Wild Card Project

We chose to synthesize two metal nitrosyl complexes for our Wild Card experiment. We tried to synthesize tricholoronitrosylbis(triphenylphosphine)ruthenium (II) and dinitrosylbis(triphenylphosphine)ruthenium (-II). For the first compound, we made separate solutions of 78 mg of hydrated ruthenium (III) chloride and 125 mg of Diazald each in 6 ml of absolute ethanol. In a round-bottom flask, we mixed 475 mg of triphenylphosphine in 18 ml of absolute ethanol. We hooked the flask up to a water condenser with a CaCl2 drying tube and brought this solution to a boil.

After it was brought to a boil, we removed the condenser and added the two solutions we had made into the flask. At this point, it turned a dark green color.

We let the solution cool to room temperature and we saw that something had precipitated in the solution. We vacuum-filtered it and got a green-gold precipitate.

We let the precipitate dry overnight and then we extracted this solid with 20 ml of methylene chloride, and the methylene chloride turned yellow.

We put a boiling stone in and boiled off the solvent until there was very little solvent left in the beaker. We cooled this in an ice bath, and crystals were supposed to form at this point, but we didn't really see anything happening. There was some kind of precipitate after a while, so we added some hexane and boiled off the solution again. We got some yellow-brown solid at this point.

We took the melting point of this solid, which was about 190 degrees Celsius. However, we did not have any reference data for this compound, so we couldn't really tell if this would help us to identify that we had made the product that we wanted to.

For the part 2 of the Wild Card, we placed triphenylphosphine in a round-bottom flask with 12 ml of absolute ethanol and stirred it until it dissolved. We attached a water condenser to the flask and heated the solution until it boiled. While we were waiting for the solution to boil, we prepared a solution of 50 mg of ruthenium (III) chloride hydrate in 4 ml of ethanol and a solution of 80 mg of Diazald in 4 ml of ethanol. We added the ruthenium solution to the flask first, at which time the solution was a dark brown.

We added triethylamine to the flask via pipet until the solution turned a dark reddish-purple. At this point, we added the Diazald to the solution and it turned a dark yellow. There was a precipitate that we vacuum-filtered and it turned out to be a reddish, coppery precipitate.

The manual, however, said that this was supposed to be a gray precipitate! We took the melting point of the solid and got 140 degrees Celsius. We have to do a KBr pellet IR on each of these, but we have yet to do this. Again, we have no reference for the IR data, so we have no way to determine whether we have made the products we were supposed to. Hopefully we can get the IR to work for us so we can see the NO stretches and compare them.

Challenge Day and Continuing the Project

October was a busy month, so we haven't had a lot of time to update the blog, but now it's time to catch this thing up to speed!

On Thursday 10-20-11 we had our Challenge Booth in honor of National Chemistry Week, which went well. People were educated about tooth decay (and a little freaked out about the fact that we used real teeth), but they mainly enjoyed the free gum we handed out at the booth! The other group's booths and demos were really interesting and we had a ton of fun with the Challenge. Here's a picture of our poster that we made for the occasion:

We had to get back to work after the Challenge, so we started another reaction for our project. The last reaction that we did was benzene, and that worked really well, so we decided to change our arene to N,N-diethylaniline. We set up the reaction the same way as we did before: we vacuum-filled and argon-filled the flask and then added the two solvents, dibutyl ether and THF, into the flask with a stir bar. We then measured out the Cr(CO)6 and the N,N-diethylaniline and added them into the flask. Once we started heating the solution, it turned yellow and then got darker as it kept heating. When the heating was stopped, the solution got lighter in color:

We set up the solution the Thursday before fall break, which caused the reaction to take a lot longer than it should have because it had to sit without heating over the weekend. It stirred and heated for 11.5 hours and then we tested it via IR to see that the two peaks in the CO region that corresponded to our desired solution. After this, we had to evaporate off the solvent, so we let it sit out in the hood for a week. We had light green crystals once the solvent had evaporated.

On Thursday 11-3-11 we tried to do a C13 NMR of our product in deuterated DMSO, but even with 512 scans the final scan was very noisy. It is a good thing that the IR is such a helpful way to identify the products, because we have had a lot of trouble with the NMR giving us good data.

While this one was sitting in the hood evaporating, we started another reaction, this time with methyl-3,5-dimethoxybenzoate. Again, we set up the two-necked flask, vaccum-filled and argon-filled it, and added the dibutyl ether and THF with a stir bar. We measured out the Cr(CO)6 and the arene and added them both to the flask. This time, because the reaction had to stir for 70 hours, we started it on Thursday at the end of lab and let it stir through Friday over the weekend until Monday morning. As soon as we started to heat the reaction, it turned light yellow. When we went back on Friday morning, we really couldn't see the reaction because the flask was blackened on the inside. The only problem was that we didn't have the data for this complex, so we didn't have anything to compare our IR to. We got a brown solid, and then we washed this with methylene chloride to get a yellow liquid. We then put this in the hood to evaporate off the solvent. After the solvent evaporated off, we had a light yellow powder in the beaker. We haven't had a chance to do an NMR on this yet, but we think we will try this next week.

Benzene Chromium Tricarbonyl and Challenge

On Tuesday 10-4-11 we checked via IR to see if we had made our desired compound. First, we got an IR of the pure Cr(CO)6 in methylene chloride to compare to our experiment. There was only one carbonyl peak at 2000 1/cm. We pipetted out a small sample of our solution from the flask. There was both a solid yellow-green precipitate and a similarly colored liquid in the reaction flask. We used the liquid for the IR and got a spectrum that had two carbonyl peaks that were slightly lower than the peak on chromium hexacarbonyl. The values were very close to tabulated values for the complex, so we are confident that we got the desired complex. We then suction-filtered the contents of the flask to get a light green precipitate but there were also some black specks in the solution. We recrystallized our product by putting the precipitate in a mininum of methylene chloride and letting it sit overnight to evaporate the methylene chloride. The next day when we went to go check the product, we had green crystals in the beaker:



We also wanted to take a C-13 NMR and an H-NMR of our product. We did this by scraping out some of the crystals and placing them in an NMR tube with some deuterated DMSO. Our product dissolved in this and we got both NMR spectra. They both correspond very well to expected values for our complex.

We had to come up with a demonstration for National Chemistry Week that had to do with health, hygiene, or medicine. Purple Chrome decided to do a demonstration about acid erosion of teeth. Pepsi and other soft drinks contain phosphoric acid, so we wanted to test and see what prolonged exposure to your teeth actually does. We made a 2 M and a 7 M solution of phosphoric acid, a 2 M solution of NaF (which should theoretically make the tooth stronger, not weaken it), and we also had some Pepsi. We massed 4 teeth and placed one in each of the solutions. Immediately, the teeth in the acid and in the Pepsi started fizzing:

The tooth in the NaF didn't really do anything once it was put in the solution. We left the teeth sit in the solution for 4 and a half days, checking in on them periodically. We could see the erosion of the teeth in the acid happening very quickly. Even the tooth in the Pepsi wasn't safe from some acid erosion! We took them out on Tuesday 10-11-11 to dry, and then we massed them. The teeth that had been in the acid were very soft and almost disintegrated when we tried to get them out onto the watchglasses to mass them. Our hypothesis was correct that the teeth in the acid would lose mass due to erosion ("demineralization") and the tooth in NaF would gain some mass due to remineralization. Here is what each of them looked like after we took them out of the solutions:

Look at how the coloring in the Pepsi stained the tooth! It was just white before it sat in solution.

The tooth in NaF wasn't eroded like the teeth that were in the acid.

This tooth, before it sat in the acid, actually looked a lot like the tooth that was in NaF. See how the top of the tooth (facing right) is almost completely eaten away, and there are just deep craters remaining!

This one USED to be a whole tooth, but it was so soft and degraded that it fell apart when we tried to get it out of the vial of acid. In places, it was so thin it was translucent!

This experiment definitely made us think twice about drinking Pepsi!!



Not Quite Perfect

The next day, we went up to the lab after the solution had 20 hours to reflux to find that during the night, we had an air leak and all of our solvent had boiled away. Nothing was left except a black residue on the inside of the flask and all over the stir bar. We got this cleaned up and decided to start the reaction again on Thursday.

On Thursday 9-29-11 we set the reaction up in the same way except for two differences: we used a smaller flask so that the contents would have more volume in the bottom of the flask (hopefully this would prevent the solvent from boiling away too fast) and we used a two neck flask instead of a three neck flask.

This would have one less way for the solvent to escape, so the reaction has one less way to fail. We didn't want to leave the reaction to run overnight again in case it would fail, so we set it up at the end of lab, and one of us could come in on Friday morning to turn the heat on.

On Friday 9-30-11 we turned the heat on at about 10:30 AM and let it go all day until 4 PM. The heating mantle was turned to 3 this time instead of 4. We still got the black residue on the inside of the flask, but we could tell that we still had solvent in the flask because nothing had bubbled up through the joints and there was still liquid dripping from the condenser back into the flask.

On Monday 10-3-11 we started a second round of heating at 11 AM and didn't turn it off again until 5. The total cook time at this point was 11.5 hours, which is less than the 20 hours we originally decided to do but we decided to do an IR spectrum of the solution the next day during lab to see if the reaction had proceeded at all, or whether it had failed again.

Finishing Ferrocene and Beginning Benzene

FINALLY...we got our acetylation of ferrocene to work. We ran the GC on Tuesday 9-27-11 and the highest peak on the spectrum was monoacetylated ferrocene. That is the most compelling evidence we have, and the only evidence we have that still contradicts the presence of monoacetylated ferrocene is the low melting point we got. However, 3 out of 4 isn't bad! That successfully finishes the ferrocene lab, which is good because we have gotten tired of writing about it!

Along with finishing ferrocene, we finished our purple crystals lab on Tuesday. Allen was responsible for this while I (Emily!) was working on other things. He did the isolation like with the benzene inclusion compound, but this time it was just the pure [Ni(en)2(NCS)2] crystals without any benzene added to it. These crystals took so long to grow, and even after five weeks, there were still only a couple of crystals in the vial (nothing like the vial full of benzene crystals we got). We finally decided to purify them and take the melting point since they didn't seem to be growing any more crystals. After the isolation, we got some very pretty dark purple crystals:

These actually look nothing like the benzene inclusion crystals, which were not shiny and dark purple but more dull and light purple. They were also much smaller crystals than these. Here's a picture of the benzene crystals to jog your memory:

We massed the new crystals so we could find percent yield for the lab report, and then we took the melting point, which ended up being above 220 degrees Celsius (that is the limit on our thermometer, so we couldn't get more precise than that!).

Since those two things didn't take much time, we were able to set up our first reaction for our final project. We are doing our project on Cr-Arenes, in which Cr(CO)6 is reacted with an arene in a solvent mixture of dibutyl ether and THF. There are so many arenes to choose from, but we just picked 6 of them to try and synthesize, purify, and characterize. The first arene we wanted to try was benzene.

We set up a three neck flask exactly the same as in the synthesis of ferrocene except with a condenser on the middle neck of the flask:

The condenser is needed to air-cool the reaction so the solvent doesn't boil away. We vacuumed and argon-filled the flask three times and then left the argon running throughout the experiment. We then added in the two solvents via syringe. We added 8 ml of dibutyl ether and 1 ml of THF.

 Now we needed to bubble argon through the solvents to get rid of any oxygen that might ruin the reaction. We "adapted" a disposable syringe to fit into a hose from the rack and stuck the needle through the septum so that the argon bubbled through the solvents. It actually looked like the solvents were boiling because of the gas bubbles:

While this was bubbling, we got 1 g of Cr(CO)6 (which is a white solid) and measured out 1 ml of benzene in a syringe. We had to take the septum out before we could add these two reactants plus a stir bar, so we just replaced the septum with a greased glass stopper. We had to wire down all the attachments and the hoses to prevent any accidents. After that was done, we turned on the stirring mechanism on the hot plate, and turned the heating mantle on to 4. Once it started refluxing, the color of the solution changed quickly from clear with the white Cr(CO)6 floating around undissolved to a light yellow-green color:

Since we have been reading about these complexes, we have seen that they usually have a yellow or orangish color so this color change was a good sign! We left the lab on Tuesday night feeling pretty confident that we would just let it stir for 20 hours, and we would come back on Wednesday to a perfect product that we could purify and characterize.

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!!