SYNTHESIS AND ANTICORROSION PROPERTIES OF N-ARYL-N¹-PYRIDYLTHIOUREAS AND THEIR BENZYLATED PRODUCTS.

N-Phenyl-, 1- and 2-naphthyl-N¹-2- and 4-pyridylthioureas were synthesized via the reaction of phenyl-, 1- and 2-naphthylisothiocyanates with 2- and 4-aminopyridines, and the corresponding pyridine salts were prepared by benzylation of the latter. The anticorrosive properties of the synthesized compounds were studied by the gravimetric method in 3 M HCl at 80°C using the 08 kp steel samples. The introduction of a benzyl fragment into the structure of N-aryl-N¹-pyridylthioureas led to the emergence of a new adsorption ammonium center, which increased the overall anti-corrosion efficiency of the obtained compounds. When using N-aryl-N¹-pyridylthioureas, the corrosion inhibition coefficient had the values of 4.5 to 59.0, whereas it increased to 90.8-629.0 for their salts. To explain the different anti-corrosion activity of N-aryl-N¹-pyridylthioureas and their pyridine salts, quantum-chemical calculations of the energy parameters E_HOMO, E_LUMO and ΔE=E_LUMO-E_HOMO were carried out and the dependences of the corrosion inhibition coefficients on EHOMO and ΔE, e^ΔE were obtained. A correlation was established between the inhibitory efficiency and energy parameters of the studied compounds. [ABSTRACT FROM AUTHOR]