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This paper aims to synthesize 6-ethyl-4-hydroxyquinolin-2(1H)-one as a new enol-type coupling component in the preparation of some 3-arylazo-4-hydroxyquinolin-2(1H)-one dyes and evaluate the solvent effects on their absorption in ultraviolet-visible spectra.

6-Ethyl-4-hydroxyquinolin-2(1H)-one was synthesized by thermal cyclocondensation reaction of N, N′-bis(4-ethylphenyl) malonamide at 130–140°C in polyphosphoric acid. This compound was then applied in the azo-coupling reaction with some aniline-based diazonium salts, so as to prepare seven new mono-heterocyclic azo dyes. The structures of the compounds were confirmed using mass spectroscopic technique. Fourier transform infra red (FT-IR) and 1H proton nuclear magnetic resonance (1H NMR) and carbon-13 nuclear magnetic resonance (13 C NMR) studies on the structure of the azo compounds revealed that they exist as two E- and Z-isomers of hydrazone tautomer both in solid and solution state. The effects of acid and base on the visible absorption spectra of the dyes were also evaluated and discussed.

Ultra violet-visible UV-vis absorption spectra of the dyes didn’t show significant variation by changing of solvents because of intramolecular H-bonding between proposed hydrazone forms and 2- and 4-keto functions in their structures. The spectra of the dyes were not sensitive to the addition of acid but were very sensitive to base.

The synthesized 3-arylazo-4-hydroxyquinolin-2(1H)-one dyes are new members in the 4-hydroxyquinolin-2(1H)-one azo dyes family, where very few details regarding the synthesis of such dyes are reported before in the literature. They are unique in terms of synthesis and spectral properties.

The purpose of this paper is to investigate the inhibiting properties of four N‐3‐hydroxyl‐2‐naphthoyl hydrazone derivatives in 0.5 M H₂SO₄ solution and to study the mechanism of their action.

The effect of various parameters on the behavior of these inhibitors has been studied using the weight loss and polarization measurements.

The inhibiting action of the investigated compounds depends primarily on their concentration and molecular size. The compounds act as mixed type inhibitors and function via adsorption on carbon steel surface, which follows Frumkin adsorption isotherm. The addition of KI, KBr and KSCN to N‐3‐hydroxyl‐2‐naphthoyl hydrazone derivatives had a synergistic effect in enhancing the efficiency of corrosion inhibition.

This paper provides useful information regarding inhibition effect of N‐3‐hydroxyl‐2‐naphthoyl hydrazone derivatives and clarifies the role of the molecular structure and substituents on the inhibition efficiency of these investigated compounds on the corrosion of carbon steel in acidic solutions.

The corrosion behaviour of iron in M HNO3 containing furfural hydrazone derivatives was studied by electro‐chemical, polarographic and scanning electron microscopy measurements. Polarization data indicates that all inhibitors tested were of a mixed type, affecting both the cathodic and anodic processes. The inhibition efficiency of the additives increases in the order I<II<III<IV<V. It was found that the compounds under consideration are adsorbed on the iron surface. The degree of surface coverage is influenced by the presence of functional groups and interaction between adsorbed molecules. Within the given homologous series the contribution of the functional group to adsorption increases with the length of the chain.

The purpose of this study, 3-aminopyridine, 8-aminoquinoline and some new synthesized 2-aminobenzothiazoles were diazotized with nitrosyl sulfuric acid and subsequently coupled with 5-chloro-8-hydroxy quinoline to synthesize the corresponding heteroarylazo dyes 6–13.

The structures of dyes were characterized by mass, Fourier transform infra red, ¹H proton nuclear magnetic resonance and ultra violet-visible spectroscopic techniques. Absorption spectra of the dyes were measured in acetic acid, ethanol, chloroform, acetonitrile, dimethyl formamide and dimethyl sulfoxide and correlated with the nature of the solvents and substituents. The effects of varying pH on the absorption wavelengths of the azo dyes were also studied. In addition, the acidity constants (pKa) of the dyes were determined using the spectrophotometric method in an ethanol-water mixture (80:20, v/v) at 20–23°C. Besides, density functional theory (DFT) calculations were carried out to compare the energies of proposed azo and hydrazone tautomers of the dyes.

The results showed that the withdrawing chloro groups on the diazo moiety have significant influence (red shift) on the electron absorption spectra of these dyes. In addition, introducing electron withdrawing chloro groups into the benzothiazoles moiety increased the acidic character of dyes.

The synthesized 7-hetroarylazo-5-chloro-8-hydroxy quinoline dyes are new members in the 8-hydroxyquinoline azo dyes family, where very few details regarding the synthesis of such dyes are reported before in the literature. They are unique in terms of synthesis, spectral properties and DFT calculations.

Cations such as Cu2+, Co2+, Ni2+, Zn2+ or Ba2+ increases the corrosion rate of aluminium in 2 mol.L−1 HCI. This corrosion rate could be decreased by the addition of inhibitors which may form complexes with the cation used. Measurements of the corrosion rate of aluminium in 2 mol.L−1 HCI with and without addition of aliphatic substituted P‐hydroxy acetophenone hydrazone derivatives (10−4 — 10−5 mol.L−1) has been studied by weight loss and galvanostatic polarization methods. The same inhibition efficiency of the compounds has been found using either of the methods. In general, the efficiency of the inhibitors increases with an increase in aliphatic chain length. Activation energies in the presence and in the absence of inhibitors has been evaluated. Galvanostatic polarization data indicate that all these compounds are predominantly cathodic inhibitors. The rate of corrosion increases with increase in temperature together with a decrease in protection efficiency indicating that inhibition occurs through adsorption of the additives.

The efficiency of some 2‐heterocarboxaldehyde‐2′‐pyridyl‐hydrazones as inhibitors for the acid dissolution of Al was studied by mass loss, hydrogen evolution and polarization measurement techniques. The corrosion rate was measured in 2M HCI at different temperature and concentrations; maximum percentage protection (85%) was obtained at 103M for the compound containing oxygen atom. The activation energies were calculated for all the additives used. The rate constant decreases as the inhibition efficiency increases. The results show that the studied materials influencing both the cathodic and anodic process. The mechanism of inhibition was proposed on the basis of the formation of a protective monolayer by the inhibitors molecules on the metal surface according to Langmuir isotherm.

The purpose of this paper is to prepare new disperse dyes and apply for dying polyester fabrics.

The synthetic reaction was carried out through two steps: preparation of arylhydrazones and alkylation using enaminone and dimethylaminovinyl-pyridazine. The high temperature method was used to apply these dyes to polyester fibres.

The study revealed that there is a significant effect of the new prepared disperse dyes on polyester fabrics. The structures of the prepared dyes were established based on elemental analysis and spectral data (infra red (IR), mass spectrometry (MS) and proton nuclear magnetic resonance (¹H-NMR), carbon 13^th nuclear magnetic resonance (¹³C-NMR)).

Disperse dyes containing heterocyclic moiety have attracted great academic and industrial attention owing to their significant. The potential of using disperse dyes easily prepared from arylhydrazones are promise broad applications for these dyes.

The presence of N-thienyl and N-pyridazinyl in the structure of the synthesised disperse dyes would be expected to add the bioactivity advantage. Also, it can be used in formulating the antimicrobial fabrics.

The N-thienyl and N-pyrdiazinyl derivatives of azo dyes are expected to be superior to in the application for fabrics. It may be useful for other applications like painting.

This paper helps to synthesise novel thiophene or pyridazine-based dyestuff for application in dying properties on polyester fabric and study their fastness properties.

Cu(II) complexes with some hydroxy azo compounds derived from thiazole and benzothiazole have been synthesized. The structures of the complexes are inferred from data of elemental analysis, electronic, IR and H¹ NMR spectra. It is found that the Cu(II) coordinated to ligands through the nitrogen atom of azo group and hetero ring. This coordination lead to lower the energy of CT transition of ligands. The effect of molecular structure of the ligands and nature of the metal ion on complex formation are also examined. The free energy and stability constant of complexes formed in solution have been determined spectrophotometrically. Thiazole azo dyes were found to behave as an inhibitor with respect to the corrosion of copper in acidic solutions.

The aim of this paper is synthesis of some new hydrazo, dihydropyridazinyl and triazolyl derivatives containing indole nucleus and their antimicrobial evaluation.

Treatment of 3-(1H-indol-3-yl)-3-oxopropanenitrile (1) with different aryl diazonium salts 2a-j gave the corresponding arylazohydrazone derivatives 3a-j. The azo derivatives 3d and 3e were used as the key intermediate for the synthesis of some new diazines 5d, e and triazoles 7d, e. The newly synthesized compounds were characterized by electronic absorption properties – IR, 1HNMR and MS studies – and screened for their biological evaluation. Compounds 3a-j, 5d, e and 7d, e showed promising results as antimicrobial agents.

Compounds 3a-j, 5d, e and 7d, e showed promising results as antimicrobial agents.

No details regarding the synthesis of such dyes are reported before in the literature.

Treatment of diethyl 2-(4-methoxyphenyl)-4-methyl-6-oxocyclohex-4-ene-1,1-dicarboxylate (1) with hydrazine hydrate in ethanol affords the corresponding indazole derivative (2). Coupling of 2 with diazotized aromatic amines furnishes the corresponding new azo compounds (3). Compound 1 is subjected to a Japp-Klingemann reaction in an alkaline medium, where hydrazones (4) are formed. Treatment of 4 with hydrazine hydrate and phenylhydrazine in ethanol gives the corresponding new azo compounds (5 and 6, respectively). The structures of all compounds are confirmed by elemental and spectral analyses. Compounds 3-6 are applied as disperse dyes for dyeing polyester and nylon fabrics, and their characteristics and fastness properties have been measured.