B5() 



namely tlie tracing of the progressive change of the reduction, was 

 soon attained by applying tliis method. 



A series of ketones dissolved in u great variety of alcohols and 

 a few othei' substances, was exjmsed lo sunlight (or to the light of 

 the quartz-lamp) ; 'in nil cast's irherc induction set in. not a trace of 

 Injdrol mas ohtahicd. 



The ketone was usually quantitatively converted into pinacone ; 

 occasionally, namely with benzylalcohol and a prolonged exposure 

 to sunlight a cond)ination ol" the half pi]iaconc molecule with a 

 group of the benzylalcohol, namely tri])henylglycol was obtained as 

 a by-product. ^). 



When to the alcohol some etlioxide was added hy drol was formed, 

 as was to be fully expected. 



Hence, we arrive at the result that in the reduction of aromatic ketones 

 the h) drogen unites exclusively with the oxygen. 



The experiments were carried out as follows : 



Ouantities of 5 grams of the ketone were dissolved in 50 cc of 

 alcohol rendered carefully anhydrous ') and ex|)Osed in sealed tn.bes 

 of common glass to direct snnlight. 



The drying of the lower terms was pei-formed by snccessively 

 boiling with CaO, allowing to lemain over metallic calcinm at 0°, 

 and distilling ; the Ingher ones were purified l)y distillation and both 

 were then immediately sealed into the tube together with the ketone. 

 After exposnre to the light for some time, during which the conrse 

 of the reduction conld be traced by noticing the deposition of the 

 sparingly soluble pinacone, the tube was opened, the pinacone was 

 tillered off, the tiltrate distilled, the residue united with the pinacone 

 and in the distillate the aldehyde or ketone was tested and in 

 some cases determined quantitatively. 



The exact details will be published elsewhere by one of ns, a 

 few remarks may snffice here. 



First of all was investigated the behaviour of benzophenone in 

 regard to methyl, ethyl, «-propyl, .sy^c- propyl, wo-bntyl, ;i-heptyl, 

 sec.-OQ,iy\ and cetylalcohol. The latter only was not attacked, not 



1) This had already been noticed by Ciamician and Silber (B. 3(5,1577(1903)); 

 the formation thereof is moreover a confirmation of our conception that as the 

 first reaction product the half pinacone molecule is formed. 



~) Water acts in this reaction in a remarkable manner as a powerful negative 

 catalyst ; in 80 "/„ alcohol no reduction takes place after exposure for months, 

 whereas in absohjte alcoliol in the same conditions, about two grams of pinacone 

 are formed during ten hours' action of sun-light. 



