Chlorine in chlorosulfonation

Indanthrene blue RS dyes cotton a pure, deep blue from its blue hydrosulfite vat. The dye has exceptional light fastness. Its fastness to chlorine is only moderate, but this can be improved by chlorination. This cUorination can be effected by the action of chlorine on the sulfuric acid solution in the presence of sodium nitrite (GCD brand), by the action of sulfuryl chloride on the nitrobenzene solution (BCS brand), or by the action of chlorine in chlorosulfonic acid, possibly in the presence of a carrier such as iron chloride or antimony pentachloride. 

The sulfonation of l-(2-hydroxyethyl)-2,4,6-trinitrobenzene 114 by reaction with chlorosulfonic acid followed by treatment with aqueous ammonia yields novel energetic sulfonate salts 115 (Equation 37). These salts can be used in conjunction with ammonium nitrate in explosive formulations. Studies of the relative reactivity of nitrobenzene and w-chloronitrobenzene towards chlorination in chlorosulfonic acid showed that the former compound was 4.77 times more reactive. 

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