Louis Pasteur, Chemical Linguist: Founding the Language of Stereochemistry

Abstract

Pasteur’s major discovery in chemistry was the recognition of molecular chirality, in 1848. He understood that his new science needed its own language, and introduced new terminology and nomenclature, thereby launching modern stereochemical language. He was eminently prepared for this task as a refined user of language, skills recognized by his election to the Académie française, the supreme institution for the protection and promotion of the French language. The terms chiral and chirality did not exist at the time and he adopted the French word dissymmétrie (dissymmetry) for the phenomenon of handedness. Although in his time almost nothing was known about molecular constitution and configuration, his insights allowed him to create useful language some of which is still used today in stereochemistry, e. g., racemic for the 1 : 1 mixture of the two enantiomers, and the use of the prefixes levo‐ and dextro‐ in the names of optically active substances. On the other hand, the limitations in the knowledge of organic chemistry at the time prevented him from creating some needed terms, e. g., for the phenomenon of diastereoisomerism. He also failed to adopt the enantio terminology introduced in the 1850s by German mineralogist Carl Friedrich Naumann. Analysis of Pasteur’s linguistic innovations is of interest from the point of view of the history of chemistry and is also useful in throwing light on the fundamental nature of the concepts of stereochemistry. Such understanding has acquired a new relevance due to the considerable misuse and misunderstanding of this language seen in the literature today.

When Stereochemistry Raised Its Ugly Head in Coordination Chemistry—An Appreciation of Howard Flack

“…It cannot be stressed strongly enough that chirality is a property of an object as a whole rather than something associated with a portion of that object, such as an "asymmetric atom". The term chirality equates exactly with the term dissymmetry (dissymmétrie) originally used by Pasteur [28,29,[41][42][43]. Note that dissymmetric and asymmetric are not equivalent-asymmetric means without symmetry whereas dissymmetric is more specific and means "lacking improper symmetry elements".…”

“…Not only was this description being used by the United Kingdom chemical community in the 1890s [20,21], but also had a long tradition in the German literature [22][23][24] being introduced by Naumann in 1856 [25] and treated at length in Schoenflies' 1891 text on crystallography [26]. The IUPAC has subsequently made recommendations on the basic terminology of stereochemistry [27] and Gal has published extensively on the early etymology of stereochemical terms [28][29][30][31][32].…”

Through a Glass Darkly—Some Thoughts on Symmetry and Chemistry

“…In 1874, the time was ripe for the correlation of ideas concerning the spatial arrangement of atoms about carbon and optical activity into a single cohesive model. Two young researchers published the same ideas almost contemporaneously [168][169][170][171][172][173]. Jacobus Henricus van't Hoff (1852Hoff ( -1911 and Joseph Achile Le Bel (1847-1930) used the asymmetry of a tetrahedral carbon atom to explain the origin of optical activity.…”

Chirality in Geometric Algebra

“…According to science historian Joseph Gal [1], Pasteur discovered molecular chirality in 1848, but used the term dissymmetry (a detailed history is given in Gal's paper). However, dissymmetry should not be confused with asymmetry, which means a lack of both direct and indirect symmetry.…”