IN PURSUIT OF AN UNDERSTANDING OF STILBENE

by Summer Halas

It took me two weeks to make a tube that didn't leak. I made eight sets of gel layers before I made one without bubbles. What felt like a lifetime passed before I got my hands on a potentiostat, but I finally got to throw my chemical into a flask and flip on the switch. Not all the parts were available, the potentiostat was in questionable shape and the solvent hadn't been dried, but I didn't care. For sixteen months, Dr. Fry and I had waited to see what would happen when I flipped the switch, and such seemingly minor details had to be ignored. When we saw the results a day later, those details became much more important. But discouraging results, I had learned by then, are the norm in the world of research.

I work in a lab where certain chemicals are made from other chemicals in a specific process that involves electricity. The chemicals are specific arrangements of carbons, hydrogens and a few other select elements from the periodic table. I am using electricity because I am working with chemicals that won't react without it. I immerse my chemicals in a liquid and allow an electric current to pass through the liquid. The electric current, however, can pass through the liquid only when all the tubes and gels and potentiostats are assembled correctly. My chemicals develop a charge from this electric current and can proceed to react with the liquid in which they are immersed. The reaction of my chemicals with the liquid forms new chemicals.

The chemicals Dr. Fry assigned me to examine stem from an observation one of his graduate students, John Porter, made a few years ago. When John was working with his chemical, stilbene, and many tubes, gels and whirring machines, he saw results different from those he or Dr. Fry had hoped to see. But when Dr. Fry's researchers gave him lemons, he made lemonade. This insatiably curious and extraordinarily patient man decided to explore the implications of John's results, and his decision to do so had dire consequences on my future as an undergraduate Chemistry major.

John's chemical, stilbene, consists of two six-carbon rings, called benzene rings, connected to two other carbons. John placed stilbene in a liquid very much like alcohol and passed an electric current through the liquid via the tubes and gels and machines. When his reaction was complete he saw that two products had been made. That is to say, mother stilbene had fraternal twins. Both of John's products resulted from the liquid combining twice with stilbene at opportune locations, specifically at the two carbons to which the benzene rings were connected. The first product (figure 1 -- product a) reflected combination with the liquid at both carbons, whereas the second (product b) reflected addition of the liquid at only one of the carbons. Product b came from one of the benzene rings actually moving to the other carbon. The carbon that lost this benzene ring was therefore available to combine with the liquid, and did so twice.

Figure 1 -- The liquid can combine once with each of the two designated carbons (a) or one of the benzene rings can switch carbons (b) and the liquid will combine twice with the carbon that lost the benzene ring.

In terms of the lemonade that Dr. Fry was about to make, the chemistry community usually looks for processes that make only one product. However, since understanding the reaction was still useful, Dr. Fry presented an explanation for the appearance of products a and b. Soon after, both Burchelle Blackman '97 and I, fresh out of organic chemistry class, joined Dr. Fry's research group, and we tested his explanation over the summer. Testing his explanation proved more difficult than we had expected and consumed more than just one summer. Burchelle altered stilbene's composition slightly to prevent the appearance of product b. I tried to encourage its production with a different alteration to the chemistry. Specifically, we replaced one of the hydrogens on the benzene rings with other elements. With our respective replacements, we encouraged the electrons bouncing about on the stilbene to hang out in certain regions. Burchelle discouraged the benzene ring from moving to the other carbon; I persuaded it to move.

An oxygen, a carbon and three hydrogens did the trick for Burchelle's research, though not until a week before her thesis was due. By replacing one of the hydrogens on the benzene ring with an oxygen, a carbon and three hydrogens (chemical d), she completely prevented the formation of product b. She didn't see her results until that last week because her altered stilbene was neither commercially available nor found in nature, so she had to make it first. She used a recipe published in one of the chemical journals, but it was well into the winter when she finally made her altered stilbene and passed electricity through it. Burchelle's results showed that no product b was made. This confirmed Dr. Fry's explanation of John's results.

A few months after Burchelle and I began working for Dr. Fry, I learned that Burchelle had it easy. I entered Dr. Fry's lab the first week of June 1996 and started making my first chemical outside of an instructional lab. Like Burchelle, I began the summer replacing one of the hydrogens on each benzene ring of the stilbene. Instead of replacing the hydrogens with an oxygen, a carbon and three hydrogens, as Burchelle had, I replaced the hydrogens with chlorine (chemical e) to encourage production of product b. I followed the recipe Burchelle used, adapting it to compensate for the difference with the chlorines, but the research soon took a different turn.

It took about three weeks for Dr. Fry and me to establish unequivocally that the stilbene with the chlorines would not be made -- several steps had to be taken to actually make the altered stilbene, and we couldn't get past the first one. We next tried to make the stilbene with flourines (chemical f), because they are said, with regards to the production of product b, to have properties similar to those of the chlorines. For entirely different reasons, this chemical was just as impossible to make. Halfway through my junior year, Dr. Fry and I decided to try replacing the aforementioned hydrogens with a nitrogen and two oxygens (chemical g). By the end of the spring I was able to make the stilbene but those nasty nitrogens and oxygens made the steps to come more difficult than I'd expected. The separation process alone took four months. I followed a different recipe than before, and I expected that a majority of the product from this recipe would be the altered stilbene. I knew more than one unwanted product might also be formed, but separation of the stilbene from the unwanted products was crucial.

I finally separated the stilbene, nitrogens and oxygens from the rest of the unwanted materials four months after I had made it. The recipe I used claimed nearperfect results, but I only ended up with a small quantity. While my results were far from those alleged, I was more alarmed that the article hadn't mentioned that the stilbene, nitrogens and oxygens would stick to every surface possible before I would be able to persuade it to enter any glassware. In addition, it was impossible to combine with ANYTHING. The stilbene altered with nitrogens and oxygens possessed certain properties, including the stickiness, that made it one of the most stubborn chemicals I would ever work with. It couldn't be persuaded to stay in any liquids. One of these liquids was the one I wanted to pass electricity through. It was very difficult to introduce the electric current to the chemical because the chemical would not combine with the liquid. Dr. Fry's reason for John's observation of products a and b remained untested.

With another summer approaching and my love for the research only mildly weakened, Dr. Fry decided I should try a fourth change in the stilbene. I tried to replace the two hydrogens on the benzene rings with three flourines affixed to a carbon (chemical h). This altered stilbene was by far the easiest and most interesting chemical to make. When I was making this chemical I saw several brilliant color changes. The greatest feature of this chemical was the ease with which it mixed with the liquid through which the electric current was passed. This was the point where I finally got to flip the switch with all the tubes and gels and potentiostats connected. The results? I saw three major and four minor products. Dr. Fry and I could not be discouraged with these results, however. Two of the products were products a and b. The other five products indicated that a few other processes had taken place, and we were just as interested in these new processes. By considering all the products and the processes they implied, Dr. Fry and I were able to describe a great deal about this previously unobserved reaction. By replacing the hydrogens with this last group of elements (chemical h), I had encouraged the electrons bouncing about on the chemical to hang out in a certain region, though it produced more results than I'd expected.

Figure 2 -- This diagram shows the hydrogens that Burchelle and I replaced on stilbene (c). Burchelle worked with a stilbene replaced with oxygen, a carbon and three hydrogens (d). I researched four different replacements. I tried to work with chlorines (e) followed by flourines in a different location (f), followed by a nitrogen and two oxygens (g) --the sticky material -- and finally with a carbon and three flourines (h).

Three months before my thesis was due and nineteen months after I'd started the research, Dr. Fry suggested that since my results were difficult to analyze alone, it would be to my advantage to return to the stilbene with the nitrogen and two oxygens that stuck to everything --chemical g. I managed to introduce a small amount of the chemical to the electric current by mixing the liquid and chemical vigorously. I expected to compare the results of this process with the previous observations made with the stilbene, a carbon and three flourines (chemical h). Suffice it to say, the new chemical presented an entirely new set of results.

Even though I rarely see pleasing results, I don't mind the great deal of patience and stubbornness required for research. On a day-to-day basis, I enjoy stepping into the lab to start a new reaction, to check up on one that's running for more than one day, or to try to figure out what happened in a particular reaction. I'm still very reliant on Dr. Fry's knowledge, and I can't thank him enough for taking me under his wing.

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