Bowdoin Student Scientists

Science in Informal Language by Students at Bowdoin College - Brunswick, Maine

“Cooking” in the lab

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“Cooking” in the lab

For one gloriously, beautiful Maine summer—the summer after my sophomore year—I worked in an organic chemistry lab at Bowdoin College under Professor Rick Broene’s guidance. Now, it’s my senior year and I have chosen to continue the same project for an honors project. I spend all of my time in lab trying to synthesize a ligand—I’m essentially cooking with chemicals.

The goal is to make a ligand; a ligand is a compound that will “stick” to another chemical compound. For my project, I plan to attach a ligand to a chemical compound that will speed up a specific chemical reaction, known as a catalyst (in the Broene lab, we work with a cobalt catalyst). The first step is to synthesize the ligand (its full name is 4-phenylphosphabenzene). Next, I will stick the ligand to the catalyst. Then, I will run a reaction to see if the catalyst is improved with the addition of the ligand.

What does this cobalt catalyst do?

The cobalt catalyst is a special compound created by the Broene lab. The purpose of the catalyst is to dimerize linear a-olefins. Dimerize essentially means to double the length of a compound; in a dimerization reaction, a compound is added to an identical compound, creating a dimer. For example, the dimerization of a 4-carbon-long chain results in an 8-carbon-long chain (Figure 1).

Why bother doubling the length of carbon chains? These carbon chains are ubiquitous; they are in detergents, plasticizers, synthetic lubricants, and more. In Figure 1, a linear alpha olefin with four carbons and a double bond at the end is dimerized with a catalyst to create a longer linear a-olefin (an eight-carbon chain with the double bond at the end). The current method used by industry to produce linear alpha olefins is oligomerization. Oligomerization is a full-range process that produces linear alpha olefins 4-30+ carbons long. However, the most marketable linear alpha olefins contain 8-18 carbons. Thus, there is a lot of waste and thus, is not efficient because the different carbon-length chains need to be separated. Dimerization may be a solution to this inefficient and environmentally harmful process. Dimerization would allow for selective synthesis of linear alpha olefins. If you need a lot of 10-carbon long linear alpha lefins, then just dimerize 5-carbon long linear alpha olefins.

The cobalt catalyst the Broene lab created makes the dimerization reaction possible—well, it has potential. Currently, the catalyst is not wonderful at dimerizing linear alpha olefins. Sometimes, it takes a different chemical path and we do not get that double bond at the end (at the alpha position). If the double bond is not at the end position, then it’s not a linear alpha olefin and it’s useless. We need to modify the catalyst with a ligand so that it favors creating linear a-olefins instead of other, unwanted side products.

If you’re still not convinced my research is important…

In 2012, North America was responsible for 50% of world production of linear alpha olefins. With a growing demand from the polyethylene industry, the linear alpha olefin market is expected to grow by 4.2%, reaching 4.6 million metric tons by 2018. By 2020, the market demand for linear a-olefins is projected to be worth $19.85 billion. So, this is a large-scale process!

The chemistry behind making the ligand

The first step of my project is to synthesize the ligand (the 4-phenylphosphabenzene) (Figure 2).

Figure 2. The ligand to improve the cobalt catalyst: a 4-phenylphosphabenzene.

If I showed all the steps it takes to make this ligand, then you might cry; it sometimes makes me cry. But to give you an idea, take a glance at Figure 3; essentially, I am constantly adding something to a compound and the other “ingredients” help make it happen. The synthetic scheme to make this ligand is about 5 steps; you start with one chemical compound (A) and add some different chemicals to it to produce a different chemical compound (AB), purify AB, add more chemicals to AB to get ABC, purify ABC, and so on, until you get the compound depicted in Figure 2. So far, I’ve managed to make the immediate precursor of this synthetic scheme (in very small yields). Currently, I am working to improve this reaction to get a higher yield of the immediate precursor to the ligand.

Figure 3. The first three steps to synthesize the ligand.

Making the ligand is proving to be quite difficult. I constantly have to be producing earlier compounds that lead to the final product. I spend all day mixing together compounds and throwing them together in a flask without any oxygen (all of my reactions have to be oxygen free, don’t ask why, probably just to complicate my life). Then, I wait to see if I made my desired product; some reactions take only 3 hours, some take 24 hours, and some take 40 hours. I use this instrument called a NMR to verify I made my compound. Often times, I see impurities. So, I have to purify my product; this process can take one hour or take 3 hours.

One day, I might actually make the ligand and attach it to the cobalt catalyst to see if I’ve improved its dimerization abilities. Time will tell. Research is slow and it is frustrating. Some days it feels like you’re hitting your head against a wall. But it is so rewarding to be at the head of a project, to be the expert on your topic of research, to dig into literature when you’re stumped, and to be challenged.

Author Bio: Hi, I’m Jade Willey. I grew up in San Diego and now I’m finishing my last year of college in Maine. I am majoring in biochemistry major and minoring in English. I spent two years on the Bowdoin Varsity Sailing team. I was out on the water multiple times a week, one with nature, breathing in that fresh Maine air. It was such a splendid experience, though quite grueling at times. Now I spend too much time in an organic chemistry lab where I work with toxic chemicals and break glass flasks and glass syringes on a too frequent basis. But don’t worry, I love it, even if some days I despise it. Anyway, since you know I’m a senior, the words on the tip of your tongue are probably, “What are you doing after graduation?” I believe I will be working as a clinical research coordinator at Vanderbilt for one year as I apply to medical school.

The research discussed in this article was funded by the American Chemical Society and the Petroleum Research Fund.

References

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