Preparation and characterization of hydroxypropyl-β-cyclodextrin inclusion complex of eugenol: differential pulse voltammetry and (1)H-NMR

The objective of present investigation was to improve the solubility of Eugenol by preparing the inclusion complex of Eugenol with hydroxypropyl-β-cyclodextrin (Hp-β-CD) and characterize the prepared complex by using NMR and differential pulse voltammetry (DPV). Phase solubility curve was plotted using Hp-β-CD in ranging from 0-40 mM of Hp-β-CD and found to be linear. Therefore, inclusion complex was prepared in equimolar ratio of Eugenol and Hp-β-CD by lyophilization method. Fourier transform infrared spectroscopy (FT-IR), (1)H-NMR and DPV were performed for Eugenol, Hp-β-CD and prepared inclusion complex of Eugenol. 2D (two dimensional) NMR was also performed for prepared inclusion complex. The proton of phenol moiety of Eugenol experienced a pronounced chemical shift variation in (1)H-NMR. The positive sign of the variation for proton in (1)H-NMR indicated that the proton was located near to an oxygen atom in the Hp-β-CD cavity and its magnitude showed a strong interaction between -OH proton of Eugenol and Hp-β-CD. 2D NMR confirms the interaction between phenolic group and hydrogen atoms of Hp-β-CD. A well defined anodic peak current corresponding to oxidation of Eugenol in non-encapsulated and Hp-β-CD-Eugenol inclusion complex in phosphate buffer (pH 6.8) was obtained at about 0.35 V and 0.40 V, respectively. The positive shift in oxidation potential indicated the formation of complex via hydrophobic interactions. The oxidant power of Eugenol was retained in complex form as indicated by DPV results. Thus, its oxidation dependent pharmacological property such as antimicrobial activity is not affected after complexation with Hp-β-CD. Thus, (1)H-NMR, 2D-NMR and DPV techniques can be used as valuable tools to determine the mechanism of complexation and state of electrochemical active drug in inclusion complex.     

Effect of substrate texture on the growth of hematite nanowires

The effect of texture of iron foil substrate on the growth of hematite nanowires by annealing method has been investigated in detail. Three substrates of different textures were prepared from a [2 0 0] oriented iron foil by some simple processes. The hematite nanowires on these substrates were synthesized by annealing iron foil at 700 °C in moist oxygen. The growth pattern of nanowires on these substrates showed that the growth of hematite nanowires depends strongly on the iron substrate texture and [1 1 0] oriented iron grains are necessary for their growth. The samples were characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD), Electron Back Scatter Diffraction (EBSD) and Raman Spectroscopy. We have also tried to explain the various observations on the mechanism of growth. Mainly, the presence of water vapor significantly enhanced the formation of hematite nanowires which resulted in a very dense and aligned growth of nanowires on the substrate areas of favorable texture. Finally, the study proved the substrate texture to be a powerful tool to control growth of nanowires and can be used efficiently for patterning and large scale synthesis of the nanowires.     

Mechanically stable and corrosion resistant superhydrophobic sol-gel coatings on copper substrate

Development of the anticorrosion coatings on metals having both passive matrix functionality and active response to changes in the aggressive environment has raised tremendous interest in material science. Using a sol-gel deposition method, superhydrophobic copper substrate could be obtained. The best hydrophobic coating sol was prepared with methyltriethoxysilane (MTES), methanol (MeOH), and water (as 7 M NH₄OH) at a molar ratio of 1:19.1:4.31 respectively. The surface morphological study showed the ball like silica particles distributed on the copper substrate with particle sizes ranging from 8 to 12 μm. The coatings showed the static water contact angle as high as 155° and the water sliding angle as low as 7°. The superhydrophobic nature was maintained even though the deposited copper substrate was soaked for 100 h in 50% of HCl solution. The coatings are stable against humidity and showed superhydrophobic behavior even after 90 days of exposure. The coatings are mechanically stable and water drops maintained the spherical shape on the bent copper substrate, which was bent more than 90°.     

Algorithm for forming derivative-free optimal methods

We develop a simple yet effective and applicable scheme for constructing derivative free optimal iterative methods, consisting of one parameter, for solving nonlinear equations. According to the, still unproved, Kung-Traub conjecture an optimal iterative method based on k+1 evaluations could achieve a maximum convergence order of $2^{k}$ . Through the scheme, we construct derivative free optimal iterative methods of orders two, four and eight which request evaluations of two, three and four functions, respectively. The scheme can be further applied to develop iterative methods of even higher orders. An optimal value of the free-parameter is obtained through optimization and this optimal value is applied adaptively to enhance the convergence order without increasing the functional evaluations. Computational results demonstrate that the developed methods are efficient and robust as compared with many well known methods.     

A branch-and-cut method for 0-1 mixed convex programming

We generalize the disjunctive approach of Balas, Ceria, and Cornuéjols [2] and devevlop a branch-and-cut method for solving 0-1 convex programming problems. We show that cuts can be generated by solving a single convex program. We show how to construct regions similar to those of Sherali and Adams [20] and Lovász and Schrijver [12] for the convex case. Finally, we give some preliminary computational results for our method. Received January 16, 1996 / Revised version received April 23, 1999?Published online June 28, 1999     

Effect of a cocatalyst modifier in the synthesis of ultrahigh molecular weight polyethylene having reduced number of entanglements

The use of a hindered phenol to trap free trimethylaluminum (TMA) in methylaluminoxane (MAO) solutions has been reported to improve the performance of single‐site, homogeneous catalysts for olefin polymerization. In the present study, with the help of rheological analyses, we have investigated and compared the molecular weight, molecular weight distribution and entanglement density of ultrahigh molecular weight polyethylene synthesized with a single‐site catalyst activated by MAO and phenol‐modified MAO. While the number average molecular weight (M_n) of the obtained polymers remains the same for both activations, a higher yield and a higher entanglement density are found in the initial stages of polymerization on using phenol‐modified MAO as the cocatalyst. These results suggest that on using the phenol‐modified MAO as activator, a higher number of active sites are obtained. Surprisingly in the presence of untreated MAO, a tail in the higher molecular mass region is produced. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013     

Recent advances in the synthesis of C-5-substituted analogs of 3,4-dihydropyrimidin-2-ones: A review

3,4-Dihydropyrimidin-2-ones act as a versatile scaffold in organic synthesis, which serves as a significant template for the development of various therapeutic agents and shows a wide spectrum of activities. The attractive application of 3,4-dihydropyrimidin-2-ones in organic synthesis is undoubtedly owing to C-5 ester group, which is responsible for the change in its bioactivity. Introduction of various groups like electron-withdrawing and electron-donating groups at positions 1, 2, 3, 5, and 6 greatly increased biological activity. Significant efforts have been undertaken to exploit different synthetic routes to synthesize various derivatives of 3,4-dihydropyrimidin-2-ones. This review article gives a comprehensive account of the synthetic utility of C-5 substitution of 3,4-dihydropyrimidin-2-ones used in the design and synthesis of different types of compounds with greater emphasis on recent literature.     

Ionic liquid: an efficient and recyclable medium for the synthesis of octahydroquinazolinone and biscoumarin derivatives

Abstract  

A facile and environmentally benign procedure for the synthesis of octahydroquinazolinone and biscoumarin derivatives in ionic liquids is reported. Octahydroquinazolinones were synthesized in the presence of trimethylsilyl chloride (TMSCl) while the synthesis of biscoumarins required no additive. The ability to reuse the ionic liquid, the high yields, and ease of purification are the important features of this process.