242 



Pope, Kipping and their collaborators were also able to prove 

 the validity of these views in the case of the asymmetric tetravalent 

 sulphur-atom l ), of the asymmetric selenium-atom 2 ), of the asym- 

 metric tin-atom 8 ), while the work of Kipping 4 ) on the asymmetric 

 silicon-atom has also splendidly confirmed the applicability of this 

 doctrine in these cases. Moreover, for the pentavalent phosphorus- 

 atom, if asymmetric, the analogous fact was proved by Meisen- 

 heimer and Lichtenstadt 5 ), and by Kipping 6 ), and for arsonium- 

 compounds of this kind 7 ) may be so in nearest future ; so there 

 can be no doubt whatever as to the general correctness of the view, 

 that all higher-valent atoms (valency>3) may eventually reveal 

 the said phenomenon. 



As the subject of the application of Van 't Hoff-Le Bel's- 

 theory to organic chemistry, and to the numerous particulars and 

 special cases of isomerism in this field, e. g. with unsaturated com- 

 pounds and the derivatives of /n'valent nitrogen, etc., - - is too 

 large to be dealt with in detail in this book, the reader must for 

 that purpose be referred to the many excellent text-books on stereo- 

 chemistry now in use. It need only be remarked that a final result 

 as to the arrangement of the radicals round the asymmetric 

 pentavalent nitrogen-atom, could up to now not be obtained from 

 the study of the- possible isomerides in the case of such compounds 

 as: N v (obcde), N v (aJ>cd), and N v (aJ>c). 8 ) Much work in this field 

 remains yet to be done. 



16. The foregoing leaves the impression, that the truth of 



Ges., 38, 1838, 3438. (1905); M. Scholtz, Ber. d. d. Chem. Ges., 37, 3627, (1904); 

 38, 1289, (1905); F. S. Kipping, Journ. Chem. Soc. London, 83, 873, 918, (1903); 

 O. Aschan, Zeits. f. phys. Chemie, 46, 293, (1903); A. W. Harvey, Journ. 

 Chem. Soc., 87, 1481, (1905), W. J. Pope and J. Read, Journ. Chem. Soc. London, 

 101, 519, (1912). 



*) W. J. Pope and S. J. Peachy, Journ. Chem. Soc., 77, 1072, (1900); S. 

 Smiles, ibid., 77, 1174, (1900). 



?) W. J. Pope and A. Neville, Journ. Chem. Soc., 81, 107, 1552, (1902). 



3 ) W. J. Pope and S. J. Peachy, Proceed. Chem. Soc., 16, 42, 116, (1900); 

 Cf.: A. Werner, Lehrbuch der Stereochemie, p. 316. 



4 ) F. S. Kipping, Journ. Chem. Soc., 91, 209, 717, (1907); 93, 457, (1908); 

 95, 69, 408, (1909). 



5) J. Meisenheimer and L. Lichtenstadt, Ber. d. d. Chem. Ges.,44,356,(191 1), 



6) F. S. Kipping and F. Challenger, Journ. Chem. Soc. London, 99, 626, (1 191). 



7) T. F. Winmill, Journ. Chem. Soc., 101, 718, (1919); Proceed. Chem. Soc. 

 28, 931. Optically active compounds were not yet obtained. 



8) F. S. Kipping, Journ. Chem. Soc. London, 83, 873, 918, (1903). 



