220 



SCIENCE PROGRESS 



This change being accompanied by the reproduction of a 

 molecule of hydrogen chloride the cycle of operations could 

 be repeated until a steady state ensued. As the secondary 

 chlorination of the benzene ring is not accompanied by any 

 reverse action the conversion of the chloro-amide into a stable 

 ring-substituted compound would in this case be complete. 

 The transference of the halogen into the ring may therefore, 

 as an alternative hypothesis, be regarded as an example of 

 simultaneous chlorination and reduction, comparable with the 

 /3-bromination of camphor, and involving no special mechanism 

 peculiar to the interconversion of isomers. 



It is of interest to notice that owing to the affinity of 

 hydrogen chloride for water the extent to which the amino 

 group of the anilides is acted on by chlorine varies very greatly 

 with the proportion of water in the acetic acid that is used 

 as a solvent : the effects are, indeed, so pronounced that as a 

 rule no interaction at all takes place in glacial acetic acid, 

 although in some cases the nucleus is directly chlorinated. 

 The chlorination of the amino group can however be brought 

 about, either by the addition of water, of which 50 per cent, 

 is sufficient to ensure practically complete interaction, or by 

 adding a molecular proportion of sodium acetate to remove the 

 hydrogen chloride, when about 90 per cent, of the chlorine reacts. 



(6) Transference of a Sulphonic Group. — The introduction of 

 a sulphonic group into the benzene nucleus is probably de- 

 pendent in many cases on the sulphonation of a —OH or 

 — NH 2 group and the subsequent wandering of the — S0 2 . OH 

 into the 0- or /-position, by a process precisely similar to that 

 by which a halogen atom enters the ring system of the anilines 

 .and anilides. 



OH O.SO...OH OH OH 



SO.,. OH 



-> 



SO,. OH 



Phenyl sulphate o- and ^-Phenolsulphonic acids 



NH.SO,.OH NH 3 NH, 



-> Q S0 ^ H 



Aniline 



Anilino-sulphonic acid 



SO...OH 



o- and />-Sulphanilic acids 



The sulphonation of naphthalene compounds has been fully 



