On Descartes’ rule for polynomials with two variations of signs

Lithuanian Mathematical Journal - For sequences of d + 1 signs + and ? beginning with a + and having exactly two variations of sign, we give some sufficient conditions for the (non)existence...     

Organophosphorus chemistry,XII. Reaction of furil with alkyl phosphites and ylide-phosphoranes

Summary The reaction of furil (1) with trialkyl phosphites2 yielded caged phosphorane derivatives of types3a-c. Dry hydrogen chloride gas converted3a-c into the respectivea-hydroxyvinyl-phosphates8a-c which are equally produced by reacting furil with the appropriate dialkyl phosphite7. The reaction of furil with ylide-phosphoranes10 proceeded according to the Wittig reaction mechanism to give the respective ethylenes11a-c. The new compounds have been characterized by their spectroscopic data (IR, PMR,³¹P-NMR, MS) and elementary analyses.Dedicated to Prof. M. Sidky on the occasion of his 60th birthday     

Preparation of cellulose and cellulose derivative azo compounds

Wood pulp and cotton linter are the most common sources of cellulose forindustrial use. Methyl cellulose (MC) and cellulose sulfate (CS) were preparedusing bleached wood pulp and cotton linter. Coloured azo compounds were alsoprepared from coupling cellulose, wood pulp, MC and CS with aromatic diazoniumsalt. The presence of electron-releasing or withdrawing substituents affectedthe electrophilic substitution reaction. The produced azo compounds werecharacterized by FT-IR methodology, as well as mass spectrometry, in which thefunctional groups and the ion fragments of the products were analyzed.     

Polarographic behaviour and determination of paracetamol and salicylamide after treatment with nitrous acid

A polarographic procedure is described for the determination of paracetamol (acetaminophen) and salicylamide after treatment with nitrous acid. The different experimental parameters affecting the derivatization process and the polarographic analysis were studied. The derivatization products were found to be reduced at the dropping mercury electrode over the whole pH range in Britton-Robinson buffers. At pH 7.0, well defined diffusion-controlled cathodic waves were produced for both compounds. Plots of limiting current vs. concentration were linear over the ranges 0.05–0.75 and 0.25–1.5mM for paracetamol and salicylamide, respectively, in the d.c. mode, with minimum detectability of 2.5 × 10^–6 and 1.25 × 10^–5 M, respectively. The procedure was applied to the analysis of some pharmaceutical dosage forms and the results were in good agreement with those obtained by official and compendial methods.     

Brightly phosphorescent trinuclear copper(I) complexes of pyrazolates: substituent effects on the supramolecular structure and photophysics

Synthetic details, solid-state structures, and photophysical properties of a group of trimeric copper(I) complexes containing pyrazolate ligands are described. The reaction of copper(I) oxide and the fluorinated pyrazoles [3-(CF(3))Pz]H, [3-(CF(3)),5-(Me)Pz]H, and [3-(CF(3)),5-(Ph)Pz]H leads to the corresponding trinuclear copper(I) pyrazolates, {[3-(CF(3))Pz]Cu}(3), {[3-(CF(3)),5-(Me)Pz]Cu}(3), and {[3-(CF(3)),5-(Ph)Pz]Cu}(3), respectively, in high yield. The {[3,5-(i-Pr)(2)Pz]Cu}(3) compound was obtained by a reaction between [Cu(CH(3)CN)(4)][BF(4)], [3,5-(i-Pr)(2)Pz]H, and NEt(3). These compounds as well as {[3,5-(Me)(2)Pz]Cu}(3) and {[3,5-(CF(3))(2)Pz]Cu}(3) adopt trimeric structures with nine-membered Cu(3)N(6) metallacycles. There are varying degrees and types of intertrimer Cu...Cu interactions. These contacts give rise to zigzag chains in the fluorinated complexes, {[3-(CF(3))Pz]Cu}(3), {[3-(CF(3)),5-(Me)Pz]Cu}(3), {[3-(CF(3)),5-(Ph)Pz]Cu}(3), and {[3,5-(CF(3))(2)Pz]Cu}(3), whereas the nonfluorinated complexes, {[3,5-(Me)(2)Pz]Cu}(3) and {[3,5-(i-Pr)(2)Pz]Cu}(3) form dimers of trimers. Out of all the compounds examined in this study, {[3-(CF(3)),5-(Ph)Pz]Cu}(3) has the longest (3.848 Angstroms) and {[3,5-(Me)(2)Pz]Cu}(3) has the shortest (2.946 Angstroms) next-neighbor intertrimer Cu...Cu distance. The Cu...Cu separations within the trimer units do not vary significantly (typically 3.20-3.26 Angstroms). All of these trinuclear copper(I) pyrazolates show bright luminescence upon exposure to UV radiation. The luminescence bands are hugely red-shifted from the corresponding lowest-energy excitations, rather broad, and unstructured even at low temperatures, suggesting metal-centered emissions owing to intertrimer Cu...Cu interactions that are strengthened in the phosphorescent state. The {[3-(CF(3)),5-(Ph)Pz]Cu}(3) compound exhibits an additional highly structured phosphorescence with a vibronic structure corresponding to the pyrazolyl (Pz) ring. The luminescence properties of solids and solutions of the trimeric compounds in this study show fascinating trends with dramatic sensitivities to temperature, solvent, concentration, and excitation wavelengths.     

Two validated chromatographic determinations of an antifungal drug,its toxic impurities and degradation product: A comparative study

Tolnaftate, a thionoester anti‐fungal drug, was subjected to alkaline hydrolysis to produce methyl(m‐tolyl)carbamic acid and β ‐naphthol (tolnaftate impurity A). N‐Methyl‐m‐toluidine, tolnaftate impurity D, was synthesized and structurally elucidated along with tolnaftate alkaline degradation products using IR, H¹NMR and MS. Two stability‐indicating HPTLC and RP‐HPLC methods were developed and validated, for the first time, for determination of tolnaftate, its alkaline degradation products and toxic impurities in the presence of methyl paraben, as a preservative in Tinea Cure^® cream. The proposed HPTLC method depended on separation of the studied components on TLC silica gel F₂₅₄ plates using hexane–glacial acetic acid (8:2, v/v) as a developing system and scanning wavelength of 230 nm. The proposed RP‐HPLC method was based on separation of the five components on an Eclipse plus C₁₈ column. The mobile phase used was acetonitrile–water containing 1% ammonium formate (40:60, v/v), with a flow rate of 1 mL/min and detection wavelength of 230 nm. The proposed methods allowed the assay of tolnaftate toxic impurities, β ‐naphthol and N‐methyl‐m‐toluidine, down to 2%, allowing tracing of β ‐naphthol that could be absorbed by the skin causing systemic toxic effects, unlike tolnaftate, indicating the high significance of such determination. International Conference on Harmonization guidelines were followed for validation.     

High-performance hybrid supercapacitor based on pure and doped Li4Ti5O12 and graphene

Journal of Solid State Electrochemistry - Graphene nanosheets (G) and pure, as well as doped Mg-, Mn-, V-Li4Ti5O12, spinel structure have been synthesized. As-prepared materials were characterized...     

SYNTHESIS AND BIOLOGICAL ACTIVITY OF SOME NEW 8-HYDROXYQUINOLINE SULPHONAMIDE DERIVATIVES

Abstract

Some new derivatives containing both 8-hydroxyquinoline and sulphonylamino β-lactams and thiazolidinones have been prepared. These compounds were synthesized from the corresponding 8-hydroxyquinoline sulphonylhydrazide (1) by converting it to hydrazones (2). The latter hydrazones (2) were easily transformed to β-lactams (3) and thiazolidinones (4) by cyclocondensation reaction with chloroacetyl chloride and/or mercaptoacetic acid. Some metal chelates with Fe³⁺. Co²⁺+, Ni²⁺, Cu²⁺ and Cd²⁺ have been prepared for some of the compounds and screened in vitro for their biological activity.     

Silica Sulfuric Acid: An Efficient,Reusable, Heterogeneous Catalyst for the One-Pot,Five-Component Synthesis of Highly Functionalized Piperidine Derivatives

A series of highly functionalized piperidine derivatives was synthesized through one-pot, five-component reaction of aldehydes, amines, and β-ketoesters. Silica sulfuric acid efficiently catalyzes the reaction to afford the corresponding piperidine derivatives in good yields. As a representative example, heating of 4-methylaninle, 4-fluorobezaldehyde, and methyl-acetoacetate in methanol in the presence of silica sulfuric acid furnished the corresponding ethyl 2,6-bis(4-fluorophenyl)-1-p-tolyl-4-(p-tolylamino)-1,2,5,6-tetrahydropyridine-3-carboxylate in excellent yield (85%). Most of the synthesized compounds were screened in vitro for their antibacterial and antifungal activities. Most of compounds showed significant antibacterial activity.     

Application of a Chitosan-Immobilized Talaromyces thermophilus Lipase to a Batch Biodiesel Production from Waste Frying Oils

Waste frying oil, which not only harms people’s health but also causes environmental pollution, can be a good alternative to partially substitute petroleum diesel through transesterification reaction. This oil contained 8.8 % of free fatty acids, which cause a problem in a base-catalyzed process. In this study, synthesis of biodiesel was efficiently catalyzed by the covalently immobilized Talaromyces thermophilus lipase and allowed bioconversion yield up to 92 % after 24 h of reaction time. The optimal molar ratio was four to six parts of methanol to one part of oil with a biocatalyst loaded of 25 wt.% of oil. Further, experiments revealed that T. thermophilus lipase, immobilized by a multipoint covalent liaison onto activated chitosan via a short spacer (glutaraldehyde), was sufficiently tolerant to methanol. In fact, using the stepwise addition of methanol, no significant difference was observed from the one-step whole addition at the start of reaction. The batch biodiesel synthesis was performed in a fixed bed reactor with a lipase loaded of 10 g. The bioconversion yield of 98 % was attained after a 5-h reaction time. The bioreactor was operated successfully for almost 150 h without any changes in the initial conversion yield. Most of the chemical and physical properties of the produced biodiesel meet the European and USA standard specifications of biodiesel fuels.