Scholarlink

<p>Hydroxamic acids (<i>N</i>-hydroxyamides) are relevant as ligands for metal ions, which are usable in agriculture and medicine and also present in nature. Their acidity constants in aqueous systems are needed to rationalize their metal ion complexation behaviour and parametrize-related prediction models. In this study, a detailed methodology is presented for determining the acidity constants (p<i>K</i><sub>a</sub> values) in water using a combination of nuclear magnetic resonance (NMR) spectroscopy with potentiometry. It includes the acidity constants of five <i>N</i>-hydroxyamides, two <i>N</i>-hydroxyimides and three other compounds: 1<i>H</i>-1,2,3-benzotriazole, 4-hydroxy-3-methoxybenzoic acid (vanillic acid) and pyrrolidine-2,5-dione (succinimide). Besides directly measured absolute p<i>K</i><sub>a</sub> values of the individual compounds, relative acidity (∆p<i>K</i><sub>a</sub>) measurements between pairs of compounds were carried out as well, resulting in a p<i>K</i><sub>a</sub> “ladder”, i.e. a system, where all acids were linked together by Δp<i>K</i><sub>a</sub> measurements. The absolute and relative measurement results were combined together to improve the results’ reliability. As a result, twelve reliable p<i>K</i><sub>a</sub> values are now available, of which three have not been reported previously.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Determination of Hydroxamic Acids’ Acidity Constants in Water by NMR

  • 期刊论文

  • 发表日期：

    2025年4月26日

查看全文
  • Ricardo A. L. S. Santos,
  • Andre Leesment,
  • Célia M. P. G. Amorim,
  • Ivo Leito,
  • M. Clara F. Magalhães,
  • Diana C. G. A. Pinto

摘要

Hydroxamic acids (N-hydroxyamides) are relevant as ligands for metal ions, which are usable in agriculture and medicine and also present in nature. Their acidity constants in aqueous systems are needed to rationalize their metal ion complexation behaviour and parametrize-related prediction models. In this study, a detailed methodology is presented for determining the acidity constants (pKa values) in water using a combination of nuclear magnetic resonance (NMR) spectroscopy with potentiometry. It includes the acidity constants of five N-hydroxyamides, two N-hydroxyimides and three other compounds: 1H-1,2,3-benzotriazole, 4-hydroxy-3-methoxybenzoic acid (vanillic acid) and pyrrolidine-2,5-dione (succinimide). Besides directly measured absolute pKa values of the individual compounds, relative acidity (∆pKa) measurements between pairs of compounds were carried out as well, resulting in a pKa “ladder”, i.e. a system, where all acids were linked together by ΔpKa measurements. The absolute and relative measurement results were combined together to improve the results’ reliability. As a result, twelve reliable pKa values are now available, of which three have not been reported previously.