849 



ments it may be mentioned thattlie I'ulio CI : NHj is very large. 

 The above velocily series inust, therefore, be resolved into two parts : 

 OH a)id NH.^ which cause a great substilulion velocity and \vhich 

 are presuiuably of (he same order of magnitude; on the other side 

 the halogens and CH, with a lessei- velocity, also of the same order 

 of magnitude. A more detaded description of the above experiments 

 will be published iji the Recueil. 



Oct. '14. Oiy. Client. Lab. IJnlüewnty Amsterdam. 



Physics. — '''The reduction of arooxUlr ketones. III. Contribution 

 to the knowledije of the photocheiuicd/ phenomena." By Prof. J. 

 BöKSEKEN and Mr. W. D. CV)iien. (C-ommunicated by Prof. A. 



F. HoJJ-KMAx\). 



(Gommnnicated in tlie meeling of October ol, 1914). 

 I. The reduction of the aromatic ketone.'^' in a perfectJi/ neutral ineditim. 



In our former communicati(jns ') we have shown that the reduction 

 of the aromatic ketones does not proceed any further than to pinacone, 

 which is presumably formed from the primary generated half pina- 

 cone molecule !)y rapid polymeiisaiion. Tiie fact tliat in an alkaline 

 medium hydrol is always obtained, must be attributed to the rapid 

 transformation of the pinacone, undei- the influence of the hydroxyl- 

 ions, into an equimolecular mixture of hydrol and ketone, the latter 

 of which can be again reduced to pinacone. 



This explanation was confirmed by the study of the reduction of 

 ketones by means of aluminium amalgam. 



Here is formed a mixture of pinacone and hydrol ; the pro[)ortion 

 in which these two substances are formed differs from ketone to 

 ketone and now it appeared that the quantities of hydrol ran strictly 

 parallel to tlie velocities with which the diverse pinacones are con- 

 verted into a mixture of ketone and hydrol under the influence of 

 sodium ethoxide. 



Hence, alumininm amalgam in SO"/^ alcohol may by no means 

 be considered as a neutral reducing agent. 



The only modus operandi that gives the necessary guarantee that 

 complete neutrality would prevail during and after the I'eduction is 

 the action of the aromatic ketone on an alcohol under the cooperation 

 of sunlight. The original intention of this part of the research, 



1) Proc. XV! p. 01 and 962 (1913). 



56* 



