Chemistry. — “The velocity of the diazotisation reaction as a contri- 
bution to the problem of substituiion in the benzene nucleus.” 
By Prof. J. BörseKeN, W. F. Branpsma and H. A. J. SCHOUTISSEN. 
(Communicated at the meeting of February 28, 1920). 
1. In regard to the problem of tbe substitution in benzene, the 
question has been considered whether only the group already present 
is decisive as to the place where the group newly introduced is to 
come or whether the nature of that new group too plays an 
important part. 
Supposing the last alternative to be right, one of us *) has projected 
the following scheme of the subsequent stages during the substitution, 
by which at the same time the answer was given to the question 
why in one case meta-, in another case para- and ortho-derivatives 
are formed by preference. 
If the acting molecule has an inclination to combine with group 
X of the benzene derivative C,H,X, then two courses may be taken: 
a. The acting molecule combines or reacts with this group; then 
no substitution in the nucleus takes place. 
6. The acting molecule has some inclination to combine with 
group X, which inclination however only tends to effect a shifting 
of affinity (electrones). In this case a change of condition will take 
place in the benzene nucleus, designated by him as a ‘“chinoid 
shifting of the affinities’, and which consists of an accumulation of 
attraction at the para and at one of the ortho places. 
If the acting molecule has no inclination to combine with group 
X, then no preference will be shown for ortho- and para-substitution 
and substitution of the meta H-atoms is sooner to be expected. 
The stress in these considerations is therefore laid on the affinity 
between the molecule to be introduced and the group already present ; 
an experimental illustration and eventually ‘a comfirmation of this 
theory may be expected, if quantitative data can be acquired on 
this reciprocal effect. When e.g. we could determine the rate of 
1) BOESEKEN: Koolwaterstoffen Il, (Hydrocarbons II, edited by WALTMAN, Delft) 
page 125 —127 and 134—137. See also these Proc. of March 30, 1912, 
