Monday, August 25, 2008

Let's talk about TLCs Part 4 - Ninhydrin Stain

2008 was the year where I became an amino acid chemist and as a consequence the Ninhydrin Stain has become my new friend. Many of the amino acids I handle these days are not UV active but fortunately the Ninhydrin Stain is great for visualising free amines and primary amines. Most of my amines are BOC-protected but they still develop nicely with ninhydrin because the BOC group is cleaved upon treatment with the stain.
Ninhydrin Stain Recipe
100 ml container
0.2 g Ninhydrin
0.5 ml Acetic acid
100 ml n-Butanol
4.5 ml Water
After treatment with a heat gun Ninhydrin Stain tends to give brightly coloured pink to purple spots as shown above. The spots can fade rather fast so record the result immediately. In the past I have been using a Ninhydrin Stain that didn't contain water, however adding a bit of water seems to improve the result a fair bit. D!

Tuesday, August 19, 2008

How to make a primary amide - The Ley Way

Steven Ley's Group really produces some cracking results. This time they have developed a really simple method for preparing primary amides from carboxylic esters. This is very good news because this seemingly simple transformation is in fact not as simpel as one could have hoped for. In the past I have used ammonia in methanol to achieve this. The commercially available NH3 in MeOH is rather variable in quality so making it fresh by saturating methanol with ammonia using a gas cylinder is preferable. It's an annoying exercise making the solution and the actual reaction CO2R to CONH2 doesn't really work that well.So when Steven Ley comes up with a method that involves scooping solid magnesium nitride into a flask with your ester and some methanol, heating it to 80 oC for 24 hr, work up, filter, done! then that is really exciting good news to the synthetic organic chemist.
Magnesium nitride is reasonably priced, e.g. Aldrich (#415111) 10 g for less than 40 Euros. D!

Monday, August 18, 2008

Guidelines for giving a truly terrible talk

I'm giving a presentation in a month's time which reminded me of the stuff below. Unfortunately, I can't remember what web site I got this stuff from but apparentely it's from "35-mm Slides: A Manual for Technical Presentations", by Dan Pratt og Lev Ropes. Surprisingly many scientists seem to use these guidelines. Here we go:

"Strict adherence to the following time-tested guidelines will ensure that both you and your work remain obscure and will guarantee an audience of minimum size at your next talk. Continuity of effort may result in being awarded the coveted 5:00 P.M. Friday speaking time at the next national meeting." Slides:
(1) Use lots of slides. A rule of thumb is one slide for each 10 seconds of time allotted for your talk. If you don’t have enough, borrow the rest from the previous speaker, or cycle back and forth between slides.
(2) Put as much information on each slide as possible. Graphs with a dozen or so crossing lines, tables with at least 100 entries, and maps with 20 or 30 units are especially effective; but equations, particularly if they contain at least 15 terms and 20 variables, are almost as good. A high density of detailed and marginally relevant data usually prevents penetrating questions from the audience.
(3) Use small print. Anyone who has not had the foresight to either sit in the front row or bring a set of binoculars is probably not smart enough to understand your talk anyway.
(4) Use figures and tables directly from publications. They will help you accomplish goals 2 and 3 above and minimize the amount of preparation for the talk. If you haven’t published the work, use illustrations from an old publication. Only a few people in the audience will notice anyway.
(1) Don’t organize your talk in advance. It is usually best not to even think about it until your name has been announced by the session chair. Above all, don’t write the talk out, it may fall into enemy hands.
(2) Never, ever, rehearse, even briefly. Talks are best when they arise spontaneously and in random order. Leave it as an exercise for the listener to assemble your thoughts properly and make some sense out of what you say.
(3) Discuss each slide in complete detail, especially those parts irrelevant to the main points of our talk. If you suspect that there is anyone in the audience who is not asleep, return to a previous slide and discuss it again.
(4) Face the projection screen, mumble, and talk as fast as possible, especially while making important points. An alternative strategy is to speak very slowly, leave every other sentence uncompleted, and punctuate each thought with "ahhh", "unhh", or something equally informative.
(5) Wave the lights pointer around the room, or at least move the beam rapidly about the slide image in small circles. If this is done properly, it will make 50 % of the people in the front three rows (and those with binoculars) sick.
(6) Use up all of your allotted time and at least half, if not all, of the next speaker’s. This avoids foolish and annoying questions and forces the chairman to ride herd on the following speakers.
Remember, the rest of the speakers don’t have anything important to say anyway. If they had, they would have been assigned times earlier than yours. D!

Wednesday, August 13, 2008

Melting point then and now - Kofler Hotbench vs. OptiMelt

I think that most chemists will agree that doing melting point determinations sucks big time. Especially when you have been putting it off for 6 months and have to do 22 in one day (yes I learnt my lesson and it took two days). Until recently I only knew of a few ways to determine melting points. My preferred method was to get a rough melting point using a Kofler Hotbench followed by an accurate determination using a full-on old school Reichert melting point microscope. The microscope beats getting your compound into a melting point tube and watching it melt through a crappy magnifying glass. Firstly, you place your crystals between two wafer thin glass plates (very simple). Secondly, you get to see your beautiful crystals through the microscope. On one occasion I managed to have a small rainbow in my crystals which sure beats staring at a melting point tube. Nevertheless, melting point determinations suck so I have toyed with the idea of having a camera record the melting in my absence and then come back a couple of hours later and fast forwarding the movie to the melting point and recoding the numbers. Now that would be easy.
As always someone else got the idea first and where I work now melting point determinations are fully automated using an OptiMelt system. It records a little movie and prints out the numbers while you are at home watching Buffy. Amazing stuff!
So what happened to the redundant Kofler Hotbench? I found it on display in the Departments historical collection of hopelessly ancient relics. Strange to think that where I worked only two months ago this was state of the art equipment. D!