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4-Chlorobenzenesulphonic acid is the major polar by-product formed during the chemical synthesis of 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)ethane (DDT).
C 2020 (OTTO) p-Chlorobenzenesulphonic acid, 90% Cas 98-66-8 - used to synthesize a variety of sulfonyl azides.