ox ISOMERIC NAPHTHALENE DlJaVATIVE?. 269 



One of these exceptions is that afforded by the formation from napli- 

 thalene 1 : 3' disuliilionic acid on nitnition of a nitro-acid of the formula 



(cf. 'Chem. Soc. Proceedings,' 1801, p. 27) ; this acid, however, is but a 

 subsidiary product, the main product being an acid of the formula 



NO,, R 



It has long been known that when the 1 : 4' disulphonic acid is 

 nitrated, it yields an ct-nitro-acid ; recently Mr. Wynne and the writer 

 Lave found that the product also contains the isomeric /3-nitro-acid. 



Other exceptions are afforded by the production of beta-chloro- and 

 bromo- naphthalene on cblorination and brominationof naphthalene;' and 

 by the pi'eSence of a certain proportion of beta-naphthylamine in com- 

 mercial alpha-naphthylamine — a proof that naphthalene yields some beta- 

 nitronaphthalene on nitration ; the writer's attention has been called to 

 this last fact both by Dr. H. Caro and by Professor Noelting. 



Lastly Mr. Rossiter and the writer have found that beta-naphthol 

 when brominated yields a dibromo-derivative of the formula 



Br 



and in this case there appears to be no alpha-compound formed, so that 

 the departure from the alpha-law is complete. 



But the explanation of these results is not difficult. In no case 

 probably is the substitution derivative the direct product of change ; but 

 its formation is preceded by that of an addition compound. This is 

 generally admitted in the case of chloro- and bromo-derivatives, but 

 evidence of the formation of addition compounds has not hitherto been 

 forthcoming in other cases. Mr. Rossiter and the writer, however, have 

 recently given proof that a compound with nitric acid is initially formed 

 in the process of nitration.'^ Obviously, in the case of a symmetrical 

 molecule such as that of bromine, either an alpha- or a beta- derivative will 

 result, according as either the beta- or the alpha-atom of bromine becomes 

 eliminated from the bromide, thus : — 



HBr Br 



HBr H 



^/\ HBr /\/\ Br 



I \^^^ = I I I + HBr 



• Cf. Chevi. Soc. Proceedings, 1890, p. 85. - IhiiL, 1891, p. 89. 



