( GOO ) 



Chemistry. - - "Contribution to the knowledge~o f the action of absolute 

 nitric acid on heterocyclic compounds-." By Prof. A. P. N. 

 Franchimont. 



(Communicated in the meeting of January 26, 1907). 



When searching about twenty years ago for the rules according 

 to which nitric acid ') acts on hydrogen compounds, not only on 

 those which contain the hydrogen in combination with carbon, but 

 also on those which contain it in combination with nitrogen, I 

 found that the hydrogen combined with nitrogen to the atomic group 

 NH, does not act on nitric acid, when, in cyclic compounds, this 

 group is placed between two groups of CO, but it does act if placed 

 therein between the group ('<> and a saturated hydrocarbon residue a ), 

 and it may be added: not if placed therein between two saturated 

 hydrocarbon residues, although I have not mentioned this previously. 



Tt is a peculiar fact that the hydrogen of the group NH does not 

 act on nitric acid if this group is placed between two similar groups 

 such as CO, or saturated hydrocarbon residues, but it does act if 

 placed between two dissimilar ones; so that it might be thought 

 that a tautomeric form is essential for the reaction. 



There are, therefore, in reality three rules, which, when considered 

 more closely, apply also to acyclic compounds and which, although 

 the cycle also exerts an influence, appear to spring mainly from the 

 nature of the substance in which the group NH is placed: viz. 

 secondary amine, amide or imide. In acyclic amides it was found 

 that not only the acyl group in particular, but also the alkyl group 

 exerts an influence on the reaction ; we may, therefore, expect 

 something similar in the cyclic ones. 



The first of the above rules was mainly deduced from the behaviour 

 of penta- and hexa-atomic cyclic urea derivatives, but was confirmed 

 also in the case of other compounds. For instance 



CO— NH 

 CO— N H | \ 



I \ nn , CO CO 



^CO and , 



CO— N H CO— NH 



parabanic acid alloxan 



1 ) Namely the real (absolute) acid which may be obtained by distilling a mixture 

 of nitric acid 1.4-2 with twice its weight of sulphuric acid at a gentle heat under 

 reduced pressure (Recueil XVI. p. 386). 



2 ) Which, however, need not be the group CH 2 as stated wrongly by Harries 

 (Annalen 327. p. 358). The pages of the Recueil referred to by him contain 

 exactly the proof of the contrary. I have also never spoken of "höchst concen- 

 trirter Salpetersaure" as he says, and of which he thinks he must "den Begriff 

 festlegen", and for which he then recommends something which in many cases 

 cannot give a good result. 



