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Ionic Liquids as "Masking" Solvents of the Relative Strength of Bases in Proton Transfer Reactions.
ChemPlusChem ( IF 3.4 ) Pub Date : 2018-01-01 , DOI: 10.1002/cplu.201700514
Romina Zappacosta 1 , Antonello Di Crescenzo 1 , Valeria Ettorre 1 , Antonella Fontana 1 , Marco Pierini 2 , Gabriella Siani 1
Affiliation  

Equilibrium constants for the proton transfer reaction between pyridines and trifluoroacetic acid were measured in room-temperature ionic liquids (ILs) of different cation-anion compositions. The experimental equilibrium constants for ion-pair formation were corrected according to the Fuoss equation. The calculated equilibrium constants for the formation of free ions were taken as a quantitative measure of the base strength in IL solutions and compared with the relative constants in water. The effect of IL composition is discussed for a series of fixed IL anions and fixed IL cations. Finally, the sensitivity of the proton transfer reaction to the electronic effects of the substituent groups on the pyridine ring was quantified by applying the Hammett equation. A more marked levelling effect on the base strength was observed in ILs than in water. The Hammett reaction constants ρ were then correlated with solvent parameters according to a multi-parametric analysis, which showed that both specific hydrogen-bond donor/acceptor and non-specific interactions play an important role, with α and permittivity being the main parameters affecting the ability of the IL to differentiate the strength of the base.

中文翻译:

离子液体作为质子转移反应中碱的相对强度的“掩盖”溶剂。

吡啶和三氟乙酸之间质子转移反应的平衡常数是在不同阳离子阴离子组成的室温离子液体(ILs)中测量的。根据Fuoss方程校正了离子对形成的实验平衡常数。计算出的形成游离离子的平衡常数作为IL溶液中碱强度的定量度量,并与水中的相对常数进行比较。针对一系列固定的IL阴离子和固定的IL阳离子,讨论了IL组成的影响。最后,通过应用哈米特方程来量化质子转移反应对吡啶环上取代基的电子效应的敏感性。与水相比,在离子液体中观察到的对基础强度的更显着的流平效果。
更新日期:2018-01-04
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