Next Arene: Fluorobenzene

On Tuesday 11-8-11, we started another reaction for our project and this time the arene was fluorobenzene. We chose this arene because we read that electron-withdrawing substituents (such as fluorine) on the ring will make the reaction proceed more slowly, and can sometimes stop the reaction from happening at all. From what we saw, one fluorine on the ring would only make the reaction a little bit slower, so we decided to try it. We found a procedure for the reaction that used large amounts of all the reactants, so we scaled it down to fit with the microscale approach we were taking to the project.

We set up the flask and did the vacuum/argon-fill procedure again, the same as all the ones before.

We added 10 ml of dibutyl ether and 1 ml of THF to the flask via syringe through the septum, and then we took the septum out and added 1.67 ml of fluorobenzene and 0.167 g of chromium hexacarbonyl to the flask. We started heating it and stirring it and let it sit overnight because the procedure we found said to let it heat for 24 hours. It started turning  green and there was a little bit of green solid that formed on the bottom when we started heating it:

We have found that the color change to green or yellow is always a good sign in this reaction!
We let it run for 24 hours and then tested it, but the IR didn't have the characteristic peaks of the solution. It may have been because of the IR which has been on the fritz lately, but more likely it was because it didn't have enough time to react, so we decided to try this one over again once we got a few more reactions done that were successful.

We also tried to get IRs for the Wild Card Project on this Tuesday, but we couldn't do the KBr pellet method, so we had to try dissolving the solids in something that wouldn't show up in the IR. We tried both of them in methylene chloride, but we didn't get anything conclusive from the IRs. Unfortunately, we didn't have a lot of solid from Part A in the first place, and after this we completely ran out. We decided that we would also do the Wild Card Project again to see if our yield was better for Part A (and to also see if Part B would still yield that coppery precipitate or if it would actually give us a gray precipitate like it says in the book!).

Since the IR wasn't being very helpful in our characterizations, we spent a little time trying to see if we could get GC-MS for two of our Cr Arenes (N,N-diethylaniline and methyl-3,5-dimethoxybenzoate) and the two parts of the Wild Card. Unfortunately, we ran all four samples twice, but we didn't get any conclusive peaks in the GC-MS. When we consulted Dr. Daryle Fish on this problem, he told us that maybe the products just weren't volatile enough to get good data from the GC-MS. This was a little bit of a waste of time, but we got to learn how to set up a method in the GC-MS that is tailored to our specific sample, so we did learn something useful that day!