Researches on the molecular asymmetry of natural organic products / by Louis Pasteur (1860).

  • Pasteur, Louis, 1822-1895.
Date:
1905
Catalogue details

Licence: Public Domain Mark

Credit: Researches on the molecular asymmetry of natural organic products / by Louis Pasteur (1860). Source: Wellcome Collection.

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    XI. But the difference in properties of corresponding right and left substances when they are subjected to asymmetric forces, seems to me to be interesting in the highest degree on account of the ideas which it suggests to us in regard to the mysterious cause which presides over the asym¬ metric arrangement of the atoms in natural organic sub¬ stances. Why this asymmetry ? Why the one asymmetry rather than its inverse? Carry yourselves back with me in thought to the time when, having recognised the absolute identity of the chemical and physical properties of the corresponding right and left substances, I had not any idea, not even the suspicion, of possible differences between these sub¬ stances. It was, in fact, after an interval of several years that I recognised these similarities and differences. It was then impossible for me to understand how nature could make a right substance without at the same time making the left substance. For the same forces which are at work at the moment at which the molecule of right tartaric acid is elaborated, must, it seemed, yield a left molecule also, and there would have been nothing but paratartaric compounds. Why even right or left substances at all ? Why not simply non-asymmetric substances ; substances of the order of inorganic nature ? There are evidently causes for these curious manifesta¬ tions of the play of molecular forces. To indicate them in a precise manner would certainly be a difficult matter. But I believe that I am not deceived when I say that we know one of their essential characters. Is it not necessary and sufficient to admit that at the moment of the elabora¬ tion of the primary principles in the vegetable organism, an asymmetric force is present ? For we have just seen