( 271 ) 



differ in fliis wav that tlio two liydroijcii atoms of tlic flrsj oompound 

 (indicated bv asterisks) lia\'e been replaced in the second one by the 

 bivalent gron|i (-II., — ('II., — (Ml., ; piperidine and tetramethylpipei'idinc 

 differ because the first one contains hydrog-en atoms where the other 

 possesses methyl gi-oups, namely at the a C atoms in regard to the 

 nitrogen. 



As piperidine reacts strongly u ilh the above substances and tetra- 

 methylpiperidine does not do so and as there exists an analogous 

 difference between dinonnalpropylamine and di-isopropylamine it is 

 natural to look for the cause of this in the methyl groups. As, 

 however, their nature does not explain this difference we are bound 

 to consider their mass and their position in space in regard to the 

 nitrogen. This is then a case of so-called sterical obstacle which is 

 to a certain extent comparable with a number of other cases which 

 have been chiefly observed in the aromatic compounds; a case which 

 may, perhaps, affect the views held as to the nitrogen atom. 



It must be finally observed that tetramethylpiperidine yields like 

 di-isopropylamine a crystalline compound with nitrous acid, which is 

 fairly stable and is only decomposed at a higher temperature into 

 water and the nitroso-compound. 



Chemistry. — "■On inti'mnoh'cular //lomic rPdrrruKji'menf.-; in henz- 

 pinaconcs." By P. J. MoNTACiNK. (C'oinmumcaled i>y Prof. 

 A. P. N. Franchimont). 



(Communicated in the meeting of Seplember 24, 1904). 



The following research originated in an effort by Nef') to explain 

 the intramolecular atomic rearrangement in the conversion of benz- 

 pinaconc into benzpinacoline by assuming the presence of an inter- 

 mediate product. His explanation wiien pul into formulae is as 

 follows : 



Benzpinacone is dissociated info water and unsaturated hydrocarl)on: 



Am .c«H, y)H y\u, 



C«H — C C -» ^\,H — C C 



I ! M' ft ' H' H 



C,H, .11 OH*^""^ CJI, .H y* 



^OH ^C„H3 



then addition to : C„H,— C C 



CeH, 



1) Ann. 318 p. 38. 



