Unexpected results are among the things that makes it so interesting to be a chemist. You can never be completely sure what is the result of a reaction, even though I have seen this specific experiment many times before. Chemistry can become an art form. You can catch a skyline in a small glass.
Every spring, we have the most beautiful chemistry at the Department of Chemistry. At this time, the secondary organic synthesis lab course is in progress, where the students perform seven 2-day manual syntheses and a 3-week research project where they work on relevant syntheses in the six different research groups. A synthesis is the formation of more complex chemical compounds by reaction from simpler materials.
On March 7, 2017, Masters student Elise Østrem (one of 22 students on the course) performed an experiment with the synthesis of a diol (alcohol with two OH groups). In the experiment, the goal is that the aqueous phase (the water) to which the reaction is carried out and the organic solvent (here dichloromethane) where the alcohol product is withdrawn from the aqueous phase, should not be mixed and stabilized. It will then form a so-called emulsion, which is not the goal. (Emulsion is used, for example, in the manufacture process of cosmetics). Instead, you want to extract the product from the reaction mixture, which is the aqueous phase. When Elise did this, a strange little “assembly” appeared from the water layer inside the separating funnel. One would expect a phase difference between the water and the dichloromethane due to different densities, but here they had changed places. Even though dichloromethane has a higher density than (pure) water, the water phase ended up at the bottom.
The supervisors, including myself have never seen anything like this (this experiment is done each year), and I, as a super excited teacher, grabbed my mobile and took several pictures. One of my first thoughts was to send one of the photos to the Chemical & Engineering news, the weekly journal of the American Chemical Society – read by 157,000 chemists worldwide every week!! Including myself. And part of my masters students also. Sometimes, I am trying to sneak in some articles both from the basic course students and the students at the lab courses. It is important to follow what the world’s chemists and industry are doing. Generally, organic chemical synthesis is not very colorful visually, but here it really was a beautiful sight – and that seemed to be the opinion of the editor also!
The photo was published
Delicate skyline – These wispy towers rose up inside Elise Østrem’s separation funnel as she worked up a reaction. Østrem, a graduate student at Norwegian University of Science & Technology, conducted a Sharpless dihydroxylation on trans-stilbene and then separated the reaction mixture using water and dichloromethane (DCM), which each formed their own layer in the funnel. The wisps are likely an emulsion between the water and DCM. Normally, the water layer would float on top of the DCM layer because water is less dense. But because of the reactants dissolved in this mixture, the water layer sank to the bottom, which may have caused this unusual emulsion behavior.
“None of the other students had the same result”
Elise Østrem is on her fourth year of her master studies of industrial chemistry and biotechnology with organic direction. At first, she did not think about the result of the synthesis:
“It was not until I saw Elisabeth’s reaction that I realized that this was something special. Eventually I noticed that Ane, whom I shared fume hood with, or any of the other students got the same result”, she says.
Shanghai skyline in a glass
Small differences, such as the purity of the glass or how the glass is shaken can have a big impact and may be the reason for this unexpected result. This is so interesting about being a chemist. You can never be completely sure what is the result of a reaction, even though I have seen this specific experiment many times before. Chemistry can become an art form. You can catch a skyline in a small glass.
This blog post was written by Elisabeth Jacobsen, associate professor at the Department of chemistry.