1S 
Chemistry. — “On the velocity of substitutions in the benzene 
nucleus.” By Dr. F. B. C. Scnerrer. (Communicated by Prof. 
A. F. HOLLEMAN). 
(Communicated in the meeting of Jan, 25, 1918). 
1. In the preceding paper the dependence of the velocity con- 
stant on the temperature was represented by the equations ; 
dink &,— & I 
ae Re 8 
and 
ET, 
Inis tk a Gee 
——— (2) 
and it was shown that the greater part of the experimental data 
allows the substitution of a constant value for e — «. According to 
the considerations of the preceding paper this value furnishes a 
pretty accurate measure for the energy difference between the react- 
ing substances and the intermediate state during the reaction, at 
least if the velocities have been measured with sufficient accuracy, 
and the value of the energy difference is not too small. 
In order to arrive at an opinion about the efficiency of these con- 
siderations and the equations 1 and 2 derived from them, I have 
tried to apply the latter to the experimental data. IT have for this 
purpose tried to find those examples where we may expect the sim- 
plest behaviour, and in my opinion they are to be found in the 
department of organic chemistry. 
If we imagine a reaction which is indicated by the equation of 
reaction A+ B=... and if we determine the reaction velocities 
at different temperatures, the above mentioned energy value can be 
calculated. If we then replace the molecule A by another A’, we 
can find the required quantity of energy also for the reaction of this 
molecule A’ with B, and in this way obtain an insight into what 
influence a substitution of <A’ for A exercises on the differences of 
energy with the intermediate state. 
Let us e. g. suppose that the molecule benzene is nitrated ; we 
might then calculate from measurements of the nitration velocity at 
different temperatures what quantity of energy is required to force 
the nitric acid molecule into the sphere of action of one of the hy- 
drogen atoms in the benzene nucleus. If we then replace the mole- 
cule benzene e. g. by chloric benzene, we can calculate the quantity 
of energy required for this reaction also by measurement of the ni- 
