Chemistry's Quixotic Beginnings

CHASING THE MOLECULE, by John Buckingham, Sutton Publishing, 2004, 259 pages, $24.95 (ISBN 0-7509-3345-3)

In the preface to their 1923 classic, "Thermodynamics," Gilbert Newton Lewis and Merle Randall likened the creation of thermodynamics to the construction of a medieval cathedral. But something equally extraordinary and inspiring had occurred among chemists in the development of the structural theory of organic chemistry.

Yet within a little more than a half-century, a language was developed that assigned a separate name and diagram to every organic compound, a language so sophisticated that the name and diagram suggested the properties and often the ways the substance could be made from simpler molecules. Suddenly, thousands of new substances were being made in the laboratory, and chemistry became almost unique among the sciences in creating much of the world of materials that was the object of its studies.

The story of that development has now been told in its full social, cultural, and institutional context in "Chasing the Molecule," by John Buckingham. This book is written for the intelligent reader not necessarily trained in science, and remarkably it has much to teach the chemist, the scholar, and the historian of science. Having spent much of my life thinking and reading and writing about chemistry, I expected my task as reviewer would be to check how far the author understood the details of what he was relating. It was not long before I realized that my approach was totally inappropriate, that the author had much to teach me and was in total command of his subject.

In short, the book is a masterpiece that brings to life the intricate and entangled story of brilliance and obtuseness, the national rivalries and personal ambitions, a passionate interest in the subject all were studying, and a theoretical framework growing almost surreptitiously. Its growth was at times barely perceptible in the avalanche of published papers. Those were full of new syntheses and analyses and were expressed using various systems of atomic weights and adorned with theoretical speculations.

Buckingham taught organic chemistry at University College London, where long ago I obtained my chemical training. Famed organic chemist Christopher Ingold was my teacher in advanced organic chemistry, and he invariably placed each subject in its historical context. As far as possible, I tried to do the same in my own teaching, and I'm fascinated to think that perhaps Ingold's pedagogical approach has survived in England or at least in University College. Buckingham, who now divides his time between London and France, was founding editor of the "Dictionary of Natural Products."

Geography is clearly one of the author's fascinations, as can be seen up front in the table of contents chapter headings: "Adieu, Monsieur!" is about the French chemists Auguste Laurent and Charles Gerhardt. Their brilliant insight into the classification of organic compounds in the 1800s was not appreciated by the chemical establishment in the capital. "A Cross-Channel Excursion" focuses on the English trio Alexander Williamson, Edward Frankland, and William Odling, who clarified the concept of valence, including the tetravalence of carbon. "The Kingdom of the Two Italians" discusses Amedeo Avogadro and Stanislao Cannizzaro.

And Chapter 13 (out of a total of 15) is "The Man on the Clapham Bus," which is about the phenomenal August Kekulé. Kekulé also holds center stage in the book's introduction, which describes the 1890 celebration of Kekulé's benzene-ring structure, which he had enunciated 25 years earlier. In that quarter-century, the chemical industry had flourished, largely due to the dyes, medicines, and explosives made possible once benzene's structure was understood. The chapter describes the dreams or reveries Kekulé claimed were the sources of his insight--claims that have raised so many questions that a whole book on the controversies appeared a century later.

Rather than beginning with vital force and Friedrich Wöhler's accidental synthesis of urea, Buckingham introduces them after seven chapters. First, he covers the Greeks, the Chinese, and the alchemists, and deals also with the spice trade. He describes the pharmaceutical properties of plants and the isolation of the classic organic chemicals strychnine, morphine, and quinine. He wisely points out that early thinkers tried to explain everything, and humans only slowly learned that more progress would be made by studying and explaining small areas first.

Then comes John Dalton and the ups and downs of the views of whether or not atoms exist, the encounter with isomerism, the genius and dogmatism of Jöns Jakob Berzelius, and the remarkable friendship of Justus von Liebig and Wöhler. Liebig late in life described it as "an infrequent example of two men who faithfully, without envy or ill-feeling strove and disputed in the same field and yet remained throughout closely related in friendship."

Wöhler once called organic chemistry "a monstrous and boundless thicket, with no way of escape, into which one may well dread to enter." Yet he and Liebig found a way into it in their exploration of the oil of bitter almonds. They discovered a group of carbon, hydrogen, and oxygen atoms that remained unchanged when benzaldehyde was converted to benzoyl chloride, benzoic acid, and several other chemicals.

Here emerged the possibility that these unchanging groupings or radicals played the role in organic chemistry that atoms played in the inorganic world. Berzelius tried to designate these radicals as either positive or negative, but some radicals had their positive hydrogen changed to negative chlorine with no fundamental change in chemical behavior. And throughout the period, controversies raged about how to assign correct atomic weights, controversies not stilled until the Congress of Karlsruhe in 1860, organized by Kekulé, when the two Italians were shown to have the obvious answer.

Thanks to Laurent and Gerhardt, most organic chemists had already agreed to use one set of atomic weights. With the tentative understanding of valence, Scotsman Archibald Couper and Kekulé, in 1858 recognized independently the chain-forming capacity of carbon atoms, and thus made possible the assigning of usually correct formulas.

Then, Russian chemist Aleksandr Butlerov, who explicitly credited Couper for his basic ideas, and Austrian chemist Joseph Loschmidt, who wrote out over 300 structures without even using bond lines, wrote numerous mainly correct formulas. Although Loschmidt's 1861 diagram for aniline suggests a six-carbon benzene ring, Buckingham doesn't make it clear that Loschmidt's large circle merely represented a six-carbon cluster whose internal arrangement Loschmidt said he didn't know.

Yet, as the author points out, Kekulé, who claimed his inspiration for the ring formula for benzene came from a dream of a snake eating its tail, almost certainly saw Loschmidt's diagrams. Loschmidt's circular form is as likely as a reverie in front of a fireplace to have suggested to Kekulé a six-member carbon ring for benzene. Of course, the Loschmidt diagram might have resurfaced in Kekulé's subconscious while dozing. Kekulé published his ring formula in 1865.

Butlerov pointed out that the formulas of the structural theory of 1858 were topological, telling which atoms were linked to which others. The book's penultimate chapter then extends organic chemistry into Euclid's three dimensions with the work of Jacobus Henricus van't Hoff and Joseph Achille Le Bel. And to introduce handedness and chirality, the author attaches New Zealand instead of Italy to mainland Europe, its boot pointing in the opposite direction from Italy's. That is just one example of the author's whimsical humor. Discussing Albert Ladenburg's alternative benzene structure, a triangular prism, which generations of teachers have called pup-tent benzene, the author instead calls it a Toblerone package.

In the concluding pages, the book revisits the vitalism debate, wondering why DNA always runs one way and why our bodies are built of one set of chiral molecules and not their mirror images. The author also talks about the phenomenal growth of chemistry as a profession, and he returns to strychnine, the race to find its formula, and the impact of the instrumental revolution.

Twenty-one photographs grace the center of the book, each with a caption--such as the one for Cannizzaro: "Soldier, politician, and family man who still found time for chemistry." Chapters begin with a quotation--from sources as diverse as Conan Doyle, Lewis Carroll, Alexander Pope, Anthony Trollope, and the famous tome by Jane Marcet, "Mrs. Marcet's Conversations on Chemistry (1807)." The book includes helpful notes to the chapters, an extensive bibliography, and a glossary where the author's sense of humor occasionally shines once more. I was startled by his third definition of organic: "Modern variation: overpriced product said not to contain chemicals (q.v.) but, as all material substances are chemicals, obviously it does."

Two final comments: The early chapters are a bit unkind to the many inquisitive people who over the centuries wondered about the nature of the living world, as if they sought but failed to become organic chemists. They usually had very different aims, and the context of their writing was often religious as much as scientific.

I was enormously impressed by the book's pedagogic structure. It did not slavishly follow the chronological order of historic events. Buckingham takes shortcuts and tells you what he is doing. He gives previews of what later will be discovered and explained. And he often shows us the modern formula instead of or alongside the formula proposed from earlier times. Remarkably, these strategies do not falsify the story. Instead, they help make the book a joy to read. I hope it will be read by many.

Theodor Benfey is Dana Professor of Chemistry & History of Science emeritus at Guilford College, Greensboro, N.C. He was editor of the ACS magazine Chemistry (1963–78) and is currently editor-at-large of Chemical Heritage.