96 



EEPOET — 1888. 



Third Report of the Committee, consisting of Professors Tilden: 

 and Armstrong {Secretary), appointed for the purpose of in- 

 vestigating Isomeric Naphthalene Derivatives. {Drawn up by 

 Professor Armstrong.) 



The folio-wing is an outline of the -work accomplished during the past 

 year in the reporter's laboratory chiefly with the invaluable co-operation 

 of Mr. W. P. Wynne, B.Sc. 



In discussing the laws of substitution for naphthalene, attention was 

 directed in the tirst report to the alpha-lav: as the dominant law; and it 

 was pointed out that whenever departures from this law occur, as a rule, 

 either the conditions are such as to favour secondary changes — as in the 

 formation of /3-sulphonic acids at high temperatures in presence of an 

 excess of sulphuric acid — or a radicle such as OH or NH2 is present 

 which exercises a special influence. It was mentioned, however, in the 

 same report, that when /D-chloronaphthalene is sulphonated by means of 

 SO3HCI, two isomeric acids are formed which there is reason to believe 

 a.re represented by the formulae : — 

 SO3H 



or 



HSO. 



a-acid. SO^H /3-acid. 



The conditions are such that the formation of the /5-acid cannot be- 

 attributed to the occurrence of secondary changes such as in all pro- 

 bability take place when sulphuric acid is the agent ; the production of this 

 derivative, therefore, cannot well be reconciled with the alpha law, but 

 is suggestive of the existence in the naphthalene molecule of a ' plane of 

 symmetry ' passing through the /t3''^/3"''-carbon atoms in which an influence 

 is exercised. The observations on isomeric change briefly described in- 

 the last report prompted us, however, to determine whether the a-acid 

 could not readily be converted into the /3-acid by heating : the results 

 entirely favour the view that the latter acid is in reality the product of 

 isomeric change, and that its formation is in no way an exception to the 

 alpha-law. When the snlphonation was effected in the cold, only three 

 to four per cent, of the product consisted of the /3-acid ; after heating the 

 product at 100° for half an hour the amount rose to eleven per cent.; 

 heating at 150° for one hour increased the proportion of /3-acid to twenty 

 per cent. ; and no less than fifty-three per cent, was present after heating 

 at 150° for five hours. 



These results have led us to study the behaviour of the chloro- 

 naphthalenesulphonic acids generally when heated, in order to determine 

 whether, and in what way, they undergo isomeric change. In preparing 

 the necessary material for these experiments we have converted the four 

 isomeric modifications of betanaphthylaminesulphonic acid by Sandmeyer's 

 method into the corresponding chloronaphthalenesulphonic acids, and 

 by distilling these with phosphorus pentacbloride have prepared the cor- 

 responding dichloronaphthalenes. The designation of the amido-acid, the 



