268 KEPOKT— 189i. 



Isomeric Naphthalene Derwatives. — Eighth Report of the Committee, 

 consisting of Professor W. A. Tilden and Professor H. E. Arm- 

 strong. {Brawn up by Professor Armstrong.) 



The Conversion of Sulphochlorides into the corresponding Chloro- 

 derivatives. — In the case of naphthalene derivatives no interaction is of 

 greater practical importance than that which occurs when sulphochlorides 

 are heated with phosphorus pentachloride, whereby they are converted 

 into chloro-derivatives. At one time it was argued that reliance could 

 not be placed on this interaction as a means of determining constitu- 

 tion, but of late years no such objection has been raised, and the idea 

 that isomeric change may attend the displacement of the sulphonic radicle 

 by chlorine appears to have been abandoned. The results obtained, 

 especially by Cleve and by Dr. Wynne and the writer, are so uniformly 

 consistent inter se that, bearing in mind the extent of the field covered, 

 there is no longer room for doubt. Observations made during the past 

 year are of interest as throwing light on the nature of the interaction. 



There have long been instances on record of the conversion of sulpho- 

 chlorides into corresponding chloro-derivatives and sulphur dioxide 

 (E,S02Cl=RCl-f SO2) by mere distillation. The successful use recently 

 made of this method in the writer's laboratory in preparing chloro- and 

 bromo-derivatives of camphor by Dr. Kipping and Mr. Pope has led him 

 and Dr. Wynne to systematically study the behaviour of naphthalene 

 sulphochlorides, which they had long known underwent decomposition, 

 evolving sulphur dioxide, when heated. The conclu.sion arrived at is that, 

 in all probability, phosphorus pentachloride acts merely by facilitating the 

 resolution of the sulphochloride into sulphur dioxide and the chloro-deriva- 

 tive by attacking the former and converting it into thionyl chloride ; and 

 that, in fact, the chlorine in the chloro- derivative is not improbably the 

 original chlorine of the sulphochloride and not chlorine derived from the 

 pentachloride. In most cases the amount of chloro-derivative produced 

 by directly distilling the sulphochloride is inferior to that obtained by means 

 of pentachloride, as the decomposition is facilitated by the chloride, and 

 therefore takes place at a lower temperature in its presence. There is 

 always more or less of a resinoid condensation product formed on distilling 

 the sulphochloride, but the amount is in some cases very small, while in 

 others practically nothing else is obtained. On the other hand, in the 

 case of compounds which are very readily chlorinated, the method permits 

 of the production of chloro-derivatives corresponding to the sulpho- 

 chlorides which are almost unprocurable from them by the ordinary method. 

 For example, 1 : I'-chloronaphthalenesulphonic chloride yields a very large 

 proportion of 1 ." I'-dichloronaphthalene when distilled, although when 

 heated with phosphorus pentachloride it is almost entirely converted into 

 1:4:1' trichloronaphthalene. The a-sulphochlorides appear all to 

 decompose more readily and to yield a larger proportion of chloro-derivative 

 than do the /j- sulphochlorides. It may be added that, taking into account the 

 readiness with which change occurs during sulphonation, the non- occurrence 

 of isomeric change on distilling sulphochlorides is probably significant. 



Bromo-derivatives of Naphthalene. — The conversion of naphthalene 

 sulphobromides into corresponding bromonaphthalenes by means of phos- 

 phorus pentabromide is attended with great difficulty, as the bromide 

 frequently acts almost exclusively as a brominating agent, owing to the 

 readiness with which it is resolved into the terbromide and bromine. Far 



