2008 Student Comments: The Ugi Synthesis Collaborative Project
When performing the second part of this lab (week 2) the goal is to obtain crystals. My solution was brown and "goopy" with some crystals. When I was trying to filter the crystals I added methanol dropwise. The methanol turned the top of the product a whitish-yellow and then did nothing to the product underneath the surface. I suggest that you mix up your "goop" after every few drops of methanol so that more surface is reached and therefore crystals are more easily obtained. Be careful mixing because the product is sticky like molasses so mixing it up can be difficult and you might accidentially tear your filter paper. -Becki H.
If you want to save yourself some time, definately check the reaction just after a couple of days. In my case, after 3 days a precipitate had formed so I was able to filter it and let it dry in a vacuum chamber. By the next lab period I was able to obtain the mass of my product and perform the rest of my spectroscopic analysis. If you wait until the next lab period to filter your precipitate, this lab will take a lot more time than you want it to! Also, singing the Ugi song speeds up the vortexing process. --Patrick Hughes
In order to obtain solid, defined crystals in the second portion of the lab, instead of starting with the addition of methanol start with the most polar solution hexane. I started with methanol and ended up with a sticky semi-solid that had the crystals trapped within it. --Allison Kolman
To go along with what Pat said, if a precipitate doesn't form within a few days, you might want to go to lab and take the cap off the vial to allow for evaporation. This will increase your chances of having crystals form by the next lab period. --Megan Wasz
I saw a precipitate by the end of the first lab period. It looked like white sand at the bottom of a bottle of liquid. I decided to wait the full week before filtering because when I shook the vial the precipitate would become suspended for several minutes before it re-settled, and I was worried that it would go through the filter paper. After a week I could still suspend the precipitate (and it seemed I had the same amount I had the first day), but it filtered fine. Don't wast time waiting, the first precipitate you get is probably fine to filter. --Sarah Perz
After prepareing your KBr handle it with care because any little hit to it or drop could cause a hole in your window that you created.--Kendall Moore
Be patient. I didn't see a precipitate after a couple of days, but when I went back to check on it in a week, I came out with a good amount. Also, to go along with what Pat said, definitely sing the Ugi song while vortexing, not only does it help your reaction, it also makes you feel better about your lab. --Marc Daher
When preparing the KBr pellet, you would like the sample in the hole in the window of the pellet to be clear so you can obtain an accurate IR spectrum. If your window is still not clear, ask your professor if you can still obtain an IR or you might have to make another pellet.--Marie-France Likanje
As a heads up, I, as well as another student, came out with negative masses for our products. This was due to the weight of the vial and product being smaller than the weight of the vial alone. Though we don't know how this could be, weighing things on the same scale could possibly prevent this from happening. --Melanie Bonifacio
I think this lab was a bit complicated. After the first week in lab, there seemed to be a lot of confusion about what to do next. I would advise future students to discuss what to do after the first lab week with the teacher before the start of the next lab period. That way you will not have to wait your turn to talk to dr. friesen for guidence. This will be a big time saver--Andrea Prosperi
I learned that to save yourself some time you should check the reaction after a few days because, a precipitate might not have formed and then you will not be able to filter it. Another suggestion is to take the cap off the vial to evaporate it. I was happy to see that precipitate formed rather quickly and many crystals formed. And ofcourse you shouldn't forget to sing the Ugi song which speeds up the vortexing as process! Tamara Pike
Using the 3,4-dimethoxybenzaldehyde and 2,4,6-trihydroxybenzoic acid combination, I was able to allow everything to dry out by unscrewing the vial open. After all the evaporation, I saw that there was a heterogeneous solid present. To help separate the solid mixture, I added a minimum amount of methanol to dissolve the solid. At first it would not dissolve, so instead of adding more methanol solvent, I chose to heat the mixture first, since solubility increases as temperature increases. Once everything dissolved after heating, I allowed the liquid mixture to cool to room temperature, and then proceeded to cool in an ice bath. This recrystallization gave me white crystals and a brown/red solution. I proceeded to separate using buchner filtration. So for these two reactants, methanol with heating and cooling will help separate the UGI product and biproducts.
-Ricardo Rodriguez
Make sure that you go back to filter your reaction early. Evaporation might not have been the best way to go. It left thick solid on the bottom that was hard to dissolve and deal with. Filtering might have made the next lab period a bit less frustrating (so get back to lab to check your solution EARLY for precipitate!!!)--K.S.
This experiment takes many days to see results. Be sure not to rush through the procedure, it may affect results. Do not be alarmed if you do not get a precipitate to form crystals. You may need to put the reaction mixture under pressurized air for a couple of days to see results. Alicia P.
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