1M HCl Research Articles

Valorized rice husk as green corrosion inhibitor for Al 6061 in 1M HCl

This study investigated the inhibition characteristics of rice husk (RH) on corrosion of Aluminum 6061 in 1M hydrochloric acid. Gravimetric analysis and Scanning Electron Microscopy (SEM)/ Energy Dispersive X-ray analysis (EDX) as well as electrochemical studies revealed the potency of RH as a good inhibitor of the corrosion of Al 6061 in 1M HCl. Fourier Transform Infrared Spectroscopy (FTIR) indicated that –OH, C=C, and C=O with signals at (3317.19, 2932.9, 2848.2), (1631.8) and (1105.73, 1030.2, 447.15), respectively in RH were the viable active functional groups which adsorbed on the metal surface to effect reduction of corrosion rates. However, literature suggested the presence of amorphous silica in RH which served as a complimentary corrosion inhibitor. The corrosion current density of Al 6061 was reduced to 3.46 × 10−7 A/cm2 at 24 h as against 9.27 × 10−7 A/cm2 at the commencement of the potentiodynamic polarization measurements in inhibited 1M HCl. The control specimens exhibited an average corrosion rate of 3.86 × 10−6 A/cm2 in HCl solution at the start of this investigation as compared to the corrosion rate of 3.46 × 10−7 A/cm2 at 24 h of exposure in 5 mg RH- inhibited HCl. The obtained results gave a corrosion inhibition efficiency of about 90 to 92%.

Investigation of Laurus Tamala leaves extract as an environmentally acceptable corrosion inhibitor for soft steel in 1M HCl: Electrochemical, DFT, and surface characterization techniques

Investigation of Laurus Tamala leaves extract as an environmentally acceptable corrosion inhibitor for soft steel in 1M HCl: Electrochemical, DFT, and surface characterization techniques

N-BENZYLIDENE - 4 -NITROANILINE SCHIFF BASE COMPOUND CORROSION INHIBITION MILD STEEL IN ACIDIC MEDIA

Schiff base N ̶ benzylidene 4-nitroaniline (NB4NA) synthesized and examine corrosion inhibition belongings mild steel (MS) within acidic solutions 0.5 H2SO4 and 1M HCl. The weight loss method confirms inhibition capacity prolonged with enhancing the concentration of synthesized Schiff base NB4NA. Electrochemical studies reveal that NB4NA acts as an anodic and cathodic sortof inhibitor impedance studies exposed rising Schiff base attention with inhibition efficiency of about 70-75%. Furthermore, thermodynamic parameters confirm the positive attraction behavior of MS with inhibitor due to both physical adsorption and Chemisorptions observed. The scanning electron microscopic studies show that synthesized NB4NA has strong interaction with MS and elevates inhibition efficiency. The electron distribution HOMO and LUMO established quantum chemical parameters.

Nutrients and trace elements of semi-arid dwarf and fully developed mangrove soils, northwestern Venezuela

Mangrove forests are characterized by a high carbon storage capacity. Anthropogenic activities and the climate change are threatening the stability of these ecosystems, specially those that are surviving on extreme environmental conditions, representing the most susceptible groups. This study aims to understand the geochemical differences of soils of mangrove forest with diverse degree of development of Rhizophora mangle and Avicennia germinans, located in two semi-arid regions from the Falcon state, Venezuela. The soil samples were collected in Punta Caimán region (dwarf mangroves of less than 2 meters height) and Boca de caño lagoon (fully developed mangroves of up to 8 meters height). The trace elements and macronutrients were determined in two sequential extraction, first with 1M HCl followed by an extraction with ultrapure grade HNO_{3}. Results showed that, in general, dwarf mangroves have limited capability to accumulate organic matter in the soil (average TOC of 0.6 pm 0.2%) and that the sampled surface soils from the dwarf mangrove region had no differences with deeper material. On the other hand, the TOC of soils dominated by developed mangroves is 6 pm 2 %, representative of semi-arid conditions. Moreover, the soils dominated by dwarf mangroves are characterized high concentrations of trace elements related to the chalcophile group. The difference in soil chemistry between Rhizophora mangle and Avicennia germinans becomes significant when mangroves are fully developed. Finally, soils of dwarf mangrove forests presented a greater concentration of trace elements than soils of fully developed mangroves, which might be due to a different sediment source, to an anthropogenic influence or to the difference in organic matter.

Synthesis, Electrochemical, Morphological, Computational and Corrosion Inhibition Studies of 3-(5-Naphthalen-2-yl-[1,3,4]oxadiazol-2-yl)-pyridine against Mild Steel in 1 M HCl

1,3,4-Oxadiazole derivative, namely, 3-(5-naphthalen-2-yl-[1,3,4]oxadiazol-2-yl)pyridine (NOP) as a corrosion inhibitor against mild steel in 1M HCl has been evaluated using the weight-loss technique (303-323 K), electrochemical analysis [potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS)], as well as surface morphology investigations (SEM). Additionally the computational studies such as density functional theory (DFT), the synthesized molecule (NOP) were utilized to better insight into molecular structure and electronic aspects relating to the anti-corrosion activities of the examined inhibitors and to envisage the interaction between designed inhibitors with the mild steel surface. The synthesized molecule (NOP) expressed high inhibition efficiency of 88.62% at an optimal concentration of 500 ppm at 298 K. A mixed-type inhibition mechanism is suggested by potentiodynamic polarization (PDP) analysis. The DFT calculations complement well with the experimental outcomes. This article provides in-depth insights to comprehend the mild steel inhibitor interactions mode and can be very helpful in accentuating the approach to mitigate the metal dissolution occurring in acidic corrosive media.

A case study on expired drugs: The potential corrosion inhibitory activity of expired labetalol drug in 1M HCl for plain carbon steel

In this work expired drug namely, labetalol has been used as a corrosion inhibitor in a stirred acidic medium (1M HCl) with mass loss measurement and electro analytical techniques. . The efficiency of the inhibitor increases as the temperature increases from 30-60°C. The results reveal that maximum inhibition efficiency is observed as 91.66% for 500 ppm. Potentiodynamic polarization measurement implies that it perform as a mixed type inhibitor. FT-IR analysis prove that corrosion product is formed on the mild steel surface. When compared with metal in IM HCl, it includes a shielding layer on the surface of mild steel by controlling further attack of acid. SEM and SFM surface morphology study have also been performed to confirm the effect of labetalol on metal. In addition to that, DFT is also carried out to analyse HOMO, LUMO, ΔE and Mulliken charges.

Antikorozivna svojstva leka ropinirol (ERN sistem) sa isteklim rokom trajanja kao inhibitora za meki čelik u 1M HCl

Ropinirole is utilized to forestall sickness and spewing brought about by disease chemotherapy and radiation treatment. It works by hindering serotonin, a characteristic substance in the body that causes queasiness and retching. After lapse, they can be utilized as consumption added substances or inhibitors. The consumption obstruction activity of terminated Ropinirole drug (ERN) on the erosion of mild steel in 1M HCl medium has been assessed by the weight reduction strategy. The weight reduction estimations showed that erosion restraint effectiveness expanded with expanding the convergence of the inhibitor, with greatest security productivity at 0.001 M. The temperature influences the pace of erosion; at high temperatures, the consumption restraint effectiveness diminishes, and erosion is noticed. The robotic parts of consumption obstruction have been concentrated by the potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS). The potentiodynamic polarization strategy uncovers that the inhibitor framework capabilities as a cathodic kind of inhibitor, controlling cathodic responses. An inhibitor can decrease corrosion current due to inhibited reaction rate and increase Linear polarization resistance due to the formation of a barrier on the electrode surface. time., since, within the sight of an inhibitor framework, the charge moves opposition esteem increments and the twofold layer capacitance esteem diminishes. The surface morphology of repressed gentle steel was dissected by filtering electron microscopy (SEM). The natural constituents on the gentle steel surface have been portrayed by energy dispersive X-beam spectroscopy (EDAX). The harshness of the gentle steel surface in cleaned MS, clear MS, and inhibitor frameworks has been described by nuclear power microscopy (AFM). The outcomes have obviously shown that ERN has a repressing limit with regards to decreasing the erosion of gentle steel submerged in hydrochloric corrosive medium.

Evaluation of the inhibitory action of essential oil from Eucalyptus globulus leaves on the corrosion of mild carbon steel in 1M HCl medium

Abstract The present work aims to valorize an aromatic and medicinal plant of Eucalyptus globulus found in the region of Dakar, Senegal. To do so, we first extracted the essential oil contained in the leaves of the plant harvested in October 2020. We obtained the essential oil by hydrodistillation using a Clevenger type extractor with a yield of 1.70% of the dry plant mass. This value is quite appreciable compared to the different values in the literature. The essential oil extracted from the leaves of Eucalyptus globulus was tested as a green inhibitor on carbon steel type XC38 in 1M HCl acid medium by the mass loss method. The results obtained led to a maximum inhibitory efficiency of 89.03% for a concentration of 1.6 g/L of essential oil at room temperature of 298 K. The effect of temperature on the inhibitory behavior of the essential oil was also studied over a range of 298 K to 338 K. In this temperature range, a loss of efficiency was observed with increasing temperature, reaching a value of 15.33% at 338 K. Thermodynamic quantities were then determined. The plot of the different isotherms showed that the adsorption of the essential oil obeys the Langmuir isotherm. The results obtained showed a physical character of adsorption of this essential oil.

Zaštita od korozije mekog čelika korišćenjem premaza od nanomaterijala

Effectiveness of nanoparticle coatings in preventing corrosion of mild steel metal samples were experimentally determined. TiO2 and ZrO2 nanoparticles coatings were done by brush coating. Different samples were prepared by varying the parameters such as thickness of coatings, concentration of nanoparticles and temperature of heat treatment. Corrosion rate of both uncoated mild steel and coated using TiO2, ZrO2 samples was determined in the corrosive environments of 1M HCl and 3.5 wt% NaCl. From the experiments it was found that the coated mild steel samples prepared at temperature 80oC are more effective than samples prepared at 200 oC. It is observed that TiO2 coatings prepared with ratio 2:0.3, 0.182 mm coating thickness and heat treated at 80oC, and ZrO2 coatings with thickness of 0.185 mm, prepared from nanoparticle paste of 1:0.3 ratios, heat treated at 80 oC, have shown better protection for mild steel in 1M HCl and 3.5% NaCl solutions compared with other TiO2 and ZrO2 coatings.

Experimental investigation of new compound adsorption on carbon steel in 1M HCl

The effect of new compounds named, 6,6'-(((2,2-dimethylpropane-1,3-diyl)bis(azanediyl))bis(methylene))bis(2- methoxyphenol) (RSH) on the corrosion inhibiting of ST- 37 low carbon steel in 1.0 M HCl has been studied. The inhibitor effects on the corrosion behaviour of the samples have been determined at three different concentrations, 0.5, 1.0, 1.5 and 2.0 mg/L. Weight loss, polarization curves, AC impedance measurements and Atomic Force Microscopy (AFM) have been utilized to study the corrosion behaviour of carbon steel in corrosive environment in the presence and absence of new ligand. Results show that the inhibition occurs through adsorption of the inhibitors molecules on the metal surface. The inhibition efficiency was found to increase with increasing inhibitor’s concentration. Polarization data indicated that this compounds act as mixed-type inhibitors. The corrosion efficiency of RSH at an optimal concentration of 2mg/L is 86. The adsorption of inhibitors follows the Langmuir isotherm. The values of free energy of adsorption in the presence of the corrosion inhibitor are around -32 KJmol-1, which indicate chemiosorption of the molecules. Powerful Atomic Force microscopy is used for the surface morphology studies.

Thermal Stability and Surface Area Modification of Natural Zeolite Through HCl & NaCl Treatment to Apply in Pyrolysis Systems

Pyrolysis technology relies on efficient catalyst materials to expedite the process and improve the quality of the final product. Modified natural zeolite has emerged as a promising heterogeneous catalyst in this regard. This study presents a comprehensive analysis of natural zeolite sourced from Tasikmalaya, West Java, with the primary aim of evaluating its potential as a catalyst. The samples underwent acid treatment procedures and were extensively characterized using BET, TGA, SEM-EDX, X-Ray Diffraction (XRD), and FT-IR tests. XRD results indicated that the predominant frame structure of the Indonesian raw natural zeolite was mordenite, with a Si/Al ratio ranging from 5.0 to 6.0 and a surface area of approximately 23 m²/g. Following the 1M HCl acid treatment, a significant enhancement in the Si/Al ratio to 7.8 and a considerable expansion in surface area to 125.37 m²/g were observed. Moreover, the natural zeolite demonstrated remarkable thermal stability, thus underscoring its potential as a highly suitable catalyst for various pyrolysis applications.

Optimization of avocado seed nanoparticle extract (ASNE) as green inhibitor on API X65 steel corrosion using response surface methodology

The use of natural products as inhibitors has become increasingly popular due to environmental concerns and the need for sustainable corrosion solutions. In this investigation, response surface methodology (RSM) was utilized to optimize the process variable of ASNE on API X65 steel in 1M HCl acid solution through gravimetric and surface analysis. The influence of concentration, temperature, and exposure time on the inhibition efficiency of avocado seed nanoparticle extract (ASNE) was examined using a central composite design (CCD). The optimum values obtained for the highest inhibition of 95.7% were a temperature condition of 25 °C, a concentration of 5 g/L, and exposure time of 24 hours. Microstructural examination of the studied samples showed a significant surface difference, confirming the formation of a protective layer on the steel surface. Experimental data was in good agreement with the model hence, the study provides valuable insights into the use of ASNE as an inhibitor for API X65 steel and demonstrates the effectiveness of RSM in optimizing the inhibition process variables.

Effect of syzygium cumini leaf extract as a green corrosion inhibitor on API 5l carbon steel in 1M HCL

Corrosion in API 5L steel under 1M HCl is a common issue; hence, creating a more effective and naturally-based inhibitor is critical. In this research, Syzygium Cumini leaf extract (SCLE) was used as a new green corrosion inhibitor under acidic conditions. The inhibition properties of the novel cumini extract were thoroughly characterized using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), Fourier-transform infrared spectroscopy (FTIR), and atomic force microscope (AFM). The results show that the cumini inhibitor has excellent corrosion inhibition with 93 % inhibition efficiency. The adsorption behavior of the inhibitor follows the Langmuir Adsorption Isotherm due to the nearness of R2 to unity. The potentiodynamic and electrochemical measurements demonstrate the mixed type of corrosion inhibitor. Thermodynamic calculation of ΔGads is – 18.41 kJ mol-1 showing the physical adsorption process between the inhibitor and metals. Further inspection of ΔHads at ‒58.93 kJ mol-1 considers releasing energy during adsorption. The FTIR results agree with the increased growth of passive layers due to the adsorption of polyphenol and flavonoids on metals. Remarkably, the adsorption peak at 3266.59 cm-1 corresponds to the adsorption of –OH. The peak at 1612.56 and 1698.4 cm-1 is attributed to C=C and C=O functional groups. The above functional groups serve as adsorption centers to reduce the corrosion effect. The surface treatment of AFM indicated a good relationship with the functional group characterization and confirmed the significant corrosion rate reduction. This work can be used as a benchmark to develop a natural plant as a corrosion inhibitor.

Phosphate Determination in Aqueous Samples by Complex Formation with Rhodamine B

Abstract In this study novel approaches for determining trace levels of phosphate in aqueous pore water solutions are described. Phosphate in aqueous samples (freshwater, drinking water, soil pore water) forms an aggregate compound with molybdate and Rhodamine B in 1M HCl. Incident light directed at the Rhodamine B molybdo-phosphate aggregate follows a second order light scattering behaviour. A bench top fluorescence spectrophotometer was used for examining the light scattering properties of the aggregate as well as for examining the feasibility of using this species for quantitative analysis. In this study this approach was adapted for quantitative analysis using capillary electrophoresis equipped with laser induced fluorescence. Quantifying phosphate with CE-LIF could be achieved by detecting the Rhodamine B phospho-molybdate aggregate directly in aqueous samples. Capillary electrophoresis was also used to indirectly detect phosphate by detecting Rhodamine B that dissociated from the aggregate species prior to electrokinetic injection.

Acetylsalicylic acid as an environmentally friendly corrosion inhibitor for carbon steel XC48 in chloride environment

In this study we evaluated the corrosion inhibition potential of an environmentally friendly, cost effective and beneficial compound on carbon steel in an acidic environment.We investigated electrochemical as well as gravimetric measurements for corrosion performance inhibition of the acetylsalicylic acid ASA molecules used from carbon steel XC48 in HCl 1M solution. The results show that aspirin inhibits the corrosion of carbon steel in acidic environment. It was found that the inhibition efficiency of aspirin increased with increasing inhibitor concentration and decreased with increasing temperature. The maximum inhibition efficiency was 96% with 5×10−3 M aspirin at 308 K. The inhibition efficiency increased with increasing concentration of ASA. This inhibitor adsorbs on the metal surface according to the Langmuir model and a physical adsorption mechanism is proposed for the adsorption of the inhibitor on the carbon steel surface, the scanning electron microscopy (SEM), the Thermodynamic and the kinetic parameters were calculated and discussed.

Molecular dynamic simulation and experimental investigation on the synergistic mechanism and synergistic effect of (1Z) N [2 (methylthio) phenyl] 2oxopropanehydrazonoyl chloride [formula omitted] corrosion inhibitor on mild steel in acid medium1M HCl

Inhibitory activity of Schiff base namely: (1Z)-N-[2-(methylthio) phenyl]-2-oxopropane hydrazonoyl chloride (S1) against the corrosion of mild steel in HCl (1M) was investigated using mass loss, electrochemical impedance spectroscopy, potentiodynamic polarization, surface analysis (Scanning Electron Microscope coupled with Energy Dispersive X-Ray Analysis (SEM/EDX), X-Ray diffraction (XRD), Ultraviolet–visible spectroscopy (UV-VIS) and contact angle). The experimental results were showed thatschiff base (S1) has a good inhibitory effect on mild steel, and their effectiveness was increasedwith increasing inhibitor concentration and decreased with increasing temperature (from 25 °C to 55 °C). The maximum inhibition efficiency of 87% was obtainedwith2.5×10−3M solution S1 at 25 °C. From the contact angle results, it was found that the angle in the presence of S1 is 75°.This value was higher than in the case of the absence of the inhibitor. As for the results of the adsorption isotherms, they showed us that the highest correlation value of 99.997 has been found with the Langmuir isotherm. From all the experimental results, it was concluded that the S1 was adsorbed on the metal surface according to the Langmuir isotherm. Therefore, the corrosion reactions of mild steel were inhibited. In this study, it was also investigated the effect of the synergistic action between the S1 and the iodine anions on the corrosion inhibition of mild steel, experimentally by polarization and theoretically using MC simulation. The results revealed a strong inhibitory activity of 85% at 5×10−5 M. It was also found that there was a strong correspondence between the theoretical and experimental study.

Gamalama Volcanic Soil Potency as a Low-cost adsorbent for Mercury Removal

The increase in metal mining in the North Maluku region poses a threat of mercury pollution. In order to overcome this problem, a study was conducted on the utilization of Gamalama volcanic soil as a low-cost adsorbent for mercury removal. Gamalama is one of five active volcanoes in North Maluku, Indonesia, that have erupted hundreds of times and produced millions of tons of volcanic soil. Before being used as a mercury adsorbent, Gamalama volcanic soil was first activated using 2M HCl. The effect of activation was studied using FTIR and XRD spectroscopy. The activation treatment has an effect on decreasing the diffraction intensity of albite as a result of dealumination. Mercury adsorption was carried out by adding 20 grams of activated volcanic soil to 50 mL Hg2+ 5 ppm. The mixture was stirred with time variations of 10, 30, 60, 90 and 120 minutes. The highest percentage of mercury removal was 41.6% at a contact time of 120 minutes with an adsorbent mass of 40 mg. The adsorption process followed the pseudo-second-order kinetic model with the values of K2 and qe being 0.0451 and 3.212 respectively.

Chlorophyll and pheophytin: experimental aspects of corrosion regulation

The introduction indicates the object of research – natural porphyrin chlorophyll and its derivative pheophytin, as possible inhibitors of steel corrosion. Modern, reasoned data on the structure and physico-chemical properties of chlorophyll, such as aromaticity, chelate effect, amphotericity, ability to redox transformations are presented. The basic concepts are defined: porphyrin, pheophytin, aromaticity, pyrrole nitrogen, complexing ability, acidophobia, diphilicity of porphyrin and pheophytin, mass and volume corrosion indicators, corrosion inhibitor, degree of protection, inhibition coefficient. The aim of the research was to study the anticorrosive activity of chlorophyll and its derivative, pheophytin, in relation to carbon steel St3. The main part describes a method for extracting chlorophyll from the leaves of nettle dioecious (Nettle dioecious L.) and the subsequent production of feofitin from it. The methods of determining the mass and volume indicators of the corrosion rate are described. The absence of pronounced anticorrosive activity of chlorophyll in relation to carbon steel St3 in hydrochloric acid medium is shown. The effect of absorption by chlorophyll of hydrogen released at the cathode is demonstrated, which makes the use of a volumetric corrosion rate indicator vulnerable under these conditions. It was found that the pheophytin layer deposited on the metal surface exhibits an inhibition effect under conditions of acid and atmospheric corrosion. The inhibitory effect of feofitin (4,4) was established during 96 hours of exposure with subsequent damping dynamics in the experiment with 3M HCl. Under the influence of feofitn, an elongation of time was observed before the appearance of visible foci of atmospheric corrosion. Studies of the efficacy of porphyrins as corrosion inhibitors should be supplemented by the results of the long-term effects of these compounds.

Pomegranate arils extract as a green corrosion inhibitor for mild steel: effect of concentration and temperature in hydrochloric acid

Corrosion inhibitors generated from plants and organic compounds are critical for achieving a greener environment. In this work we investigated the corrosion inhibition of pomegranate arils extract (PAE) for mild steel in 1M HCl by potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and profilometry measurements. The effects of PAE concentration (100, 200, 400 mg l–1) and temperature (298, 313, and 333 K) on the PAE inhibition efficiency were evaluated. Polarization measurements revealed that PAE was a mixed anodic-cathodic inhibitor. Corrosion inhibition efficiency was around 74% at a PAE concentration of 400 mg l–1 at 298K. However, at 333 K, the corrosion current density in the solution containing 400 mg l–1 of PAE was measured to be 1.28 mA cm−2, which was higher than that in the blank solution (0.92 mA cm−2). This increase in corrosion rate at 333 K demonstrates the negative influence of high temperatures on PAE inhibition efficiency. The PAE green inhibitor was discovered to have a physical adsorption characteristic and to obey the Langmuir adsorption isotherm.

Controlling C-steel dissolution in 1 M HCl solution using newly synthesized ρ-substituted imine derivatives: Theoretical (DFT and MCs) and experimental investigations

• ρ- substituted imines as C-steel corrosion inhibitor. • Δ N of SB-OCH 3 is higher than SB-CH 3 . • SB-OCH 3 enhances the R ct of C-steel to 374.9 Ω.cm 2 . • Adsorption type of tested imine compounds was physicosorption. • SB-OCH 3 resisted C-steel corrosion under severe conditions. Corrosion is an inevitable process, but its control is the goal of the researchers using organic inhibitors. So, newly successfully prepared ρ-substituted imine compounds namely;( E )- N,N -dimethyl1-4-((tolylimino)methyl)aniline (SB-CH 3 ) and ( E )-4 (((4methoxyphenyl)imino)methyl)- N,N -dimethylaniline (SB-OCH 3 ) have been fabricated to control the C-steel dissolution in 1M HCl. Hammett concept and theoretical calculated parameters were applied to predict the adsorption affinity of the prepared imine derivatives and the laboratory gravimetric and electrochemical tests accompanied with surface analysis tools were conducted to confirm these predictions. The fabricated imine compounds suppressed the C-steel reaction with efficacy of more than 90 %. The SB-OCH 3 exhibited higher adsorption affinity than SB-CH 3 and they acted as hydride C-steel corrosion inhibitors and followed Langmuir isotherm. The Δ G a d s * values of C-steel reactions in presence of these compounds were around -37 kJmol −1 . The inhibition performance of SB-CH 3 and SB-OCH 3 was function in their concentrations, molecular weight, and solution temperature. SB-CH 3 and SB-OCH 3 suppressed C-steel reaction at high temperature and the SB-OCH 3 showed highest efficiency (76.8%) at 60 °C. The activated thermodynamic parameters of C-steel reaction in existence and nonexistence of 1 × 10 −3 M imine compounds were calculated and discussed. The comparison findings with the previously published compounds confirmed the superiority of the understudied imine derivatives.