the mixed LB films at various molefractions of PA in two different matrices reveal that formation of I-type aggregate in PMMA matrix whereas both I- and H-type aggregates are playing their dominant role in SA matrix. Moreover, fluorescence spectroscopic study reveals reabsorption effect. Molecular movement persists in the freshly prepared LB films, as is evident from the time dependent changes in both UV-vis absorption and fluorescence spectra of the mixed LB films in both matrices. From our observation it is evident that about 200 h is required to get the LB films in a stable condition. Dimers and higher order n-mers are formed at a higher surface pressure of 30 mNm(-1).     

Raman scattering investigation of the orientational dynamics of methyl iodide

A Raman scattering study of the v₃ vibration—rotation band in methyl iodide as a function of temperature and dilution (in cyclohexane) has been performed. All the data satisfy the second moment criterion. Detailed information about rotational correlation function, angular velocity correlation function, various correlation times and mean-square torque has been obtained. The correlation function, in the pure liquid, decays slowly with decrease in temperature whereas it decays faster with decreasing concentration in cyclohexane. It has been shown, from a consideration of the second moment as a function of concentration, that the contribution of collision-induced scattering to the v₃ band of methyl iodide is negligible. Applicability of a simple “damped librator model”, with a view to understanding certain aspects of the rotational motion in methyl iodide, is discussed.     

Retro-Claisen condensation versus pyrrole formation in reactions of amines and 1,3-diketones

Cyclic amines and 1,3-diketones readily react under microwave irradiation to form ring-fused pyrroles in a single operation. A competing retro-Claisen pathway is efficiently suppressed by employing p-toluenesulfonic acid as an additive.