Researches on the molecular dissymmetry of natural organic products : presented to the Chemical Society of Paris, January 20 and February 3, 1860 / by L. Pasteur ; translated from "Leçons de chimie professées en 1860" by W.S.W. Ruschenberger.

  • Pasteur, Louis, 1822-1895.
Date:
[1862]
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Licence: Public Domain Mark

Credit: Researches on the molecular dissymmetry of natural organic products : presented to the Chemical Society of Paris, January 20 and February 3, 1860 / by L. Pasteur ; translated from "Leçons de chimie professées en 1860" by W.S.W. Ruschenberger. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    Bear in mind the definition of chemical species just now men- tioned, namely, the collection of all individuals identical by the nature, the proportion and arrangement of elements. All the properties of bodies are the functions of these three terms, and the object of all our efforts consists in recurring by experiment on properties to the knowledge of these three things. In isomeric bodies, the nature and proportion [of constituents] are the same. The arrangement alone differs. The great in- terest of isomerism has been to introduce into science this principle—that bodies may be and are essentially different by that alone, that the arrangement of atoms is not the same in their chemical molecules. But no isomeric bodies existed whose relations of molecular arrangements were known. This gap is filled for the first time by the discovery of the constitution of paratartaric acid and the relations of constitution of the right and left tartaric acids. We know, in fact, on the one hand, that the molecular arrange- ments of the tartaric acids are dissymmetric, and on the other, that they are rigorously the same, with the sole difference of presenting dissymmetries in opposite directions. Are the atoms of the right acid grouped according to the spire of a dextrorse helix, or placed at the summits of an irregular tetrahedron, or disposed according to such or such determined dissymmetric as- semblage ? We are unable to reply to these questions. But what cannot be doubted is, that there is a grouping of atoms according to an order dissymmetric to a non-superposable image. What is not less certain is, that the atoms of the left acid precisely realize the inverse dissymmetric grouping of this one. We also know, that paratartaric acid results from the juxtaposition of these two groupings of inversely dissymmetric atoms. From this moment the ascertaining the resemblances and the chemical and physical differences which correspond to these arrangements whose relations are known, affords particular in- terest, and gives to the molecular mechanism assured bases. It permits us to establish the connexion of physical and chemical properties with the molecular arrangement which determines their proper existence, or inversely it permits us to recur from properties to their first cause.