Thursday, November 16, 2006

JSpecView Demo

I spent some time today going over EXP042, the experiment done by Khalid and Lin recently to monitor by NMR the formation of an imine by mixing phenylacetaldehyde and t-butylamine in CDCl3. Since we have recently figured out how to save all of our NMR spectra in JCAMP format and view them using Robert Lancashire's JSpecView, I thought it would be a good idea to do a brief screencast demonstrating how this wonderful software can be used in a real chemistry experiment.

First I analyze the H NMR of phenylacetaldehyde and demonstrate the underintegration problem of the aldehyde proton. (Anyone out there know why the integral is only coming out to 0.65 H? This shows up in the printed spectra as well so it is not a JCAMP problem.)

Then I do expansions of the peaks that start to form 5 minutes after adding the amine. There is a triplet and a doublet with the same coupling constant that are consistent with imine formation. Finally, I show the mess that results after 42 minutes.

For more details read the discussion section of the experiment and please feel free to comment. To actually update the wiki directly just request an account. I don't allow anonymous guest updates because it is too easy for my students to forget to log in and I want to make sure they get credit for what they did.

I think this is a pretty good example of a "failed experiment" that would never be published to this level of detail by traditional publishers. How often do you get to do spectrum expansions even on supplementary data associated with a paper? I know that there are a lot of people doing Ugi reactions and the formation of the imine in some cases is apparently problematic. They can learn from what we have done and hopefully give a little back in comments from their own experience.

The video ipod compatible vodcast is available here.

Here it is on YouTube:

3 Comments:

At 4:28 PM, Anonymous Anonymous said...

Anyone out there know why the integral is only coming out to 0.65 H

Relaxation time?

 
At 2:36 PM, Anonymous Palladium Man said...

I agree. The relaxation time is too long. If the delay between pulses was increased, the integral value should increse.

 
At 3:32 PM, Blogger Jean-Claude Bradley said...

you mean too short...

 

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