2‐Methyl‐1,3‐disulfoimidazolium polyoxometalate hybrid catalytic systems as equivalent safer alternatives to concentrated sulfuric acid in nitration of aromatic compounds

Ionic liquid‐derived polyoxometalate salts [mdsim]₃[PM₁₂O₄₀] (where M = W and Mo) of two heteropolyacids H₃PW₁₂O₄₀.nH₂O and H₃PMo₁₂O₄₀.nH₂O were synthesized using 2‐methyl‐1,3‐disulfoimidazolium chloride ([mdsim][Cl]) ionic liquid and the corresponding heteropolyacids. Three equivalents of [mdsim][Cl] were treated with the respective Keggin‐structured heteropolyacids (one equivalent) in aqueous medium at room temperature to afford the water‐stable ionic polyoxometalates as acidic solids. They were completely characterized using spectroscopic and other analytical techniques including thermal analysis and Hammett acidity studies. The inherent Brønsted acidic properties of ─SO₃H group of these polyoxometalate salts were studied for the nitration of aromatic compounds with 69% HNO₃ at normal temperature and 80°C without use of any external concentrated sulfuric acid. These strongly acidic polyoxometalates display good recyclability and efficient reusability.     

Rhodium(I) carbonyl complexes of quinoline carboxaldehyde ligands and their catalytic carbonylation reaction

The dimeric rhodium precursor [Rh(CO)₂Cl]₂ reacts with quinoline (a) and its three isomeric carboxaldehyde ligands [quinoline-2-carboxaldehyde (b), quinoline-3-carboxaldehyde (c), and quinoline-4-carboxaldehyde (d)] in 1:2 mole ratio to afford complexes of the type cis-[Rh(CO)₂Cl(L)] (1a-1d), where L = a-d. The complexes 1a-1d have been characterised by elemental analyses, mass spectrometry, IR and NMR (¹H, ¹³C) spectroscopy together with a single crystal X-ray structure determination of 1c. The X-ray crystal structure of 1c reveals square planar geometry with a weak intermolecular pseudo dimeric structure (Rh?Rh = 3.573 Å). 1a-1d undergo oxidative addition (OA) with different electrophiles such as CH₃I, C₂H₅I and I₂ to give Rh(III) complexes of the type [Rh(CO)(COR)Cl(L)I] {R = -CH₃ (2a-2d), R = -C₂H₅ (3a-3d)} and [Rh(CO)Cl(L)I₂] (4a-4d) respectively. 1b exhibits facile reactivity with different electrophiles at room temperature (25 °C), while 1a, 1c and 1d show very slow reactivity under similar condition, however, significant reactivity was observed at a temperature ∼40 °C. The complexes 1a-1d show higher catalytic activity for carbonylation of methanol to acetic acid and methyl acetate [Turn Over Frequency (TOF) = 1551-1735 h⁻¹] compared to that of the well known Monsanto’s species [Rh(CO)₂I₂]⁻ (TOF = 1000 h⁻¹) under the reaction conditions: temperature 130 ± 2 °C, pressure 33 ± 2 bar, 450 rpm and time 1 h. The organometallic residue of 1a-1d was also isolated after the catalytic reaction and found to be active for further run without significant loss of activity.     

Bakers’ yeast-catalyzed reductive cleavage of 3-aryl-2,1-benzisoxazoles and its quaternary salts: an efficient green synthesis of 2-aminobenzophenones

Abstract  

3-Aryl-2,1-benzisoxazoles and its salts underwent reductive cleavage of the N–O bond leading to 2-aminobenzophenones with bakers’ yeast under non-fermenting conditions in aqueous media. The procedure gives excellent yields of 2-alkylamino- and 2-aminobenzophenones.     

Effect of Sn-doping at Mo-site on the conductivity of La2Mo2O9 series of compounds

Taking oxygen ion conductor La₂Mo₂O₉, as a base compound, a series of Sn-doped La₂Mo_2−x Sn _x O_9−δ, x = 0, 0.01, 0.02, 0.03, 0.05, 0.1, 0.15, 0.2 specimens were prepared and characterized by XRD for phase and crystal structure determination and ac impedance spectroscopy for ac and dc conductivity measurement. We have found that there is slight improvement in overall conductivity of the specimen with x = 0.03 at 800°C compared to the undoped compound at the same temperature. The value of conductivity when extrapolated to 800°C is found to be 0.055 S cm-1 for the specimen with x = 0.03, whereas conductivity of undoped specimen at the same temperature is found to be 0.033 Scm⁻¹.     

Asymmetrical hippocampal connectivity in mesial temporal lobe epilepsy: evidence from resting state fMRI

Background

Recent studies have shown that the human right-hemispheric auditory cortex is particularly sensitive to reduction in sound quality, with an increase in distortion resulting in an amplification of the auditory N1m response measured in the magnetoencephalography (MEG). Here, we examined whether this sensitivity is specific to the processing of acoustic properties of speech or whether it can be observed also in the processing of sounds with a simple spectral structure. We degraded speech stimuli (vowel /a/), complex non-speech stimuli (a composite of five sinusoidals), and sinusoidal tones by decreasing the amplitude resolution of the signal waveform. The amplitude resolution was impoverished by reducing the number of bits to represent the signal samples. Auditory evoked magnetic fields (AEFs) were measured in the left and right hemisphere of sixteen healthy subjects.

Results

We found that the AEF amplitudes increased significantly with stimulus distortion for all stimulus types, which indicates that the right-hemispheric N1m sensitivity is not related exclusively to degradation of acoustic properties of speech. In addition, the P1m and P2m responses were amplified with increasing distortion similarly in both hemispheres. The AEF latencies were not systematically affected by the distortion.

Conclusions

We propose that the increased activity of AEFs reflects cortical processing of acoustic properties common to both speech and non-speech stimuli. More specifically, the enhancement is most likely caused by spectral changes brought about by the decrease of amplitude resolution, in particular the introduction of periodic, signal-dependent distortion to the original sound. Converging evidence suggests that the observed AEF amplification could reflect cortical sensitivity to periodic sounds.     

Conductivity study of some polymer electrolytes based on polyacrylonitrile

The present paper deals with the room temperature conductivity study of some polymer electrolytes based on polyacrylonitrile, ammonium tetraflouroborate as dopant, and propylene carbonate (PC) and polyethylene glycols (PEG300 and PEG600) as plasticizers. The additions of plasticizers having different dielectric constant have been found to modify the conductivity of polymer electrolytes. The increase in room temperature conductivity with plasticizer addition has been found to depend upon (1) the amount of salt present and (2) amount of plasticizers added. The polymer electrolytes prepared were characterized by X-ray diffraction, scanning electron micrographs, infrared, thermogravimetric, and AC impedance measurements. The highest room temperature conductivity observed in case of these polymer electrolytes was ∼10–13 s/cm.     

Synthesis of 1,3-Dioxanes Catalyzed by TsOH-SiO2 Under Solvent-Free Conditions

Silica-supported p-toluene sulfonic acid is found to be an excellent catalyst for the Prins reaction to produce 1,3-dioxanes in good yields from olefins and aliphatic aldehydes in dichloromethane at room temperature and solventless microwave irradiation within a short reaction time.     

Nonlinear pulsational eigenmodes of a planar collisional dust molecular cloud with grain-charge fluctuation

We try to present a theoretical evolutionary model leading to the excitations of nonlinear pulsational eigenmodes in a planar (1D) collisional dust molecular cloud (DMC) on the Jeans scale. The basis of the adopted model is the Jeans assumption of self-gravitating homogeneous uniform medium for simplification. It is a self-gravitating multi-fluid consisting of the Boltzmann distributed warm electrons and ions, and the inertial cold dust grains with partial ionization. Dust-charge fluctuations, convections and all the possible collisions are included. The grain-charge behaves as a dynamical variable owing mainly to the attachment of the electrons and ions to the grain-surfaces randomly. The adopted technique is centered around a mathematical model based on new solitary spectral patterns within the hydrodynamic framework. The collective dynamics of the patterns is governed by driven Korteweg-de Vries (d-KdV) and Korteweg-de Vries (KdV) equations obtained by a standard multiscale analysis. Then, simplified analytical and numerical solutions are presented. The grain-charge fluctuation and collision processes play a key role in the DMC stability. The sensitive dependence of the eigenmode amplitudes on diverse relevant plasma parameters is discussed. The significance of the main results in astrophysical, laboratory and space environments are concisely summarized.