Ionic Liquid Effects on Nucleophilic Substitutions
Author(s)
Fraser, Georgina
Type
Thesis
Abstract
In this thesis we demonstrate a fundamental difference between nucleophilic substitution reaction mechanisms in ionic liquids versus conventional solvents. Reported herein are the effects of ionic liquid solvents on substitution reactions between a cationic electrophile and the chloride anion of various organic and inorganic salts. We have combined novel quantitative studies of the nucleophilic source [Cat]Cl with our studies of [C4C1im]Cl and compared their reactivities, k2. For the first time, Eyring activation parameters have been calculated for substitution reactions between charged species in ionic liquid solvents and reveal a hitherto unprecedented role of the cation in the transition state. The activation parameters (ΔH≠ and ΔS≠) suggest the reactivity of the chloride anion can be manipulated by varying the size and chemical nature of the cation, and also shed light on cation hydrogen bond donating effects. The superior ability of ionic liquid solvents to fully screen the charges of reactant ions is shown to break down as ions become larger, less charge dense and display a tendency to self-aggregate.
Version
Open Access
Date Issued
2013-08
Date Awarded
2013-11
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Welton, Tom
Sponsor
Engineering and Physical Sciences Research Council
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)