g's 
tration velocity, and obtain an insight in this way into what in- 
fluence the chlorine atom in the benzene has on the required quan- 
tity of energy for the substitution. In this way a value can then 
be found which ean quantitatively be expressed for that which is 
generally expressed by the intensity of the binding of the atoms which 
are liable to substitution. 
Such calculations, however, cannot be carried out in the absence 
of the required material of facts. Determinations of velocity of sub- 
stitutions as mentioned above have been hardly carried out as yet; 
though Prof. HorrrMAN and his pupils have collected a considerable 
number of data on the relative velocity of the substitution of the 
different hydrogen atoms in the same aromatic molecule. All these 
measurements refer to simultaneous reactions, and it is just for this 
kind of reactions that the application of the above mentioned 
equations is very simple. 
When we expose the molecule toluene to the action of nitric acid, 
three substitutions appear simultaneously. In the toluene three diffe- 
rent kinds of hydrogen atoms liable to substitution occur, two on 
the ortho-, two on the meta, and one on the para-place with respect 
to the chlorine atom. So we have here three reactions proceeding 
simultaneously, each with a definite velocity constant. If we now 
want to apply the above equations we must first of all bear in mind 
that the velocity constant is determined by the energy and entropy 
difference required for the substitution, and that accordingly if these 
quantities were equal for the ortho-, meta-, and para-substitution, 
there would yet be formed twice as many ortho- and metadisubsti- 
tution products as paraproducts, because in a definite quantity of 
toluene there are twice as many ortho- and metahydrogen atoms 
liable to substitution, as para-hydrogen atoms. If therefore the ve- 
locity constants for ortho-, meta-, and para-substitution are repre- 
sented by £,,4m, and &,, the substitution velocities v,, v,, and Vv, are 
represented by the equations: 
ee Wie 2 DP 
v, = 2k, “C;H;Cl HNO; ? (2a) 
4 == 1 an ’ ») 
Um ZE Dn CC: H;CI CHNOg e e e e . . ° (2b) 
and 
Op ki og mrt NOg 0 et es C6) 
The ratio of the quantities ortho, meta-, and para-products, which 
are formed in the unity of time, therefore, amounts to 2%, : 2h: : hi; 
hence it is independent of the time. If therefore the reaction is 
allowed to proceed regularly to its close, or if it is stopped at an 
arbitrary moment, the ratio of the obtained substitution products is 
73 
Proceedings Royal Acad, Amsterdam, Vol, XV, 
