Investigation of hydrazine addition to functionalized furans: synthesis of new functionalized 4,4′-bipyrazole derivatives

The addition of hydrazine to functionalized furans 2a-d leads to a variety of 4,4′-bipyrazoles 4a-c depending on the structure of the starting materials. In one example, compound 2c was first converted to an intermediate, furo[3,4-d]pyridazine 3c which was then transformed into 4,4′-bipyrazole 4c on reacting with hydrazine.     

Ethoxylated Melamine as Corrosion Inhibitor for Carbon Steel in 1M HCl

The inhibition effect of a new 1,3,5-triazine-2,4,6-triaminoethoxylate (ethoxylated melamine, MEO) on the corrosion of carbon steel in 1 M HCl was studied at 298 K. Surface activity, thermodynamic properties, and potentiodynamic polarization methods were used for the evaluation of the prepared surfactants. Results show that MEO is a good inhibitor, and inhibition efficiency reaches 91% at 500 ppm. Polarization curves revealed that this organic compound acts as a mixed-type inhibitor. The concentration effect on the corrosion behavior of steel in 1 M HCl with and without MEO at 100–500 ppm was studied at a temperature of 298 K. Additionally, the associated activation energy was determined.     

Inhibition of copper corrosion by bipyrazole compound in aerated 3% NaCl

The corrosion behaviour of copper in aerated 3% NaCl solution was investigated by rotating electrode at various rates. The reduction of O₂ obeys the Levich equation. The inhibition of the copper corrosion in aerated 3% NaCl solution was studied by using potentiodynamic polarisation and linear polarisation resistance (LRP) in the presence of different concentrations of a bipyrazolic compound named N,N-bis (3-carbomethoxy-5-methylpyrazol-1-ylmethyl) cyclohexylamine (BiPyA). The presence of this compound in the solution decreases the corrosion current density and increases the linear resistance polarisation. The inhibition efficiencies obtained from cathodic Tafel plots and LRP methods are in good agreement. BiPyA compound presents an efficient inhibitor of copper corrosion, acts as a mixed-type inhibitor and adsorbs on the copper surface according to the Langmuir isotherm model.     

1,3-Bis(3-hyroxymethyl-5-methyl-1-pyrazole) propane as corrosion inhibitor for steel in 0.5 M H2SO4 solution

The effect of addition of 1,3-bis(3-hyroxymethyl-5-methyl-1-pyrazole) propane (M = 264 g). HMPP on steel corrosion in 0.5 M sulphuric acid is studied by weight-loss, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements at various temperatures. The results obtained showed that HMPP acts as a good corrosion inhibitor. The inhibition efficiency increases with the bipyrazole compound to attain 88%. It acts as a mixed-type inhibitor. Trends in the increase of charge-transfer resistance and decrease of capacitance values also show the adsorption of the molecule on the metal surface. The bipyrazole adsorbs on the steel surface according to the Langmuir isotherm adsorption model. Effect of temperature indicates that inhibition efficiency decreases with temperature between 25 and 85 °C.     

Two new dinuclear complexes with flexible bipyrazole ligand bridged via μ-Cl or μ1,1-N3

Two dinuclear complexes, {[Cd(bdpp)Cl₂](CH₃OH)}₂ (1) and [Cd(bdpp)(N₃)(NO₃)]₂ (2), have been synthesized by reactions of bdpp with cadmium salts (bdpp?=?1,3-bis(3′,5′-dimethylpyrazol-1′-yl)propane), and characterized by IR, element analysis, fluorescence properties and single crystal structural analysis. Cd in 1 has a trigonal bipyramidal coordination geometry and two such units form a dimer through two μ-Cl bridges. Each Cd in 2 has a distorted octahedral coordination geometry and two Cd units form a dimer through μ_1,1-N₃ bridges. The emission spectra show λ_em?=?413?nm for 1 and λ_em?=?338?nm for 2.