Acetylation of Ferrocene, Part Two

On Thursday 9-22-11, we had to redo the acetylation part of the ferrocene lab because it did not work the first time. The GC of our product did not yield anything, so we decided to try a different procedure to make the same product. This new procedure was scaled up considerably so we hoped that there would be enough of our product to run tests on.

We began by adding ferrocene, acetic anhydride, and phosphoric acid in a round bottom flask and placing this flask in a sandbath with an air condenser hooked up to a steady flow of argon gas. We heated and stirred it until the temperature reached 100 degrees Celsius, and then heated it for 10 minutes after that.

When we took the flask off to empty the precipitate, we found that in addition to the precipitate, we had a tar-like black substance stuck on the bottom of the flask. It had actually formed around our stir bar, so the stir bar was probably not stirring for a long time before we realized it! We did have some precipitate so we washed that into a large beaker of ice and waited for the ice to melt before we added some sodium hydrogen carbonate until the solution stopped bubbling with the addition of the base. This took a huge amount of NaHCO3 (around 7 grams) and by this time, the solution was starting to look like we were just boiling a beaker of mud. Once in the ice bath, it started to look a little better. It looked like a brown precipitate in a reddish solution.

We suction filtered it and got a large amount of brown precipitate, which we then used to make a GC sample, an IR sample, and a Mel temp sample.

The trouble is, we didn't get the GC yet due to technical difficulties and the Mel temp gave a melting point of about 59 degrees Celsius while pure acetylated ferrocene has a recorded melting point of about 81 degrees Celsius.

We thought that maybe there were impurities in the sample causing the melting point aberration, so we decided to recrystallize our product. We did this by adding the minimum amount of petroleum ether to our sample to make most of it dissolve. We then decanted the clear yellowish liquid (which was the product dissolved in the pet ether) into a clean beaker and let it sit overnight. After the night was up, the ether had all evaporated off and a layer of orange crystals was left on the side of the beaker--this was our pure product.

Unfortunately, a Mel temp test of the pure product gave us the same results as the unpurified product, so at this point we need our GC to give us some proof of acetylation. We know from the drastically lower melting point that there is a new chemical formed from this reaction, we just don't know what it is!

Silicon Polymer (Bouncing Putty)

On Tuesday 9-20-11, we made a silicon polymer that looked like a clear gel and bounced like a bouncy ball. We started by combining diethyl ether and dimethyldichlorosilane in a round bottom flask. When we started adding some water dropwise into the mixture, the flask got very hot (even when we had it in an ice bath!) and emitted some fumes. The fumes were actually hydrogen chloride gas, which is given off in the reaction we were doing-- hydrolysis of dimethyldichlorosilane. The product of the hydrolyzation (a silanol) was what we needed to make our putty. Of course, now there were two layers in the flask so we had to hearken back to organic chemistry and grab a separatory funnel.

We wanted to keep the organic layer, so we separated, washed the aqueous layer with hexanes, separated again, and combined the two organic phases. We used sodium hydrogen carbonate to neutralize the HCl that was formed in the reaction.

We dried the product over magnesium sulfate and filtered it. Then, we got to use the rotary evaporator to evaporate off the ether and obtain our product. Here are a few pictures of the roto vap:

We put our sample in the roto vap, filled the condenser up with ice, and turned it on. It heated the sample and evaporated the ether from it. The ether then went over to the condenser, where it was turned from gas to liquid and was collected in the round flask at the side. This left just our product in the vial inside the roto vap.

After this, we took the IR of the oily product and massed it to find out how much boric acid to add to the liquid (we needed about 7% by mass). When we added the boric acid, it just sat on the bottom of the beaker and wouldn't dissolve into solution. When we heated it with continual stirring, it started to get thick and gummy after about 15 minutes.

Once it seemed like all the liquid had turned to putty, we scraped it out of the beaker, put it on a preweighed watchglass, and found the mass. If it was left to sit too long on the watchglass, it would "melt" into a liquidy puddle but then would form right back into a putty again if you rolled it in your hands. Here is our bouncing putty...which actually did bounce!!

More Ferrocene and A Bit of Spectroscopy

The first thing we did on Thursday 9-15-11 was look at the product of our acetylation reaction that had been sitting for two days. Surprisingly, the solution was no longer blue-green, but had turned completely orange and there appeared to be an orange precipitate on the bottom (along with what looked like some excess NaHCO3).

We vacuum-filtered this and below is the picture of the orange precipitate. We then let it dry in the oven for a little bit, and it turned a light brown after this.

The yield was very small, but then the amounts of reactants were small as well. We barely had enough for a sample to be dissolved in methylene chloride to run through the GC-MS. We can only know if the acetylation of ferrocene worked once we get the spectra back from the GC-MS!

The purification of our ferrocene sample by sublimation was a really neat thing to watch. We put our crude sample in a glass petri dish on top of a hot plate and turned the hot plate on. We placed a beaker full of ice on top of the petri dish.

 As the sample heated up, we began to see little bright orange crystals forming on the inside of the petri dish lid under where the ice beaker was placed.

Finally, after about 20 minutes, there were crystals all over the sides of the petri dish bottom and all over the top of the petri dish. What was left of the crude sample was a black pile of dust:

Here is a picture of the top of the petri dish, which is definitely nicer to look at than the bottom:

We had to scrape all the crystals out of the petri dish and mass them so we could calculate percent yield.

The rest of the lab period involved getting spectra to see if we actually made what we thought we made. We ran the ferrocene crystals through the Mel-temp device and got a melting point very close to that of pure ferrocene, so it's looking good so far! We also ran an IR, H-NMR, and a GC-MS on ferrocene. We left the GC-MS to run overnight, so we don't have those spectra yet but we do have the IR and NMR:

IR Spectrum of our Product

The only thing that was weird about this was the carbonyl peak that shows up at about 1750 1/cm. We ran background scans several times, but it never showed up in the background scan, just in the spectrum of our product.

H-NMR Spectrum of our Product:

The single peak at about 4 ppm is characteristic of ferrocene because of the aromatic cyclopentene rings on either side of the Fe atom in the "sandwich compound":

                        

Structure from http://chemistry.about.com/od/factsstructures/ig/Chemical-Structures---F/Ferrocene.htm

So far, we seem to have a lot of evidence in  favor of us actually making ferrocene, so we'll see if the GC-MS disputes that or supports it.

Finally...Ferrocene!

This Tuesday (9-13-11) we tried the ferrocene lab again, but this time we used a different procedure. The reaction stayed the same except for the solvent and the amount of reactants. In the last one, we used ethylene glycol but in the new procedure we used 1,2-dimethoxyethane (also known as "Glyme") as the solvent. This reaction was scaled up considerably--in the last one, we used 2 g of KOH and in this one we had to use 7 g of KOH (which is a lot more than is pictured below!). We were worried that the large amount of KOH might not dissolve and the reaction would fail, but it seemed to dissolve quickly.

The whole setup of the reaction went the same as the last one, so we had some practice and the step where we put the flask under a vacuum and inert argon atmosphere went a lot faster this time.

We didn't really notice anything changing from the last reaction to this reaction until we added the FeCl2/DMSO solution using the cannula. The last time, it was a very pretty dark red color but this time it was more of a dark brown color. The biggest change we noticed is when the HCl and ice was added at the end. The last time, the solution immediately turned a bright lime green (and was almost completely clear) but this time, it turned a murky dark blue-green color. The reason it was murky? The bunch of orange solid that precipitated out, AKA ferrocene!!!! At least, we really hoped that our spectroscopic evidence would tell us that it was actually ferrocene. What the heck, we were just excited that the reaction had produced SOMETHING! We vacuum filtered the solid, dried it in the oven, and massed the chunky reddish-brown solid that it had become.

That same day, we tried the acetylation of ferrocene reaction with commercial ferrocene that was available in the lab (we were trying to save time since we lost a day with the first ferrocene experiment). The only reactants that went into this reaction were ferrocene, phosphoric acid, and acetic anhydride. This stirred at 100 degrees celsius for 10 minutes under an air cooled condenser. The mixture changed from a light orange to a dark brown color at the end of the heating. After this, NaHCO3 was added in small increments, the key word here being "small" because each time we added some, the mixture bubbled very high in the flask and expelled CO2 gas. After the mixture stopped bubbling, it had turned a strange blue-green color but we didn't see any evidence of the brown solid we were supposed to be making. We set it in an ice bath, and then let it sit at room temperature until Thursday since we were out of time. We weren't feeling too confident about this reaction, but we would have to wait and see what happened with it!

No Luck With Ferrocene

In the first part of the Ferrocene experiment that we did on 9-8-11, our goal was simply to make ferrocene. The fun part of this lab was all the new tricks of the trade we got to learn, such as making an inert atmosphere in the reaction flask by flushing it with argon gas. The entire setup for the experiment was pretty extensive:

And this was just the first part of the reaction! The vaccuum and inert gas technique was neat, and the practice will be really helpful for our final project because it has to be done under an inert atmosphere too. We made a light brown liquid called potassium cyclopentadienide in this flask.

In a Schlenk flask (the flask on the left), we dissolved some iron (II) chloride tetrahydrate in DMSO, and then added that slowly to the other mixture using a cannula (new technique for us!). A cannula is basically a long two-sided needle that uses pressure differences to transfer liquid from one flask to another without using a syringe.

This stirred together into a dark red solution until we added ice and HCl, and then it turned bright lime green!

At this point, there was supposed to be orange solid forming in the green liquid, but we didn't see any. We added more ice and more HCl and some solid finally formed, but our yield was terrible. We vaccuum-filtered it anyway, and this is what we ended up with:

NOT a good result to the lab! This means that we will have to do this part of the lab over again, so hopefully we get a better yield next time.

Explosive!

In this lab (performed on 9-6-11) we got to make an explosive called nitrogen triiodide monoamine and then even better, we got to detonate it! The preparation itself was extremely simple: stir iodine and ammonium hydroxide together and spread the mixture out on filter paper:



 The wet solid is not explosive, so it had to dry before we could do anything with it. Once it dried, we detonated it with a yardstick, and got a good recording of it:



Our favorite part of the detonation was the little puff of red smoke that happens when it explodes. We thought the explosion just made a lot of noise, and that was the only way it released its energy. However, when we looked at our filter paper after the detonation, we saw that it blew a hole right through the three layers of paper that we dried it on!



Benzene Inclusion Compound (AKA Purple Crystals)

We actually started this experiment on 9-1-11, but it's taken us a while to figure this whole blog thing out, so we'll try and get this up to speed with where we are now in the experiment! We made a dark purple/blue solution on the first day of the experiment, which is a metal complex named trans-bis(ethylenediamine)di-N-thiocyanatonickel (II). This was separated into two vials: we didn't add anything to one, and to the other we added benzene which sat on top of the purple solution like oil on water. Very small, light purple crystals began to form about 30 minutes after we added the benzene, and they formed right at the meeting place of the benzene and the purple solution.

After our long Labor Day weekend, we analyzed the benzene inclusion crystals. The pure solution (the one without the added benzene) had only the very beginnings of crystals on the sides, so that might not be ready for analysis for another week.

It was very hard to get the crystals out of the bottle because the texture most resembled a grape slushie, so this was a time-consuming part of the process. We were surprised at the amount of crystals that formed- almost the whole vial was filled with them!



We used vaccuum filtration to separate the crystals from the solution they were in, and then dried them in the oven for an hour until they looked like this:

We used the Mel-temp device to find the melting point range of these crystals (a very cool piece of equipment where you can see a tiny portion of your sample melt through a microscope lens). We will just have to wait and see how the pure crystals compare to these ones!