On character amenability of semigroup algebras

Let S be a foundation locally compact topological semigroup, and let M _a (S) be the space of all measures μ∈M(S) for which the maps x?|μ|?δ _x and x?|μ|?δ _x from S into M(S) are weakly continuous. The purpose of this article is to develop a notion of character amenability for semigroup algebras. The main results concern the χ-amenability of M _a (S). We give necessary and sufficient conditions for the existence of a left χ-mean on M _a (S)^?.     

Preparation,surface state and band structure studies of SrTi(1 − x)Fe(x)O(3 − δ) (x = 0–1) perovskite-type nano structure by X-ray and ultraviolet photoelectron spectroscopy

In this report, SrTi_(1 ? x)Fe_(x)O_(3 ? δ) photocatalyst powder was synthesized by a high temperature solid state reaction method. The morphology, crystalline structures of obtained samples, was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM), respectively. The electronic properties and local structure of the perovskite STF_x (0 ≤ x ≤ 1) systems have been probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. The effects of iron doping level x (x = 0–1) on the crystal structure and chemical state of the STF_x have been investigated by X-ray photoelectron spectroscopy and the valence band edges for electronic band gaps were obtained for STF_x by ultraviolet photoelectron spectroscopy (UPS). A single cubic perovskite phase of STF_x oxide was successfully obtained at 1200 °C for 24 h by the solid state reaction method. The XPS results showed that the iron present in the STF_x perovskite structure is composed of a mixture of Fe³⁺ and Fe⁴⁺ (SrTi_(1 ? x)[Fe³⁺, Fe⁴⁺]_(x)O_(3 ? δ)). When the content x of iron doping was increased, the amount of Fe³⁺ and Fe⁴⁺ increased significantly and the oxygen lattice decreased on the surface of STF_x oxide. The UPS data has confirmed that with more substitution of iron, the position of the valence band decreased.     

Succinimide sulfonic acid (SuSA): an efficient and recyclable catalyst for the chemoselective <Emphasis Type="Italic">N</Emphasis>-Boc protection of amines

Abstract  

Succinimide sulfonic acid (SuSA) as a stable reagent is easily prepared by the reaction of succinimide with neat chlorosulfonic acid. This compound is able to catalyze the chemoselective conversion of amines to their corresponding N-Boc protected derivatives with (Boc)₂O. All reactions were performed under mild conditions, giving the desired products in good to high yields.     

Computational study of aza-adamantanes as multivalent bases

Structure and bonding characteristics, and gas phase stepwise basicities of proposed multivalent bases 1,3,5,7-tetraazatricyclo[3.3.1.1(3,7)]decane, 1,3,5,7,9,10-hexaazatricyclo[3.3.1.1(3,7)]decane and tricyclo[3.3.1.1(3,7)]azadecane, named and abbreviated here respectively as tetra-aza-adamantane (TAA), hexa-aza-adamantane (HAA) and deca-aza-adamantane (DAA), have been studied using B3LYP/6-311++G** method. Effects of protonation on the bond lengths and angles, and atomic charges, and on their correlations are studied in detail. Results show that the most affected characteristics by protonation are the N–H bond lengths and the charge of the hydrogen atoms. It is found, interestingly, that in the protonation of DAA, electric charges of the unprotonated nitrogen atoms are increased more than that of the protonated nitrogen atoms. Because of very small effects of protonation on the skeletal C–N and N–N bond lengths, it can be said that the aza-adamantane cage volume is not changed significantly upon protonation. The protonation energies approve multivalent nature of these bases with the order of TAA ≈ HAA > DAA. Different isomers for the unprotonated and protonated HAA and DAA are also studied.     

The quantum chemical calculation of NMR two-bond spin–spin coupling constants in the N?···H–OH?→?N–H···OH? switching

A quantum chemical study has been carried out to investigate the effects of the size of H₂O cluster and substituents (X = H, Me, OMe, CHO, NO, and NO₂) in the para position of the anilide ion on the two-bond spin–spin coupling constants (SSCCs) ^2h J _N···O across in the N–H–O switching at B3LYP/6-311 ++G(2d,2p) level of theory. The changes in ^2h J _N···O SSCCs due to variation of substituent and H₂O cluster size were well monitored by changes in binding energy, structural parameter, electron density topography, natural charge, charge transfer, and percentage of p-character of N atom in the C–N bond. Linear correlations were found between ^2h J _N···O and above-mentioned properties.     

The stability of limit cycles in nonlinear systems

In this paper, a necessary condition is first presented for the existence of limit cycles in nonlinear systems, then four theorems are presented for the stability, instability, and semistabilities of limit cycles in second order nonlinear systems. Necessary and sufficient conditions are given in terms of the signs of first and second derivatives of a continuously differentiable positive function at the vicinity of the limit cycle. Two examples considering nonlinear systems with familiar limit cycles are presented to illustrate the theorems.     

Solid-phase synthesis of arylidene and alkylidene malonates,as versatile intermediates,catalyzed using mesoporous poly-melamine–formaldehyde as a nitrogen-rich porous organic polymer (POP)

Research on Chemical Intermediates - An efficient solid/slurry-state synthesis of arylidene and alkylidene malonates as versatile intermediates is developed in the presence of mesoporous...     

4,4′-Trimethylenedipiperidine,a safe and greener alternative for piperidine,catalyzed the synthesis of N-methyl imines

A practical and facile synthesis of various N-methyl imines, versatile scaffolds, was conducted at 85 °C using 4,4′-trimethylenedipiperidine as a safe and green catalyst. This reagent is a commercially available solid and can be handled easily. It has high thermal stability, low toxicity, and good solubility in green solvents such as water and ethanol. The regenerated catalyst demonstrated stable activity after several recycle runs, and any changes were detected in its chemical structure by ¹H NMR monitoring. The novelty of the current work is that the 4,4′-trimethylenedipiperidine can act as a promising alternative for piperidine in organic reaction at higher temperatures due to its broad liquid range temperature, thermal stability, acceptor/donor hydrogen bond property, and other unique merits. Furthermore, the current protocol avoids waste generation in the workup process, which is a drawback in most previous reported procedures.

     

Green Oxidations. Manganese(II) Sulfate Aided Oxidations of Organic Compounds by Potassium Permanganate

Summary. The oxidation of arenes and sulfides by potassium permanganate was accomplished in good yields under solvent free and heterogeneous conditions when manganese(II) sulfate is used as a solid support. After extraction of the organic products, the inorganic products can be reoxidized to permanganate. This result is important because it provides an approach to oxidation reactions that is, in theory, infinitely sustainable.     

Development of air‐assisted dispersive micro‐solid‐phase extraction‐based supramolecular solvent‐mediated Fe3O4@Cu–Fe–LDH for the determination of tramadol in biological samples

A simple method, air‐assisted dispersive micro‐solid‐phase extraction‐based supramolecular solvent was developed for the preconcentration of tramadol in biological samples prior to gas chromatography–flame ionization detection. A new type of carrier liquid, supramolecular solvent based on a mixture of 1‐dodecanol and tetrahydrofuran was combined with layered double hydroxide coated on a magnetic nanoparticle (Fe₃O₄@SiO₂@Cu–Fe–LDH). The supramolecular solvent was injected into the solution containing Fe₃O₄@SiO₂@Cu–Fe–LDH in order to provide high stability and dispersion of the sorbent without any stabilizer agent. Air assisted was applied to enhance the dispersion of the sorbent and solvent. A number of analytical techniques such as Fourier transform‐infrared spectrometry, field emission scanning electron microscope, energy‐dispersive X‐ray spectroscopy and X‐ray diffraction measurements were applied to assess the surface chemical characteristics of Fe₃O₄@SiO₂@Cu–Fe–LDH nanoparticles. The effects of important parameters on the extraction recovery were also investigated. Under optimized conditions, the limits of detection and quantification were obtained in the range of 0.9–2.4 and 2.7–7.5 μg L^?1 with preconcentration factors in the range of 450–472 in biological samples. This method was used for the determination of tramadol in biological samples (plasma, urine and saliva samples) with good recoveries.