ON THE TRANSFORMATION OF AROMATIC NITROAMINES. 83 



Ifc is hoped that by study of a number of substances of suitable 

 constitution iho lehitive activities of directing groups in chlorination 

 might be expressed as numerical values. The investigation is not of 

 the simplest, for direct measurement in the case of an aniline or 

 phenol, and so forth, is rarely possible owing to the very great speed 

 of entrance of the first and often furtlier chlorine atoms. Derivatives 

 in which other gi'oups, such as the nitro- group, are present, must be 

 used in order to obtain a measurable rate of chlorination. Holleman 

 has, in recent years, made attempts to compare the activities of direct- 

 ing groups by nitrating compounds which contain two directing groups 

 and then estimating the proportion of the different nitro- derivatives 

 in the product. By this means he has arrived at certain relations, which 

 can be expressed numerically. Our method has the advantage of being 

 simpler in manipulation, and should at least yield more direct values. 



Experimental Method. — The method of experiment ^ has now been 

 thoroughly tested and has not been modified in these lat^r experiments. 



(1) The Effect of the Nitro- Group. — A nitro- group in the para 

 position with respect to the directing group greatly inhibits chlorina- 

 tion; the effect is still more marked when the nitro- group is in the 

 ortho- position. Tn the case of phenols the nitro- group appears to 

 have some definite specific action ; phenols are chlorinated with" very 

 great speed, but chlorination of o- and p-nitrophenols, especially of the 

 former, is very slow, o- and p-nitroaniline, on the other hand, are 

 chlorinated at speeds which differ little from those observed with the 

 coiTesponding monochloroanilines. Although the amino- group is a 

 far more active directing group in chlorination than the hydroxy- group, 

 this result would indicate that a free hydroxy- group is not present in 

 0- and p-nitrophenol. 



(2) Alhoxy- Groups as Directing Groups in Chlorination. — Measure- 

 ments have shown that the methoxy- and ethoxy- groups have a quite 

 unexpectedly high activity in chlorination. The entrance of the first 

 chlorine atom into anisole, C6H..OCH3, and into phenetole, CeHs.OC^H^, 

 is 'instantaneous.' The values of the velocity-coefficients, hn, for the 

 second chlorine atom, together with those of the corresponding 'phenols, 

 arc given in the table. 



0-Chlorophenol ... 57 Chloroanisole ... 1-5 



;)-Chlorophenol ... 32 Chlorophenetole ... 3-0 



Acetanilide ... 40 p-Chloroacetanilide 0-2 



The alkoxy- groups are less active than the hydroxy- groups, but 

 their value is brought out by a comparison with acetanilide and 

 p-chloroacetanilide. For acetanilide li-„ is 40, whilst for anisole and 

 phenetole it is too rapid for measurement (' instantaneous '), that is, 

 over 1,000; and for p-chloroacetanilide the value is 0"2 as compared 

 with 1'5 or 3"0 for the ethers. 



This high activity of the methoxy- and ethoxy- groups accounts 

 for the high values observed by us ^ in the chlorination of acetoanisidide 



' Oiton and Jones, Reports, 1910 ; Oiton and King, he. cit. 

 ' Oiton and King, loc. cit. 



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