E2 Brutus? Part III

The manner of heating and stirring the reaction was also an issue I considered. I decided to use boiling stones rather than stirbars. Stirbars are expensive and students tend to dump them down the drain or wash them into the waste bucket. I went with using the thermwells rather than the boiling water bath. We will be using the thermwells next week as well. This is the first time for the students to use thermwells and set up a reflux apparatus. We did not use drying tubes on the top of the condenser.

We did a liquid-liquid extraction of the reaction mixture after adding water and pentane. We added the water first to dissolve the solids that form during the reaction. I went with pentane though petroleum ether or hexanes are cheaper solvents. The cheaper solvents show several peaks on the GC that makes things pretty confusing. I made the mistake of using heptane as the hydrocarbon solvent the first couple times I tried the experiment. It turns out that the heptane has about the same GC retention time as the heptene products. So I ordered some pentane. Tert-butanol is fairly soluble in pentane so I gave it a slightly different extraction procedure than for the other two.

I was challenging for the students to do an extraction in a 25 mL round bottom flask with about 4 or 5 mL of total liquid. The first extraction was fairly easy because the aqueous is darker than the organic layer. However, for the next two extractions both layers are clear and colorless so it is difficult to see the interface. I had to check every GC vial the students prepared to make sure there were not two phases in the vial. This is something to troubleshoot for next time. We could have used more pentane and more water for the extractions. A different flask , or even their 125 mL separatory funnels, may be beneficial as well.

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