Chapter 1: Introduction
Chapter 1: Introduction
Ionic liquids (ILs) can be viewed as a new and remarkable class of solvent. They are also a type of materials that have a long and useful history, where the earliest material that meets the current definition of IL was observed in the mid-19th century when a separate liquid phase called the “red oil” was observed in Friedel-Crafts reaction . Over the following years, there has been a rapid growing of interest in ILs due to the realization that these materials may have greater utility as reaction solvent, although they were formerly used for specialized electrochemical applications.
Unlike the more volatile organic solvents, ILs are non-volatile, non-flammable and thermally stable. The physiochemical properties of the ILs can be altered by changing the anion and cation combination. These not only offer new opportunities on how to perform known reactions, but the ILs can even be tailored to meet specific synthetic needs.
One notable application of IL is the salt ability to act as solvent in many organic reactions is known to accelerate product formation or alter the selectivity of the reaction. For example, in the Diels-Alder reaction, where higher reaction rate and selectivity are obtained in polar solvents compared to non-polar solvents .
However, the vast applications of ILs are not without problems, one being that yields, purity and selectivity can vary according to the batch of ionic liquid used and the methods used to synthesis and purify the ILs. Therefore it is of great interest to study methods on how to minimize this problem.
The Objective of Research.
The objective of this research is to synthesize and characterize eight ionic liquids using 1-methylimidazole as the starting material by using the alkylation and metathesis synthesis methods. H1-NMR and Ion Chromatography (IC) analysis will be used to verify the characteristic and presence of impurities to determine the purity of products.
Chapter 2: Literature Review
2.1 What is Ionic Liquid?
Ionic liquid (IL) is a new class of solvent and considered as the green solvent to replace the conventional volatile organic solvents used in the chemical industries and laboratories, both for catalyzed and un-catalyzed reactions due to their unique properties: non-volatile, non-flammable and thermally stable solvents [1, 2, 12, 17]. ILs are molten salts, which are made entirely of cations and anions. However, unlike the common inorganic molten salts such as the sodium halides which are solid in room temperature due to the their high melting point, IL has low melting point, which allows many of them to be in liquid phase in room temperature. In other words, a given salt must have a melting point of 100oC or below it, sometimes as low as -96oC. The IL is called room-temperature ionic liquid (RTILs) if the salt’s melting point is below room temperature (~25oC) . The building blocks of RTILs can be seen in Figure 2.1. Much research has been done to study the physical and chemical properties of ILs during the last few years and will be discussed further.
Figure 2.1 Building blocks of Common Room Temperature Ionic Liquids [ (K. R. Seddon, A. Stark and M-J Torres, 2000) ]
ILs are very popular materials and they enjoy a plethora of applications in various domains of physical sciences. For some applications, ILs offer the advantage of both homogenous and heterogenous catalysts. This is because selected ionic liquids can be immiscible with the reactants and products but dissolve the catalysts. ILs can act as biological reactions media since enzymes are also stable in ionic liquids. This opens the possibility for ionic liquids to be used in biological reactions, such as the synthesis of pharmaceuticals. In another application, several ionic liquids can be used to remove cadmium and mercury from contaminated water. When these water-insoluble...
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