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Instrumental Journey

Pierre Laszlo

Shifting and Rearranging: Physical Methods and the Transformation of Modern Chemistry. Carsten Reinhardt. x + 428 pp. Science History Publications/USA, 2006. $49.95.

Organic spectroscopy, which uses physical methods to determine the structure of molecules, came of age during the Golden Sixties. Historian Carsten Reinhardt chronicles the era in his new book, Shifting and Rearranging: Physical Methods and the Transformation of Modern Chemistry. As he explains, the twin engines to lift organic spectroscopy to prominence were nuclear magnetic resonance spectroscopy (NMR), which drew on the advances in electronics during World War II (particularly the development of radar), and mass spectrometry, which was pioneered by engineers in the 1950s for analyzing the hydrocarbons present in oil.

Organic spectroscopy arose in a bleak landscape. The only instrumental techniques available just after the war had one sort of limitation or another: Some (dipolemetry, ultraviolet electronic spectra interpreted with the Woodward rules, infrared spectroscopy) were indirect, others (electron diffraction, microwave spectrometry) were applicable only to small or highly symmetrical molecules in the gas phase, and still others (x-ray diffraction, for example) were excruciatingly labor- and time-intensive.

Fred W. McLafferty...Click to Enlarge Image

Reinhardt focuses on mass spectrometry in chapters 3 and 5 and on NMR in chapters 2, 4 and 6. He follows six scientists—Klaus Biemann, Fred W. McLafferty and Carl Djerassi for mass spectrometry, and Herbert Gutowsky, John D. Roberts and Richard Ernst for NMR—whom he terms "lead users" for their mediation between the chemical industry, instrument makers and academic chemists.

Reinhardt collected his information from interviews with these six scientists. Such an approach has archival value, but it also has shortcomings. To define a field by its leaders is akin to viewing a mountain range only in terms of its highest peaks. It leads the historian to miss out on much that is of substance. It behooves one to study not just the work of those in the forefront of a discipline or subdiscipline but also the achievements of scientists who were less in the limelight; more can be learned from the latter than from the former—numbers alone see to it.

Important strands of the story involved others whose omission, partial or total, grates: Frank Anet found the nuclear Overhauser effect in organic molecules; Elias J. Corey, the synthetic organic chemist, was well-versed in NMR from the start; Paul Lauterbur started carbon-13 NMR; Sture Forsén and Ragnar A. Hoffman devised a relaxational approach to chemical kinetics; Martin Saunders elucidated the kinetics of the cornerstone bullvalene rearrangement; John S. Waugh initiated high-resolution NMR of solids.

In addition, historians rightly distrust accounts such as those elicited by Reinhardt. Interview responses tend to be self-serving, lack cross-checks and omit the context; they also often conflict with the narratives that historians themselves are trained to construct. Moreover, oral history misses testimonies from sources who died too early. In this instance, an example would be William D. Phillips, who pioneered NMR of proteins.

However, Reinhardt is an especially skilled narrator, and his recounting of the twists and turns of early NMR and mass spectrometry as applied to organic chemistry is captivating. He is also very good at describing the industry-university nexus, pointing out, for example, that instrument makers such as Varian Associates initiated training for users at universities.

A major factor in the success of organic spectroscopy was its close association with physical organic chemistry, which reached the zenith of its influence in the 1960s. Several American universities had departments of chemistry that were powerhouses of physical organic chemistry. Reinhardt only alludes to this crucial part of the story.

His narrative describes how the new instrumentation fertilized chemistry only after having been made part of the chemical culture, by having been imported by chemists such as the above-named lead users. Within chemistry, the subdiscipline of physical organic chemistry was uniquely suited to host the new methodologies. To give a single example, Gerhard Closs, who was a physical organic chemist at the University of Chicago, promptly explained the new phenomenon of chemically induced dynamic nuclear polarization. More generally, American universities that were, at the time, powerhouses of physical organic chemistry were the sites for major advances in chemical knowledge induced by the new instrumentation. This relative neglect of the key role of physical organic chemists is one of the few shortcomings of the book.

Information about NMR and mass spectrometry quickly penetrated the organic community via several outstanding books. A number of these were written by Reinhardt's six protagonists, but three of the books had other authors: The Principles of Nuclear Magnetism, by Anatole Abragam (1961); High-Resolution Nuclear Magnetic Resonance, by John A. Pople, W. G. Schneider and H. J. Bernstein (1959); and Applications of Nuclear Magnetic Resonance Spectroscopy in Organic Chemistry, by Lloyd Miles Jackman (1959).

The OCEANS conference (later renamed the Experimental Nuclear Magnetic Resonance Conference, or ENC), which was held every spring at the Mellon Institute in Pittsburgh, translated leading-edge research into routine laboratory practice. This process was further facilitated by an informal monthly newsletter (initially Mellon NMR,and subsequently Texas A&M University NMR Newsletter). Reinhardt, who is very good on the educational role of instrument manufacturers, such as Varian Associates, is less attentive to the self-teaching within the chemical community.

Institutional policies governing the status of the new spectroscopies were diverse. In the leading German universities, the conservatism of the ruling professors, who had been nurtured on synthetic chemistry rather than analytical organic chemistry, saw to it that specialists in organic spectroscopy were barred from holding chairs. The dominant American mentality was somewhat similar. The enormously influential chemistry department at Harvard University viewed NMR as an ancillary technique; the person in charge of it there was not deemed worthy of the rank of tenured professor. Accordingly, NMR experts rose to eminence only in schools that were training engineers, such as MIT, or in departments of chemistry rather remote from the Ivy League, such as those at the University of Illinois, the University of Arizona, Florida State University and Stanford. Others found employment in government laboratories.

Moreover, granting agencies such as the National Science Foundation were initially shortsighted. Given the high capital expenditures necessary to acquire the new technologies, they encouraged setting up university-wide or even regional centers for instruments and technical staff. (Here they were adapting the model of contemporary computer centers with their hugely costly mainframe computers.)

There are two sides to the story of the rise of spectroscopy: the taming of the technology by organic chemists and the profound changes the new methodologies induced in chemistry. Reinhardt's book is eloquent on the former but silent on the latter. What a shame! The enrichment of organic chemistry by NMR was bedazzling. Conformational analysis took off in a big way. Fluxional molecules, starting with bullvalene as a seminal case, presented chemists with a fascinating new aspect of molecular reality. Organometallic chemistry blossomed enormously on the strength of multinuclear magnetic resonance. NMR took over from existing physical methods, too. For instance, it replaced polarimetry in determinations of enantiomeric excesses in reactions.

The whole story is well worth telling. By covering half of it, Reinhardt makes a good start toward such a narrative.

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