Submitted by Chip Nataro / Lafayette College on Tue, 01/26/2010 - 15:42
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Research
Is anyone out there in VIPEr-land tremendously skilled at measuring barriers to nitrogen inversion? I haven't done it before and I have a few compounds I would like to study. I will take references, suggestions, you name it. The more detail as to what I need to do the better. I've got some prelim data that suggests no significant line broadening or anything down to -60C. There don't appear to be any changes up to 50C. So, I fear I might run into some solvent issues. Any insight would be appreciated.
Nancy Williams / Scripps College, Pitzer College, Claremont McKenna College
Chip, I've measured phosphorus inversion rates, but I've never tried doing it with nitrogen. My understanding is that the process is pretty stupidly fast--I suspect your problem is that your spectrometer has not gone (cannot go?) sufficiently low to freeze out the procedure. I don't know what a typical nitrogen inversion barrier is, but wikipedia (http://en.wikipedia.org/wiki/Nitrogen_inversion) claims it's about 24 kJ/mol. If so, you're trying to freeze out a 6 kcal barrier, which is not achievable by normal means.
Tue, 02/09/2010 - 11:48 Permalink
John Gilje / James Madison University

Over the years there have been quite a few studies of nitrogen inversion. As a possible entry to the literature:

J. H. Brown and C. Hackett Bushweller "Stereodynamics of Isopropyldimethylamine. 13C{1H} and 1H Dynamic NMR Studies. Molecular Mechanics Calculations," J. Amer. Chem. Soc. 1992, 114, 8153-8158.

In this paper they were looking at  temperatures down to about 90K. Except in some unusual cases nitrogen inversion barriers are low and would not be slowed at -60C.


Wed, 04/14/2010 - 10:30 Permalink