STEREO-CHEMISTRY OF NITROGEN 125 



and it is at present uncertain if the observed activity is to 

 be ascribed to an active ammonium chloride. 



On the other hand, isomerism in bodies of the type 



ACB 



II 



N 



Y 



is fully established, both in the acetoximes which are 

 derived from an asymmetrical ketone, i. e. 



ACB C 6 H 5 CC 6 H 4 C1 



ft such as li- 



OH 



and in the aldoximes which correspond to the special case 

 B = H, a simple example being acetaldoxime : 



HCCH 3 



II 

 NOH. 



The two isomers thus arising are inactive, but differ 

 physically like ordinary isomers, and chemically, amongst 

 other ways in that one compound easily gives off water 

 with formation of a nitril, which may be supposed due to 

 proximity of the hydroxyl to hydrogen. The structural 

 difference is therefore fco be expressed by the formulae 



HCCH 3 HCCH 3 



II and || 



HON NOH 



which recall those of fumaric and maleic acid. 



Concluding remark on stereochemistry. As in deter- 

 mining constitutions in the earlier cases intramolecular 

 displacement of the atoms may lead to wrong conclusions, 

 making it desirable for a satisfactory determination to 

 have two lines of argument, so in the more exact deter- 

 mination of configuration in stereochemistry the same 

 thing must be borne in mind. Such direct changes have 

 indeed often been observed within the region of stereo- 



