AbstractThe sulfation and sulfonation resulting from the reaction of the dihydroxybenzenes and their mono‐ and dimethyl ethers with SO3in nitromethane have been studied, and their product distributions are reported. As to the non‐hydroxy‐substituent‐containing substrates, 1,2‐dimethoxy‐benzene (3) yields the4‐sulfonic acid (3‐4‐S) which, upon further sulfonation, yields a 1:4 mixture of the 3,5‐ and 4,5‐S2. The 1,3‐ (6) and 1,4‐isomer (9) yield initially the 4‐ and 2‐S, respectively, and subsequently exclusively6‐4,6‐ and9‐2,5‐S2, respectively.With the substrates containing one hydroxy substituent, the sulfonation isomer distribution is dependent on the SO3to substrate ratio if the OH and OMe substituents are inorthoorparaorientation, due to increasing sulfonation of the corresponding methoxyphenyl hydrogen sulfate. Thus, 2‐methoxy‐ (2) and 4‐methoxyphenol (8) with one equiv of SO3at 0°C yield a 3:1 mixture of2‐4‐S and2‐5‐S and a 9:1 mixture of8‐2‐S and8‐3‐S, respectively, but, with ≥4 equiv of SO3, the former reactant yields only2‐5‐S and the latter only8‐3‐S. 3‐Methoxyphenol (5) yields initially a 1:1 mixture of the 4‐ and 6‐sulfonic acid. Further sulfonation yields only5‐O,4,6‐S3which slowly cyclizes to the 1,3,2,4‐benzodioxadithiin 2,2,4,4‐tetraoxide derivative11.As to the dihydroxy‐containing substrates, 1,2‐dihydroxybenzene (1) with 1 equiv of SO3first yields the hydrogen sulfate 1‐O‐S which rearranges to1‐4‐S; on using an excess of SO3, the eventual product isl‐O(2),4‐S2. Similarly, the 1,4‐isomer (7) with 1 equiv of SO3yields initially7‐O‐S which isomerizes to7‐2‐S. With 6 equiv of SO3, initially7‐O,O‐S2is formed and subsequently its 2‐sulfonic acid, which eventually cyclizes slowly to the 1,3,2,4‐benzodioxadithiin 2,2,4,4‐tetraoxide derivative12. The 1,3‐isomer4with 1 equiv of SO3yields the 4‐sulfonic acid. With 4 equiv of SO3, initially4‐O,O‐S2is formed and subsequently4‐4,O,O‐S3, which is converted in