The inhibition effect of 2-mercaptobenzothiazole (MBT) on the corrosion of steel (API 5L X52) in 1 M H2SO4 was investigated by electrochemical and theoretical methods. The results of the investigation show that this compound has excellent inhibiting properties for steel corrosion in sulphuric acid and the inhibition efficiency increases with the increase in inhibitor concentration. The adsorption of the inhibitor on the surface of steel was found to obey a Langmuir adsorption isotherm. The effect of temperature on the corrosion behavior of steel without and with the inhibitors was studied, and the activation and thermodynamic parameters were calculated. Ab initio quantum chemical calculations at the density functional theory (DFT) level were performed to correlate electronic structure parameters of MBT and its different tautomers and conformers with its inhibition performance. The quantitative structure activity relationship (QSAR) approach was also used to correlate the quantum chemical parameters with the experimentally determined inhibition efficiencies.

Schiff base N,N′-bis(2-hydroxyethoxyacetophenone)-2,2-dimethyl-1,2-propanediimine (H2(hppnptn)) as corrosion inhibitor for API 5L grade B low carbon steel in hydrochloric acid solutions has been studied using electrochemical techniques and surface techniques. Results showed that the inhibition occurs through adsorption of the inhibitor molecules on the metal surface. Thermodynamic parameters for adsorption and activation processes were determined. Polarization data indicated that this compound acts as mixed-type inhibitors, and the adsorption isotherm basically obeys the Langmuir adsorption isotherm. The calculations of reactivity indices of H2(hppnptn) such as the localization of frontier molecular orbitals, E HOMO , E LUMO , energy gap (Δ E ), dipole moment (D), hardness (η), softness (σ), the fractions of electrons transferred (ΔN), electrophilicity index (ω), total energy change (Δ E T ), and natural bond orbital (NBO) charge distributions together with local reactivity by means of Fukui indices were used to explain the electron transfer mechanism between the H2(hppnptn) molecules and the steel surface.

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We present a simple, direct method to prepare monohydroxylated cucurbit[7]uril (CB7-OH) through the direct oxidation of its precursor host, cucurbit[7]uril (CB7). Although the conversion takes place in low yield (14%), the isolation of CB7-OH from the reaction mixture is straightforward, and the unreacted CB7 can be easily recovered. ITC measurements with several selected guests confirmed that CB7-OH binds all of them in aqueous solution with similar, albeit slightly lower, binding affinities than those observed with the unmodified CB7 host. ESI mass spectrometric competition experiments are consistent with the ITC measurements. A variety of spectroscopic and voltammetric measurements also verify that the CB7-OH complexes exhibit properties essentially identical to those of the CB7 complexes. DFT computational data also confirm the similar thermodynamic stabilities and structures of the CB7-OH and CB7 inclusion complexes. Finally, the high thermodynamic stability of the CB7-OH complexes was used to improve on the extraction efficiency of stir bar sorptive extraction methods after suitable modification of the active coating with CB7-OH.