1-Ethyl-3-methylimidazolium acetate (EMIMAc) is an ionic liquid (IL) often investigated as a solvent, especially in the context of biopolymers and biomass pretreatment. A reduced solvent efficacy occurs upon the addition even of low amounts of water to EMIMAc. Molecular mechanisms have not yet been fully understood. It is expected that the functionality as hydrogen bond donor and acceptor is key for the solvent–solute interactions. In this work, we analyze the solvent efficacy of EMIMAc in terms of hydrogen–deuterium (H/D) exchange at the C(2)-position in mixtures with water or acetic acid added as proton donors. Low-field NMR spectroscopy and deuterated solvents are used for a time-resolved evaluation of H/D exchange reactions. The H/D exchange is also modeled to explore changes in the reaction kinetics as a function of the mixture composition. The significant difference in calculated rate constant values among the concentration regimes shows that the chosen model equations of a possible pseudo-first-order and second-order reaction mechanism including water dissociation do not cover all interaction phenomena that influence the exchange in the individual concentration ranges. However, the modeling also indicates that the investigated interaction of EMIM+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {EMIM}^+$$\end{document} and Ac-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {Ac}^-$$\end{document} remains constant for concentrated IL mixtures containing 70mol%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$70\, {\text{mol}}\%$$\end{document} of EMIMAc in water up to diluted mixtures as low as 30mol%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$30\, {\text{mol}}\%$$\end{document} EMIMAc. This exemplifies the change between ions strongly associated in networks in concentrated mixtures suitable for biomass pretreatment and the much less associated anion–cation pairs in diluted mixtures which leads to the decreased efficiency of EMIMAc with increasing water content.

中文翻译：

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EMIMAc 混合物中 C(2)-氢-氘交换的变化

1-Ethyl-3-methylimidazolium 醋酸盐 (EMIMAc) 是一种离子液体 (IL)，经常作为溶剂进行研究，尤其是在生物聚合物和生物质预处理的背景下。即使向 EMIMAc 中加入少量水，溶剂效力也会降低。分子机制尚未完全了解。预计作为氢键供体和受体的功能是溶剂-溶质相互作用的关键。在这项工作中，我们分析了 EMIMAc 在与作为质子供体添加的水或乙酸的混合物中 C(2) 位的氢-氘 (H/D) 交换方面的溶剂功效。低场 NMR 光谱和氘化溶剂用于 H/D 交换反应的时间分辨评估。还对 H/D 交换进行建模，以探索作为混合物组成函数的反应动力学变化。不同浓度范围内计算的速率常数值的显着差异表明，包括水解离在内的可能的伪一级和二级反应机制的所选模型方程并未涵盖影响单个浓度范围内交换的所有相互作用现象. 然而，\setlength{\oddsidemargin}{-69pt} \begin{document}$$70\, {\text{mol}}\%$$\end{document} 的 EMIMAc 在水中直至稀释的混合物低至 30mol%\documentclass [12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt } \begin{document}$$30\, {\text{mol}}\%$$\end{document} EMIMAc。这举例说明了在适用于生物质预处理的浓缩混合物中与网络中强烈关联的离子与稀释混合物中关联少得多的阴离子 - 阳离子对之间的变化，这导致 EMIMAc 的效率随着含水量的增加而降低。{\text{mol}}\%$$\end{document} 在水中的 EMIMAc 稀释至低至 30mol%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{ amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$30\, {\text{mol}}\% $$\end{document} EMIMAc。这举例说明了在适用于生物质预处理的浓缩混合物中与网络中强烈关联的离子与稀释混合物中关联少得多的阴离子 - 阳离子对之间的变化，这导致 EMIMAc 的效率随着含水量的增加而降低。{\text{mol}}\%$$\end{document} 在水中的 EMIMAc 稀释至低至 30mol%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{ amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$30\, {\text{mol}}\% $$\end{document} EMIMAc。这举例说明了在适用于生物质预处理的浓缩混合物中与网络中强烈关联的离子与稀释混合物中关联少得多的阴离子 - 阳离子对之间的变化，这导致 EMIMAc 的效率随着含水量的增加而降低。{\text{mol}}\%$$\end{document} EMIMAc。这举例说明了在适用于生物质预处理的浓缩混合物中与网络中强烈关联的离子与稀释混合物中关联少得多的阴离子 - 阳离子对之间的变化，这导致 EMIMAc 的效率随着含水量的增加而降低。{\text{mol}}\%$$\end{document} EMIMAc。这举例说明了在适用于生物质预处理的浓缩混合物中与网络中强烈关联的离子与稀释混合物中关联少得多的阴离子 - 阳离子对之间的变化，这导致 EMIMAc 的效率随着含水量的增加而降低。