Final Cr Arene!

On Tuesday 11-22-11 we tested the fluorobenzene chromium tricarbonyl that had been reacting for 5 days. We were a little apprehensive because this is what the flask looked like after it had burnt the preceding week:

When we took out the stopper, there was a greenish liquid in it, and there also looked to be a precipitate in it. We took out some of the liquid and tested it in the IR. The tabulated frequencies were 1982 and 1903 inverse centimeters. We got two peaks in the IR; one was at 1913 and the other was at 1985. These were so close to the tabulated data that we considered this reaction a success! We then vacuum-filtered the product to separate the liquid from the solid. The liquid was actually a dark yellow-green color once the precipitate was taken out:

The precipitate was light green in color, and we kept it in case we had time to recrystallize it and get pure crystals:

There were insoluble black specks in it like there were in the benzene chromium tricarbonyl, but we got rid of these easily when we dissolved the solid in methylene chloride to recrystallize it.

The next Tuesday (11-29-11) we set up the reaction for our last Cr Arene. This time, the arene was para-phenylenediamine. Since nitrogen-containing groups are electron-donating and this one has two amines on it, it shouldn't take very long to react!
We set up the two neck flask and gas condenser like all the other experiments, and vacuum-filled and argon-filled it. We added the solvents (10.1 ml of dibutyl ether and 1.05 ml of THF) to the flask through the septum and then we bubbled argon through the solvent to remove any oxygen. Since the para-phenylenediamine is so reactive, we needed to make sure that we had a completely inert atmosphere for the reaction. To do this, we cut the end off a syringe and stuck it into a tube attached to the vacuum line. Then we opened the gas valve and allowed the argon to flow through the syringe needle. We placed the syringe needle into the solvent and then added an exit needle to relieve the pressure (we had to close the stopcock on the gas inlet valve in order to get the gas to bubble in the solvent because the incoming pressure was too much, so we needed to have some way for the extra pressure to escape). We let the gas bubble through for 10 minutes and then we removed the exit needle and the syringe.
We removed the septum and added a stir bar, 0.330 g of chromium hexacarbonyl, and 0.160 g of para-phenylenediamine. We placed a greased stopper into the neck and began heating and stirring the reaction. We are going to leave this one react for two days because we can check it Thursday during lab, which will be a little less than 48 hours. As soon as the reaction reached reflux, it turned a bright yellow color, like many of the other reactions before. Tomorrow we get to check it out and see if we were successful for our final reaction of the semester!