Johansson K M, Izgorodina E I, Forsyth M, MacFarlane D R, Seddon K R
School of Chemistry, Monash University, Clayton 3800, Victoria, Australia.
Phys Chem Chem Phys. 2008 May 28;10(20):2972-8. doi: 10.1039/b801405a. Epub 2008 Mar 20.
We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine-acetic acid mixtures. The simple 1 : 1 acid-base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species (AcO)(x)H(x-1) stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1 : 1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.
我们描述了一项关于N-甲基吡咯烷-乙酸混合物中流动性和电导率随组成变化的研究。这种简单的1:1酸碱混合物似乎形成了一种离子液体，但其离子化程度相当低，这类液体更适合被认为是酸和碱的弱解离混合物。由3摩尔乙酸和1摩尔N-甲基吡咯烷组成的混合物在该二元体系中形成了离子化程度最高的混合物，这是由于存在通过氢键稳定的低聚阴离子物种(AcO)(x)H(x - 1)。这些低聚物种作为比乙酸根阴离子弱的碱，将质子转移平衡向离子物种的形成方向移动，从而产生比1:1组成时更高的离子化程度。瓦尔登图分析、热重行为和质子核磁共振数据，以及低聚物种的从头算计算，均支持这一结论。
