mi) 



group, because 4-phenjlbenzophenone (14) and the two phenjl- 

 riapbthylketones (J 5 and 16) are not reduced. 



Halogen atoms and metlijl groups do diminish the single substitution, 

 but (with one exception) do not prevent the same. Para substitution 

 has the least influence, ortho the greatest; this, howevei' does not 

 apply to the cidorobenzophenones (3), so that we can hardly speak 

 of a universal rule. 



The symmetry of the molecide seems to accelerate the velocity. 



Whereas the 4-methjlbenzophenone has a smaller velocity than 

 the benzophenone (5), the 4.4'-dimethylbenzophenone has a somewhat 

 greater one. The fairly considerable decrease in velocity in the 

 4-chlorobenzophenone (4) is not continued in the 44'-dichlorobenzo- 

 phenone (9). In connexion with the considerable decrease in the 

 2-chlorobenzophenone (2) that in the 2.2'.4.4'-tetrachlorobenzophenone 

 (10) is unexpectedly high. 



A remarkable fact is the slight influence of the methyl group on 

 the meta position (18) in regard to the great one of the chlorine atom (3). 



2"^^. Of more importance is the fact that the alcohol, the reducing 

 agent, is of very secondary significance as regards the ratio of the 

 reduction velocities; this is shown from the comparison of tables 

 V and VII. The ratio of the velocities in ethyl and amy! alcohol 

 is practically the same. We have completed these observations with 

 a few on methyl and propyl alcohol, selecting methyl alcohol because 

 the velocities therein are generally much less, whereas o-chloro- 

 benzophenone with benzophenone were compared as ketones, because 

 the velocities in ethyl (and amyl) alcohol diffei' strongly. 



The subjoined table VIII gives a surv^ey of the results. 



TABLE VIII. 



