industrial applications being readily available since 1998 with the

Industrial applications being readily available since

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industrial applications being readily available since 1998 with the introduction of ionic liquids as designer solvents [ 6 ]. With such a large number of available systems the task of finding a set of parameters to describe them for comparison has been daunting. No one parameter thus far has proven applicable to every situation until the introduction of the concept of degree of association as a solubility parameter [ 1 ] based upon the work by Gutmann [ 2 ]. The difficulty lies with finding a way to measure association in an ionic liquid. Thus far, the only available method has been to combine conductivity and diffusion measurements to measure the degree of association indirectly. This report shows that eNMR can be used to measure the degree of association of an ionic liquid more directly and with accurate and reproducible results. Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful and widely used technique. The foundation of NMR was laid by Rabi [ 7 ], Purcell [ 8 ], Bloch [ 9 ] and Hahn [ 10 ] between 1938 and 1950. NMR is used in many applications, from process control in industry to research. It is able to distinguish between chemical entities by subtle differences. Diffusion NMR allows for the study of self-diffusion for different chemical entities with a high degree of accuracy. Self-diffusion is central to chemical reactions, considered together with activation energy and molecular orientation. This stems from the fact that molecules typically need to collide before they can react with one another. The study of diffusion can give information about molecular size and shape as well as kinetics for low activation energy reactions. eNMR was introduced three decades ago and builds upon the principle of elec- trophoresis where charged particles can be separated based on drift velocities as they migrate to one of two electrodes supplying a constant electric field. eNMR combines electrophoresis with diffusion NMR to give information on electrophoretic mobility and effective charge distribution of the investigated sample. The goal of this project has been to develop a way to use eNMR to directly measure the ionic association of ionic liquids, specifically of 1-butyl-3-methyl trifluoroacetate that has been chosen as the system to be investigated. The method could then be used to provide a set of parameters to systemize ionic liquids. iv
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Chapter 1 Background 1.1 Ionic liquids 1.1.1 Introduction Ionic liquids constitute a fairly new term in the world of science and refer to systems that consist solely or almost solely of ions. For the past 20 years the term ionic liquid has mainly been used for systems that are liquid below 100 , sometimes referred to as Room Temperature Ionic Liquids (RTIL). The origin of what is now known as ionic liquids (then molten salts) can be traced to the works of Paul Walden [ 5 ] and his article ¨ Uber die Molekulargr¨ osse und elektrische Leitf¨ahigkeit einiger geschmolzener Salze , published 1914. Walden reported using molten salts that were liquid at low temperatures which were used to carry out his experiments in a water-free environment. After this, the work
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