Department of Chemistry
Summer 2007 Research
Research Projects offered by Dr. Hoffmann
1. Phase Behavior of ionic liquids with Supercritical Carbon Dioxide
Ionic liquids are salts that are liquid at room temperature conditions. A liquid salt is an unusual medium for chemistry because this solvent is entirely composed of charged species, cations and anions. You might recall from general chemistry that salts like table salt dissolve easily in water but have little tendency to “dissolve in air”. Their vapor pressure is so small that it is nearly immeasurable. The same is true for ionic liquids, i.e., liquid salts. Thus, unlike traditional organic solvents such as acetone or ether, ionic liquids don’t smell, are nonflammable and are inherently safer to use because one does not get exposed to the ionic liquid solvent through inhalation. Because of these benign properties, ionic liquids have been included on the list of "green solvents". Supercritical carbon dioxide (scCO2) also belongs to the list of “green solvents” because it is non-flammable, incombustible, and non-toxic. ScCO2 is compressed carbon dioxide at temperatures above 31 ° C where it cannot be liquefied anymore. Variation in pressure will gradually change the density of this compressed solvent without undergoing a phase transition.
While ionic liquids are generally speaking good solvents for polar solutes, scCO2 is more appropriate as a solvent for non-polar solutes. In chemical synthesis, one often encounters the difficulty of dissolving polar and non-polar reactants in the same solvent. A mixed solvent system of ionic liquid and scCO2 would therefore be an attractive medium for such reactions between disparate reactants because both components, ionic liquid and scCO2, are considered green solvents. Of course, first one needs to find a suitable ionic liquid that is able to dissolve in scCO2. That is the motivation and goal or this research that investigates the phase behavior of various ionic liquids with scCO2. Recently, we discovered that the particular ionic liquid trihexyltetradecylphosphonium chloride dissolves in liquid and scCO2 up to 8 mass%. In a follow-up study on a similar ionic liquid (different anion but same cation) we observed that also this ionic liquid dissolves into the CO2 phase but the amount was to miniscule to reliable determine the conditions of the phase transition. However, we observed that the presence of the ionic liquid caused an enormous collapse of the CO2 volume requirement in absence of the ionic liquid. In other words the partial molar volume of the ionic liquid would actually be negative. This initial observation needs further careful investigations, which would be the subject of the summer research activities.
2. Physico-chemical studies of surfactants
This project is sponsored by Rochester Midland Corporation (RMC). RMC is a small chemical firm specializing in the area of cleaning agents, i.e., surfactants ( surface activating age nts). Over the past five years we have been working on a number of projects to better understand the properties of these chemical agents. Such understanding will aid in product design and in optimizing product manufacturing. Although not limited to NMR spectroscopy, the projects have been utilizing primarily this spectroscopic tool. For example, we have investigated the spectral changes that occur upon incremental addition of small amounts of water to the native surfactant. This project already led to a number of interesting results including the revelation of two distinct sites in the surfactant structure where water is tightly bonded and thus preferentially resides for surprisingly long time scales. This summer’s project will continue these types of investigations building upon our previous findings. In particular, we will most likely conduct relaxation NMR measurements for which we have developed in the summer of 2006 own pulse sequences to suppress the large water solvent resonance. RMC is also interested in building up an NMR database of all their processing chemicals. This will aid, for example, in monitoring product variations for the chemicals RMC receives from their suppliers. With the Department’s new NMR instrument now in place we are in much better position to carry out these projects.
3. Using liquid surfactants for chemical synthesis
This project is sponsored by Rochester Midland Corporation (RMC). The idea is simple. Given that liquid nonionic surfactants (of the kind we have been studying with RMC over the past three years) posses a negligibly low vapor pressure, may dissolve a wide variety of substances because of their amphiphilic structure, are of little toxic concern because they are already widely used in household products, and are biodegradable, why not exploit them as a possible new class of "green solvents" for chemical synthesis? So far we have accomplished one successful proof of concept: a particular Diels-Alder reaction. More recently, in collaboration with Dr. Anja Müller from Eastern Michigan University, we had some successful polymerization reactions to form polyester material that may have suitable properties for skin replacement. Currently, we are in the process of characterizing and evaluating the obtained product. Given these promising results the focus of synthesis in surfactants during summer 2007 research is expected to remain on these polymerization reactions although we might attempt another type of reaction as well in liquid surfactants.
All applications materials must be received in Rm 229 Smith Hall by Monday, March 26, 2007 at 4:00 pm.
Emma Lazarus Exhibit on Display at Brockport's Drake Memorial Library
Death Penalty Discussion Takes Various Forms on Brockport Campus
Rev. James Netters delivers powerful address at Martin Luther King, Jr., Memorial Lecture
Prison Drama to Help Engage Brockport Campus in Discussion of Death Penalty
Red Cross Blood Drive
10 am - 4 pm
CSA Newlyweds
9 pm - 11 pm
CSA Success VS Sell-Out
9 pm - 11 pm
Thursdays In The Cafe
7 pm - 8:30 pm
CSA Speed Dating
9 pm - 11 pm
