School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.
Org Biomol Chem. 2019 Oct 23;17(41):9243-9250. doi: 10.1039/c9ob01753d.
The effects of solvate ionic liquids as solvents have been considered for two substitution processes where the solvent effects of typical ionic liquids have been extensively investigated previously; the bimolecular nucleophilic substitution (SN2) reaction between pyridine and benzyl bromide and the nucleophilic aromatic substitution (SNAr) reaction between ethanol and 1-fluoro-2,4-dinitrobenzene. It was found that use of solvate ionic liquids gave rise to similar trends in the activation parameters for both substitution processes as typical ionic liquids, implying the microscopic interactions responsible for the effects were the same. However, different effects on the rate constants compared to typical ionic liquids were observed due to the changes in the balance of enthalpic and entropic contributions to the observed rate constants. From these data it is clear that the reaction outcome for both of these substitution reactions fall within the 'predictive framework' established in previous studies with a cautionary tale or two of their own to add to the general knowledge of ionic liquid solvent effects for these processes, particularly with respect to potential reactivity of the solvate ionic liquids themselves.
已考虑将溶剂化离子液体的影响用于两个取代过程，其中先前已经广泛研究了典型离子液体的溶剂效应；吡啶和溴化苄之间的双分子亲核取代（SN2）反应以及乙醇和 1-氟-2,4-二硝基苯之间的亲核芳香取代（SNAr）反应。结果发现，使用溶剂化离子液体导致这两个取代过程的活化参数与典型离子液体相似，这意味着导致这些效应的微观相互作用是相同的。然而，与典型离子液体相比，由于焓和熵对观察到的速率常数的贡献之间的平衡发生变化，观察到的速率常数存在不同的影响。从这些数据可以清楚地看出，这两个取代反应的反应结果都属于先前研究中建立的“预测框架”，对于这些过程的离子液体溶剂效应的一般知识，尤其是对于溶剂化离子液体本身的潜在反应性，都有一些警示或补充。
