ON ISOMERIC NAPHTHALENE DERILATIVES. 



293 



xjhloronaphthalenes (cf. Armstrong and Wynne, 'Proc. Chem. Soc' 1897, 

 152). 



It has been found that the chloronaphthalene-disulphonic chlorides 

 «,fford a relatively small amount of trichloronaphthalene, and that a con- 

 siderable portion of the product is an intermediate compound — the di- 

 chloronaphthalene-wiono-sulphonic chloride. From the results obtained 

 in the case of several u-/3-disulphonic acids, it appears that of the two, as 

 was to be expected, the a-sulphonic group is the more readily displaced. 



A series of remarkable observations have been made of the occurrence 

 ■of isomeric change in the case of 1 : I'-dichloronaphthalene and its deri- 

 vatives. 



The a-sulphonic acid of 1 : I'-dichloronaphthalene is hydrolysed at 

 about 230°, and gives only 1 : I'-dichloronaphthalene whatever be the 

 ■hydrolytic agent used. The /3-sulphonic acid represented by the formula. 



CI 



CI 



S 



however, which cannot be hydrolysed below 285°, gives one or other of no 

 fewer than three isomeric dichloronaphthalenes — the 1 : 1', 1 : 2', or 1 : 4' 

 modifications — according to the agent used. 



When hydrolysed at 290° by means of a solution containing 1 per cent, 

 of sulphuric acid or one containing about 50 per cent, of phosphoric acid, 

 it behaves normally, yielding 1 : I'-dichloronaphthalene. But if stronger 

 solutions of either acid be used, much of the salt is carbonised, and in this 

 case a small amount of 1 : 4'-dichloronaphthalene is obtained as the sole 

 volatile product. When concentrated muriatic acid is used as the hydro- 

 lytic agent, as much as 20 percent, of the theoretical amount of the 1:4'- 

 conipound is formed. 



Lastly, if the potassium salt be mixed with sulphuric and phosphoric 

 acids, and superheated steam be passed through the mixture, 1 : 2'-di- 

 chloronaphthalene is the sole product of hydrolysis. In this last case it 

 is not improbable that further sulphonation precedes hydrolysis, and that 

 this has the eflTect of preventing the transference of chlorine to the para- 

 position, so that the 1 : 2' is formed instead of the 1:4' modification ; 

 thus : 



CI 



CI 



CI 



CI 



CI 



CI 



CI 



CI 



The tricliloronaphthalenes derived from 1 : 4'-dichloronaphthalene are 

 also, it appears, susceptible of ' isomeric ' change. 



Considerable attention has been paid during the year to the study of 

 the derivatives of a-methoxy- and «-ethoxy-naphthalene in comparison 

 with those of a-naphthol. It appears to be a much less ' active ' compound 



