Molecular Structure Of Inhibitors Research Articles

Inhibition effect of green Betaine type surfactants on Q235 steel in 1 mol·L−1 hydrochloric acid: The experimental and theoretical research

The corrosion inhibition efficiency of Betaine, 3-(N, N-dimethyldodecylammonio) propanesulfonate (SB3–12) and 2-(DodecyldiMethylaMMonio) acetate (BS-12) on Q235 steel in 1 mol⋅L−1 hydrochloric acid (HCl) solution were studied at various inhibitor concentration and temperature by means of the weight loss method (WLM), electrochemical impedance spectroscopy (EIS), potential polarization curve, atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), Raman spectra, scanning electron microscopy (SEM) and electronic energy spectrum analyzer (EDS). The weight loss results showed that the increase of inhibition efficiency mainly attributed to its high concentration. While Betaine had almost no protective effect for metals, SB3–12 and BS-12 were powerful inhibitors with the inhibition efficiency of 89.06% and 95.98%, respectively at 1 × 10−1 mol⋅L−1 at 30 °C. The blocking effect of BS-12 for metal corrosion that induced by HCl was stronger than SB3–12. The potential polarization curve potential demonstrated that SB3–12 and BS-12 were both mixed type corrosion inhibitors. The surface analysis results revealed that SB3–12 or BS-12 could be well adsorbed on the Q235 surface to form a compact membrane that is responsible for the protection of Q235 steel from corrosion. The theoretical calculations including quantum chemical calculations and molecular dynamics simulations, which based on density functional theory provided strong evidence for the close relationship between the molecular structure of inhibitor and its inhibition efficiency. Our study of corrosion inhibition efficiency of green betaine type surfactants laid a theoretical foundation for the application of betaine derivatives in metal anti-corrosion.

Insight into the corrosion inhibition of new benzodiazepine derivatives as highly efficient inhibitors for mild steel in 1 M HCl: Experimental and theoretical study

This work reports the synthesis of two organic compounds based on benzodiazepine derivatives, namely 11-phenyl-2,3,4,10,11,11a-hexahydro-1H-dibenzo[b,e][1,4]diazepine (CSBO) and 11-methyl-11-phenyl-2,3,4,10,11,11a-hexahydro-1H-dibenzo[b,e][1,4]diazepine (TVBO). The Anti-corrosion properties for mild steel (MS) in molar HCl have been investigated by standard electrochemical and gravimetric methods, the surface of steel and corrosive solutions was analyzed by UV–Visible and Scanning electron spectroscopy (SEM). The experimental results were encouraged by the theoretical calculations (DFT and molecular dynamics (MD) simulations). The results obtained by experimental studies show that both organic compounds are good corrosion inhibitors of mild steel in acidic media, and act as mixed type inhibitors. The thermodynamic parameters show that these two compounds adsorb on the metal surface according to the Langmuir adsorption isotherm. UV–visible spectrometry and the scanning electron microscope show that the addition of the two compounds lowers the dissolution of iron ions in the corrosive solution and forms a protective layer on the surface of the steel. Quantum chemical calculations and MD simulations were used to investigate the correlation between the molecular structure of inhibitors and their corrosion inhibition performances, which agree well with the experimental results.

Detailed DFT/MD simulation, surface analysis and electrochemical computer explorations of aldehyde derivatives for mild steel in 1.0 M HCl

Corrosion prevention in mild steel (MS) is a major issue in the industry. The development of an effective protection strategy is a popular research area. In this work, two molecules, namely methoxy cinnamaldehyde (MCA) and methyl cinnamaldehyde (MeCA) were evaluated as corrosion inhibitors for mild steel in 1.0 M HCl solution, providing a strong basis for the development of new inhibitors platform in the field of corrosion. The corrosion inhibition performance of MCA and MeCA has been studied by using weight loss, Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, quantum chemical calculations and molecular dynamics (MD) simulation. Results showed that inhibition effectiveness of MCA and MeCA increases with their concentration. Polarization results showed that MCA and MeCA displayed mixed type behaviour. Inhibition efficiencies of MCA and MeCA followed the order: 88% (MCA) < 74% (MeCA). MeCA and MCA inhibit corrosion by adsorbing on MS surface and their adsorption mode followed Langmuir adsorption isotherm via physico-chemical adsorption. SEM/EDX observations of the electrode surface confirm the formation of a film on the metal surface. Theoretical calculations obtained from DFT and Molecular Dynamics (MD) simulation were used to investigate the correlation between the molecular structure of inhibitors and their corrosion inhibition performances, which agree well with the experimental results.

Mitigation effect of quinazolin-4(3H)-one derivatives on the corrosion behaviour of mild steel in HCl

In the present study, two piperazine-substituted quinazolin-4(3 H )-one derivatives, namely 2-phenyl-3-(2-(4-phenylpiperazin-1-yl)ethyl)quinazolin-4(3 H )-one (PPQ) and 3-(2-(4-(2-methoxyphenyl)piperazin-1-yl)ethyl)-2-phenylquinazolin-4(3 H )-one (MPPQ), have been designed and investigated as effective corrosion inhibitors for mild steel in HCl, providing a strong basis for the development of new inhibitor platform in the field of corrosion. The corrosion inhibition performance of PPQ and MPPQ has been studied by using weight loss tests, electrochemical techniques, surface analytical techniques, quantum chemical calculations and molecular dynamics (MD) simulations. The experimental results revealed that PPQ and MPPQ are effective corrosion inhibitors for mild steel in 1.0 M HCl solution, and their maximum corrosion inhibition efficiencies at 0.4 mM are 96.6% and 96.1%, respectively. The effects of immersion time and temperature were studied by weight loss tests to assess the stability of the adsorbed film in protecting mild steel surface. Both PPQ and MPPQ behave as mixed-type inhibitors based on potentiodynamic polarization studies, and their adsorption on the mild steel surface follows the Langmuir adsorption isotherm. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) further confirmed the formation of a protective film on the steel surface. Quantum chemical calculations and MD simulations were used to investigate the correlation between the molecular structure of inhibitors and their corrosion inhibition performances, which agree well with the experimental results. The inhibition mechanism has also been discussed in terms of the mixed type of chemical and physical interactions that lead to its adsorption on the steel surface.

Antagonistic effect and performance of CO2 corrosion inhibitors: Water chemistry and ionic response

The synergism effect of urea and potassium iodide (KI) has been studied in two synthesized inhibitors, Inhibitor A (imidazole-free) and Inhibitor B (imidazole-containing) on the corrosion inhibition of A516 steel. The experiment was carried out in CO2–saturated 3wt% NaCl solutions through an electrochemical test and surface analysis. The electrochemical measurement showed the corrosion inhibition efficiency (%IE) for Inhibitors A gives 69–90%, while 65–88% for Inhibitors B. The surface morphology of steel after 7days immersion in both synthesized inhibitors shows a reduction in corrosion attack as viewed through a Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray (EDX). Analysis through X-ray Photoelectron Spectrometer (XPS) revealed the coordination of nitrogen elements on the steel surface indicating the interaction of significant functional groups. Both inhibitors performed competitive adsorption which characterized an antagonistic reaction. The inhibition mechanism was influenced by the molecular structure of inhibitors. The heterocyclic ring of imidazole with the possible anchoring site favors the ionic interaction. Functional groups of unshared electron pairs on nitrogen atoms have contributed to the coordination complexes roles as a ligand. Besides, the involvement of co-counter ions also influenced corrosion inhibition. The occurrences in bulk-interface-surface prior to the adsorption were discussed.

Prevention and Disintegration of Human Serum Albumin Fibrils under Physiological Conditions: Biophysical Aspects.

An anomaly in the protein folding process can lead to aggregation or fibrillation of proteins which has been related to neurodegenerative and peripheral diseases. Therefore, it is important to understand the mechanism of prevention of aggregation/fibrillation and to design suitable inhibitors for this process. Literature information suggests that most of the work on these systems has been done on heat induced fibrils (57-65 °C). As a step ahead, in the present study, efforts have been made to understand the inhibition process under physiological conditions (37 °C, pH 7.4), which is more relevant to the fibrils formed under natural cellular environment. The qualitative and quantitative aspects of the interactions of the surfactant sodium dodecyl sulphate (SDS) and antiinflammatory drug diclofenac sodium (DCF) with human serum albumin at different stages of the fibrillation process have been studied employing a combination of spectroscopic, calorimetric, and microscopic techniques. Fibril formation understudied conditions was confirmed by transmission electron microscopy images and thioflavin T binding assay along with dynamic light scattering measurements. Energetics from isothermal titration calorimetry provided insights into the nature of interactions and the mechanism of inhibition. We found inhibition efficiency of the additives in the order, micellar SDS > 45 mM DCF > monomeric SDS > 5 mM DCF. The energetics of interaction, correlated with the molecular structure of inhibitors provides guidelines for effective synthesis and design of inhibitors. ITC results have imparted important relationship between inhibition efficiency and exothermicity of interactions and have demonstrated the significance of polar interactions in fibril prevention by these inhibitors. Interestingly it was found that the micellar SDS not only inhibits the process but also effectively disintegrates the formed fibrils.

Schiff-base derivatives as corrosion inhibitors for carbon steel materials in acid media: quantum chemical calculations

ABSTRACTQuantum chemical calculations based on Hartree–Fock, AM1 and B3LYP functions were performed on the three Schiff-base compounds used as corrosion inhibitors for carbon steels in acid media. The quantum chemical calculations were conducted to determine the relationship between inhibition efficiency (IE) and the molecular structure of inhibitors. Several quantum chemical parameters, such as charge distribution, energy and distribution of the highest occupied molecular orbital (EHOMO) and lowest unoccupied molecular orbital (ELUMO), absolute electronegativity (χ) and the fraction of electrons (ΔN) transferred from inhibitors to the steel surface, were calculated and correlated with inhibition efficiencies. The results showed that the IE of Schiff-base compounds enhanced with increasing EHOMO or decreasing ELUMO; meanwhile, N atoms on Schiff-base molecules were the most probable sites for adsorption of inhibitor molecules on the metal surface. The inhibition mechanisms of three Schiff-base compounds were obtained from different calculation methods, and the results from each method are consistent.

Citrus aurantium leaves extracts as a sustainable corrosion inhibitor of mild steel in sulfuric acid

Corrosion inhibition of mild steel in 1 M H2SO4 was investigated in absence and presence of Citrus aurantium leaves extracts as a friendly inhibitor. The effect of temperature, time, and inhibitor concentration were studied using weight loss technique. The result obtained revealed that Citrus aurantium leaves extracts act as an inhibitor for mild steel in H2SO4 and reduces the corrosion rate. The inhibition efficiency was found to increases with increase in inhibitor concentration whereas the temperature shows otherwise. Higher inhibition efficiency was 89% at 40 °C and 10 ml/l inhibitor concentration. The adsorption of Citrus aurantium leaves extracts was found to follow Langmuir adsorption isotherm model. The values of the free energy of adsorption was around −20 kJ/mol, which is indicative of physical adsorption between charged molecules and a charged metal. Quantum chemical calculations were also used as a theoretical support to the experimental results. Finally the scanning electron microscope and Fourier transform infrared spectroscopy were evaluated to examine surface morphology and molecular structure of inhibitor respectively.

Electrochemical and quantum chemical studies of azoles as corrosion inhibitors for mild steel in hydrochloric acid

The inhibition effect of three azole compounds, 2-aminobenzimidazole(ABM), 2-aminothiazole(AT) and 2-aminobenzothiazole(ABT), on the corrosion of mild steel in a 1 mol/L HCl solution was investigated by means of potentiodynamic polarization measurement, electrochemical impedance spectroscopy(EIS) and scanning electron microscopy( SEM). The correlation between inhibition efficiency and molecular structure of inhibitor was theoretically studied via quantum chemical calculations. The results show that the inhibition efficiency(η) of the inhibitors follows the order of ηABT>ηAT>ηABM. Moreover, ABM, AT and ABT belong to mixed-type inhibitors. The adsorption of the inhibitors on the steel surface follows the Langmuir adsorption isotherm, with both physisorption and chemisorption.

Quantum chemical studies on some new bipyrazole derivatives as corrosion inhibitors for steel materials

Purpose The purpose of this study is to perform quantum chemical calculations based on the DFT method on four bipyrazoles used as corrosion inhibitors for the plain carbon (“mild”) steel in acid media to determine the relationship between inhibition efficiency and the molecular structure of inhibitors. Design/methodology/approach Several quantum chemical parameters, such as the charge distribution, energy and distribution of highest occupied molecular orbital and lowest unoccupied molecular orbital, the absolute electronegativity (χ) values and the fraction of electrons (△N) transferring from inhibitors to the steel surface, were calculated and correlated with inhibition efficiencies. Findings The results showed that the inhibition efficiency of bipyrazole increased with the increasing in EHOMO, and the areas containing N atoms were the most probable sites to donate electrons for adsorbing the inhibitor molecules onto the metal surface. Originality/value It is a useful method to investigate the mechanisms of reaction by calculating the structure and electronic parameters, which can be obtained by means of theoretical quantum theory. Thus, the behavior and mechanism of the organic inhibitors can be obtained. Quantum chemical method can also be used to guide the selection and molecular design of inhibitors.

Quantum Chemical Study on the Corrosion Inhibition of Some Oxadiazoles

Quantum chemical calculations based on DFT method were performed on three nitrogen-bearing heterocyclic compounds used as corrosion inhibitors for the mild steel in acid media to determine the relationship between the molecular structure of inhibitors and inhibition efficiency. The structural parameters, such as energy and distribution of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), the charge distribution of the studied inhibitors, the absolute electronegativity (χ) values, and the fraction of electrons (ΔN) transfer from inhibitors to mild steel were also calculated and correlated with inhibition efficiencies. The results showed that the inhibition efficiency of inhibitors increased with the increase in energy of HOMO and decrease in energy gap of frontier molecular orbital, and the areas containing N and O atoms are most possible sites for bonding the steel surface by donating electrons to the mild steel.

Electrochemical and thermodynamic studies to evaluate the inhibition effect of synthesized piperidine derivatives on the corrosion of mild steel in acidic medium

The inhibition ability of three newly synthesized piperidine sulphonamides toward the mild steel (MS) corrosion was investigated using mass loss and electrochemical techniques. The adsorption of all the piperidine sulphonamides on MS complies with the Langmuir isotherm model in all studied temperatures. Associated activation and adsorption thermodynamic parameters were computed and discussed. The polarization results indicated that all the studied inhibitors act as mixed type of corrosion inhibitors. The protective layer of organic compounds on MS surface was confirmed by scanning electron microscopy (SEM). The values of free energy of adsorption (ΔG ads) revealed that the inhibitors adsorbed on the MS surface via both chemisorption and physisorption mechanisms. The relationship between inhibition efficiency and molecular structures of inhibitors was discussed using quantum chemical parameters. The inhibition efficiencies obtained from mass loss and electrochemical measurements were in good agreement.

English

The effect of a schiff base 2-(2-hydroxybenzylideneamino)phenol (HBAP) and its corresponding three 3d-transition metal complexes viz. Mn-HBAP, Co-HBAP and Ni-HBAP on the corrosion inhibiting behaviour against chrome steel bearing balls in 0.1 N HNO3 solution were investigated by means of conventional weight loss method, potentiodynamic polarization and scanning electron microscopy (SEM) studies. The adsorption nature of all inhibitors over chrome steel surface were spontaneous and were best fitted by Langmuir's adsorption isotherm. Stability of complexes in acid media were supported from spectrophotometry measurements. The mixed mode of inhibition was confirmed from polarization and inhibition efficiency (% I.E.) could be increased with concomitant increase in inhibitor concentration in bulk experimental solution. Correlation between the inhibitive effect and molecular structure of inhibitor's was further supported by Density Functional Theory (DFT) like quantum chemical calculation. An effective quick prediction about each and individual inhibitor on inhibitor/metal interface about simultaneous effect of varying concentration and reaction time was successfully exploited by Design of experiments (DOE).

Synthesis and corrosion inhibition of α-amino acids alkylamides for mild steel in acidic environment

New compounds of alkylamides derived from α-amino acids were tested as corrosion inhibitors for carbon steel in an aqueous solution of hydrochloric acid. The chemical synthesis of these amides performed by aminolysis of α-amino acid methyl esters resulted in good yields. Electrochemical testing was carried out using polarization scans and weight loss measurements. Polarization scans indicated that compounds act as mixed corrosion inhibitors with an efficiency of 80–90% when dissolved in the testing solution at ≥50 ppm, whereas gravimetric results displayed a similar tendency. Microtox testing indicated a correlation with the molecular structure of inhibitors. Apparently, a long aliphatic chain (C > 12) promoted not only higher corrosion efficiency, but also a higher toxicity. The higher efficiency of dodecyl amine of tyrosine was apparently derived from its longer aliphatic chain, with some contribution from its phenyl ring, which reinforces the molecular interactions of π type bonding to the d orbital metal favouring film formation.

A neural network based virtual screening of cytochrome P450 3A4 inhibitors

A virtual screening test to identify potential CP450 3A4 inhibitors has been developed. Molecular structures of inhibitors and non-inhibitors available in the Genetest database were represented using 2D Unity fingerprints and a feedforward neural network was trained to classify molecules regarding their inhibitory activity. Validation tests revealed that our neural net recognizes at least 89% of 3A4 inhibitors and suggest using this methodology in our virtual screening protocol.

Defining the active site of cytochrome P-450: the crystal and molecular structure of an inhibitor, SKF-525A.

The crystal and molecular structure of the cytochrome P-450 inhibitor, SKF-525A [2-(diethylamino)ethyl 2,2-diphenylpentenoate; proadifen hydrochloride] is described. Proadifen hydrochloride crystallized from an ethyl acetate and acetic acid mixture in the space group P2(1)/c with one molecule in the asymmetric unit. Cell constants are a = 18.716(4), b = 8.906(1), c = 14.201(3), beta = 109.41(1) degrees. The structure was solved using direct methods and was refined to an R value of 0.047; weighted R of 0.061 using 3757 reflections. From the crystal and molecular structure, it is seen that SKF-525A has two principal modes of complementary interactions with the enzyme available: polar and non-polar. Polar interactions that principally involve the chloride anion, the quaternary nitrogen atom and the carbonyl oxygen atom. In particular, there are two strong hydrogen bonds, one between Cl ... H-N, 3.090(1) A, the other between O2 ... H-C111 (one of the ethyl hydrogen atoms) at 3.411(2) A. The other is through non-polar interactions involving the phenyl and alkyl groups. Comparisons between proadifen hydrochloride and other inhibitors whose atomic coordinates are available reveal common features which correlate with their function. These include groups to provide necessary intermolecular contacts and bulk, such as a phenyl group and a hydrogen bond acceptor, as well as a tetrahedral atom, which allows for substrate flexibility.