Microwave-assisted Sinthesis of Thymyl Ethers and Esters in Aqueous Medium

Various thymyl ethers and esters have been synthesized by reactions of thymol with alkyl halides and acid chlorides, respectively, in aqueous medium under environmentally benign conditions using micro-wave irradiation. The products are important as potent pest managing agents.     

Cooling Characteristics During Bath Quenching of Test Probe Using Inverse Heat Transfer

It is of engineering importance to accurately predict the surface cooling characteristics in bath quenching of metals and alloys. In this investigation, the surface cooling characteristics in quenching of Wolfson probe are estimated with reasonable accuracy by solving an inverse heat conduction problem. Regularization method is used for smoothening the input temperature measurements at probe center, for superior inversion estimates. The reverse pool-boiling curve is captured on bath quenching characteristic, plotted as cooling velocity versus surface temperature. The prime advantage is the bypassing of convection coefficients, which are uncertain in pool boiling.     

Acylation Studies with Meldrum's Acid

Meldrum's acid (1) on bisacylation with succinyl chloride afforded a neutral diketo product (2); however, the dimer enolic products (3) with acidic nature resulted in glutaryl and adipyl dichlorides. Monoacylation of (1) with acetyl chloride gave acidic 5‐acetyl Meldrum's acid (4) in enol form.     

CsF promoted rapid synthesis of spirooxindole-pyran annulated heterocycles at room temperature in ethanol

A newer, versatile, and straightforward synthetic strategy for the construction of functionalized spirooxindole-pyran annulated heterocycles is described. The procedure is based on CsF-promoted rapid tandem Knoevenagel-Michael-Cyclocondensation reaction of isatin, malononitrile, and 4-hydroxycoumarin/barbituric acids/pyrazolone at room temperature in ethanol. This methodology has various advantages like easy operational, excellent yields within short reaction time (3-25 min), and simple isolation of products. The CsF has a dual role as a base and carbonyl activator.     

Variable Fluid Property Effect on Heat Transfer and Frictional Flow Characteristics of Water Flowing through Microchannel

The effects of temperature-dependent viscosity and thermal conductivity on heat transfer and frictional flow characteristics of water flowing through a microchannel are numerically investigated in this work. The hydrodynamically and thermally developing flow with no-slip, notemperature jump, and constant wall heat flux boundary condition is numerically studied using 2D continuum-based conservation equations. A significant deviation in Nusselt number from conventional theory is observed due to flattening of axial velocity profile due to temperaturedependent viscosity variation. The Nusselt number shows a significant deviation from conventional theory due to flattening of the radial temperature profile due to temperature-dependent thermal conductivity variation. It is noted that the deviation in Nusselt number from conventional theory is maximum for combined temperature-dependent viscosity and thermal conductivity variations. The effects of temperature-dependent viscosity and thermal conductivity on the Fanning friction factor are also investigated. Additionally, the effects of variable fluid properties on Poiseuille number, Prandtl number, and Peclet number are also investigated.     

Facile one-pot clean synthesis of benzimidazole motifs: Exploration on bismuth nitrate accelerated subtle catalysis

In the present letter, an efficient, clean and one-pot synthesis of 2-substituted benzimidazole and 1,2-disubstituted benzimidazole derivatives has been explored by reacting o-phenylenediamine with aromatic aldehydes using bismuth nitrate as a catalyst in ethanol at ambient temperature. This methodology avails with faster reactions, excellent yield, mild reaction conditions, use of inexpensive and non-toxic catalyst compared to literature reported hitherto.     

Microwave‐mediated synthesis and antibacterial activity of some novel 2‐(substituted biphenyl) benzimidazoles via Suzuki‐Miyaura cross coupling reaction and their N‐substituted derivatives

A series of some novel 2‐(substituted biphenyl) benzimidazoles and their N‐substituted derivatives were synthesized via microwave‐mediated Suzuki‐Miyaura coupling of 2‐(4‐iodophenyl)‐1H‐benzimidazole or 2‐(4‐iodophenyl)‐6‐amino‐1H‐benzimidazole and arylboronic acids. The method reported herein offers advantageous shorter reaction times, higher yields and is applicable to a large set of substrates. All the synthesized compounds were screened for their antibacterial activity against Staphylococcus aureus and Salmonella typhimurium bacterial species. J. Heterocyclic Chem., (2011).     

Fluid friction in incompressible laminar convection: Reynolds' analogy revisited for variable fluid properties

The Reynolds' analogy between the Stanton number (St) and the skin friction coefficient (c_f) is popularly believed to hold when St increases with increasing c_f, for simple situations. In this investigation, the validity of Reynolds' analogy between St and c_f for micro-convection of liquids with variations in fluid properties is re-examined. It is found that the Sieder-Tate's property-ratio method for obtaining Nusselt number corrections is theoretically based on the validity of Reynolds' analogy. The inverse dependence of Reynolds number and skin friction coefficient is the basis for validity of the Reynolds' analogy, in convective flows with fluid property variations. This leads to the unexpected outcome that Reynolds' analogy now results in St increasing with decreasing c_f. These results and their analyses indicate that the validity of Reynolds' analogy is based on deeper foundations, and the well-known validity criterion is a special case.     

Synthesis of waterborne nanopolyanilne latexes and application of nanopolyaniline particles in epoxy paint formulation for smart corrosion resistivity of carbon steel

Polyaniline (PANI) latexes were synthesized by emulsion polymerization using dodecyl benzene sulfonic acid (DBSA) and sodium dodecyl sulfate (SDS) as a surfactant. Synthesized PANI–DBSA and PANI–SDS latexes were characterized by IR and UV‐visible spectroscopies, and surface morphology was analyzed by transmission electron microscopy. The PANI–DBSA were found to be nanograin shaped whereas PANI–SDS were as nanofibers. In the second stage rheological properties of waterborne PANI latexes were characterized by viscosity measurement and their dispersion stability in water. The surface morphology of the coating was examined by scanning electron microscope (SEM). The anti‐corrosion performance of uncoated carbon steel, PANI–DBSA and PANI–SDS coated carbon steel was evaluated by tafel slope analysis and immersion test studies of 0.5, 1, and 1.5% PANI/Epoxy coatings were done in 5% NaCl aqueous solution. The results indicated that the nanoPANI in epoxy coating might work as an adhesion promoter and corrosion inhibitor. The waterborne latexes, thus, were found to be highly suitable and avoid the use of organic solvents or strong acids under environmentally benign conditions. Copyright © 2010 John Wiley & Sons, Ltd.