Gravimetric, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP) studies were carried out to investigate the comparative corrosion protection efficiency of four condensed uracils (CUs) on mild steel in 1 M HCl. EIS plots indicated that the addition of inhibitors increases the charge-transfer resistance (Rct), decreases the double-layer capacitance (Cdl) of the corrosion process, and hence increases inhibition performance. Moreover, the thermodynamic activation parameters for the corrosion reaction were calculated and discussed in relation to the stability of the protective inhibitor layer. The morphology of the surface was examined by scanning electron microscopy (SEM), and the surface composition was evaluated using energy-dispersive X-ray spectroscopy (EDX) to verify the presence of inhibitor on the mild steel surface. Quantum chemical study suggests that the heterocyclic rings in these compounds are structurally essential for the pr...

Application of Some Condensed Uracils as Corrosion Inhibitors for Mild Steel: Gravimetric, Electrochemical, Surface Morphological, UV–Visible, and Theoretical Investigations

Solvent-free multicomponent synthesis of pyranopyrazoles: per-6-amino-β-cyclodextrin as a remarkable catalyst and host

Publisher Summary This chapter focuses on the synthesis and applications of Pyrazol-3-ones. The chapter also highlights the reactions of the ring atoms of pyrazol-3-ones. It explores the reactivity of the ring substituents of pyrazol-3-ones. This chapter illustrates that the majority of pyrazol-3-ones have been synthesized from open chain precursors, and relatively few from5-,6-, 5,6-, 6,6-and 5,6,7-membered rings. Due to the growing use of combinatorial chemistry in various applications, use of polymer-supported methodologies have increased. The oxidation potentials as well as the hydroxyl radical scavenging activities for some pyrazol-3-ones have been detected and compared with edavarone's. The Schiff base 4-[(4-hydroxy-3-hydroxymethylbenzylidene) amino]-1,5-dimethyl-2-phenyl-1,2 dihydropyrazol-3-one retards the corrosion of steel. The chapter concludes that certain azopyrazol-3-ones may prove useful as labels for chromatographic analysis of carbohydrates.

Chapter 2 Pyrazol-3-ones. Part IV: Synthesis and Applications

Synthesis of some novel bioactive 4-oxy/thio substituted-1H-pyrazol-5(4H)-ones via efficient cross-Claisen condensation

A novel pyrazolone, 4,4-dichloro-1-(2,4-dichlorophenyl)-3-methyl-5-pyrazolone, as a potent catalytic inhibitor of human telomerase.

The bifunctional pyrazolopyridine (2) and pyrano-pyrazole (3) derivatives were prepared by the reaction of 2-(2,4-dinitrophenyl)-5-methyl-2,4-dihydro-3H-pyrazol-3-one (1) with p-methoxybenzaldehyde, malononitrile in the presence of ammonium acetate or piperidine, respectively. Compound 2 was used as the key intermediate to prepare the pyrazolo-pyrido-pyrimidine derivatives through its reaction with formic acid, formamide-formic acid-DMF, ammonium thiocyanate or reaction with triethyl orthoformate followed by cyclization with hydrazine hydrate. Reaction of 3 with triethyl orthoformate followed by cyclization with hydrazine hydrate gave the pyrazolo-pyrano-pyrimidine derivative 11. Reaction of ethyl-3-oxo-2-[2-phenyl-diazenyl]butanoate and ethyl 2-[2-(4-chlorophenyl)diazenyl]-3-oxobutanoate with 1 to give the pyrazolone derivatives 13a and 13b, was also considered.

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Synthesis of some new annulated pyrazolo-pyrido (or pyrano) pyrimidine, pyrazolopyridine and pyranopyrazole derivatives.

Pyrazolone derivative 3 was prepared by the nucleophilic addition of 2,5-diphenyl-2,4-dihydro-3H-pyrazol-3-one (1) to chalcone (2). Reaction of 3 with hydrazine hydrate, phenylhydrazine, hydroxylamine hydrochloride, p-chlorobenzaldehyde, acetyl chloride and phosphorus pentasulfide afforded the corresponding hydrazone, phenylhydrazone, oxime, arylidene, O-acetyl and dithio derivatives. Pyrazolone 1 was condensed also with cyclohexanone and aromatic aldehydes; the behaviour of the obtained arylidene derivatives towards hydrazines, cyclohexanone, malononitrile and urea was also investigated. Some of the new compounds showed antimicrobial and antifungal activities.

Saied Abdullah El-Assiery

Papers

Synthesis of some new annulated pyrazolo-pyrido (or pyrano) pyrimidine, pyrazolopyridine and pyranopyrazole derivatives.

Synthesis and potential antimicrobial activity of some new compounds containing the pyrazol-3-one moiety