Branching Regulation in Olefin Polymerization via Lewis Acid Triggered Isomerization of Monomers

We present a new strategy to regulate branching in chain‐walking olefin polymerization by triggering a rapid isomerization of 1‐alkene monomers into internal olefins by adding a Lewis acid. Polymerization of internal alkenes proceeds via chain‐walking to give polymers with much higher branching than 1‐alkene analogues. The utility of this approach is exemplified by synthesis of well‐defined block copolymers with distinct branching characteristics per block by addition of Lewis acid midway through a reaction. We propose a novel mechanism whereby Lewis acid undergoes a counterion swap with the complex which favors isomerization as well as forming adducts with ancillary ligands, freeing coordination sites for internal alkene coordination polymerization.     

Photophysical and antimicrobial properties of new double-armed benzo-15-crown-5 ligands and complexes

Research on Chemical Intermediates - New double-armed crown ether ligands linked to pyridine derivatives have been synthesized and characterized. These macrocyclic ligands (1–5) have been...     

Selective synthesis of fluorinated benzyl- or phenylpyrimidines from the heterocyclisation of α-trifluoroacetylarylpropanenitriles

Some 5-benzyl-6-trifluoromethyl-2,4-diaminopyrimidines analogous to trimethoprim and 6-aryl-5-trifluoroethyl-2,4-diaminopyrimidines analogous to pyrimethamine were prepared from the same synthons, trifluoromethylated β-ketonitriles. The heterocyclisation between enol ether of β-ketonitrile and guanidine leading to these compounds was studied.These fluorinated novel compounds were tested for their in vitro activity against Toxoplasma gondii, a widespread apicomplexan protozoa responsible for congenital toxoplasmosis and cerebral toxoplasmosis in immunocompromised patients.     

Pre-service mathematics teachers’ concept images of radian

This study investigates pre-service mathematics teachers’ concept images of radian and possible sources of such images. A multiple-case study was conducted for this study. Forty-two pre-service mathematics teachers completed a questionnaire, which aims to assess their understanding of radian. Six of them were selected for individual interviews on the basis of theoretical sampling. The data indicated that participants’ concept images of radian were dominated by their concept images of degree. As the data in this study suggested, pre-service mathematics teachers were reluctant to accept trigonometric functions with the inputs of real numbers but rather they use value in degrees. More interestingly, they have two distinct images of π : π as an angle in radian and π as an irrational number.     

Synthesis,antimicrobial and thermal studies of nitropyridine-substituted double armed benzo-15-crown-5 ligands; alkali (Na+ and K+) and transition metal (Ag+) complexes; reduction of nitro compounds

Journal of Inclusion Phenomena and Macrocyclic Chemistry - Nitropyridine substituted double-armed benzo 15-crown-5 compounds (1–4) were synthesized by the reactions of...     

Covalent Immobilization and Characterization of a Novel Pullulanase from <Emphasis Type="Italic">Fontibacillus</Emphasis> sp. Strain DSHK 107 onto Florisil® and Nano-silica for Pullulan Hydrolysis

A novel pullulanase partially purified from Fontibacillus sp. was covalently immobilized on Florisil® and nano-silica through both glutaraldehyde and (3-glycidyloxypropyl)trimethoxysilane spacer arms. The pullulanase immobilized on Florisil® and nano-silica through glutaraldehyde spacer arm showed 85 and 190 % activity of its free form, respectively, whereas no activity was observed when it was immobilized on the same supports through (3-glycidyloxypropyl)trimethoxysilane spacer arm. The maximum working pHs of both the immobilized pullulanases on Florisil® and nano-silica through glutaraldehyde spacer arm were determined as 5.0; however, the maximum working pH of the free pullulanase was pH 6.0. The maximum temperatures of all the pullulanase preparations were determined as 35 °C. The apparent K _m values were 1.49, 1.54, and 0.59 mg/mL pullunan, respectively, for the free and immobilized pullulanases on Florisil® and nano-silica. The corresponding apparent V _max values were 0.59, 1.53, and 1.57 U mg prot.^?1?min.^?1. Thermal stability of pullulanases immobilized on Florisil® and nano-silica was enhanced 6.5- and 15.6-folds, respectively at 35 °C and 6.6- and 16.0-folds, respectively, at 50 °C. The pullulanases immobilized on Florisil® and nano-silica protected 71 and 90 % of their initial activities after 10 reuses.     

Decolorization kinetics of the azo dye drimaren blue X3LR by laccase

Summary An extracellular Drimaren Blue X3LR decolorizing enzymatic activity was found in the crude filtrate of Funalia trogii grown by solid-state fermentation using wheat bran and soya bean waste. Decolorization of the azo dye Drimaren Blue X3LR by the crude filtrate and partially purified enzyme of Funalia trogii were investigated and compared. In the absence of additional redox mediator, maximum decolorization ratios of 81.33 % and 77.4 % were observed for Drimaren Blue X3LR using crude filtrate and partially purified enzyme respectively. Decolorization yield was found to be higher with crude enzyme preparations. Na₂S₂O₅ inhibited laccase and dye decolorizing enzyme activities but a significant peroxidase activity inhibition was not observed. Since the reaction was catalyzed in the absence of H₂O₂ as co-substrate, it could be concluded that this enzyme is not a peroxidase but may be a laccase.. The kinetic parameters of decolorization were calculated according to Michaelis constant (Km of 1.700 x 10^-5 mol dm^-3 and W_max = 8.02 x10^-7 mol dm^-3 sec^-1).     

Detailed studies on the reduction of aliphatic 3-, 4-, 6-, and 13-oximino esters: Synthesis of novel isomeric amino esters,oximino alcohols,and amino alcohols

The preparation of novel 3-, 4-, 6-, and 13-amino-tetradecanoic acid methyl esters (2a–d) obtained by the reduction of 3-, 4-, 6-, and 13-oximino-tetradecanoic acid methyl esters (1a–d), was investigated. Oximino esters were reduced to afford the corresponding amino esters using NaBH₄–ZrCl₄ reducing system with good yields (58–82%). However, the reduction of oximino esters with LiAlH₄ and BH₃. Tetrahydrofuran gave the corresponding novel 3-, 4-, 6-, and 13-oximino alcohols (3a–d), and 3-, 4-, 6-, and 13-amino alcohols (4a–d) respectively with good chemical yields.