Category: benzoxazole. The reaction of aromatic heterocyclic molecules with protons is called protonation. Aromatic heterocycles are more basic than benzene due to the participation of heteroatoms. Compound: 2-Mercapto-5-methylbenzimidazole, is researched, Molecular C8H8N2S, CAS is 27231-36-3, about Electrochemical study of 2-mercaptoimidazole as a novel corrosion inhibitor for steels. Author is Alvarez-Bustamante, R.; Negron-Silva, G.; Abreu-Quijano, M.; Herrera-Hernandez, H.; Romero-Romo, M.; Cuan, A.; Palomar-Pardave, M..
From electrochem. methods, polarization resistance and electrochem. impedance spectroscopy, the corrosion susceptibility of pipeline steel samples immersed in 1 M H2SO4 was determined using nil and different concentrations of the mol. 2-mercaptoimidazole (2MI). A corrosion inhibiting efficiency, IE, value of 98.5% was reached when the 2MI concentration in the system increased to 25 ppm. Also, at this concentration, the 2MI IE was measured as a function of time finding that the IE kinetics follows the relation: %IE = 98.5-0.03t after 800 h of evaluation. During the 1st 200 h 2MI IE was higher that 90% then, it decreased to 70% and it remained constant up to 1200 h. This compound can affect both the anodic and cathodic processes, thus it can be classified as a mixed-type inhibitor however, from variation of both corrosion potential and polarization resistance with [2MI] it was possible to state that the anodic reaction rate, of the corrosion process, decreases at a greater proportion than the cathodic one. 2MI follows an adsorption mechanism, which can be adequately described by the Langmuir isotherm with an adsorption standard free energy difference (ΔG°ads) of -26.8 kJ mol-1. To analyze the influence of substituting groups, both electron-donating and electron-attracting and the number of π-electrons on the corrosion inhibiting properties of organic mols., an electrochem. study was carried out on four different mols. having similar chem. framework structure: 2-mercaptoimidazole (2MI), 2-mercaptobenzoimidazole (2MBI) 2-mercapto-5-methylbenzimidazole (2M5MBI) and 2-mercapto-5-nitrobenzimidazole (2M5NBI). The IE order followed by the mols. tested was 2MI > 2MBI > 2M5MBI > 2M5NBI. Thus 2MI turned out to be the best inhibitor, even superior to the 2MBI. This fact strongly suggests that, contrary to a hitherto generally suggested notion, an efficient corrosion inhibiting mol. does not require to be a large one, also bearing an extensive number of π-electrons.
In addition to the literature in the link below, there is a lot of literature about this compound(2-Mercapto-5-methylbenzimidazole)Category: benzoxazole, illustrating the importance and wide applicability of this compound(27231-36-3).
Reference:
Benzoxazole – Wikipedia,
Benzoxazole | C7H5NO – PubChem