Ionic studies of sodium alginate isolated from Sargassum terrarium (brown algea) karachi coast with 2,1-electrolyte

Physical and chemical analysis of the polysaccharide isolated from Sargassum Terarrium (brown algae) of Karachi coast showed characteristics of the sodium alginate. Optical rotations and sulphated ash content were found and FTIR spectra showed a sharp and strong absorption band at 1600 cm^?1 representing carboxylate ion which conforms high uronic acid content of the product. The viscosities of aqueous 0.1% sodium alginate solution were measured in the presence of copper II chloride (CuCl₂). The viscosities were found to be increased with the increase in the concentration of electrolyte. Viscosities were also found affected with temperature. ‘A’ and ‘B’ coefficients of Jones–Dole equation were evaluated. The increase in positive values of ‘B’ coefficient with the rise of temperature led to conclusion that given electrolyte in 0.1% aqueous sodium alginate solution behaves as structure maker. Thermodynamic parameters regarding to activated state like energy of activation E_η, change in free energy of activation ΔG_η and change of entropy of activation ΔS_η were also evaluated. Straight-line plots of log η versus 1/T observed with positive slopes show the effect of temperature on the viscosities of solutions. Energy of activation (E_η) was found to be decreased with the rise of temperature. Change in free energy of activation (ΔG_η) was also found to be increased with increase in concentrations of electrolyte and also with rise of temperature. The values of change in entropy of activation (ΔS_η) were also calculated. Negative values of ΔS_η were found to be increased with increase in concentration of electrolyte and also with rise of temperature.     

A study on melt grafting of maleic anhydride onto low‐density polyethylene and its blend with polyamide 6

Graft copolymerization of low‐density polyethylene (LDPE) with a maleic anhydride (MAH) was performed using intermeshing corotating twin‐screw extruder in the presence of benzoyl peroxide (BPO). The LDPE/polyamide 6 (PA6) and LDPE‐g‐MAH/PA6 blends were prepared in a corotating twin‐screw extruder. The melt viscosity of the grafted LDPE was measured by a capillary rheometer. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microcopy (SEM). The influence of the variation in temperature, BPO and MAH concentration, and temperature on the grafting degree and on the melt viscosity was studied. The grafting degree increased appreciably up to about 0.45 phr and then decreased continuously with an increasing BPO concentration. According to the FTIR analysis, it was found that the amount of grafted MAH on the LDPE chains was ～5.1%. Thermal analysis showed that melting temperature of the graft copolymers decreases with increasing grafting degree. In addition to this, loss modulus (E″) of the copolymers first increased little with increasing grafting and then obviously decreased with increasing grafting degree. Furthermore, the results revealed that the tensile strength of the blends increased linearly with increasing PA6 content. The results of SEM and mechanical test showed that the blends have good interfacial adhesion and good stability of the phase structure, which is reflected in the mechanical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 267–275, 2010     

MgCl2/Et3N Base System as a New Catalyst for the Synthesis of α‐Hydroxyphosphonate

An efficient and simple synthesis of α‐hydroxyphosphonates via reaction of aldehydes and ketones with dimethylphosphite in the presence of MgCl₂/Et₃N base system is reported. The use of readily available and easy to handle reagent MgCl₂/Et₃N makes this method simple, convenient, and practical.     

New insecticidal amides from petroleum ether extract of dried Piper nigrum L. whole fruits

The petroleum ether extract of dried ground whole fruits of Piper nigrum L. afforded 20 compounds (1-20) including two new insecticidal amides named as pipnoohine (1), and pipyahyine (2), seven reported for the first time from this plant (12, 13, 15-17, 19, 20), and eleven known compounds (3-11, 14, 18). The structure of 1 has been elucidated as (2E,4E,12Z)-N-(4-methylpentyl)octadeca-2,4,12-trienamide and that of 2 as (2E,4E,11E)-12-(benzo[1,3]dioxol-5-yl)-N-(3-methylbutyl)dodeca-2,4,11-trien-amide through extensive ID-, 2D-NMR spectral studies and chemical reactions. The known compounds have been identified through comparison of their spectral data with those reported in literature. 1 and 2 exhibited toxicity at 35.0 and 30.0 ppm respectively against fourth instar larvae of Aedes aegypti L. by WHO method.     

Synthesis of New Aza Macrocyclic Diamides 2,2′‐Diaminodiphenyl Sulfide Using Crab‐Like Method

Six new aza crown ethers (4–9) were synthesized based on the conventional route crab‐like method with the reaction of corresponding bis‐α‐chloroacetamidediphenylsulfide (BCADPS) (3) and aliphathic diamines (a–e) in refluxing acetonitrile in good yields. BCADPS (3) was synthesized with the reaction of 2,2′‐diaminodiphenyl sulfide (2) and chloroacetyl chloride. Interestingly, only the macrocyclization of BCADPS (3) with diamine (e) was led to the cryptand (9) in which methylene hydrogens were found as diastereotopic nucleis which is attributed to the rigidity of the cryptand ( 9 ). The formation of this cryptand ( 9 ) may be related the template effect of potassium ion. The structures of all compounds were confirmed using IR, ¹H‐NMR, ¹³C‐NMR, mass spectroscopies, and elemental analysis.     

Synthesis of (R)-alpha-benzylmethionine: a novel rearrangement during alkylation of the Seebach (R)-methionine oxazolidinone

Alkylation of the enolate of the Seebach (R)-methionine oxazolidinone with benzyl bromide gave the expected benzylated product in low yield. The major product was a novel amine arising from oxazolidinone cleavage, decarboxylation, alkylation and finally hydrolysis. The rearrangement could be suppressed by using a more reactive electrophile or by using the N-Cbz instead of the N-benzoyl protecting group, and the required (R)-alpha-benzyl-methionine was obtained in 78% yield and in an enantiomeric ratio of 90:10.     

CH_4 reforming with CO_2 for syngas production over La_2O_3 promoted Ni catalysts supported on mesoporous nanostructured γ-Al_2O_3

Nanostructured γ-Al2O3 with high surface area and mesoporous structure was synthesized by sol-gel method and employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by XRD, N2adsorption-desorption,TPR, TPO, TPH, NH3-TPD and SEM techniques. The BET analysis showed a high surface area of 204 m2 g-1and a narrow pore-size distribution centered at a diameter of 5.5 nm for catalyst support. The BET results revealed that addition of lanthanum oxide to aluminum oxide decreased the specific surface area. In addition, TPR results showed that addition of lanthanum oxide increased the reducibility of nickel catalyst. The catalytic evaluation results showed an increase in methane conversion with increasing lanthanum oxide to 3 mol% and further increase in lanthanum content decreased the catalytic activity. TPO analysis revealed that the coke deposition decreased with increasing lanthanum oxide to 3 mol%. SEM and TPH analyses confirmed the formation of whisker type carbon over the spent catalysts. Addition of steam and O2 to dry reforming feed increased the methane conversion and led to carbon free operation in combined processes.     

New Polydentate Trimethylsilyl Chalcogenide Reagents for the Assembly of Polyferrocenyl Architectures

A series of polychalcogenotrimethylsilane complexes Ar(CH₂ESiMe₃)_n, (Ar=aryl; E=S, Se; n=2, 3, and 4) can be prepared from the corresponding polyorganobromide and M[ESiMe₃] (M=Na, Li). These represent the first examples of the incorporation of such a large number of reactive ?ESiMe₃ moieties onto an organic molecular framework. They are shown to be convenient reagents for the preparation of the polyferrocenylseleno‐ and thioesters from ferrocenoyl chloride. The synthesis, structures, and spectroscopic properties of the new silyl chalcogen complexes 1,4‐(Me₃SiECH₂)₂(C₆Me₄) (E=S, 1 ; E=Se, 2 ), 1,3,5‐(Me₃SiECH₂)₃(C₆Me₃) (E=S, 3 ; E=Se, 4 ) and 1,2,4,5‐(Me₃SiECH₂)₄(C₆H₂) (E=S, 5 ; E=Se, 6 ) and the polyferrocenyl chalcogenoesters [1,4‐{FcC(O)ECH₂}₂(C₆Me₄)] (E=S, 7 ; E=Se, 8 ), [1,3,5‐{FcC(O)ECH₂}₃(C₆Me₃)] (E=S, 9 ; E=Se, 10 ) and [1,2,4,5‐{FcC(O)ECH₂}₄(C₆H₂)] (E=S, 11 illustrated; E=Se, 12 ) are reported. The new polysilylated reagents and polyferrocenyl chalcogenoesters have been characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ⁷⁷Se), electrospray ionization mass spectrometry and, for complexes 1 , 2 , 3 , 4 , 7 , 8 , and 11 , single‐crystal X‐ray diffraction. The cyclic voltammograms of complexes 7 – 11 are presented.     

Synthesis,Characterization, and Photoluminescence Properties of Silver(I) Metal‐Organic Polymers with Nanochannels Based on 2‐Sulfoterephthalic Acid and Di(pyridin‐2‐yl)amine Ligands

Two new silver(I) 3D coordination polymers, namely [Ag₃(2‐stp)(dpa)]_n ( 1 ) and {[Ag₂(2‐stp)(H₂O)]?Hdpa}_n ( 2 ) (2‐NaH₂stp=sodium 2,5‐dicarboxysulfonate, dpa=di(pyridine‐2‐yl)amine) were synthesized. The complexes were characterized by elemental analysis, FT‐IR spectra, thermogravimetric analyses (TGA), and single‐crystal X‐ray diffraction. In complex 1 , three neighboring Ag ions are bridged by N‐ and O‐atom, forming a 3D coordination network. The molecular structure of 2 is cation? anion species, forming 3D host? guest supramolecular network with the [Hdpa]⁺ cations encapsulated in the nanochannels. The photoluminescence properties of the complexes were also investigated in the solid state at room temperature.