A series of novel amino acid derivatives has been synthesized by the reaction of 4-[4-methoxy-3-methylphenyl]-4-oxobutenoic acid with primary and secondary amines. The treatment of amino acids with hydrazine afforded pyridazine. Phenylhydrazone was obtained from the reaction of the acid with phenyl hydrazine in ethanol. On the other hand, the acid underwent heterocyclization upon the treatment with 2-aminopyridine, o-phenylenediamine, aryldithiocarbamates and thiourea derivatives to give the corresponding pyridopyrimidine, quinoxalone, 2-thioxo-1,3-thiazole and 4-hydroxy-1,3-thiazole, respectively. The thiazolopyridazine derivatives were obtained from the reaction of 4-hydroxy-1,3-thiazole with hydrazine and phenylhydrazine, respectively. The behaviour of the 4-hydroxy-1,3-thiazole toward acetic anhydride and bromine was also studied. The proposed structures of the products were based on microanalytical and spectroscopic data. Some of the synthesized compounds also exhibited anti-microbial activities.
4-(4-methoxy-3-methyl-5 amino phenyl)-1(2H)-phthalazinone (APP), and [4-(4-mehoxy-3-methyl phenyl)-1-oxo-1H-phthalaz-2yl]acetic acid hydrazide (PPH) were synthesized as a novel independently corrosion inhibitor for carbon steel in 0.5 M H 2 SO 4 . Nuclear magnetic resonance, Fourier transform infrared and mass spectroscopy were used to validate the structure of the two anticorrosion compounds. The corrosion rate was studied by electrochemical methods (electrochemical impedance spectroscopy and potentiodynamic polarization) and gravimetric techniques, which clarify that the average corrosion inhibition efficiency of APP and PPH are 86 and 89 %, respectively. Impedance measurements showed that corrosion processes on the surface of LCS are controlled by a charge transfer mechanism. The PPH compound has a greater inhibitory effect on corrosion of low carbon steel. The quantum chemical calculations of APP and PPH were studied using AM1, PM3, and DFT/B3LYP/31G. Moreover, both APP and PPH acted as mixed type corrosion inhibitors. Adsorption of APP and PPH on low carbon steel (LCS) surface was physisorption and best fit to Langmuir isotherm.
We report the synthesis of novel [4-(3-amino-4-mehoxy-5-methyl phenyl)-1-oxo-1H-phthalaz-2-yl] acetic acid hydrazide (APPH), followed by its characterization using X-ray diffraction (XRD), Fourier transforms infrared (FT-IR) spectroscopy, 1H-NMR spectroscopy, and LC/MS. Further, the inhibition effect of the varying concentration of APPH on the corrosion of low steel (LCS) in 0.5 M H2SO4 was investigated by weight loss and electrochemical measurements at 30 °C. The percentage inhibition efficacy of APPH increased with concentration and reached about 84% at 0.5 mM at 30 °C, also rising to 88% after 6 h of exposure. According to the polarization measurements, the investigated APPH works as a mixed-type inhibitor. Furthermore, the synergistic corrosion inhibition mechanism APPH showed that the inhibition efficiency maximizes with increasing inhibitor concentration, and the maximum value was 83% at 0.5 mM APPH. The adsorption of APPH on the LCS surface is more fitting to the Langmuir isotherm model. The free energy value (–ΔG° ads) was 33.3 kJ mol−1. Quantum chemical calculation was applied to APPH and acted as excellent support for the experimental data.
Different nitration methods were investigated on 4-(4-mthoxy-3-methyl phenyl)-1(2H)-phthalazinone and its derivatives using HNO 3 as a nitrating agent with different catalysts. LC-MS/MS has been used to determine the product's structure. The results showed that the most suitable catalyst was P 2 O 5 at room temperature to introduce an ortho mono-nitrated group for the phthalazinone derivatives bearing donating groups on the phenyl ring. In contrast, 4-halophenyl phthalazinone derivatives gave a high yield of mono-nitrated products using H 2 SO 4 as a catalyst. All mono-nitrated products were separated with good to excellent yields, and their structures were confirmed by FT-IR, NMR, LC-MS/MS and elemental analyses.
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