Sustainable and efficient flame retardant materials for achieving high fire safety for polystyrene composites

Journal of Thermal Analysis and Calorimetry - Novel porous carbon sheets were developed as green, renewable, cost-effective, and efficient flame retardant material for thermoplastic polymers....     

Simple and efficient cleavage reaction of the boc group in heterocyclic compounds

Dedicated to the memory of Pr. Ladjama Daif A series of chiral cyclosulfamides have been synthesized by alkaline cyclisation starting from N‐benzoylamino acids (Ala, Val, Leu, Phe) derivatives and chlorosulfonyl isocyanate. A simplified and regioselective deprotection of the cyclic compounds (cyclosulfamides) containing the tert‐butyloxycarbonyl group (Boc) has been achieved in good yield by fusion under reduced pressure.     

Tailoring approach for exploring electron densities and electrostatic potentials of molecular crystals

Experimental and theoretical studies of electron densities and the corresponding derived entities such as electrostatic potentials have been the primary means of understanding the chemical nature and electronic properties of crystalline substances. Conventional crystal calculation methods such as the embedded cluster models are capable of performing calculations on small and medium-sized molecules, while periodic ab initio methods can treat crystals with up to 200 atoms per unit cell. A linear scaling method, viz. the molecular tailoring approach, has recently been developed for obtaining ab initio quality one-electron properties. In the present study, the molecular tailoring approach is employed to generate electron density, electrostatic potential and interaction density maps with the ibuprofen crystal as a test case. The interaction density and electrostatic potential maps produced in the present work succinctly bring out the actual crystalline environment around a given reference molecule by including the interactions with atoms in its neighborhood. The results obtained from the molecular tailoring approach may thus be expected to enhance our understanding of the environment in the crystalline material with reasonably small computational effort.Contribution to the Jacopo Tomasi Honorary Issue     

Purification of DNA-derived deoxynucleotides from leukocytes involving nuclease elution of an ion-exchange column

A method has been developed in which the DNA of leukocytes (as the buffy coat from blood) is isolated in the form of its constituent deoxynucleotides. The steps in this method are as follows: (1) lyse the leukocytes with sodium dodecyl sulfate (SDS) and enzymatically digest the proteins and RNA, (2) remove the SDS on a non-polar adsorbent (Bio-Beads SM-4) and then trap the DNA on a quaternary amine silica cartridge, (3) wash the column with 1 M NaCl-buffer, (4) digest the DNA on the column with staphylococcal nuclease and (5) elute the digested DNA with 0.5 M NaCl-buffer and digest it further with bovine spleen phosphodiesterase II to deoxynucleotide-3′-monophosphates. From a 40-μl sample of butty coat was obtained 126 ± 14 μg (two experiments, eight sample total) of deoxynucleotides. Reversed-phase high-performance liquid chromatography, which removed the added enzymes, showed only peaks for deoxynucleotides. For comparison, the amount of deoxynucleotides obtained from the leukocytes by an automated phenol extraction procedure was 101 ± 5.4 μg (one experiment in triplicate).     

Microdetermination of some xylenols via investigation of their catalyzed reactions with iodine

The oxidation of some xylenols with iodine in aqueous ethanolic solutions in the presence of silver ions as a catalyst was investigated and used for microdetermination of these reductants. The study of these redox reactions and the microdetermination of these phenols were performed by volumetric and spectrophotometric methods. These methods were compared. The spectrophotometric method was more accurate at very low concentrations (60–488 μg). The volumetric methods used silver ions as catalyst. The potentiometric method is more accurate than the visual method. Possible schemes for the course of these redox reactions were suggested. One electron processes for oxidation of xylenols have been indicated.     

A sequential injection spectrophotometric method for the determination of penicillamine in pharmaceutical products by complexation with iron(III) in acidic media

A simple, robust and sensitive sequential injection spectrophotometric method for the assay of penicillamine (PA) in pharmaceutical formulations is developed. The method was based on the complex formation when PA is reacted with iron(III) solution in hydrochloric acid media. The deep blue colored PA-iron(III) complex produced is monitored at a maximum wavelength of 600 nm. A five level orthogonal array design coupled to genetic algorithm was employed to obtain the optimum experimental conditions for the determination of PA using peak absorbance as the measure of the system's performance criterion. A linear dynamic range for the determination of PA of 25-300 ppm was obtained with a sampling frequency of 50 h⁻¹ and a relative standard deviation of less than 0.98%. The method was successfully applied to the determination of PA in pharmaceutical formulations.     

Ligand Functionalization and Its Effect on CO2 Adsorption in Microporous Metal–Organic Frameworks

We report two new 3D structures, [Zn₃(bpdc)₃(2,2′‐dmbpy)] (DMF)_x(H₂O)_y ( 1 ) and [Zn₃(bpdc)₃(3,3′‐dmbpy)]?(DMF)₄(H₂O)_0.5 ( 2 ), by methyl functionalization of the pillar ligand in [Zn₃(bpdc)₃(bpy)] (DMF)₄?(H₂O) ( 3 ) (bpdc=biphenyl‐4,4′‐dicarboxylic acid; z,z′‐dmbpy=z,z′‐dimethyl‐4,4′‐bipyridine; bpy=4,4′‐bipyridine). Single‐crystal X‐ray diffraction analysis indicates that 2 is isostructural to 3 , and the power X‐ray diffraction (PXRD) study shows a very similar framework of 1 to 2 and 3 . Both 1 and 2 are 3D porous structures made of Zn₃(COO)₆ secondary building units (SBUs) and 2,2′‐ or 3,3′‐dmbpy as pillar ligand. Thermogravimetric analysis (TGA) and PXRD studies reveal high thermal and water stability for both compounds. Gas‐adsorption studies show that the reduction of surface area and pore volume by introducing a methyl group to the bpy ligand leads to a decrease in H₂ uptake for both compounds. However, CO₂ adsorption experiments with 1′ (guest‐free 1 ) indicate significant enhancement in CO₂ uptake, whereas for 2′ (guest‐free 2 ) the adsorbed amount is decreased. These results suggest that there are two opposing and competitive effects brought on by methyl functionalization: the enhancement due to increased isosteric heats of CO₂ adsorption (Q_st), and the detraction due to the reduction of surface area and pore volume. For 1′ , the enhancement effect dominates, which leads to a significantly higher uptake of CO₂ than its parent compound 3′ (guest‐free 3 ). For 2′ , the detraction effect predominates, thereby resulting in reduced CO₂ uptake relative to its parent structure 3′ . IR and Raman spectroscopic studies also present evidence for strong interaction between CO₂ and methyl‐functionalized π moieties. Furthermore, all compounds exhibit high separation capability for CO₂ over other small gases including CH₄, CO, N₂, and O₂.     

Ionic liquid behavior and high thermal stability of silver chloride nanoparticles: Synthesis and characterization

Silver chloride was found to be stable even after calcination at 650 °C for 10 h. SEM studies revealed the morphology of silver chloride as hexagonal particles. TEM studies show the size of silver chloride particles to have an average size of 6–7 nm. Thermal studies suggest that silver chloride nanoparticles behave like ionic liquid or molten salt in the range of 455–650 °C.     

Synthesis and Biological Activity of New Chiral N‐Acylsulfonamide Bis‐oxazolidin‐2‐ones

A new series of chiral 5‐substituted bis‐oxazolidinones containing an acylsulfonamide moiety has been synthesized starting from chlorosulfonyl isocyanate, (l )‐ethyl lactate, and oxazolidin‐2‐ones. All the reactions were conducted at ambient temperature, and the N‐acylsulfonamide bis‐oxazolidin‐2‐ones were obtained with high yields within 2 h. Some of the newly synthesized compounds were evaluated in vitro against the virulent strain RH of Toxoplasma gondii and the human lymphocytes, and showed promising results.