NMR Impurities Tabulated

If you didn't already spot this useful paper on NMR impurities you should go get it now. An excellent addition to the classic paper by Gottlieb et al. that you can access here. D!

NMR Tube Cleaner Part 2

Some time ago I had a post about the amazing NMR tube cleaner. I love this piece of equipment and use it regularly. However, as some readers pointed out some people are remarkably good at breaking these things (repeatedly!). Where I work now we have a workshop and the guys there create the most amazing gear for us including an almost unbreakable NMR tube cleaner. It's made from hard plastic and metal and isn't affected by organic solvents. So if you are fortunate enough to also have access to a workshop you may consider ordering one of these beauties. D!

NMR tube cleaner

I have a lot of NMR tubes and as a result I don't clean them very often and when I eventually decide to do something about it I'm faced with something like 30 dirty tubes. Now firstly if you work this way you have to soak the NMR tubes as soon as you are done with them. If you just let them evaporate to dryness you are in trouble. I normally just empty the tube and fill it to the lip with acetone and cap it. This way it wont dry out for months.

When I was cleaning my tubes the other day I had three synthetic organic chemists from three different countries walk up to me and ask what I was doing. This was somewhat surprising so I've decided to share with you what I thought was common knowledge: The NMR Tube Cleaner. These things are commercially available (expensive) or you can have your glass blower make one at a reasonable price. You can see my set up on the picture above. This is how it works:

(1) take the cap of your NMR tube and attach it to its base

(2) stick the tube in the cleaner (see picture) so that the cap seals the opening at the top

(3) squirt solvent(s) into the solvent opening (see picture).

The system is under vacuum and the solvent gets sucked through a thin tube that goes to the bottom of the NMR tube. It is very effective and I usually do a combination of solvents to get rid of everything. Its smart to have a three way tap between the cleaner and the pump so that you can let air into the cleaner without having to turn the vacuum off all the time. There's an NMR tube entry at Wikipedia that also describes the NMR tube cleaner. D!

Revenge of the NMR tube

Well I guess it had to happen to someone sooner or later. It appears that I applied slightly too much pressure when I was sticking the lid on my NMR tube the other night. As a result the tube snapped and proceeded to go straight through my glove and into my finger. Now that's obviously annoying but can be fixed with band aid. However, when the tube had finally embedded itself in my finger it decided to snap for the second time. In other words I had a piece of NMR tube thoroughly buried in my finger. This is not the sort shit you want to happen to you at 11 pm on a Monday. Trying to fish the glass out myself only resulted in pain and blood everywhere so off to the hospital. Fortunately, the hospital is only a short walk from the Chemistry Department. After waiting for an hour amongst screaming people on various drugs and/or totally shit faced with blood coming out of various openings I was attended by a very nice Doctor. She told me straight away that X-ray was no good for glass so she would have to dig around for the glass bits. At this point I would like to say thank you to whoever it was that came up with anesthetics. Anyway, after some serious digging and cutting a big chunk of NMR tube was extracted. This is what my finger looked like at 1.30 am when I was finally out of the Emergency room.
No my fingers weren't really blue. I have no idea why it keeps uploading the picture like this but it looks kind off cool and scientific. Anyway, it really wasn't particularly dramatic and if it wasn't for the glass I would never have gone to the Emergency Room. I have always heard that impaling yourself with an NMR tube is a particularly common accident amongst chemists. Nevertheless, I'm the first casualty that I know off. Does anyone else know of similar incidents? Finally, I have to say that there wasn't really anything I could have done to prevent this from happening. I used a brand new tube and applied a minimum amount of pressure when putting the lid on........just got unlucky I guess. And by the way what are people thinking off getting drunk and on drugs on a Monday. Save it for the weekend people. D!

NMR and Whisky

I have a real weakness for single malt whisky so when I started my PhD in Cambridge I was pleasantly surprised to see that the NMR machines were named after Scotch single malt whiskies: Aberlour, Cragganmore, Glengrant, Glenlivet and Laphroaig. At the same time as I started my PhD they began the process of acquiring and installing a 700 MHz Bruker Cryo probe monster. Obviously this new addition to the collection of NMR machines needed a name. I'm a big fan of the Arran single malt whisky which at the time was the youngest Scottish distillery. So I thought that Arran would be an appropriate name for the departments youngest NMR machine and I suggested it to the NMR guys. I even went as far as purchasing them a little box with a selection of Arran malts. Clearly, the guys liked the idea and to my great pleasure the machine was named Arran. Here's a picture of the NMR people (from left: Duncan, Andrew and Brian) with Arran and a selection of miniature Arran bottles:

Not only do they give their NMR machines great names but they also provide a most excellent NMR service. These guys actually like what they do and will go to great lengths to help you out. The best NMR department (by orders of magnitude) that I have experienced so far. Anyway, after Arran was named we obviously had to run some 1 and 2D NMR of the Arran malt on Arran to see what the spectrum of a tasty single malt looks like. Below the HMQC spectrum of the organic phase after an extraction of Arran malt with dichloromethane is shown. We didn't use the regular stuff but a limited edition single cask Arran malt (Bottle no. 125 of 348, 58.7%, distilled 18/7-1997).

Yes a complete waste of time and resources but it was fun. We took the photo above and a bunch of the NMR spectra and sent it to Isle of Arran Distillers with a letter explaining matters and it turned out that the guys at the distillery really liked the story. They showed their appreciation by sending us a bottle of Arran malt each - nice guys! D!

Identifying old NMR solvents (in Cambridge, UK)

When I was still messing around in Cambridge I one day happened to walk into the NMR service room at the perfect time. Dudley Williams had retired and was giving his stuff away and the NMR guys had this big box of NMR stuff they wanted to get rid of. The box was jammed full of deuterated solvents, NMR tubes and shift reagents so I grabbed the whole thing and took it back to the cave. However, not all of the solvents were easily identifiable. There was a large number of ampoule's with no label on them. They did however have some interesting colour codes happening. After a quick trip back to the NMR room it turned out that Cambridge used to have its own colour coding system for deuterated solvents. Here's a selection of ampoule's and what they contain:
The Cambridge NMR service web page used to have a guide to this colour coding. However, not anymore as most of these old ampoule's are gone by now. That was probably a bit premature since there are still quite a few of these ampoule's floating around. I talked the NMR guys into sending me the old colour chart so I could post it here. So to all you Cambridge people scratching your heads in bewilderment here's the answer to all your problems:
D!