In a previous study1 from the Welton Group, the reactivity resulting from mixing two different and reactive salts together was observed to be highly dependent on the type of solvent, with molecular and ionic liquids exhibiting fundamentally different reaction pathways. Ionic liquids were shown to be extremely dissociating solvents and the salts behaved as discrete reactive species. Conversely, in molecular solvents neutral ion pairs or clusters were formed.
In this thesis, further evidence of the charge screening behaviour of ionic liquids will be presented. The investigation was carried out by using Kosower's charge-transfer complex, 1-ethyl-4-(methoxycarbonyl)pyridinium iodide,2 which is only spectroscopically active when its ions are in direct contact, hence allowing charge transfer to occur. The behaviour of this salt is therefore a good indicator of the number of pyridinium iodide contact ion pairs in solution and can be used as a probe for the amount of ion-pairing in both ionic and molecular liquids.
In the second part of the investigation, the SN2 reaction of two reactive salts (1-butyl-1-methylpyrrolidinium bromide and dimethyl-4-nitrophenylsulfonium bis(trifluoromethanesulfonyl)imide) in ionic liquid/molecular liquid mixtures was studied. The aim was to examine whether complete charge screening behaviour could be achieved in ionic liquid/molecular liquid mixtures of different compositions. This research also provided some insights of general behaviour of salts in ionic liquid/molecular solvent mixtures.