PASTEUR, LOUIS. - REVEALING A NEW KIND OF ISOMERISM.

Transformation des acides tartriques en acide racémique. Découverte de l'acide tartrique inactif. Nouvelle méthode de séparation de l'acide racémique en acides tartriques droit et gauche.

(Paris, Bachelier),1853. 4to. No wrappers. In: "Comptes Rendus Hebdomadaires des Séances de L'Academie des Sciences", Tome XXXVII, No. 5. Pp. (145-) 196. (Entire issue offered). Pasteur's paper: pp. 162-166.

First appearance of a milestone paper in chemistry in which Pasteur announced two momentous importent discoveries, that racemic acid could be separated into the two optically active tartaric acids and the discovery of "mesotartaric" acid.

For his work on racemic acid and crystallography he received the prize of 1,500 francs from the Société de pharmacie (1853), membership in the Legion of Honor, and the Rumford Medal of the Royal Society (1856).

"During this journey (travel to Vienna, Prag and Saxony) Pasteur met a German industrial chemist who claimed to have achieved what Pasteur then considered impossible - the chemical transformation of tartaric into racemic acid. Although he soon confirmed his belief that this particular claim was inaccurate, Pasteur unexpectedly achieved the transformation in May 1853 by heating cinchonine tartrate at 170°C. for five to six hours. This procedure also yielded a small amount of inactive "mesotartaric" acid, the existence of which Pasteur had predicted the year before and in search of which he had apparently undertaken the experiment. In the memoir (1 August 1853) in which he announced these two discoveries, Pasteur disclosed a new method for separating racemic acid into its left- and right- handed components. His original method, involving the manual separation of the crystals, was laborious and extremely limited in applicability. The central feature of the new method was the chemical combination of racemic acid with optically active bases. Under appropriate conditions they affected the solubility of the resulting paratartrates in such a way as to favor the crystallization of only one of the two forms that together compose the paratartrate. Although introduced by Pasteur only for the case of racemic acid, this new method clearly had wider applicability and was soon used to separate the left- and right- handed components in other "racemic" substances (substances inactive by compensation)." (DSB)

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