pierre laszlo

History of Chemistry
Rose ou Noir?


Le dernier demi-siècle arbora, pour la chimie, les couleurs de la science: on y compte plus de chercheurs que leur nombre cumulé sur toutes les périodes passées; on y répertorie de multiples applications, prises comme locomotives es économies de pays qui sont déjà les plus riches; et on y constate la fascination du public pour des domaines comme l'astronomie ou la paléontologie. Néanmoins, si l'avancement du savoir est venu remplir des cases de la science chimique restées longtemps désespérement vides (structure des protéines, synthèse organique nantiosélective, ou reconnaissance moléculaire, pour ne citer que ces trois cas), la véritable création fut souvent eléguée dans les coulisses de la recherche d'imitation, et contrainte de jouer les utilités.

In any form or shape?


This study places the history of stereochemistry into its rightful time span of the longue durée., To do so, it has been necessary to do three things.
First, I draw attention to Wollaston's and Ampère's contributions dealing with molecular geometry, and why they have been neglected. Second, I single out Ampère's paper for fleshing out Haüy's crystallographic ideas. Those ideas underline the geometric understanding of molecular structure. With their Pythagorean make-up, not only do they bridge a succession of visionary scientists across the centuries, from Kepler and Robert Hooke to Alfred Werner and others; they also attempt to link chemical structure to the incisive mathematical physics introduced by Galileo and Descartes. Finally, I shall also counter two misleading constructions: ascribing the birth of stereochemistry uniquely to Le Bel's and van't Hoff's announcement of the tetrahedral carbon atom; and the glib, hasty dismissal as "Whig" of the in-depth reworking of the historical narrative made necessary by more recent developments.

Conventionalities in formula writing


Chemical formulas, those small icons which chemists are wont to scribble in their notebooks and in odd places, such as the back of an envelope, and which to the general public have become emblems of their profession, are an excellent topic for history. These artefacts remain today tools for communication within the community of chemists. They continue serving as didactic instruments in teaching. The establishment of an individual formula for a chemical compound or a substance chronicles the laboratory methods, both routine and specific, which came into play in order for it to be written down and to assume the status of the analog of a word, to be stored within the growing lexicon of chemistry.

When addressing this topic, the historical narrative, besides its usual needs for accuracy and for an unerring sense of the strange and original taste of the bygone, demands the twin crutches of philosophical and linguistic inquiries. I wish to provide these complements if not in full, at least in a manner suggestive of some of the main issues.

I shall concern myself with the period of consolidation, when formulas entered the language of organic chemistry and started becoming sterotyped, the approximate period 1865-1905. 1 Why choose such a periodization? Because it brackets, approximately, the birth of the modern chemistry journal, JACS was started in 1879, and that of the modern comprehensive repertory of new chemical compounds, Chemical Abstracts were launched in 1907. Kekulé announced in 1865 his cyclic structure of benzene. The Chemical Society published in London, in 1882, Nomenclature and Notation, the first guidelines for establishing systematic and uniform practice. And the American Chemical Society followed suit in 1884 by establishing its Committee on Nomenclature and Notation. The international conference convened in Geneva in 1892 established norms for chemical nomenclature. 2 And Alfred Werner, in 1895, gave a systematic nomenclature for coordination complexes. Key milestones in the history of molecular formulas - so-called "structural formulas"; I favor the adjective "molecular" since the meaning of "structural" has changed considerably over the twentieth century - include the serendipitous synthesis of mauveine (1857), the first synthesis of alizarin (1868) and the identification of ibogaine (1905); Gomberg first free radical appeared in print in 1900. The forty years 1865-1905 were thus for molecular formulas of organic compounds those of the rise in their practical use, of their standardization and also of the first challenges to the rules governing them.

As always in history of science, the risk of Whig history lurks at every corner of the retrodictive narrative. The danger is to read into the structural formulas, as they were used at the end of the nineteenth-beginning of the twentieth century, meanings which they had yet to acquire in the post-Gilbert N. Lewis and post-Linus C. Pauling eras. Examples of such potential anachronisms are: (i.) viewing benzene rings as ipso facto synonyms of "aromaticity;" (ii.) reading double bonds as implying shorter and stronger interatomic linkages; (iii.) interpreting loss of a water molecule in a dehydration process as a thermodynamic driving force for the observed conversion. The eerie superficial similarity of these late nineteenth formulas to our early twenty-first century formulas can easily become misleading.