966 



One gets tlie impression tiiat in the reduction of benzophenone 

 and its derivatives, the oxvgen only is attacked and that on gentle 

 reduction tiiere talies place au exclusive addition of a hydrogen atom 

 to the oxygen. Whatevei- happens afterwards has nothing more to 

 do with that reduction. 



If there arc no ()H-lons, j)inacone ^) is formed, hut if these are 

 present a s|)littiug into hydrole and ketone taUes place and the latter 

 can be again attacked by the hydrogen. If the hydroxyl-ions are 

 exclusively present in the boundary layer, we shall obtain a definite 

 proportion of pinacone and hydrole; if the}' are found also in the 

 solution in a sufficient concentration all the ketojie is converted 

 into hydrole. 



In the case of a very violent reducliun, lor instance, with zinc amalgara and 

 strong liydrochloiic acid ~) the oxygen seems al>o to be allacked by preference 

 and becomes apparently completely detached ; the residual molecular part now, 

 however, also absorbs hydrogen and is converted into hydrocarbon. 



2. The progi'essive change of the gentle reduction is herewith 

 explained in general traits, at least in so far purely aromatic ketones 

 are concerned. 



The hydrole formation thus depends in the first place on the 

 facility with which pinacone gets resolved and this is in a high degree 

 promoted by alkalis. 



This action of bases, has meanwhile been much elucidated by the 

 researches of W. Scuknck, T. Weickki., and A. Th.al (B. 44, ij83 

 (J91i) and 46, 2840 (1913). There it was shown that pinacones 

 form with the alkali metals conipouiuls of the trivalent carbon, for 

 instance (C6H5).^COK; we notice that the central C — C-bond, which in 

 the ketones is not particularly strong, becomes much looser still 

 under the influence of these metals so that the half pinacone mole- 

 cules, under the influence of the metal atom, can indeed lead a 

 free existence. 



In the comparatively faintly alkaline solutions matters will not 

 proceed so far, but here those central carbon atoms can detach 

 themselves from each other in consequence of an intramolecular 

 displacement of atoms : 



^C^HJ^ C— H {C,¥L,\ CO 



(C,H,),C-0 H "^ (C«H,),CHOH 

 in which the mobile H-atoms will play a role. 



1) We have exposed a whole series of ketones in absolute alcohol to the action 

 of light and never obtained a trace of liydrole. 



2) E. Clemmensen, B. 46, 1887, (1913). 



