Evaluation of the corrosion inhibition effect of micro/nanocapsulated polymeric coatings: a comparative study by use of EIS and Tafel experiments and the area under the Bode plot

In this paper we propose an approach for ranking self-healing polymeric coatings containing micro/nanocapsules in order of corrosion-protection effectiveness on exposure to 3.5 % (w/w) NaCl solution. The results indicated that development of electrochemical cells was inhibited by the active components of the ruptured embedded inhibitor micro/nanocapsules which were released into a scratch inflicted in the polymeric coating on steel surface. Undamaged surface film of test and control specimens exposed to the solution had excellent corrosion-inhibition performance, as reflected by results from both electrochemical impedance spectroscopy and polarization tests. Moreover, three coatings containing capsules synthesized at three different agitation rates with the same thickness were compared to determine the optimum rate. For the optimum rate the optimum thickness was then determined. The areas under Bode plots were determined and used as useful values for evaluation and ranking the coatings. It was found that the area under the Bode plot is a good criterion for evaluating polymeric coating degradation during immersion. There was good agreement between the results of this work and those from electrochemical tests.     

SYNTHESIS AND BIOLOGICAL ACTIVITY OF SOME NEW 8-HYDROXYQUINOLINE SULPHONAMIDE DERIVATIVES

Abstract

Some new derivatives containing both 8-hydroxyquinoline and sulphonylamino β-lactams and thiazolidinones have been prepared. These compounds were synthesized from the corresponding 8-hydroxyquinoline sulphonylhydrazide (1) by converting it to hydrazones (2). The latter hydrazones (2) were easily transformed to β-lactams (3) and thiazolidinones (4) by cyclocondensation reaction with chloroacetyl chloride and/or mercaptoacetic acid. Some metal chelates with Fe³⁺. Co²⁺+, Ni²⁺, Cu²⁺ and Cd²⁺ have been prepared for some of the compounds and screened in vitro for their biological activity.     

Facile Conversion of Epoxides to Thiiranes with Ammonium Thiocyanate Catalyzed with Oxalic Acid

Epoxids are efficiently converted to the corresponding thiiranes by ammonium thiocyanate (NH 4 SCN) in the presence of catalytic amounts of oxalic acid with excellent isolated yields under mild and nonaqueous reaction conditions. This conversion performed under both conventional heating and microwave conditions. Distinct rate enhancement is observed under microwave irradiation.     

SILICA PHOSPHORIC ACID/NaNO2 AS A NOVEL HETEROGENEOUS SYSTEM FOR THE COUPLING OF THIOLS TO THEIR CORRESPONDING DISULFIDES

Silica phosphoric acid was prepared via reaction of silica chloride (I) and phosphoric acid. Thiols can be readily converted to their corresponding thionitrites with a combination of silica phosphoric acid (II), wet SiO ₂ , and sodium nitrite in dichloromethane at room temperature. Disulfides result from the homolytic cleavage of the sulfur–nitrogen bond of the unstable thionitrite and subsequent coupling of the resultant thiyl radicals.     

KF/Al2O3 as an Efficient,Green, and Reusable Catalytic System for the Solvent-Free Synthesis of N-Alkyl Derivatives of Sulfonamides via Michael Reactions

KF/Al ₂ O ₃ efficiently catalyzes the microwave-assisted Michael addition of sulfonamides to α,β-unsaturated esters under solvent-free conditions to afford N-alkyl derivatives of sulfonamides as biologically interesting compounds in high yields and in short reaction times. In this reaction, N,N-dialkylsulfonamides are also produced, but in very low yields.     

A Simple and Highly Efficient One-Pot Procedure for the Synthesis of Amides via Beckmann Rearrangements Using 1-Tosylimidazole (TsIm)

A facile and highly efficient method for one-pot Beckmann rearrangement of ketoximes into N-substituted amides using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, ketoximes are refluxed with TsIm and Cs₂CO₃ in the presence of SiO₂ as a recyclable catalyst in DMF affording the corresponding amides in high yields. This methodology is highly efficient and regioselective for various structurally diverse ketoximes including symmetrical and unsymmetrical as well as cyclic oximes. The results of quantum mechanical studies used to rationalize the experimental outcomes are discussed.     

Regioselective Syntheses of 1-Aryl-substituted-5H-[1,3]thiazolo[3,2-a]quinazoline-5-ones During Sonogashira Coupling

Abstract

Reaction of 2-mercaptopropargylquinazoline-4-one with various aryliodides catalyzed by Pd–Cu leads to the regioselective formation of 1-arylsubstituted-5H-[1,3]thiazolo-[3,2-a]quinazoline-5-ones.

GRAPHICAL ABSTRACT      

Preconcentrative separation of chromium(III) species from chromium(VI) by cloud point extraction and determination by flame atomic absorption spectrometry

Microchimica Acta - We describe a high-throughput technique for the determination of chromium species in water samples by flame atomic absorption spectrometry (FAAS) after preconcentrative...     

Synthesis and α‐glucosidase inhibitory,DPPH scavenging activity of substituted 2‐oxo‐2H‐chromen‐7‐yl‐dihydrogen phosphate derivatives

Series of phosphorylated coumarin derivatives ( 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j ) were synthesized by Pechmann condensation, phosphorylation, and debenzylation reactions in very good yields. Thus, synthesized compounds ( 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j ) were evaluated for their α‐glucosidase and 1,1‐diphenyl‐2‐picrylhydrazyl scavenging activities; few compounds showed moderate to good activity. J. Heterocyclic Chem., 00 , 00 (2011).