232 



thereby producing a distortion of the original molecule C(R l ) 4 . Such 

 a symmetrical arrangement of different groups round the central 

 carbon-atom is of course very improbable, although it is not neces- 

 sarily to be considered as wholly impossible. 



15. According to the Van 't Hoff-Le Bel-theory therefore, 

 the possibility always exists of a chemical substance occurring in 

 two enantiomorphously related isomerides, as soon as a plurivalent 

 asymmetric atom of the kind just described is present in its molecules. 



As already pointed out, this doctrine has proved admirably far 

 reaching: for not only have hundreds of such carbons-compounds 



J. H. Van 't Hoff. 

 18521911 



J. A. Le Bel. 



been since resolved into their antipodes, but also in the case of other 

 plurivalent atoms than carbon, it has been proved to hold absolutely. 

 Its truth 'was upheld in the case of the asymmetric pentavalent 

 nitrogen-atom, as Le Bel, Kipping, Pope, Wedekind, Aschan, 

 and many others, have demonstrated in a series of admirable 

 investigations J ). 



1) J. A. Le Bel, Compt. rend, de 1'Acad. d. Sc. Paris 112. 725. (1891); E. 

 Wedekind, Zur Stereochemie des funfwertigen Stickstoffs, Leipzig, (1899); 

 W. J. Pope and S. J. Peachy, Journ. Chem. Soc. London 75. 1207. (1899); 



