Adsorption of the Dyes (Methylene Blue and Acridine Orange and Their Mixtures) from Aqueous Solutions on Cholesterol Surface

The adsorption of the dyes, methylene blue and acridine orange, from their aqueous solutions individually as well as in mixtures were investigated with respect to the variation of temperature and concentration of the KCl and the bile salt, sodium cholate. The features of different isotherms were presented and discussed. The isotherms obtained differ from those described by the Langmuir equation. The adsorption process was controlled by the ion-dipole and hydrophobic interactions. While KCl retarded the adsorption, the bile salt enhanced the process due to synergistic effect.     

Single-step preparation and catalytic activity of mesoporous MCM-41 and SBA-15 silicas functionalized with perfluoroalkylsulfonic acid groups analogous to Nafion

Preparation of hybrid organic-inorganic MCM-41 and SBA-15 silicas functionalized with perfluoroalkylsulfonic acid groups has been achieved in a single step by reacting the mesoporous silicas with 1,2,2-trifluoro-2-hydroxy-1-trifluoromethylethane sulfonic acid beta-sultone; the catalysts showed higher activity than commercial Nafion-silica composite for the esterification of long chain fatty acids with ethanol.     

The effect of grass fiber filler on curing characteristics and mechanical properties of natural rubber

Natural rubber is reinforced with a novel type of grass fiber (Cyperus Tegetum Rox b). The effects of fiber loading of different mesh sizes on curing characteristics and mechanical properties of grass fiber filled natural rubber composite are studied. Since 400 mesh grass fiber loaded natural rubber composite shows superior mechanical properties, therefore the effect of silane coupling agent was studied for this particular composite. Here composites were prepared by using water leached grass fiber. Optimum cure time increases with the increase in fiber loading but the change in scorch time is less. The same trend of increase in optimum cure time is observed in the presence of Si69. But the value is higher compared to that of rubber composite without Si69. With increase in the fiber loading, modulus and hardness of the composite increases but tensile strength decreases. The mechanical properties of the composite, namely moduli at 200 and 300% elongation and hardness increase in the presence of Si69 but tensile strength is less compared to that of the composite without Si69. Elongation at break is not much affected due to the presence of Si69. Copyright © 2004 John Wiley & Sons, Ltd.     

Chain-transfer constant of fluoroalcohols

Chain transfer constants of some fluoroalcohols [HCF₂(CF₂)_n?1CH₂OH, n = 2, 4, 6] in the catalyzed polymerization of vinyl acetate, styrene, acrylonitrile, and methyl methacrylate at 60°C have been evaluated by a method based on degree of polymerization. Since fluoroalcohols are normally nonsolvents for polymers, a homogeneous reaction phase is maintained by carrying out the polymerization in benzene (except in case of acrylonitrile, where no solvent was used). The transfer constants vary, depending on the reactivity as well as the polarity of the radicals, in the following order: vinyl acetate > styrene > methyl methacrylate > acrylonitrile. Of the three fluoroalcohols studied, the transfer constants increase with the increasing value of n. The results have been interpreted in terms of polar structure contribution in the transition state of the transfer reactions.     

Complexes of NS and NSO donor ligands. Nickel(II), copper(II) and cobalt(II) complexes of glyoxal bis(morpholineN-thiohydrazone) and diacetyl bis(morpholineN-thiohydrazone)

Summary Reactions of glyoxal bis(morpholineN-thiohydrazone), H₂gbmth, with NiCl₂·6H₂O, Ni(OAc)₂·4H₂O, Ni(acac)₂· H₂O, CuCl₂·2H₂O, Cu(OAc)₂·H₂O, Cu(acac)₂, CoCl₂· 6H₂O, Co(OAc)₂·4H₂O and Co(acac)₂·2H₂O yield complexes of the type [M(gbmth)], [M=Ni^II, Cu^II or Co^II]. Diacetyl reacts with morpholineN-thiohydrazide in the presence of nickel salts to yield [Ni^II(dbmth)], [Ni^II(dmth)(OAc)]H₂O and [Ni^II(Hdmth)(NH₃)Cl₂] involving N₂S₂ and NSO donor ligands. Copper and cobalt complexes of N₂S₂ and NSO donor ligands with compositions [Cu^II(dbmth)], [Co^II(dbmth)]·4H₂O and [Co^II(H₂dbmth)]Cl₂, have been isolated. The compounds have been characterised by elemental analyses, magnetic moments, molar conductance values and spectroscopic (electronic and infrared) data.     

One-step synthesis and characterization of difunctionalized N-confused tetraphenylporphyrins

Three disubstituted N-confused porphyrins (2-4) were prepared in ca. 4% yield using a one-pot synthesis. These porphyrins bear 3,5-di-tert-butylphenyl groups substituted at the C(5) and C(20) meso positions and para-substituted (Br, NO(2), ethynyl) phenyl groups at the C(10) and C(15) meso positions. The specific orientation of the aryl rings around the macrocycle in porphyrin 2 was definitively determined using a combination of 1D ((1)H and (13)C) and 2D (gHMQC and gHMBC) NMR spectroscopy. The absorption spectra of 2-4 in CH(2)Cl(2) and dimethylacetamide are similar to those of N-confused tetraphenylporphyrin in the same solvents but have Soret and Q-bands that are shifted to lower energies. Steady-state fluorescence measurements revealed Q(x)(0,0) and Q(x)(0,1) bands similar in energy to the unsubstituted NCPs 1i and 1e. The fluorescence quantum yield results for two of these NCPs (2, 4) are atypical of porphyrin behavior and are being further investigated by time-resolved spectroscopy.     

Mode of termination in the copolymerization of vinyl acetate–isobutyl methacrylate and methyl methacrylate–methyl acrylate at 60°C

The mode of termination in the vinyl acetate–isobutyl methacrylate (VA–IBMA) and methyl methacrylate–methyl acrylate (MMA–MA) copolymerization systems has been investigated at 60°C. by using the dye-interaction technique for functional endgroup estimation. The results show that pairs of poly(vinyl acetate) radicals interact almost exclusively through a disproportionation mechanism. In the homopolymerization of methyl methacrylate and methyl acrylate, about 1.16 and 1.22 carboxyl-containing endgroups per polymer molecule have been estimated, which shows the predominance of disproportionation over combination in these termination reactions. In poly(isobutyl methacrylate) about 1.55 tagged initiator fragments per chain indicate that 29% of the total radicals terminate through the disproportionation mechanism. Cross termination in the (VA–IBMA) copolymerization system occurs almost entirely through combination for monomer feeds richer in isobutyl methacrylate content while for the MMA–MA system, combination is more important at intermediate monomer feed ratios. These results have been discussed in the light of different explanations for the reaction mechanism.     

A New Bismuth Nitrate–Catalyzed Electrophilic Substitution of Indoles with Carbonyl Compounds Under Solvent-Free Conditions

An expeditious synthetic method for the preparation of bis(indollyl)methane derivatives has been developed through a bismuth nitrate-catalyzed reaction of indole with various carbonyl compounds in mortar and pastle under solvent-free conditions.     

Highly chemoselective reduction of azides to amines by Fe(0) nanoparticles in water at room temperature

A highly chemoselective reduction of aryl, heteroaryl, acyl and sulfonyl azides to the corresponding amines has been achieved by Fe(0) nanoparticles in water at room temperature in the absence of external hydride source. Several readily reducible functionalities including alkene, alkyne, S-S linkage, OTBDMS remain unaffected during reduction.     

MASS SPECTROMETRIC FRAGMENTATION OF UNSYMMETRICALLY SUBSTITUTED METHYLPHOSPHONATE DIESTERS

Abstract

A series of structurally related unsymmetrically substituted methylphosphonate diesters have been synthesised and subjected to electron impact (El) mass spectral studies. These studies though aimed at total identification of the compounds, resulted in certain interesting observations and hence are being reported. In order to confirm the observations under electron impact and to support the mechanism of fragmentation we have also performed MSNS experiments in both daughter ion and parent ion modes.