1- Chloronaphthalene-4-sulfonic acid

Chloronaphthalene (79 X = Cl) reacts with chlorosulfonic acid in c bon disulfide in the cold to yield mainly the 8-sulfonic acid (81 X = Cl), together with a little of the 6-sulfonic acid (80 X = Cl) (4%). By treatment of (79 X = Cl) with excess reagent in chloroform, the 8-sulfonyl chloride was formed. 2-Bromonaphthalene similarly reacted with chlorosulfonic acid in chloroform to give a mixture of the 6- and 8-sulfonic acids together with some sulfonyl chloride " and with excess reagent in chloroform the 8-sulfonyl chloride was again obtained. ... 

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