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In Memory of Paul von Ragué Schleyer
In the early ‘60s, Paul von Ragué Schleyer was already making a name for himself. He had already while still at Harvard serendipitously discovered the Lewis Acid reagent used to perform rearrangements of cyclic hydrocarbons and his Princeton group continued to explore the possibilities. Specifically, rearrangement of hydrogenated cyclopentadiene with aluminum chloride produced adamantane in yields of 30-40%, far greater than yields of previous methods. This reaction and subsequent improvements made adamantane readily available. The research was extended to additional polycyclic (diamandoid) compounds. Because most of Schleyer’s research involved cyclic hydrocarbons, he purchased one of the first Hewlett-Packard A-60 NMR spectrometers. Use was not limited to the Schleyer group but if another researcher had use for an NMR spectrum they could run spectra, with instruction from Ray Fort, one of Schleyer’s grad students. My research, both as an undergraduate and graduate student, involved hydrogen-poor heterocycles so I rarely needed NMR. However, the A-60 was a great improvement over the huge, vacuum tube A-40 we had at the University of Minnesota. Both of Schleyer’s research and adjuncts like NMR were often discussed in lectures and seminars. The entire Department became well versed in the history, theory, and uses of this research even if they were not working in those areas or using that equipment.
Another feature often encountered by visiting the Schleyer labs was the camphoraceous aroma of adamantane if a preparation had been recently run. A mound of glistening white adamantane crystals would be air drying on brown paper on a lab bench. I once asked Ray Fort why he processed the run that way since adamantane readily sublimes. He answered that was the best way to dry it and not that much was lost. The Schleyer labs were also filled with the sound of classical music, much appreciated by many of us who also maintained radios for listening to classical music on our labs. In Princeton we had access to at least three stations broadcasting the classics from New York and Philadelphia so we were never without our favorites.
Schleyer was a Princeton undergraduate and proud of it (he had been on the swimming team). That, coupled with his general demeanor, led to his nickname, not necessarily in his presence, of “Big Gruff Tiger”. He rarely smiled but when he did it was more of a patented leer, but he was fair in all of his dealings and was one of the best teachers I ever had.
Princeton, through geography and reputation, was able to attract a large number and wide variety of guest speakers for seminars. The more senior professors typically sat in the front row and made cogent comments both during the presentation and the Q&A period at the end. The venerable Hugh Scott Taylor, largely responsible for the excellent reputation of Princeton in Physical Chemistry, would make very cogent comments and politely ask pointed questions, especially on Physical Chemistry subjects. Schleyer, on the other hand, would also ask probing questions but on occasion would literally assault the blackboard, grabbing the chalk, shouting, “No, that’s not correct.” He had proceed to write what he thought was correct citing, “chapter and verse,” the references for the basis of his argument. He was more civil to the more senior speakers, but he demanded intellectual honesty from everyone. He had a near photographic memory for references on a wide variety of chemistry topics.
Courses weren’t a specific requirement for Princeton chemistry graduate students. We were strongly “encouraged” to take some, often for credit, but always advised to audit any course. In our first semester, we “organikers” were encouraged to take courses in organic chemistry and instrumental methods. The latter was team taught, the subjects including NMR, taught by Schleyer, and other spectroscopic methods. References and texts included Bellamy, The Infrared Spectra of Complex Molecules; Sliverstein and Bassler, Spectrometric Identification of Organic Molecules; and Jackman, Nuclear Magnetic Resonance Spectroscopy.
The second semester featured Special Topics in Physical Organic Chemistry, also taught by Schleyer. The topic was reactive intermediates. We covered the gamut of physical organic. A single text was not required but we used at least three: Gould, Mechanism and Structure in Organic Chemistry; Hine, Physical Organic Chemistry; and Alexander, Ionic Organic Reactions. We also used those texts in a subsequent course on Physical Organic Chemistry. I still have those texts and use them on occasion. Most of what I ever learned about physical organic stemmed from that course (and the next) with Schleyer as a great teacher.
We spent about a week on free radicals, another week or so on carbanions, but then got to the meat of the course: carbonium ions. The non-classical carbonium ion (NCCI) controversy was warming up. Featured in most of the controversy was the norbornyl cation (see Nonclassical Ions by P.D. Bartlett for an excellent collection of commentary and reference reprints). NCCIs were postulated to be intermediates in the solvolysis reaction of norbornyl halides as having an indefinite rather than a discrete structure, with the positive charge smeared over more than one carbon atom. The warring camps were exemplified by Saul Winstein et al. in favor of NCCIs and H.C. Brown against. Schleyer was somewhere in the middle, employing and favoring rigorous investigation of the intermediates in these solvolysis reactions which included both his own research and critiquing the work of others. In addition to our physical organic texts, Schleyer taught the course out of the current literature and correspondence. During a break, he paid a visit to Winstein’s lab at UCLA and talked to one of Winstein’s post-docs, Chris Foote. He came back with a preprint of Foote’s research on the correlation of solvolysis rates of a wide variety of cyclic hydrocarbons with the IR carbonyl stretching frequency of the corresponding ketones. This allowed prediction of solvolysis rates, the stability of the carbonium ions, and therefore the implication of NCCIs.
Only two of us were taking the course for credit. At the end of the course, Schleyer said he would send word on the final which would be a take home exam. A couple of days later, a note appeared in our mailboxes: “See me – Paul.” When we did we were given a copy of a two page letter to Schleyer from H. C. Brown. The last paragraph was circled, “Anyone postulating the existence of non-classical carbonium ions should provide valid evidence for their existence.” The assignment: “answer the letter,” specifically the last paragraph. We were given a week. Since we in the course were collectively convinced that NCCIs did exist, I wrote an essay essentially regurgitating the NCCI contents of the course in detail, including references. I turned in the paper and waited for the results. A day or so later a similar note appeared in my mailbox. He had marked my paper with a B+ but then discussed the merits of what I had done. Any demerits were minor and he said I did a good job, but he then justified the grade as a B+ rather an A because “you should have answered the letter in the form of a letter which you did not.” That was accompanied by one of his grins. I had to agree with him. Ever since whenever I tell this story to anyone they usually say, “that wasn’t fair.” I still disagree with that, it was fair.
Besides adamantane and related compounds, NCCIs, and other research, Schleyer was also an expert in concepts like stereochemistry, hyperconjugation, hydrogen bonding, and aromaticity, the last being a primary concern later in his computational chemistry era. Early on, NMR was a favored analytical tool for aromaticity studies. Hydrogen bonding cropped up a year or so later when Schleyer gave a presentation at the monthly Princeton Section ACS meeting on “The Ubiquitous Hydrogen Bond.” However some of the publicity went out as “The Ubiquitous Hydrogen Bomb.” Some undergraduate must have picked up on that and scrawled on the upper corner of the blackboard of the main lecture hall, “Ban the Bomb.” Schleyer, always the humorist, began with observing that slogan and then launched into his presentation (as usual, without notes). After hearing him advocating hydrogen bonding in studies of properties and reaction mechanisms, some of us were surprised to hear that, once again, Schleyer was in the middle and proposed that hydrogen bonding was often postulated incorrectly. At the end, he walked over to the slogan, crossed out “Bomb” and substituted “Bond” saying maybe we should often ban the bond.
I received my PhD in February 1967 and Schleyer was on my orals board. We tapped a keg for my Orals party that night of course, and I still remember him energetically discussing some chemistry topic with another faculty member, beer in hand. He left for Germany soon after but we kept crossing paths via the literature. After 5 years in two lab jobs in pesticide synthesis I switched to my second love: chemical information. In the course of navigating the online information age as a user, I and others discovered the intricacies of searching for authors by name. As I recall, one could get by with searching for just “Schleyer” in chemistry databases but that often wasn’t sufficient or accurate. Not many people realized that Schleyer’s middle name was “von Ragué” and instead it was often linked to his last name as a compound name with regal implications. Various inaccurate listings include von R Schleyer, v R Schleyer, von Schleyer, etc. Similar confusion probably also exists for William von Eggers Doering but I’ve never researched that. Due to inaccurate editing by journal editorial staffs and general misunderstanding, Schleyer had trouble with this early on. I still remember the posting on his bulletin board (the de facto newsletter of the Department with news, chemistry, and humor thrown in) of a copy of a paper from J. Chem. Soc. with a citation to one of Schleyer’s papers where the names of all five authors were totally garbled. This was followed by Schleyer’s letter to the offending authors (all Brits) addressing them with garbled names. Appended to that was their reply acknowledging receipt “of your particularly obnoxious letter” and that a correction had been sent to the journal editor.
When we were teaching chemists and others to do effective online searching, many of us information specialists used Schleyer as the prime example of how to and how not to search for authors. Schleyer’s name exists in about a dozen forms in abstracts of his papers in Chemical Abstracts, even after their editing process. Journal reference citations, as in the Science Citation Index and Web of Science, are in even worse shape. As far as we know, in the CA file at least, all variants are listed under Schleyer in inverted form, last name first. Since there seems to be only one Schleyer, P publishing in chemistry, searching for that phrase in the Author field with a truncation symbol after the P should suffice to retrieve all of his >1000 publications. I’m told that SciFinder does some automatic grouping of author name variants but since I don’t use that service I don’t know if the retrieval is complete.
Both Schleyer and I attended the dedication of the new Frick Chemical Laboratory three years ago and I was able to have one last conversation with him. He will be profoundly missed by all who had contact with him.
Robert E. Buntrock
An incentive for me (Robert E. Buntrock) to write a memorial of my contact with Paul Schleyer was that the majority of the obituaries did not cover the Princeton years to any extent. The exception appeared later, an obituary by Henry Schafer, a colleague of Schleyer’s at the University of Georgia (Nature, 517, p. 22, Jan. 1, 2015, doi:10.1038/517022a). In the online comments to that obituary, links are given to three posts in Chemiotics II by former Princeton undergraduates who did research under Schleyer.
The Wikipedia biography of Schleyer has been updated with a death notice. Additional obituaries include those in ChemViews (Nov. 24, 2014), and C&ENews (92, 49, p, 50, Dec. 8, 2014). In addition, Martin Saunder’s letter to the editor of C&ENews (“Missing a Colleague and a Friend,” 93, 1, p. 5-6, Jan. 5, 2015) and Jorgensen, W. H. A Reflection on Paul von Ragué Schleyer. J. Chem. Theory Comput. 2015, 11, 1.