Morphological and Interaction Characteristics of Surface-Active Ionic Liquids and Palmitic Acid in Mixed Monolayers

A series of water soluble, surface-active ionic liquids (SAILs), namely, 1-alkyl-3-methyl imidazolium chlorides ([C_n-mim]Cl) and their mixtures with palmitic acid (PA) are investigated in Langmuir monolayers and Langmuir–Blodgett films. It is inferred from the surface pressure-area isotherms that C₁₆-mim-IL mixes non-ideally with PA and stabilizes the binary mixed films. In addition, the residence of mim-IL at the water surface is enhanced as a function of the increasing alkyl side chain length. Generally, the compressional moduli values decrease upon increasing the content of the mim-ILs over a wide range of compositions. Furthermore, film relaxation measurements indicate that the IL component is selectively excluded from the mixed films upon achieving a certain target pressure. Brewster angle microscope images demonstrate minimal changes on the PA domains in the presence of either C₄- and C₈-mim-ILs, whereas presence of the hexadecyl counterpart results in the formation of condensed sheets. Atomic force microscopy imaging of deposited films show the formation of propeller-like aggregates when C₈- or C₁₆-mim-IL is present in the mixed films.     

A Potentiometric Sensor for Determination of Doxycycline Hydrochloride in Pharmaceutical Preparation and Biological Fluids

This article focused on the construction and characteristics of novelty and sensitivity of modified carbon paste electrodes for determination of doxycycline hydrochloride (DC.HCl) in urine, serum and pharmaceutical preparations. It was based on the incorporation of α-cyclodextrine (α-CD) and multi-walled carbon nanotube (MWCNT) ionophores which improved the characteristics of the electrodes with tricresylphosphate (TCP) (electrode I) and o-nitrophenyloctylether (o-NPOE) (electrode II) as plasticizers, respectively. The constructed electrodes, at optimum paste composition, exhibited good Nernstian response for determination of doxycycline hydrochloride over a linear concentration range from 1.0 × 10^–7 to 1.0 × 10^–2 and 1.22 × 10^–7 to 1.0 × 10^–2 mol L^–1 with detection limit of 1.0 × 10–7 and 1.22 ×10^–7 mol L^–1 and with slope values of (58.7 ± 0.2) mV decade–1 and (58.0 ± 0.6) mV decade–1, for modified carbon paste electrodes (MCPEs; electrodes I and II), respectively. The results showed fast dynamic response time (about 6–7 s) and long lifetime in the range from 4 to 5 months where the response of the electrodes was not affected by pH variation within the range from 2 to 8 and 2 to 7.5 for electrodes I and II, respectively. Electrodes I and II showed high selectivity for doxycycline hydrochloride with respect to a large number of interfering species including foreign inorganic, organic species, excipients and the fillers added to the pharmaceutical preparation. The constructed electrodes were successfully applied for determination of DC.HCl in pure form, its pharmaceutical preparations and biological fluids (urine and serum) using standard addition, calibration curves and potentiometric titration methods. The results obtained using these potentiometric electrodes were comparable with those obtained using official method. The results were satisfactory with excellent percentage recovery comparable or better than those obtained by other routine methods.

     

Utility of 2-furan-2-yl-4-mercapto-6-methylpyrimidine-5-carbonitrile as a precursor for the synthesis of some novel pyrimidines: antibacterial activity

The starting material 2-furan-2-yl-4-mercapto-6-methylpyrimidine-5-carbonitrile 3 was reacted with various reagents resulting in the formation of a group of new pyrimidines and condensed pyrimidines including quinazoline 6 tetrazolopyrimidine 12, pyrazolopyrimidines 14, 18, and 19, triazolopyrimidine 16, and pyrimidopyridazine 20. The antibacterial activity was evaluated for a group of the synthesized compounds against examples of Gram-positive and Gram-negative bacteria.     

Crystal Structures and Spectral Studies of [Ph3Sn(O2AsMe2)], [Bu2ClSn(O2AsMe2)] and [PhClSn(O2AsMe2)(μ‐OMe)]2

[Ph₃Sn(O₂AsMe₂)] ( 1 ) and [PhClSn(O₂AsMe₂)(μ‐OMe)]₂ ( 3 ) have been synthesized by treatment of Ph₃SnCl and Ph₂SnCl₂ with Na(O₂AsMe₂) in methanol, respectively. [Bu₂ClSn(O₂AsMe₂)] ( 2 ) has been prepared by the reaction of Bu₂SnCl₂ with HO₂AsMe₂ in methanol. X‐ray diffraction studies show 1 to crystallize in the monoclinic space group P2₁/n with a = 699.8(1), b = 1961.4(2), c = 1433.6(2) pm, β = 95.17(1)°, and Z = 4. 2 also crystallizes monoclinic in the space group P2₁/m, the cell parameters being a = 480.6(1), b = 1992.7(2), c = 808.8(1) pm, β = 103.726(5)°, and Z = 2. Both compounds form infinite chains with alternating (Me₂AsO₂)^? and (R₃Sn)⁺ or (R₂ClSn)⁺ units. The dimer 3 consists of 8‐membered (OSnOAs)₂ rings in which the tin atoms are bridged by methanolate bridges. It crystallizes triclinic in the space group with a = 822.8(2), b = 910.4(2), c = 929.2(2) pm, α = 77.04(3)°, β = 82.35(3)°, γ = 68.69(3)°, and Z = 1 for the dimer. The vibrational and mass spectra of 1 , 2 and 3 are given and discussed.     

Synthesis and reactions of 3‐pyrrolidinones

This review presents a survey of the synthetic methods and reactions of 3‐pyrrolidinones I (R = H, alkyl, acyl, ester; R₁ = H, alkyl, cyano, ester, etc). 3‐Pyrrolidinones are synthetically versatiles substrate, as they can be used for synthesis of a large variety of heterocyclic compounds, such as indoles and 5‐deazapteroic acid analogues and as a raw material for drug synthesis. The high reactivity of an active methylene group next to the carbonyl of the pyrrolidine ring is useful for various syntheses.     

Adsorption Kinetics,Equilibrium, and Thermodynamics of Copper From Aqueous Solutions using Silicon Carbide Derived from Rice Waste

Adsorption of Cu(II) from aqueous solution on a novel adsorbent, silicon carbide ash (SiC ash), was studied using batch technique. The adsorbent was prepared by pyrolysis of Egyptian rice waste (rice straw and rice husk) and was characterized by scanning electron microscopy (SEM), energy-dispersive x-ray (EDX), Fourier-transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and surface area analysis by Brunauer-Emmett-Teller (BET) Theory. The influence of pH, contact time, initial Cu(II) concentration, adsorbent dose, agitation speed, and temperature was investigated. Adsorption kinetics was analyzed using the pseudo-first-order, the pseudo-second-order, and intraparticular diffusion model. The adsorption process was found to follow a pseudo-second-order rate mechanism. The adsorption isotherm data could be well described by the Langmuir and Freundlich than the Dubinin–Radushkevich adsorption model. The adsorption capacity of 22.06 mg g^?1for SiC ash was obtained at pH = 5 and temperature of 298 K. Thermodynamic parameters, change in the free energy (ΔG°), the enthalpy (ΔH°), and the entropy (ΔS°), were also calculated. The overall adsorption process was exothermic, spontaneous in nature, and proceeds with decreased randomness as the entropy is negative value. Adsorption process was successfully applied to remove Cu(II) from an industrial wastewater sample.     

Synthesis,characterization, antimicrobial activity and ultrastructure of the affected bacteria of new quinoline compounds

The reaction on 8-hydroxy quinoline-7-aldehyde azo compounds (HL _n ) (where n = 1–5) with 4-amino-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one to obtain HL _n (where n = 6–10) have been characterized by means of TLC, melting point and spectral data, such as IR, ¹H NMR, mass spectra and thermal studies. The X-ray diffraction patterns of two starting materials 8-hydroxy quinoline-7-aldehyde (start 1), 4-amino-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (start 2) and the ligands (HL_5,10) are investigated in powder form. All the ligands have been screened for their antimicrobial activity against four local bacterial species, two Gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) and two Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) as well as against four local fungi; Aspergillus niger, Alternaria alternata, Penicillium italicum and Fusarium oxysporium. The results show that the azo ligands (HL _n ) (where n = 1–5) have no antimicrobial activity against bacteria and fungi while most azomethine ligands (HL _n ) (where n = 6–10) are good antibacterial agents against E. coli and K. pneumoniae as well as antifungal agents against P. italicum and A. alternata. The results were compared to standard substances (start 1) and (start 2). Among the azomethine ligands, HL₁₀ was the most effective against the most microorganisms tested. The size of clear zone was ordered as p-(OCH₃ < CH₃ < H < Cl < NO₂) as expected from Hammett’s constant (σ ^R ). Also, the ultrastructure study of the affected bacteria confirmed that HL₈ is good antibacterial agent against E. coli and S. aureus.     

Comparative Study of Carbon Paste,Screen Printed,and PVC Potentiometric Sensors Based on Copper‐sulphamethazine Schiff Base Complex for Determination of Iodide – Experimental and Theoretical Approaches

New poly vinyl chloride (PVC) membrane, carbon paste (CP), and screen printed (SP) electrodes are constructed for iodide sensing. They are based on copper (II)‐sulphamethazine Schiff base complex as suitable carrier. Mechanism was proved by FT‐IR and UV‐Vis spectroscopy. Computational study involving binding energies calculations at DFT/B3LYP level of theory confirmed the proposed mechanism and agreed the observed selectivity pattern. Responses are near‐Nernstian (?55.0, ?51.0 mV/concentration decade) for PVC, and SP electrodes, and super‐Nernstian (?61.2 mV/concentration decade) for the CP electrode. Lower limit of detection (3.2×10^?6 mol L^?1) and improved selectivity over the highly interfering thiocyanate were obtained in comparison with the previously reported Schiff base complexes‐based iodide sensors.