Synthesis of 2-Alkyl-5-phenyl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-7-ol Derivatives from Vegetable Oils and Their Efficiency as Inhibitors of Hydrochloric Acid Corrosion of Stee
Abstract
Purpose: A method for synthesizing new derivatives of 2-alkyl-5-phenyl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-7-ol from vegetable oils (sunflower, palm, coconut) has been developed.
Experimental: The novelty of the method lies in the use of renewable feedstock – vegetable oils, and in the fact that the method is a onepot process involving oil hydrolysis, the interaction of the fatty acids formed in situ with aminoguanidine bicarbonate, and subsequent alkaline cyclization to a mixture of 3-alkyl-5-amino-1H-1,2,4-triazoles, which were further identified by HPLC/MS. In the second stage, based on these triazole mixtures, the target 2-alkyl-5-phenyl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-7-ols of sunflower, palm, and coconut oils were obtained through their two-stage condensation with cinnamaldehyde in the presence of an amphoteric surfactant. The anticorrosion properties of the synthesized triazolopyrimidinols were investigated for St3 steel in 24% HCl using direct (GOST 9.905-82, GOST 9.907-83) and electrochemical (potentiodynamic polarization, Mansfeld polarization resistance method) methods. All derivatives
showed high inhibiting activity at concentrations of 1-2 g/l. The highest efficiency was established for coconut oil derivatives: the protection degree (Z) reached 92.6% (1 g/l) and 98.0% (2 g/l) according to mass-loss measurements, and 97.2-97.4% according to polarization measurements (icor decreased to 0.026-0.028 mA/cm² compared to 6.8 mA/cm² in the background experiment).
Conclusions: It was shown that the high efficiency of the coconut oil derivative mixture is associated with the predominance of mediumchain fatty acid derivatives (C10-C14, of which ~50% are lauric acid residues) in its composition. The obtained compounds represent promising environmentally friendly inhibitors of acid corrosion for the oil production industry
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