ON ISOMERIC NAPHTHALENE DERIVATIVES. 271 



Chief product of action 

 Chief chloride. of potash on chloride. 



HCl CI 



/\^\ S0,C1 HCl /'^.'^ SOX'l /^/^i SO3K 



HCl 



HCl CI 



The influence of the substituent both as affecting tlie addition of 

 chlorine and the elimination of hydrogen chloride is especially note- 

 worthy. It will be seen that the sulphochlorides behave alike, but the 

 two chloronaphtbalenes dissimilarly towards chlorine, and that each 

 compound decomposes in a manner peculiar to itself on treatment with 

 alcoholic potash. 



As yet no evidence has been obtained that a heta-hromo-, chlorp-, or 

 nitro-derivative may result by isomeric change from a previously formed 

 aZp^a-derivative. 



With regard to the suIpJwnic acids, on reference to the previous 

 table in which the constitution of the acids formed on sulphonating 

 the ten dichloronaphthalenes is indicated, it will be observed that in some 

 cases an a- and in some cases a /3-sulphouic acid is formed, or a mixture 

 of both. Mr. Wynne and the writer have expressed the opinion that the 

 a-acid is always initially produced, and that in some cases this is so 

 unstable that it spontaneously passes over into the ^-isomeride and 

 escapes observation, while in others it is partially preserved. They base 

 this conclusion on the fact that in all cases hitherto studied in which both 

 acids are formed it is possible to convert the a- into the y8-acid by heating. 

 Thus 1 : 2-dichloronaphthalene affords about two-thirds a- and one-third 

 yS-acid ; but when the product is heated the latter is practically the sole 

 product. In like manner the initial product of sulphonation from 

 1 : 3-dichloronaphthalene contains about one-fifth /3-acid ; but if it be 

 heated at 160° during eighteen hours complete convei'sion into the yS-iso- 

 meride is effected. 



Should this conclusion with reference to the manner in which beta- 

 sulphonic acids are formed be ultimately established it would follow that, 

 unlike nitric acid, sulphonating agents regularly act in one way, and that 

 the formation of the addition compound takes place in such a manner 

 that the sulphonic radicle always attaches itself in an alpha-position. 



Isomeric cltange in the case of sulphonic acids. — The problems which 

 this subject presents are of extreme interest ; some idea of their character 

 is afforded by the following example. When heated at about 150-160'* 

 1 : 4 a-chloronaphthalene sulphonic acid undergoes a change into the more 

 symmetrical ftZ^/tot-isomeride, while 2 : l'-y8-chloronaphthalenesulphonic 

 acid is converted in a similar manner into the more symmetrical leta- 

 isomeride — results which may be regarded as indicative of a tendency to a 

 final state of symmetry, thus : — 



In the case of the dichlorosulphonic acids it is noteworthy that tlie 



