Thursday, 3 January 2008

Proctor, Yu and Dickinson

NMR is by far the most powerful and widely used tool for the determination of organic structures by chemists. Of the wealth of information that this technique provides, the chemical shift is what makes NMR so attractive to chemists as it allows them to distinguish among the different protons within a molecule.
However, despite the fact that chemical shift is what makes NMR useful in chemistry, I’m amazed about how little is known in the chemistry community about their discoverers. I have run a quick survey among 10 chemists colleagues of mine and none of them was able to cite one single name! Maybe the words of M.E. Packard had a higher impact than what he expected when he said "chemists got the point very
quickly, thanked the physicists, and took over"
I think that all chemists are in debt with the pioneering work carried out by W.G.Proctor, F.C.Yu and W.C.Dickinson and I would like to take advantage of my blog to give more recognition to these scientists. Now that we live in a world in which self-promotion and ‘rock star’ popularity are so valued, I find it necessary to acknowledge the value of what they have contributed to humankind in such a quiet way.
For a recent, worth reading, post about Chemical Shift and W. G. Proctor, do not miss Stan’s blog and Reminiscences of the Early Days of Nuclear Magnetic Resonance at Stanford University

1 comment:

Stan said...

Thanks, Carlos, for mentioning my article. The spectrum you show is posterior to what I was writing about (Arnold J.T., Dharmatti S.S., Packard M.E., Chemical Effects on Nuclear Induction Signals from Organic Compounds, J.Chem.Phys. 19, 507, 1951), but only by about 1 year! It was the first spectrum showing chemical shifts within a molecule rather then between molecules - and that, finally, made a lot of chemists listen!
It also shows that in a single year, somebody (so to say) has improved the homogeneity of a magnet by nearly two orders of magnitude!
By the way: the term "shift" was coined by W.D.Knight (Phys.Rev.76,1259,1949) to indicate what is still known as Knight shifts. The "derogatory" adjective "chemical" has been apparently appended by irritated Harvard and Stanford physicists when they encountered this "obstacle" (Proctor says: "until it is clearly understood, the accuracy of magnetic moments determined under certain chemical conditions remains somewhat in doubt").
The combination "chemical shifts" was used in print for the first time by Norman Ramsey (Phys.Rev.78,699,1950) who says:
"Furthermore, with heavier nuclei the ratios of the resonance frequencies for the same nucleus in different molecules have been measured with high precision and discrepancies have been found by various observers that are sometimes called chemical shifts".
You got it? Chemical shift == discrepancy!
Stan Sykora