594 
Chemistry. — “On the nitration of the chlorotoluenes”’. By Prof. 
A. F. HorLeEMAN and Dr. J. P. Wipaot. 
When two substituents are present in the benzene nucleus, both 
have a certain influence on the place where a third substituent 
enters. Which of the possible trisubstituted isomers will be obtained 
in a larger quantity depends, as I have shown elsewhere, on the 
velocity of substitution which both of the groups cause. 
If we consider for instance a monochlorophenol the new entering 
substituent places itself nearly exclusively on the ortho- and para- 
places with regard to hydroxyl and not on these places with regard 
to chlorine, because the velocity of substitution, which OH causes 
is much larger than that caused by chlorine. 
By considering all the cases of substitution in the bisubstituted 
benzene derivatives, I found, that the velocity of substitution to 
meta-places is always much slower than that to para-ortho-places, 
and that the substituents that direct a new substituent to the latter 
places cause a velocity of substitution which decreases in the 
following order: 
OH>NH,>halogens >methy] 
As the halogens and methyl cause no large difference in the 
velocity of substitution, it should be expected, that the entrance 
of a third group takes place para-ortho as well to the halogen as 
to methyl. Indeed, Conen and Dakin proved in an excellent and very 
laborious research that in the chlorination of erthochlorotoluene all 
the four possible chloro-o-chlorotoluenes are formed and in the chlorin- 
ation of p-chlorotoluene the two possible dichlorotoluenes, whereas with 
EEL CH? meta-chlorotoluene the same operation 
ee CI AS procured the isomers I and II, but not the 
| I | and I 1 ) symmetrical dichlorotoluene, just as might 
| ' Cl Cl be expected, because neither chlorine 
be 2 
C] nor“ methyl direct a substituent to meta- 
places. 
In order to get an insight in the ratio of these velocities, it is 
necessary quantitatively to determine the proportions in which the 
isomers are formed; and as nitrations are generally not attended with 
production of secondary products, we resolved to study again the 
nitration of the monochlorotoluenes. Through former investigations it 
was known, that o-chlorotoluene yields the product CH,,C],NO, = 1,2,5 
(Gotpscumipt, Hoxie, B. 19, 2440), m-chlorotoluene yields the isomers 
CH,,CLNO, =1,3,4 and 1,3,6 and para-chlorotoluene yields the 
isomers CH,,CI,NO, = 1,4,2 and 1,4,3. The latter nitration had been 
