Over on the Skeptical Chymist blog there's another discussion about using highly cited chemists to gauge the importance of chemical sub-fields. In the past post I suspected that highly cited chemists lists from the 50s through the 90s would reflect the now seemingly diminished importance of organic synthesis. Partly goaded by this, Michelle Francl of Culture of Chemistry drew up a list of chemist citations from the 80s and 90s. Interestingly, there are no bona fide synthetic organic chemists in there. However, as a commentator on the Chymist's blog noted, a better metric of judging trends might be to count the number of highly cited papers in every sub-field in every decade rather than just looking at highly cited chemists. In my opinion, the latter would do a much better job of indicating the supremacy of organic chemistry from the 50s through the 90s.
Or would it? To get a better idea of the whole issue I did something which I thought was obvious, and was surprised by the results. The exercise really got me thinking about the very nature of judging achievement and importance in chemistry.
I simply logged on to the ACS website and looked at the list of highest-cited JACS articles of all time. Although extrapolating to chemical significance from this exercise is as fraught with limitations as extrapolating from ISI/Thomson Reuters lists, most of us would agree that JACS has mirrored important chemical developments in the last fifty years. So is the list of heavy hitters unsurprisingly dominated by Woodward, Smalley, Corey, Djerassi, Sharpless or Grubbs? Surely the top spot would be taken by the greatest chemist of all time?
Hardly. Of the top ten articles, four including the top two belong to computational chemistry, a field that has often been regarded as relatively unfashionable compared to organic synthesis, chemical biology, materials science and polymer science. Ask scientists to name the most important chemists of the last fifty years and very few will state the names of John Pople or Michael Dewar, let alone Peter Kollman, Clark Still or Warren Hehre. Yet computational chemistry dominates the list of the top 20 highest cited papers in JACS. Where is the chemical God Woodward in the list? Or his successor Corey? In fact no one who looks at the JACS list would even suspect that organic chemistry ever dominated the chemical landscape.
Does this mean that organic synthesis was hyped for fifty years and we were convinced of the towering implications of the field by a conspiracy of chemical raconteurs led by R B Woodward? Certainly not. To me the list only signifies the signature character of chemistry: on a practical basis, in chemistry 'importance' is judged by utility rather than by any other single metric. If you look at the computational chemistry papers in the JACS list, you will realize that each one of those papers contributed techniques which became universally adopted by all kinds of chemists doing calculations on all kinds of molecules. Woodward's papers on synthesis may seem like great works of art compared to these pragmatic prescriptions, but chemists going about their daily business may have scant use for them. Considering this emphasis on utility, I was actually surprised not to see some of Corey's papers- such as the one describing the oxidation of secondary alcohols- on the list. I was also surprised not to see the work done by the palladium crowd, not to mention the Sharpless epoxidation and dihydroxylation accounts.
But the examples which are included make the context clear. Consider the solvation models developed by Clark Still which are a mainstay of molecular simulation. Consider the force fields developed by Peter Kollman and Bill Jorgensen, again incorporated in leading computer programs and used by thousands around the world. And of course, the pioneering Nobel Prize winning quantum chemical programs developed by John Pople brought high-flying theory to the bench. In fact a very few people cited by ISI/Thomson Reuters feature in the list. Whitesides does, but again, for his very practical and important work on generating monolayer films on surfaces. Ralph Pearson is similarly cited for his very helpful development of the hard/soft acid base concept. Robert Grubbs actually makes it, but again for his decidedly practical innovation of olefin metathesis.
Interestingly, when the general history of chemistry is written, the pioneering articles which make the list will almost certainly not be these highly cited ones. They will instead be the synthesis of chlorophyll or fullerene, or those detailing the reactions of CFCs with the ozone layer. The cracking of hydrocarbons will probably be mentioned. And of course there will be all those papers on the nature of the chemical bond, featuring Linus Pauling and others. In the long-term, what would stand out from the chemical canon would be the papers which laid the foundation of the field, not the ones which allowed chemists to calculate a dipole moment with better accuracy. And yet it's the latter and not the former which make the JACS list.
These observations based on a most limited data set should not be taken too seriously. But I think that they drive home an important point. In chemistry, what's regarded as important by history and what's regarded as important by chemists going about their daily work might be very different. We may wax eloquent about how Pauling's paper on hybridization lit up the great darkness, or how Woodward's synthesis of Vitamin B12 reminds one of Chartres Cathedral, but at the end of the day, all a chemist wants is to grow some thiol monolayers on gold and calculate their interactions from first principles.
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