Understanding the effects of ionic liquids on a unimolecular substitution process: correlating solvent parameters with reaction outcome

Abstract

The polarisability of an ionic liquid is key in determining the rate constant of a unimolecular substitution process.

Investigating Variation of the Pnicogen Nucleophilic Heteroatom on Ionic Liquid Solvent Effects in Bimolecular Nucleophilic Substitution Processes

“…χ 2 >0.2 is unusual and resembles trends observed for unimolecular substitution processes ,,. These observations could intimate that there are similar interactions occurring in the triphenylantimony 1 d system that are responsible for the observed effects on the rate constant as have been noted in the unimolecular substitution processes (those between the ionic liquid and the transition state), once again this shall be discussed subsequently when further data is presented.…”

“…[4d,6b,10e,f,11] Determining activation parameters at key solvent compositions in these cases allowed the microscopic interactions of the observed ionic liquid solvent effects to be elucidated. [12] Such studies have examined a variety of substitution processes, [13] with those studies focusing on bimolecular nucleophilic substitution reactions [14] being of greatest relevance to this work.…”

Proteins in Ionic Liquids: Reactions, Applications, and Futures

“…One key consideration, however, is how the ionic liquid solvent is organized around the protein (Hayes et al, 2015; Sprenger et al, 2017). Beyond the demonstrated impact of these interactions in creating the initial solubilisation, as noted through the extensive experimental work in this review, it has been well established that the organization of an ionic liquid around a potential reactive center plays a significant role in directing reactions at that center (Yau et al, 2008, 2009a,b, 2012, 2013; Tanner et al, 2013a,b; Keaveney et al, 2016, 2017, 2018; Hawker and Harper, 2018; Hawker et al, 2018; Schaffarczyk Mchale et al, 2018; Gilbert et al, 2019). The surface site interactions, leading to potential inner site interactions if hydrogen bonds are disrupted, are governed by the relative affinity of the ionic liquid ions for specific amino acids (Sprenger et al, 2017).…”

Controlling the outcome of SN2 reactions in ionic liquids: from rational data set design to predictive linear regression models

“…Systematic analysis of a variety of ionic liquids on a range of different reactions (examples include: alkyl substitution, [10][11][12][13][14][15][16][17][18][19][20] aromatic substitution, 21-30 condensation [31][32][33] and pericyclic [34][35][36][37][38][39][40] processes) has provided a greater understanding of the effects of ionic liquids on reaction outcomes. Analysis of similar reaction types has shown the solvent effects are predictable, with specific ionic liquids able to be chosen to control reaction outcome.…”

“…25,26,41 These analyses have identified some key interactions of the components of ionic liquids with species along the reaction coordinate, 3 involving both starting materials (aromatic systems [24][25][26]29,30 and lone-pairs 18,19,30,31,33,42,43 ) and transition states. [16][17][18][19][20]24 An example of a reaction that has been examined extensively in ionic liquids is the bimolecular nucleophilic substitution (S N 2) reaction between benzyl bromide 1 and pyridine 2 (Scheme 1). [41][42][43][44][45][46][47] When the commonly-used ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([bmim][N(SO 2 CF 3 ) 2 ]) was examined as a solvent in this reaction, a rate constant enhancement, ca.…”