The 15N chemical shift of formamide. Is there an NMR expert in da house?

Update 2015.03.8: I have now talked to our local NMR expert and belives the 260.0 value more because the correction for bulk magnetic susceptibility are not always terribly accurate.

All I want (for now) is the value of the nitrogen chemical shift of formamide in water, but I found two very different values in Annual Reports on NMR Spectroscopy volume 11B: 263.7 and 267.8 ppm. The reference is nitromethane and for some reason it lists negative chemical shifts (i.e. $-\delta_x = \sigma_x - \sigma_{\mathrm{MeNO_2}}$).

The 263.7 value comes from this paper which reports a chemical shift of 260.0 ppm relative to saturated sodium nitrate which is then converted to the above value by adding the difference in chemical shift between sodium nitrate and nitromethane: 3.7 ppm.

The 267.7 value comes from this paper which reports a chemical shift of 261.6 ppm relative to 1 M nitric acid, which is then converted to the above value by adding the difference in chemical shift between 1 sodium nitrate and nitromethane plus a correction for the difference in bulk magnetic susceptibility ($\Delta\chi$): 4.4 + 1.8 = 6.2 ppm.  This extra correction ($\frac{4}{3}\pi(\chi_{\mathrm{MeNO_2}}-\chi_{\mathrm{H_2O}}$) is done because the experiment was performed with the external magnetic "field parallel to the sample tube".

The question is which value is the correct chemical shift for the nitrogen chemical shift of formamide in water?

Also, how hard would it be to measure it in the gas phase?



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Slides from my group meeting presentation today at the Barcelona Supercomputer Center

Predicting accurate absolute binding energies in aqueous solution: thermodynamic considerations for electronic structure methods from molmodbasics

Open Science - a brief rant

A colleague asked me for feedback on a draft of a viewpoint article on open source and data.  I know at least one of my group members enjoys a good rant so I pasting part of my reply in here and calling it a (free) blog post:

<rant>In my mind there is one aspect in all this that is missing, which is essentially a moral or ethical one. Much of my research (and my salary being at a state run school) is payed for by tax payers.  One of the reasons I publish OA is because I feel the same tax payers have the right to read these papers and use the content  any way they see fit.  The same applies to the code my group produces.

Now, I'm not a zealot.  I actually feel that being open helps my research and career as you also point out, but the ethical principle is still there in the background.  Society is not paying me to to advance my career, society is paying me to advance society.  IMO, that is the real reason funding organizations should insist on Open: it is better for the society - who pays the bills.  All the perceived negatives affect me, the researcher, but it is not about me.

Science funding will not increase unless society sees an advantage in this and this closed, what's-in-it-for-me? attitude among scientists that has led to the reproduceability crisis (which, IMO is a much bigger crisis for long-term science funding than people realize) is incredibly damaging in that regard. </rant>


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