First Person: Vladimir Prelog

Vladimir Prelog. (John D. Roberts, CHF Collections.)

In the 1950s organic chemists were attempting to understand the 3-D structure of the molecules they studied and find accurate terminology to describe their spatial configurations. One example of this is still used today: The Cahn-Ingold-Prelog Rules. These rules help designate the “handedness” of two very similar molecules. (Handedness means that at a given location the only difference between the two molecules is that they are mirror images, just like our own hands.) Rules and terminology become important when one considers that complex molecules with “n” centers of handedness have 2n different overall spatial configurations. Thus a molecule like ephedrine with two centers of handedness really has four different structures.

The Cahn-Ingold-Prelog Rules were not decided as we might imagine, through written correspondence or consensus between peers in the lab. Instead, according to Vladimir Prelog’s 1984 oral history interview, the key conversations took place in person in a somewhat unexpected setting.

During the anniversary meeting in Manchester, the Society held a symposium on dynamic stereochemistry. After the symposium, the ICI organized a ball at the Octagon House in Blackley near Manchester. Everybody danced except for Ingold, Cahn, and myself. Not being proficient dancers, we drank beer and discussed chemistry.

Sure, they were at the 1954 joint meeting of the Royal Institute of Chemistry, the Society of Chemical Industry, and the Institute of Petroleum to discuss just such issues, but certainly not at that moment, at a ball, when they were supposed to cut loose and dance.

Instead of taking a break for relaxation, Prelog and fellow chemists Robert Cahn and Christopher Ingold discussed weightier matters—specifically, how they were going to describe the symbols and nomenclature describing spatial orientation of 3-D molecules. Prelog explains:

Cahn and Ingold asked me what I thought about their proposal and I said, "It's terrible. It will make a bigger mess than we have now." Instead of telling me to go to hell they were kind enough to ask me to write a joint paper about the issue. I immediately accepted.

Prelog and his fellow chemists met numerous times after this initially meeting at the Octagon House Ball, finally publishing their Rules two years later. They did not celebrate this moment, we can assume, with a victory dance.

Hilary Domush is a program associate in oral history at CHF. First Person, which highlights one of CHF's over 400 oral histories, appears the third Tuesday of every month.

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