| abstract |
Diphenyl-4,4'-disulfonic acid is prepared by sulfonating diphenyl with sulfur trioxide in the presence of an inert solvent. For this purpose, diphenyl and sulfur trioxide are reacted at a temperature of -30 ° C. to + 60 ° C. in such a way that the ratio during the bringing together of the reactants is 2-3 moles of sulfur trioxide per mole of diphenyl. Examples of suitable solvents are chloroalkanes, such as methylene chloride, or sulfur dioxide. The reaction can be carried out in the presence of an inhibitor that suppresses sulfone formation. Before starting the sulfonation, a small amount of diphenyl-4,4'-disulfonic acid can also be placed in the reactor. |