C07C309/52 - CPC Classification

Sulfonic acids; Halides, esters, or anhydrides thereof; Sulfonic acids having sulfo groups bound to carbon atoms of six-membered aromatic rings of a carbon skeleton containing nitrogen atoms, not being part of nitro or nitroso groups, bound to the carbon skeleton the carbon skeleton being further substituted by doubly-bound oxygen atoms

• C07C309/53 » the carbon skeleton containing carbon atoms of quinone rings 4

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