An extract of cucumber leaves (ECSL) was prepared as a green corrosion inhibitor for carbon steel. Its carbon steel corrosion inhibition performance against 0.5 mol L⁻¹ H₂SO₄ was investigated using electrochemical methods and scanning electron microscopy (SEM). Its composition was analyzed by gas chromatography and mass spectroscopy (GC−MS). Quantum chemical calculations and molecular dynamics simulations (MDS) were conducted to elucidate the adsorption mechanism of the inhibitor molecules on the carbon steel surface. The results indicated that the inhibition efficiency increases with its increasing concentration. The extract acted as a mixed type corrosion inhibitor, and its inhibition properties were ascribed to the geometric coverage effect induced by its adsorption on the metal surface in accordance with Langmuir’s law. The active components in the extract were identified as mainly organic compounds with functional groups such as aromatic moieties and heteroatoms. The inhibition activities of ECSL are delivered through the ability of the active components to adsorb on the metal surface through their functional groups to form a protective layer which hinders the contact of aggressive substances with carbon steel and thus suppresses its corrosion. This research provides an important reference for the design of green corrosion inhibitors based on plant waste materials.

Glucosamine is a natural drug widely used for treating osteoarthritis and is usually left until it expires, which will cause a waste of resources if treated as garbage. However, its molecule contains many heteroatoms, entitling it to be a potential corrosion inhibitor. In this investigation, the corrosion inhibition activities of two types of expired glucosamine drugs (glucosamine hydrochloride and glucosamine sulfate) on carbon steel were estimated by electrochemical methods in the acidic solution. The results demonstrated that the glucosamine drugs were mixed-type corrosion inhibitors. Glucosamine hydrochloride could inhibit the carbon steel corrosion more significantly than that of sulfuric style at the same glucosamine content, suggesting a possible synergistic effect of glucosamine molecules with halide ions. Then, the co-adsorption behaviors of glucosamine sulfate with iodide ions were studied by experimental research, as well as theoretical investigations. The results indicated that the inhibition effect could be significantly enhanced when the glucosamine drug was utilized in combination with iodide ions. The electronic structures played a critical role in the synergistic inhibition of glucosamine drugs and iodide ions. Neutral molecules could interact with the metallic surface vertically through the amino and carbonyl groups, while protonated molecules were able to adsorb on it in parallel with the help of multiple functional groups. Since glucosamine molecules would be protonated and positively charged in the acidic solution, they were difficult to adsorb on the solid surface with metallic cations. When the iodide ions were presented, they preferentially adsorbed on the carbon steel surface and induced it to be negatively charged. Therefore, protonated glucosamine molecules could adsorb on the metallic surface using iodide ions as a bridge and form a protective film to mitigate the carbon steel corrosion.

In the present study, the mechanism of Maillard reaction was investigated using density functional theory calculations. Glucose and aminomethane were used as initial reactants in this study. The calculations show that the Amadori rearrangement reaction is the rate-controlling step with a corresponding energy potential of 402 kJ/mol，the enthalpy change is 219 kJ/mol, which is an endothermic reaction and therefore energy needs to be supplied from outside if the reaction is to proceed. The calculated results are in good agreement with the previous findings and can provide insight into the reaction mechanism of the Maillard reaction. These findings will help further research and find out the correct reaction mechanism. KEY WORDS: Food chemistry, Mechanism, Transition State, Computational chemistry Bull. Chem. Soc. Ethiop. 2024, 38(2), 539-545. DOI: https://dx.doi.org/10.4314/bcse.v38i2.20

Three adducts SF4BF3, SF4AsF5, and SF4SbF5 were studied in this work, in gas phase, DFT method was performed to study their molecular structures and thermodynamic properties. The heat of formation was studied at the high level DFT levels.Crystal structures were predicted using the Dreiding force field and refined by DFT-GGA-RPBE method. All the obtained crystal structures belong to the P2(1)/c space group. The lattice energies were predicted to be located between -91.86 and -693.73kJ/mol at the GGA-RPBE level. Based on the optimized crystal structures, the band gap (Eg) and density of state (DOS) were predicted and the calculations indicate that they are semiconductors with the band gap between 2.22 and 2.43ev.