Experimental and theoretical investigation on adsorption and corrosion inhibition properties of imidazopyridine derivatives on mild steel in hydrochloric acid solution

Imidazopyridine derivatives, namely 4‐methoxy‐N‐((2‐(4‐methoxyphenyl)H‐imidazo[1,2‐a]pyridin‐3‐yl)methylene)benzenamine (MMPIPB) and 4‐chloro‐N‐((2‐(4‐methoxyphenyl)H‐imidazo[1,2‐a]pyridin‐3yl)methylene)benzenamine (CMPIPB), were investigated as inhibitors for mild steel corrosion in 15% HCl solution using the weight loss and electrochemical techniques. According to electrochemical impedance spectroscopy studies, MMPIPB and CMPIPB show corrosion inhibition efficiency of 84.8 and 77.2% at 10‐ppm concentration and 98.1 and 94.8% at 80‐ppm concentration, respectively at 303 K. The corrosion inhibition efficiency of both inhibitors increased with increasing inhibitor concentration and decreased with increasing temperature. The adsorption of both inhibitor molecules on the surface of mild steel obeys Langmuir adsorption isotherm. Polarization studies showed that both studied inhibitors were of mixed type in nature. Electrochemical impedance spectroscopy studies showed that for both inhibitors, the value of charge transfer resistance increased and double‐layer capacitance decreased on increasing the concentration of inhibitors. Scanning electron microscopy, energy‐dispersive X‐ray spectroscopy (EDX), and atomic force microscopy were performed for surface study. The density functional theory was employed for theoretical calculations. Copyright © 2014 John Wiley & Sons, Ltd.     

In situ determination of metastable zone width by a simple optical probe

The metastable zone width (MSZW), which denotes the region between the solubility curve and the onset of nucleation, is an important control parameter for successful operation of a solution crystallization process as it defines an operating boundary for the crystallization process. The MSZW can be approximated as the gap between the loci of cloud points that correspond to onset of nucleation and clear points that closely represent solubility. This work presents the design and application of a simple optical probe consisting of a line laser source, a light‐dependent resistor, and a simple processing circuit for in situ determination of onset of nucleation of a crystallization process. Three different crystallization processes, namely, cooling crystallization of glycine, cooling crystallization of L‐asparagine monohydrate, and anti‐solvent crystallization of glycine, are investigated to assess the performance of the in situ probe. In all the cases, the cloud points and clear points are conveniently detected by sharp changes in output voltage of the probe with reasonable accuracy. The presented optical probe can be used as a simple and inexpensive alternative tool in the area of crystallization process monitoring.     

Radon as a tracer for helium exploration in geothermal areas

High heat flow and weak structural features in geothermal areas allow easy passage for release of subsurface gases to the atmosphere. In particular, radon and helium are constantly transported from the earth's interior and vented out through exhalation points in permeable fault zones. At some places unusually large concentrations of helium may be encountered in soil airs. The possibility of trapping the released helium for bulk use has recently emerged. Because of its highly dispersive nature, helium is a difficult gas to detect during field explorations. Radon monitoring is thus taken up to locate structurally weak zones that allow helium permeation. The technique was recently adopted to determine high helium exhalation points in the Birbhum–Santhal Paragana geothermal area.     

Quantum chemical calculation of the barrier for tunneling of hydrogen in hydrogen abstraction from methane by methyl

An adiabatic reaction path for hydrogen abstraction from methane by methyl is computed by quantum chemical methods and then symmetrized by properly defining the reaction coordinate. The theoretical barriers are then fitted with the barriers defined by the parabolic and Eckart functions. Rate constants for the hydrogen and deuterium-abstraction processes via tunneling at low temperatures are then computed.     

Permanence and global attractivity for facultative mutualism system with delay

In this paper, we consider a facultative mutualism system with different delays. Sufficient criteria for permanence and global attractivity for the system are established. Ultimate uniform boundedness of the solutions ensures permanence. For the global attractivity of the system, magnitude of the delays plays a major role. Copyright © 2003 John Wiley & Sons, Ltd.     

Facile synthesis of 3-aryl/alkylamino 5-aryl/alkyl 1,2,4-oxadiazoles from acylthiourea

Facile and selective synthesis of 3-aryl/alkylamino 5-aryl/alkyl 1,2,4-oxadiazoles starting from N-acylthioureas has been demonstrated. The regio-selectivity is achieved by simply selecting an appropriate base used for the generation of hydroxyl amine from the corresponding hydrochloride salt. This method also avoids the use of toxic cyanogen bromide. The structure of the synthesized oxadiazoles has been resolved by tandem mass spectral studies.     

Duality in fuzzy quadratic programming with exponential membership functions

In this paper, we have presented fuzzy primal-dual quadratic programming problems and proved appropriate duality results taking exponential membership function.     

Effect of diffusion on a two-species eco-epidemiological model

This paper deals with the stabilizing effect of diffusion on a prey?–?predator system where the prey population is infected by a microparasite. The predator functional response is a concave-type function. Conditions for the local as well as global stability of the model without diffusion are derived in terms of system parameters. It is also shown that an unstable equilibrium of the model without diffusion can be made stable by increasing the diffusion coefficients appropriately.     

Arylations of allylic acetates with triarylbismuths as atom-efficient multi-coupling reagents under palladium catalysis

Arylation of allylic acetates employing triarylbismuths as multi-coupling reagents under palladium-catalyzed conditions was reported. Triarylbismuths as nucleophilic coupling partners were used in sub-stoichiometric amounts with respect to allylic acetates and thus served as atom-efficient multi-coupling reagents. A variety of allylic acetates were cross-coupled with triarylbismuths to furnish the corresponding functionalized 1,3-disubstituted propenes in good to excellent yields in short reaction times. The reported palladium protocol also yielded chemo-selective allylic arylations in high yields.     

Catechol oxidase activity of dinuclear copper(II) complexes of Robson type macrocyclic ligands: Syntheses, X-ray crystal structure, spectroscopic characterization of the adducts and kinetic studies

Five dinuclear copper(II) complexes, [Cu₂L¹(N₃)₂·2H₂O] (1), [Cu₂L²(N₃)₂·2H₂O] (2), [Cu₂L³(N₃)₂·2H₂O] (3), [Cu₂L⁴(N₃)₂·2H₂O] (4) and [Cu₂L⁵(N₃)₂·2H₂O] (5) of Robson type macrocyclic Schiff-base ligands derived from [2 + 2] condensation of 4-methyl-2,6-diformylphenol with 1,3-diaminopropane (H₂L¹), 1,2-diaminoethane (H₂L²), 1,2-diaminopropane (H₂L³), 1,2-diamino-2-methylpropane (H₂L⁴) and 1,2-diaminocyclohexane (H₂L⁵), respectively have been synthesized and characterized. Catecholase activity of those complexes using 3,5-di-tert-butylcatechol as substrate has been investigated in two solvents, methanol and acetonitrile. The role of the solvent and of the steric properties of the macrocyclic ligand of these complexes on their catecholase activity has been examined thoroughly. Acetonitrile is observed to be a better solvent than methanol as far as their catalytic activity is concerned. However, methanol reveals to be a better choice to identify the enzyme–substrate adduct. The investigation also prompted that chelate ring size does affect on the catalytic efficiency: 6-membered ring (as in H₂L¹) exhibits better activity than its 5-membered counterpart (as in H₂L²). The activity of the 5-membered counter parts also depend upon the steric factor. Moreover, the catalytic activity of the complexes is enhanced to a significant extent by increasing the bulkiness of the substituents on the backbone of macrocyclic H₂L² ligands.