The study of acid-base properties of 5-R-4-R1-1,2,4-triazole-3-thio(sulfo)acetic acids
Working on synthesis of 1,2,4-triazole-3-ylthioacetic acids and also salts, complex esters, amides, hydrazides, ylidene- and diacyl hydrazides, based on them, we see that the study of physical and chemical properties of the synthesized compounds in order to study biological activity of the obtained compounds and to implement original drugs into medical practice is necessary both from theoretical and practical point of view. The ascertainment of ionization constants of compounds is one of the aspects of physical and chemical properties’ study.
To identify the influence of presence and nature of substituents at the fifth carbon atom, and nature of the radicals at N4 atom in 1,2,4-triazole cycle and the degree of sulfur atom oxidation on synthesized 2-(5-R-4-R1-1,2,4- triazole-3-ylthio(sulfo))acetic acids’ acidity the pKa constants’ determination has been held. The constants have been determined by potentiometric titration of acids’ samples.
The regularities between acidity of the compounds and characteristics of their structure have been detected. So 2-(4-(2-methoxyphenyl)-1,2,4-triazole-3-ylsulfo)acetic acid has the biggest acidity (pKa = 3,87) among investigated one. Comparing the pKa of 2-(5-(4-pyridyl)-4-ethyl-1,2,4-triazole-3-ylthio)acetic acid, 2-(4- phenyl-1,2,4-triazole-3-ylthio)acetic acid and 2-(5-(4-pyridyl)-4-phenyl-1,2,4-triazole-3-ylthio)acetic acid, it should be noted that 2-(5-(4-pyridyl)-4-ethyl-1,2,4-triazole-3-ylthio)acetic acid (pKa = 4,03) has more acidic properties.
Comparing ionization constants it must be assumed that discussed acids and their salts in their oral administration will be more actively absorbed in the stomach (pH 1–3). Therefore, it is advisable to recommend this compound in tablet form for oral administration.
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