ON ISOMERIC NAPHTHALENE DERIVATIVES. 233 



3. On treating the ? /3-disulphonic acid referred to in the previous 

 report with PCI5 a dichloronaphthalene is obtained which also melts at 

 about 61°-5 ; this, however, yields a snlpho-acid distinct from that 

 obtained from the dichloronaphthalene from jS-CioHyCl, the melting- 

 point of the sulphochloride being 150°. 



4. Cleve has recently described a dichloronaphthalene melting at 61°'5 

 which he prepared from dichloro-a-naphthylamine. On sulphonating this 

 modification an acid is obtained which is identical with that prepared 

 from the dichloronaphthalene from the ? ^-naphthalenedisulphonic acid. 

 It is proposed to provisionally term this dichloronaphthalene 1ietero-6- 

 dichloronaphtJtalene = ^'-CioHeCla, as there is reason to believe that it is a 

 heteronucleal compound — probably it is 2':4 CioHgCl2. 



5. It will assuredly be found on examining the two dichloronaphtha- 

 lenes melting (?) at 61° prepared from Cleve's two nitro-/3-sulplionic 

 acids, that the one is the homo- and the other the /teiero-^-modification. 

 That obtained from Bayer's modification of /3-naphtholsulpbonic acid is 

 doubtless hetero-6-dichloronaphtlialene : the conclusion arrived at by Clans, 

 that this acid is a 2:3 di- derivative" is not only opposed to all that is known 

 of the behaviour of naphthalene compounds, inasmuch as it involves the 

 assumption that on sulphonating /?-naphthol the second /8-position con- 

 tiguous to the hydroxyl becomes displaced ; it is untrustworthy, as the 

 dichloroquinone which he obtained may have been, and doubtless was, 

 produced by the action of chloi'ine liberated during the process of oxida- 

 tion ; and there is reason to believe that the dichloronaphthalene corre- 

 sponding to such an acid would be the i-modification, which melts at 120°. 



Isomeric change in the naphthalene series. — One of the most strik- 

 ing cases of isomeric change known is that of jS-naphthylsulphate, 

 C10H7.OSO3H, into Schaefer's modification of /3-naphtholsulphonic acid 

 by mere warming on the water-bath (' Berichte,' 1882, p. 204). The 

 conversion takes place in the absence of sulphuric acid, and witli such 

 ease that there can be practically no doubt that it is a true case of 

 isomeric change ; and it is not probable either that the sulpho-group 

 becomes displaced and re- enters the molecule in another position, or that 

 one molecule acts upon another so that an exchange of sulpho-groups is 

 effected. This view is supported by the following more recent observa- 

 tions : first, that if bromo-/3-uaphthol be submitted to the action of 

 SO3HCI at ordinary temperatures, the resulting product contains very 

 little of the sulphate CioHgBr.O.SOall, but chiefly consists of the 

 bromonaphtholsulphonic acid which is formed on brominating Schaefer's 

 naphtholsulphonic acid. 



Again, if ^-naphthylsulphate be acted upon by SO3HCI without 

 heating, not only is a second sulpho-group introduced, but that already 

 present sioontaneously changes its position : a clisulphonic acid is thus pro- 

 duced, which is characterised by the readiness with which it parts with 

 one of its sulphonic radicles being converted into Schaefer's monosul- 

 phonic acid; it i.s probable that the sulpho-group, which is easily dis- 

 placed occupies the a-position contiguous to the OH group. The disul- 

 .phonic acid here referred to itself undergoes isomeric change when heated, 

 but the nature of the product is not yet finally determined. 



Lastly, experiments have been made at my suggestion by Mr. E. G. 

 Amphlett, in which the formation of the sulphate has been prevented 

 by ethylating the naphthol ; and it appears that, on sulphonating 

 /S-CioHj.OCoHj at ordinary temperatures, by means of SO3HCI, a mixed 



