Unusual neutral and radical losses in 2′-substituted N-phenylanthranilic acids on electron impact

Unusual expulsions of [H₂O + CO₂] from the M⁺˙ of N-(o-carboxyphenyl)anthranilic acid, [H₂O + CH₂O] from the M⁺˙ of N-(o-methoxyphenyl)anthranilic acid and [H₂O + ˙NO₂] from the M⁺˙ of N-(o-nitrophenyl) anthranilic acid were observed under electron impact conditions. These processes are stepwise in the corresponding para-substituted N-phenylanthranilic acids. The proposed fragmentation pathways and their mechanisms are supported by B/E linked-scan spectra, collision-activated decomposition (CAD)–mass-analysed ion kinetic energy (MIKE) spectra, high-resolution data, deuterium labelling and chemical substitution.     

Synthesis,electrochemical and e.p.r. spectral studies of binuclear copper(II) complexes with new pentadentate L-proline-based binucleating ligands

The synthesis, reduction, optical and e.p.r. spectral properties of a series of new binuclear copper(II) complexes, containing bridging moieties (OH^–, MeCO₂ ^–, NO₂ ^–, and N₃ ^–), with new proline-based binuclear pentadentate Mannich base ligands is described. The ligands are: 2,6-bis[(prolin-1-yl)methyl]4-bromophenol [H₃L¹], 2,6-bis[(prolin-1-yl)methyl]4-t-butylphenol [H₃L²] and 2,6-bis[(prolin-1-yl)methyl]4-methoxyphenol [H₃L³]. The exogenous bridging complexes thus prepared were hydroxo: [Cu₂L¹(OH)(H₂O)₂] · H₂O (1a), [Cu₂L²(OH)(H₂O)₂] · H₂O (1b), [Cu₂L³(OH)(H₂O)₂] · H₂O (1c), acetato [Cu₂L¹(OAc)] · H₂O (2a), [Cu₂L²(OAc)] · H₂O (2b), [Cu₂L³(OAc)] · H₂O (2c), nitrito [Cu₂L¹(NO₂)(H₂O)₂] · H₂O (3a), [Cu₂L²(NO₂)(H₂O)₂] · H₂O (3b), [Cu₂L³(NO₂)(H₂O)₂] · H₂O (3c) and azido [Cu₂L¹(N₃)(H₂O)₂] · H₂O (4a), [Cu₂L²(N₃)(H₂O)₂] · H₂O (4b) and [Cu₂L³(N₃)(H₂O)₂] · H₂O (4c). The complexes were characterized by elemental analysis and by spectroscopy. They exhibit resolved copper hyperfine e.p.r. spectra at room temperature, indicating the presence of weak antiferromagnetic coupling between the copper atoms. The strength of the antiferromagnetic coupling lies in the order: NO₂ N₃ OH OAc. Cyclic voltammetry revealed the presence of two redox couples Cu^IICu^II Cu^IICu^I Cu^ICu^I. The conproportionality constant K _con for the mixed valent Cu^IICu^I species for all the complexes have been determined electrochemically.     

One-pot synthesis of oligosaccharides by combining reductive openings of benzylidene acetals and glycosylations

Combining triflic acid-promoted glycosylations of trichloroacetimidates with reductive opening of benzylidene acetals with triflic acid and triethylsilane as one-pot procedures provides access to a wide range of disaccharides and 2,4- and 3,4-branched trisaccharides.     

Growth and characterization of L‐phenylalanine

L‐Phenylalanine (C₉H₁₁NO₂), having the morphology of spherulitic needles, an amino acid constituent, responsible for brain nutrition is crystallized in silica gel of pH 6.0 by single diffusion method in a period of 30 minutes. The grown crystals were characterized by X‐ray powder diffraction, Fourier Transform infrared spectroscopy and Visible Ultraviolet spectroscopy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Self assembly of C -methyl resorcin[4]arene with coumarin and thiocoumarin: A nanotubular array with a near perfect lock and key fit

The host-guest complex of C-methyl resorcin[4]arene with coumarin and thiocoumarin has been characterized by single crystal X-ray diffraction technique. Structural analysis shows that the host forms an infinitie nanotubular array in which the guest coumarin shows a ‘head to tail’ arrangement of dimers held together by π...π interaction in the host framework. Similar structural motif is observed when thiocoumarin used as a guest.     

The wavelet methods to linear and nonlinear reaction–diffusion model arising in mathematical chemistry

In this paper, we have applied an accurate and efficient wavelet scheme (due to Legendre polynomial) to find the numerical solutions for a set of coupled reaction–diffusion equations. This technique provides the solutions in rapid convergence series with computable terms for the problems with high degree of non linear terms appearing in the governing differential equations. The highest derivative in the differential equation is expanded into wavelet series, this approximation is then integrated while the boundary conditions are applied by using integration constants. With the help of operational matrices, the nonlinear reaction–diffusion equations are converted into a system of algebraic equations. Finally, some numerical examples to demonstrate the validity and applicability of the method have been furnished. The use of Legendre wavelets is found to be accurate, efficient, simple, and computationally attractive. This wavelet method can be used for obtaining quick solution in many chemical Engineering problems.     

Oral breathing increases Pth and vocal effort by superficial drying of vocal fold mucosa.

Oral breathing superficially dehydrates the airway lumen by decreasing the depth of the sol layer in humans and animals. Conversely, nasal breathing can increase the humidity of inspired air. We compared the effects of short-term oral and nasal breathing on Pth and perceived vocal effort in 20 female subjects randomly assigned to two groups: oral breathing (N = 10, age 21-32 years); nasal breathing (N = 10, age 20-36 years). We hypothesized that short-term oral breathing, but not nasal breathing, would increase Pth, and that subjects would perceive this change as an increase in vocal effort. Following 15 minutes of oral breathing, Pth increased at comfortable and low pitch (p < 0.01) with 6 of 10 subjects reporting increased vocal effort. Nasal breathing reduced Pth at all three pitches (p < 0.01), and 7 of 10 subjects reported decreased vocal effort. Over all subjects, 49% of the variance in treatment-induced change in Pth was accounted for by change in vocal effort (R = 0.70). We posit that obligatory oral breathing places healthy subjects at risk for symptoms of increased vocal effort. The facilitatory role of superficial hydration on vocal fold oscillation should be considered in biomechanical models of phonation and in the clinical prevention of laryngeal dryness.     

Synthesis,characterization, and catalytic application of ecofriendly Ca-bridged aminoclay

A novel ecofriendly Ca nanoparticle bridged aminoclay (AC) catalyst was prepared for the reduction of hazardous pollutants to treat the industrial wastewater. It was characterized by FT-IR spectroscopy, UV-visible spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectrum (EDX), differential scanning calorimetry (DSC), and thermogravimetry (TG) techniques. Water contact angle (WCA) measurement was used to confirm the hydrophobicity of AC after the structural modification reaction. Disappearance of free N−H stretching in the FT-IR spectrum confirmed the chemical modification of AC by Ca nanoparticle. The above-synthesized Ca nanoparticle bridged AC was used as a catalyst for the reduction of p-nitrophenol (NP), chromium (VI) and fluorescein (fluor) dye and also for oxidative Schiff base formation. The UV-visible spectrum confirmed the complex formation between chromium (VI) and NP by noting a peak at 390 nm. The k_app value was computed to assess the efficiency of the catalyst toward the reduction of hazardous pollutants in the industrial effluents. The catalytic reduction of a tricomponent system is disturbed due to the change in pH and complex formation between the pollutants, etc. The present catalyst system reduced the two-step reaction into a single-step reaction for the Schiff base formation.     

Characterization of L‐aspartate crystals grown in gel medium

L‐Aspartate [C₄H₇NO₄], also called as 2‐aminobutanedoioic acid, an organic amino acid was crystallized with the aid of sodium metasilicate gel. Diffusion of the supersaturated solutions in porous gel network by solubility reduction method in silica gel was carried out in our laboratory. The crystals were characterized using powder X‐ray diffraction technique. Fourier transform infrared spectroscopy reveals the presence of functional groups in the crystals. Optical absorbance of the crystals was studied by UV – Visible spectroscopy and the thermal properties were studied by thermo gravimetric analysis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)