THF solvent bomb

After improperly refilling the tetrahydrofuran solvent bomb, the color of the sodium benzophenone ketal was no longer dark purple, not even bright blue or even green, it was yellow, indicating a total loss of the flask's integrity. I emptied the bomb and quenched the remaining sodium. In the process of vacuum transferring new THF into the freshly made bomb flask, the convection in the condensed THF was so strong that it created a little fountain in the center of the bomb, with a well about 1 cm deep and spray that came up and spattered the sides of the flask. I called over Jake and Derrik to look at it but they were not as impressed with it as I was. Regardless, its a very pretty blue color.

a promising reaction

Finally, a promising reaction. The salt metathesis reaction I ran last week appears to have worked, although the NMR spectra indicate ~ 85% purity, and a pretty unassignable mess of chemical shifts. Nonetheless, I think crystallization might succeed, and if I can get some good single crystals then it will be up to Warren, the staff crystallographer, to do the rest. The first attempt will be slow evaporation of the reaction mixture.

stir plate repair

We don't have enough working stir plates. I attempted to repair one by stripping it down and washing the moving parts with hexane. No dice. I regreased it with some Loctite N-5000 (the packaging proudly proclaims "Nickel-based anti-seize lubricant for the Nuclear Power Industry") but still, no dice. I began removing parts I thought looked extraneous. This worked somewhat, and as it turns out the piece that was obstructing the bar magnet was the cooling fan. When I say it worked "somewhat" I mean that it worked until the motor overheated and seized, in spite of the newly applied Ni-based nuclear power grease. At the very least this is now a valid state of disrepair to warrant tossing the old plate and ordering a new one. A view of the carnage...


The pieces in the foreground are some of the amputated bits. The washer and lock washer appeared to have no purpose whatsoever. The shiny bits are what remains of the cooling fan after being torn out of the middle of the stir plate.

Student Grades

Well, grades are in for the class I'm a TA for. As you can see from the neatly constructed histogram, there are some winners and there are some losers in this bunch.
I don't know if it's luck of the draw, or actual TA influence, but the three high grades are from my section, and the three low grades are not. I'd like to think I personally had something to do with it, but I fear that the sample size isn't large enough to get too snobby. I'll wait to see what the TA evaluations look like before making any more presumptuous claims.

March Madness

It's tough to convince a bunch of chemistry grad students that a NCAA bracket is a good idea, even for a small amount of money. Are grad students a bunch of squares? Well, there is one bracket racket going on in the department, but the buy in is a six pack of beer, and really, who wants to win 40 six-packs of low quality beer? Someone who wants to throw a low quality party, that's who. And although I'm not so out of touch with normal society as to not want to participate, there is also enough square in me to not want to play for what is essentially the right to host a drunken frat party with all of my not so square friends.

Exam proctoring

The class for which I TA had their exam today. I helped Prof. Heller out by going over the exam questions ahead of time, just to make sure that the poor little babies weren't overly challenged. (We wouldn't want to hurt their confidence going into exam week, now would we?)

For one of the questions, Heller wanted to use some data that was actually obtained by one of the students in the class. I dug it up for him but it wasn't exactly to his liking. "Do you think you could find a spectrum which has minor impurity peaks in it?" I told him I couldn't, but I said I would have no problem inventing the data in excel and producing a fake spectrum which was indistinguishable from the real thing. This is apparently not something your PhD adviser likes to hear, although he wasn't so appalled as to not use the spectrum. It was a little frightening how easy it was to make a plausible looking spectrum from completely falsified data. A test for the reader....three of the following spectra are real, the fourth is invented. Can you tell the difference? (click on the image to enlarge it)

Drinking

Yesterday, Labmate Jake, with nothing but grading to do for the rest of the day, decides to have an afternoon beer at his desk. Soon after, three beers have been consumed and the severity of his red pen has become decidedly more docile. This will come into play later in the evening.

Our dear friend in another lab has completed his post-doc position and will be returning to his home in Europe on Thursday. In his honor, our lab as well as Prof. Heller (our fearless adviser) go out for a few beers after work at the University Inn Pub. Several snippets:

Krista: (pulls out pouch of tobacco and rolling papers, begins to roll a cigarette)
Prof. Heller: Wow, I haven't seen anyone roll their own cigarettes since I lived with my parents.
Derrik: Your father rolled his own, did he?
Prof. Heller: No, my mother was a truck driver in the army. She could roll 'em with one hand while the other was still on the wheel.
(Slight pause as the group forms their own mental pictures of Heller's mother in a truck rolling a cigarette one-handed, meanwhile Heller finishes half his beer in one pull.)

later on...

Jake: (finishes beer, sets empty glass on table)
Prof. Heller: Looks like you're empty (grabs pitcher, begins to pour Jake another beer)
Jake: (a little slurred) Oh, that's OK, I've probably had enough.
Prof. Heller: What? (continues to pour beer)
Jake: Um, maybe just half.
Prof. Heller: Nonsense (finishes pouring Jake's beer)
Jake: Hmmm (picks up beer, almost misses his mouth with it.)
Prof. Heller: (signals to waitress, holds up empty pitcher) Miss, we seem to've gone dry, could we get another?

Sublimation mixed results

After taking care of the details such as fixing thermometers and getting dry NMR solvent, the results of the purification are in. A partial success! The final material is more pure in that there are fewer products present (3 as opposed to 7) however only about 50% product, down from about 75%. Looks like I'll have to make a new batch from scratch.

wet NMR solvents

The deuterated benzene bomb in the lab is dried using CaH2, which should be a pretty effective drying agent. I prefer it to NaK alloy, mostly because you don't have to worry about the flask exploding after you finish transferring all of the solvent off. The downside is that you miss the pleasure of the deep purple color of the NaK benzophenone ketyl which tells you definitively that your solvent is indeed H2O free. After several crappy NMR spectra using the C6D6 over CaH2, a blank spectrum confirmed that my solvent was wet. I made a new bomb and then quenched the leftovers. (No fizz, of course.) The new bomb has a much whiter color to it than the wet bomb, which only brings to my attention three other solvent bombs in the lab sporting a depressingly dark grey color. SEP? you betcha. Maybe now I'll be able to tell if the sublimation worked or not.

Hg Thermometer Repair

Of course the sublimation won't work unless I have a thermometer with which to monitor the sand bath temperature. Most of our thermometers in the lab have broken threads, meaning there are gaps in the column of mercury. Argonne National Labs suggests dropping the thermometer from a short height. After a couple hundred drops with about four variations on height and padding thickness and I was ready to kick things up a notch.

I looked at the centrifuge for a couple minutes trying to figure out how I was going to counterbalance the thermometer and spin it up without breaking the top off. I settled on creating a bucket on a string, similar to the grade school experiment where you have a kid swing a bucket of water over his/her head. Except water isn't mercury. Long story short, the thermometer didn't break but the thread was still broken. On the bright side, I didn't have to bust out the mercury spill kit. After I left work frustrated, my labmate apparently put a heat gun on the bulb for about 4 minutes and viola! thermometer fixed (sort of, it's still miscalibrated by 3 C).