Thermodynamic Activation Parameters Research Articles

A dielectric, thermodynamic and volumetric investigation for heteromolecular hydrogen bonding in 2-ethoxyethanol and ethanol binary mixture

ABSTRACT The dielectric, thermodynamic and volumetric measurements of neat 2-ethoxyethanol, neat ethanol and their binary mixtures have been carried out using time domain technique at 10°C–25°C with a variation of 5°C. Various dielectric parameters are calculated from complex dielectric spectra and are used to compute Kirkwood correlation factor, Bruggeman factor and activation thermodynamic parameters. These parameters are used to predict heteromolecular hydrogen bonding between associating molecules. The classical and non-classical type H-bonding interactions among the molecules are predicted using FT-IR spectroscopy.

Thermodynamic and spectroscopic analyses of N-Methyl benzylamine-isomeric amyl alcohol binary mixtures: Jouyban-Acree model correlation and experimental validation

ABSTRACT Excess molar volume, excess isentropic compressibility, deviation in viscosity, and excess Gibbs free energy of activation for viscous flow for binary mixtures of N-Methyl benzyl amine (NMBA) with 2-Methyl-2-butanol (2M2B), 2-Methyl-1-butanol (2M1B), and 3-Methyl-1-butanol (3M1B) were determined from measured densities (ρ), viscosities (η) and speeds of sound (u) at 303.15 K to 313.15 K. Influence Structural disparities on excess properties is discussed concerning intermolecular forces. The Prigogine – Flory – Patterson (PFP) theory identifies predominant molecular interactions, and the Jouyban – Acree model correlates density, speed of sound, and viscosity with composition. Thermodynamic activation parameters were calculated using the Eyring equation to study viscous flow thermodynamics. FT-IR and 1H NMR spectra of equimolar binary mixtures were analysed to confirm experimental findings through absorption bands (cm−1) and chemical shifts.

Optimization, molecular dynamics and quantum parameters simulations of Zingiber officinale rhizome as a green corrosion inhibitor

This study combines experimental and theoretical approaches to investigate ginger root extract (GRE) as an eco-friendly corrosion inhibitor for mild steel in acidic environments at temperatures ranging from 303 to 333 K. Experimental techniques, including weight loss measurements, were used to assess the inhibiting performance and adsorption behavior of GRE, while GC-MS, FT-IR, and UV–visible spectrophotometric methods provided further characterization. Results indicated that the inhibition efficiency of GRE increased with higher concentrations and decreased with temperature, highlighting its potential to effectively prevent corrosion in H2SO4 medium. GC-MS analysis identified four major phenolic compounds—6-gingerol, 6-isoshogaol, zingerone, and vanillyl glycol—and two secondary metabolites, α-Farnesene and β-Bisabolene. Among these, 6-gingerol, the most active and abundant constituent, was selected for computational studies. Optimal corrosion inhibition of 81.3 % was achieved at 303 K with a GRE concentration of 10 g/L for 1 h. Thermodynamic activation parameters suggested a temperature-dependent process, and alignment with the Langmuir isotherm indicated a physical adsorption mechanism. Quantum chemical calculations for 6-gingerol revealed highest occupied molecular orbital energy (EHOMO) and lowest unoccupied molecular orbital energy (ELUMO) values of -6.286 eV and -0.366 eV, respectively, in its protonated state, and -8.338 eV and -0.247 eV, respectively, in its neutral state. Molecular simulations showed a binding affinity of -4.736 kJ/mol between 6-gingerol and the steel surface, supporting the experimental findings and underscoring the potential of GRE as an effective corrosion inhibitor.

Effect of agitation speed on methylene blue discoloration kinetics via ambient air cold plasma

AbstractThis research investigates the kinetics of methylene blue (MB) discoloration using ambient air cold plasma, with a focus on the impact of agitation speed (100 and 750 rpm). The study revealed pseudo‐first‐order kinetics for MB discoloration, pinpointing optimal conditions at 35.00°C and 100 rpm. These parameters minimized half‐life times, correlated with observed kobs values. A decreasing pH trend, more pronounced at 750 rpm, was attributed to increased acidic nitrogen species (HNO3 and HNO2) production, adversely affecting dye discoloration. Concurrently, enhanced electrolyte concentration was noted from rising conductivity due to plasma production of reactive species followed by solubilization in the aqueous phase. The calculated thermodynamic activation parameters comprised: Ea = 7.96 kJ mol−1, ΔH‡ = +5.53 kJ mol−1, ΔS‡ = −253.23 J K−1 mol−1, and ΔG‡ = +79.77 kJ mol−1 (100 rpm); and Ea = 12.94 kJ mol−1, ΔH‡ = +13.78 kJ mol−1, ΔS‡ = −239.06 J K−1 mol−1, and ΔG‡ = +80.58 kJ mol−1, (750 rpm). The lowest Ea and ΔG‡ values at 100 rpm reinforced lower agitation favoring the reaction. The study demonstrated a linear decay of the reaction rate constant with the square root of ionic strength. This result, besides the negative activation entropy and moderate activation enthalpy led to a proposition to the determinant step for the transition state formation, involving an associative step between a solvated electron and the protonated substrate. The optimal dye discoloration rate and energy yield were observed at 35.00°C and 100 rpm, with values of 97.2% and 3.371 × 10−2 g kW−1 h−1, respectively.

Valorization of agro-industrial residues using Aspergillus heteromorphus URM0269 for protease production: Characterization and purification

This study aimed to produce, characterize and purify a protease from Aspergillus heteromorphus URM0269. After production by solid fermentation of wheat bran performed according to a central composite design, protease was characterized in terms of biochemical, kinetic, and thermodynamic parameters for further purification by chromatography. Proteolytic activity achieved a maximum value of 57.43 U/mL using 7.8 g of wheat bran with 40 % moisture. Protease displayed high stability in the pH and temperature ranges of 5.0–10.0 and 20–30 °C, respectively, and acted optimally at pH 7.0 and 50 °C. The enzyme, characterized as a serine protease, followed Michaelis-Menten kinetics with a maximum reaction rate of 140.0 U/mL and Michaelis constant of 11.6 mg/mL. Thermodynamic activation parameters, namely activation Gibbs free energy (69.79 kJ/mol), enthalpy (5.86 kJ/mol), and entropy (−214.39 J/mol.K) of the hydrolysis reaction, corroborated with kinetic modeling showing high affinity for azocasein. However, thermodynamic parameters suggested a reversible mechanism of unfolding. Purification by chromatography yielded a protease purification factor of 7.2, and SDS-PAGE revealed one protein band with a molecular mass of 14.7 kDa. Circular dichroism demonstrated a secondary structure made up of 45.6 % α-helices. These results show the great potential of this protease for future use in the industrial area.

Proton-Coupled Electron Transfer and Hydrogen Tunneling in Olive Oil Phenol Reactions.

Olive oil phenols are recognized as molecules with numerous positive health effects, many of which rely on their antioxidative activity, i.e., the ability to transfer hydrogen to radicals. Proton-coupled electron transfer reactions and hydrogen tunneling are ubiquitous in biological systems. Reactions of olive oil phenols, hydroxytyrosol, tyrosol, oleuropein, oleacein, oleocanthal, homovanillyl alcohol, vanillin, and a few phenolic acids with a DPPH• (2,2-diphenyl-1-picrylhydrazyl) radical in a 1,4-dioxane:water = 95:5 or 99:1 v/v solvent mixture were studied through an experimental kinetic analysis and computational chemistry calculations. The highest rate constants corresponding to the highest antioxidative activity are obtained for the ortho-diphenols hydroxytyrosol, oleuropein, and oleacein. The experimentally determined kinetic isotope effects (KIEs) for hydroxytyrosol, homovanillyl alcohol, and caffeic acid reactions are 16.0, 15.4, and 16.7, respectively. Based on these KIEs, thermodynamic activation parameters, and an intrinsic bond orbital (IBO) analysis along the IRC path calculations, we propose a proton-coupled electron transfer mechanism. The average local ionization energy and electron donor Fukui function obtained for the phenolic compounds show that the most reactive electron-donating sites are associated with π electrons above and below the aromatic ring, in support of the IBO analysis and proposed PCET reaction mechanism. Large KIEs and isotopic values of Arrhenius pre-exponential factor AH/AD determined for the hydroxytyrosol, homovanillyl alcohol, and caffeic acid reactions of 0.6, 1.3, and 0.3, respectively, reveal the involvement of hydrogen tunneling in the process.

Ruthenium(II)-Catalyzed Oxidative Annulation of Imidazo[1,5-a]quinolin-2-iums Salts and Internal Alkynes via C-H Bond Activation.

Ruthenium(II)-catalyzed synthesis of π-conjugated fused imidazo[1,5-a]quinolin-2-ium derivatives have been achieved via C-H activation of quinoline-functionalized NHC (NHC=N-heterocyclic carbene) and oxidative coupling with internal alkynes. The reaction occurred with high efficiency, broad substrate scope, tolerates a wide range of functional groups and utilized into a gram-scale. Synthetic applications of the coupled product have been exemplified in the late-stage derivatization of various highly functionalized scaffolds. Moreover, most of the annulated products exhibit intense fluorescence and have potential applications in optoelectronic devices. Mechanistic studies have provided insights into the spectroscopic characterization of key five-membered ruthenacycle intermediate and Ru(0) sandwich species. Based on several control experiments, deuterium-kinetic isotope effect, and thermodynamic activation parameters the mechanistic finding demonstrated that fused imidazo-[1,5-a]quinolin-2-ium C(2)-H bond cleavage is the rate-determining step and ruling out the possibility of reductive elimination for controlling the rate of reaction.

Kinetics of 4‑nitrophenol reduction with NaBH<sub>4</sub> over Ag/CuO nanomaterial catalyst

In this paper, Ag/CuO nanomaterials were prepared via hydrothermal method combined with chemical reduction and used as catalysts in the reduction of 4-nitrophenol. Kinetic study of 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP) by sodium borohydride revealed a first order reaction. The reaction rate constant k increased with amount of silver crystals introduced into CuO nanosheets, with Ag/CuO catalyst concentrations and with temperature. The thermodynamic activation parameters such as activation energy (Ea), enthalpy of activation (∆H#), entropy (∆S#) and Gibbs energy (∆G#) of activation were determined. The value of Ea, ∆H#, ∆S# and ∆G# were 72,33 kJ/mol, –69,86 kJ/mol, –24,28 J/K.mol and –62,50 kJ/mol (303K), respectivement. Ethanol and isopropanol were able to inhibit the 4-NP reduction with NaBH4 in the presence of Ag/CuO catalyst.

Why Do Empirical Valence Bond Simulations Yield Accurate Arrhenius Plots?

Computer simulations of the temperature dependence of enzyme reactions using the empirical valence bond (EVB) method have proven to give very accurate results in terms of the thermodynamic activation parameters. Here, we analyze the reasons for why such simulations are able to correctly capture activation enthalpies and entropies and how sensitive these quantities are to parametrization of the reactive potential energy function. We examine first the solution reference reaction for the enzyme ketosteroid isomerase, which corresponds to the acetate catalyzed deprotonation of the steroid in water. The experimentally determined activation parameters for this reaction turn out to be remarkably well reproduced by the calculations. By modifying the EVB potential so that the activation and reaction free energies become significantly shifted, we show that the activation entropy is basically invariant to such changes and that ΔS⧧ is instead determined by the specific mixture of the underlying force fields in the transition state region. The coefficients of this mixture do not change appreciably when the EVB potential is modified within reasonable limits, and hence, the estimate of ΔS⧧ becomes very robust. This is further verified by examining a more complex concerted hydride and proton transfer reaction in the enzyme hydroxybutyrate dehydrogenase.

Efficiency of alcohol and ester-imidazole in preventing mild steel corrosion: An integrated approach combining experimental and computational studies

In the present work, the two imidazopyridine derivatives namely ethyl 6,8-dibromoimidazo [1,2-a] pyridine-2-carboxylate (ES-IMD) and (5-methylimidazo [1,2-a] pyridine-2-yl) methanol (OL-IMD) were presented as powerful anti-polarizing agent for steel surface in aggressive system related to the obtained results in experimental and computational methods. 1H NMR and mass spectrometry (MS) were used to confirm the structures of resynthesized molecule. We assessed the effectiveness of OL-IMD and ES-IMD inhibitors in safeguarding mild steel from corrosion in a 1 M hydrochloric acid environment. We adopted an integrated experimental and computational approach to evaluate the inhibition efficiency and mechanism of OL-IMD and ES-IMD, utilizing gravimetric method, polarization curves and electrochemical impedance spectroscopy. Quantum chemical calculations and molecular dynamics simulations provided atomic-level insights into adsorption behaviour. Scanning electron microscopy characterized surface morphology. Findings revealed that OL-IMD and ES-IMD compounds performed as mixed-type inhibitors. At the greatest inhibitor concentration (10−3 M), the polarization curves gave inhibition efficiency values of 98.91% (ES-IMD) and 95.42% (OL-IMD). Thermodynamic activation parameters indicated a spontaneous adsorption process of OL-IMD and ES-IMD on the steel surface, which effectively increased the energy barrier for the corrosion process. The EIS parameters demonstrated that when inhibitor concentration raised, the double-layer capacitance (Cdl) dropped which suggested that the dielectric constant was decreasing. The results reveal a substantial correlation produced by the three analysed approaches EIS, PDP, and WL. Thermodynamic activation parameters indicated a spontaneous adsorption process of OL-IMD and ES-IMD on the steel surface, which effectively increased the energy barrier for the corrosion process. Furthermore, the calculated ΔGads values for the considered compounds were -47.39 (kJ/mol) and 49.26 (kJ/mol) for OL-IMD and ES-IMD respectively, proving the chemical nature of the adsorption. Furthermore, SEM surface studies displayed a homogeneous surface while the tested inhibitors were present, but a damaged surface in the blank solution. The theoretical models closely aligned with the experimental data, presented an excellent overview of the investigated inhibitors' reactivity against mild steel confirming the validity of the findings.

Determinants for 1-alkyl-3-methylimidazolium chloride-induced modulation of thermodynamic stability and CO-association dynamics of horse ferrocytochrome c

This manuscript determines the factors by which the water-miscible ionic liquid (IL), 1-alkyl-3-methylimidazolium chloride [Rmim]Cl affects the thermodynamic stability and CO association dynamics of horse ferrocytochrome c (Cyt cII) at pH 7. Investigation of rate constant and activation thermodynamic parameters for CO-association reaction of Cyt cII measured at different concentrations of [Rmim]Cl (1-Ethyl-3-methylimidazolium chloride [Emim]Cl, 1-butyl-3-methylimidazolium chloride [Bmim]Cl, 1-hexyl-3-methylimidazolium chloride [Hmim]Cl) revealed that the hydrophobicity of alkyl group of [Rmim]Cl modulates the CO-association dynamics of Cyt cII. The CO-association association kinetic results were further supported by intermolecular docking studies between the Cyt cII and [Rmim]+ ([Hmim]Cl, [Bmim]Cl, [Emim]Cl). Analysis of thermodynamic parameters calculated from thermal denaturation transitions of Cyt cII at different concentrations of [Rmim]Cl ([Hmim]Cl, [Bmim]Cl, [Emim]Cl) revealed that the [Rmim]Cl decreases the denaturation free energy in the order: [Hmim]Cl > [Bmim]Cl > [Emim]Cl, which suggests that the hydrophobicity of alkyl group of [Rmim]Cl modulates the [Rmim]Cl-induced decrease in thermodynamic stability of Cyt cII. Analysis of entropy − enthalpy plots showed that in addition to the hydrophobic effect, the enthalpic effect of [Rmim]Cl also decreases the thermodynamic stability of the protein. The dependence of unfolding free energy on [Rmim]Clconcentration was also translated into preferential interaction coefficients, Γ23. Experimental and theoretical estimations of Γ23 for Cyt cII provided the positive values of Γ23 at all across the [Rmim]Cl concentrations, indicating a robust and favorable interaction between the [Rmim]Cl and Cyt cII. Furthermore, the [Rmim]Cl-mediated increase in Γ23 typically follows the order: [Hmim]Cl > [Bmim]Cl > [Emim]Cl. Molecular dynamics (MD) simulation studies of Cyt cII performed at different concentrations of [Rmim]Cl ([Emim]Cl, [Bmim]Cl, and [Hmim]Cl) further showed that the hydrophobicity of the alkyl group modulates the structural stability and conformational-fluctuations of the Cyt cII.

Oxidation of aspartic acid with molybdenum-oxime-ligand framework in acidified-aqua and interfacial active media: Menger-Portnoy kinetic model

Understanding the chemistry of amino acids as the pillar of the proteins framework is vital when elucidating their mechanisms. The oxidation of aspartic acid (ASP) with molybdenum-oxime-ligand framework (MOL) is executed with the ultraviolet–visible spectroscopy technique, and the Menger- Portnoy model is generated in order to give more explanation to the empirical kinetic data. The aspartic acid’s oxidation is inert salt (NaCl) and counter-ion effects dependent. Deprotonation of the ASP countered the accelerating effect of the proton supplied by the acid (HCl). The mole ratio shared between the ASP and molybdenum-oxime-ligand framework is singlet with the generation of aldehyde malonic radical and carbon dioxide evolution. The kinetic order in [ASP] and [MOL] is singlet, and the thermodynamic activation parameter (ΔS‡ = −134.34 Jmol−1K−1) accounts for the solvation orderliness within the activated ASP-MOL specie at the transition state and the maintenance of MOL structural integrity. The interfacial active specie (sodium dodecyl sulphate, SDS) proves useful in catalysing ASP oxidation, and it is reinforced by Menger-Portnoy kinetic parameters.

Co-pyrolysis of pine-cone and chicken feathers: a study to determine kinetic parameters, thermodynamic properties, and potential synergistic effects

ABSTRACT The increasing consumption of chemicals, fuels, and energy results in the rapid depletion of fossil reserves that are utilized as raw materials in the manufacture of the aforementioned products. This is why science has recently focused on more efficient utilization of renewable energy sources such as biomass. In this work, we have used widely available biomasses such as pine cone and chicken feather for the kinetic and thermodynamic study. The co-pyrolysis study of an equal proportion (50:50) of pine cone (PC) and chicken feather (CF) was performed using the thermogravimetry technique. The analysis was performed for the temperature range of 20-8000 C with 10, 20, and 30 0C/min heating rates. The KAS, OFW, and Kissinger methods were used for the activation energy, and the Coats–Redfern method was utilized for the pre-exponential factor estimation. The KAS and OFW methods were used to calculate the average activation energy. Using the OFW and KAS methods, the results were 179.53, 163.02 kJ/mol for PC, 177.64, 126.46 kJ/mol for CF, and 160.49, 117.01 kJ/mol for the mixture. It was observed that the mixture activation energy was lower than the individual biomass. The study has analyzed the positive synergistic effect of the co-pyrolysis. Proximate analysis, ultimate analysis, heating value, and thermodynamic activation parameters such as ΔH, ΔS, and ΔG were also determined for the mixture.

Experimental and Theoretical Investigations on the Use of Pumpkin Peel as a Sustainable Biomass Anticorrosion Agent for Aluminum in HCl Solutions

The sustainable plant‐derived biomass are now understood to be important sources for the prevention of corrosion in metallic alloys. This study examined the effect of a potential novel low‐cost, low‐toxicity inhibitor utilizing pumpkin peel extract (PPE) on aluminum corrosion hydrochloric acid 1M HCl medium. Several experimental methods were used to investigate the inhibitor effect of PPE which include, AFM‐XPS surface analysis, electrochemical studies (electrochemical impedance spectroscopy‐electrochemical frequency modulation‐potentiodynamics), and weight loss procedures. According to the weight loss results, when PPE is introduced to a 1M HCl solution, the inhibitory performance rises up to 95.42% with an increase in PPE concentration in the range of 0–300 ppm at 25°C. Potentiodynamic results showed the investigated PPE inhibitor is a mixed‐type inhibitor. Corrosion inhibition at different temperatures was also examined, and the thermodynamic activation parameters were identified. It was found that the adsorption of the inhibitor on the aluminum followed the Langmuir and kinetic isotherm models. Quantum chemical indices contributed to a greater comprehension of the inhibitory mechanism. To investigate the configurational adsorption performance of the investigated PPE on the aluminum surface, molecular dynamics (MD) simulations were carried out.

Accurate Computation of Thermodynamic Activation Parameters in the Chorismate Mutase Reaction from Empirical Valence Bond Simulations.

Chorismate mutase (CM) enzymes have long served as model systems for benchmarking new methods and tools in computational chemistry. Despite the enzymes' prominence in the literature, the extent of the roles that activation enthalpy and entropy play in catalyzing the conversion of chorismate to prephenate is still subject to debate. Knowledge of these parameters is a key piece in fully understanding the mechanism of chorismate mutases. Within this study, we utilize EVB/MD free energy perturbation calculations at a range of temperatures, allowing us to extract activation enthalpies and entropies from an Arrhenius plot of activation free energies of the reaction catalyzed by a monofunctional Bacillus subtilis CM and the promiscuous enzyme isochorismate pyruvate lyase of Pseudomonas aeruginosa. In comparison to the uncatalyzed reaction, our results show that both enzyme-catalyzed reactions exhibit a substantial reduction in activation enthalpy, while the effect on activation entropy is relatively minor, demonstrating that enzyme-catalyzed CM reactions are enthalpically driven. Furthermore, we observe that the monofunctional CM from B. subtilis more efficiently catalyzes this reaction than its promiscuous counterpart. This is supported by a structural analysis of the reaction pathway at the transition state, from which we identified key residues explaining the enthalpically driven nature of the reactions and also the difference in efficiencies between the two enzymes.

Experimental and computational insights into destruction protection of E24 carbon metal by new trifunctional sulfur-phosphorus epoxy polymer

BackgroundMetal destruction is a major problem in many industrial applications. Organic protective agents are often used to protect metals from destruction in aggressive environments. In this work, a new trifunctional sulfur-phosphorus epoxy polymer (TGEHDSEP) was synthesized and evaluated as an antidestruction agent for metal. MethodsIn the present work, the new trifunctional sulfur-phosphorus epoxy polymer (TGEHDSEP) was presented as a powerful anti-polarizing agent for metal surfaces in aggressive systems related to the obtained results in experimental and computational methods. FT-IR, 1H NMR, 13C NMR and 31P NMR were used to confirm the structure of the synthesized molecule. Main findingsThe maximum protection of TGEHDSEP was 96–97 % at 10−3 M. Thermodynamic activation parameters indicated a spontaneous adsorption process of TGEHDSEP on the metal surface, which effectively increased the energy barrier for the destruction process. Surface analysis confirmed the formation of a defender layer of TGEHDSEP on the metal surface, which was confirmed by DFT calculations and MC and MD simulations. These simulations provided a detailed picture of the adsorption of TGEHDSEP and its protonated form on the metal surface, offering insights into the mechanism of destruction protection. The epoxy functional groups are mainly responsible for the rise in the power of the anti-polarization performance of this molecule.

Development of 1-phenyl-3-(4-(pyridin-4-ylmethyl)phenyl)urea derivatives as robust corrosion inhibitors for mild steel in 1 M HCl environment: Insight from ,molecular, experimental, and microscopic-scale modelling approaches

Cost-effective, novel urea derivatives, 1-phenyl-3-(4-(pyridin-4-ylmethyl)phenyl)urea (U-1), 1‐(4‐fluorophenyl)‐3‐(4‐(pyridin‐4‐ylmethyl)phenyl)urea (U-2), and 1‐(4‐methylphenyl)‐3‐(4‐(pyridin‐4‐ylmethyl)phenyl)urea (U-3) were synthesized to investigate as the corrosion inhibitors for mild steel/1 M HCl interface. Inhibition efficiency increases with the increasing inhibitor’s concentration but decreases with increasing temperature. Thermodynamic adsorption and activation parameters demonstrate that the adsorption of inhibitors follows Langmuir isotherm via physicochemical interactions. Potentiodynamic polarization measurements reveal that the inhibitors are mixed-type, impeding the charge-transfer process. Surface analysis supports a thin inhibitor film formation on the mild steel. The maximum inhibition efficiency of U-1, U-2 and U-3 are 94.97 ± 0.38%, 93.60 ± 0.62% and 97.42 ± 0.48% respectively. The calculated electrochemical impedance spectra (EIS) parameters such as ohmic resistance, double layer capacitance, relaxation time, effective thickness, and conductivity of grain and grain boundary are in-line with the efficiencies of NHUs. The performance of corrosion inhibitors follows a sequence U-3 > U-1 > U-2, emphasizing the influence of the substituent’s inductive effect (-CH3 > -H > -F) in inhibitors. Density functional theory (DFT) was performed to understand the correlation between molecular structure and inhibition efficiency. The Fukui indices confirm the presence of local attacking sites on the metal surface where inhibitors attack. A molecular dynamic (MD) simulation is used to determine the interaction energies between the inhibitors and mild steel. Radial Distribution Function (RDF) measurements confirm the existence of the chemical nature of the interaction. Furthermore, the diffusion coefficient of corrosive particles, self-diffusion coefficient of inhibitors, fractional free volume (FFV), and interaction between inhibitor’s film and corrosive particles are examined. Theoretical studies support experimental results.

Study of expired Fuclo 500 drug as an environmentally sustainable corrosion inhibitor

This work deals with aluminium corrosion inhibition by expired drugs containing flucloxacillin in 1 M hydrochloric acid medium, using the gravimetric method and density functional theory. Weight loss results showed that the inhibitory efficiency of this compound increases with concentration and decreases with increasing temperature. The study also indicates that this molecule is adsorbed according to the modified Langmuir model (Villamil model). Furthermore, the thermodynamic parameters of adsorption (∆Goads, ∆Hoads, ∆Soads) and activation (Ea*, ΔHa*, ΔSa*) show that the adsorption is mixed type (chemisorption and physisorption). In addition, density functional theory provides access to the quantum chemical parameters of the molecule such as the lowest vacant orbital energy (ELUMO), the highest occupied orbital energy (EHOMO), the absolute electronegativity (χ), the global hardness (η), the global softness (S), the fraction of transferred electrons (ΔN) as well as the electrophilicity index (ω) for finding correlation between the inhibitor structure and the experimental data.

Probing molecular interactions in mixed system of green solvent ethyl lactate with oligomers of polyethylene glycol

Polyethylene glycol and its oligomers are potential hydrogen bond donors that act as a green, effective, non-toxic, non-corrosive and recyclable molecular component for extractive desulfurization of liquid fuels and variety of other applications. The aim of this investigation is to explore the molecular interactions via variations in viscosity that occur on mixing these glycols with green solvent ethyl lactate. Dynamic viscosities (η) for pure solvents and binary mixtures of ethyl lactate and glycols oligomers (mono/di/tri/tetra-ethylene glycol) were measured at varying temperatures T/(K) = (298.15–313.15; with an interval of 5). Viscosity deviations (Δη) along with excess thermodynamic parameters of activation for viscous flow as Gibbs free energy (ΔG∗E), Enthalpy (ΔH∗E) and Entropy (ΔS∗E) were derived from experimental data. The Δη and ΔG∗E values were further correlated using Redlich-Kister polynomial expression. The experimentally obtained viscosity values were compared with 10 generalised literature models (Arrhenius, Kendall, Kendall-Monroe, Grunberg-Nissan, Hind, Katti-Chaudhri, Heric, McAllister three-body, McAllister four-body and Jouyban-Acree models). The average standard deviation percentages (ASD %) were calculated for all the models to compare the quality of correlation with experimental data. The minimal ASD % for McAllister four-body and Jouyban-Acree models in the working systems indicate that the multiparameter relations have the best capability of reproducing the experimental values. The temperature induced variations were also discussed together with molecular interactions. Further, quantum mechanical density-functional theory and graph theoretical approaches were used to explore the extent of interactions among the components.

Adsorption Mechanism, Kinetics, Thermodynamics, and Anticorrosion Performance of a New Thiophene Derivative for C-Steel in a 1.0 M HCl: Experimental and Computational Approaches

Metal surfaces can become damaged by corrosion when they interact with their surroundings, leading to huge financial losses. The use of corrosion inhibitors is one of the most crucial ways to combat the risky and hazardous effects of corrosion. In the present research, electrochemical techniques and surface analysis have been used to characterize the inhibition properties of (3-hydroxy-4-((4-nitrophenyl)diazenyl)-5-(phenylamino)thiophen-2-yl)(phenyl)methanone for the corrosion of carbon steel in an aerated 1.0 M HCl solution. Steel’s corrosion resistance was discovered to be improved by the presence of the examined inhibitor in 1.0 M HCl medium through the adsorption of the inhibitor species to create a barrier layer. The findings showed that when inhibitor concentrations increased and solution temperatures decreased, the inhibition performance (%IE) of the compound under study enhanced. In the light of inhibitor probe’s chemical makeup and theoretical analysis, the mechanism of the inhibition process was addressed. In a 1.0 M HCl solution containing 5 × 10−5 M of the inhibitor, the inhibition performance, at room temperature, was found to be almost 97%. The electrochemical results revealed that the examined compound successfully prevented carbon steel corrosion as a mixed-type inhibitor. The Langmuir and Freundlich isotherms are pursued by the adsorption of the examined inhibitor. Additionally, using Arrhenius and transition state equations, the activation thermodynamic parameters ΔEa, ΔH*, and ΔS* were determined and explained. The adsorption process was illustrated using DFT computation and MC simulations. The experimental findings and theoretical simulations concurred surprisingly well. Finally, the paper presents a discussion of the inhibitory mechanism.