Abstract
AbstractThe homogeneous sulfonation of 1,2‐dihydroxybenzene (1), its monomethyl (2) and dimethyl ether (3) in concentrated aqueous sulfuric acid at 25°C has been studied and isomer distributions, as well as rate coefficients for the sulfonation of 1–3 and their monosulfonic acids, have been determined. In 73.5‐87.5% H2SO4, 1 yields the 3‐ and 4‐sulfonic acids in a ratio of 25:75, 2 yields the 4‐, 5‐ and 6‐sulfonic acids in a ratio of 46:36:18 in 73.5% H2SO4 and 50:39:11 in 87.5% H2SO4, whereas 3 yields only the 4‐sulfonic acid. The remarkable absence of the 3‐sulfonic acid (< 2%) with the 2‐methoxy substrates 2 and 3 is discussed in terms of conformer populations of the reactants. In sulfuric acid > 87.5% H2SO4, the 4‐sulfonic acid of 1 and the 5‐sulfonic acid of 2 are present in part in the form of their hydrogen sulfate. In that acid region, the 3‐ and 4‐sulforic acids of 1 both yield the 3,5‐disulfonic acid, the 4‐ and 6‐sulfonic acids of 2 both yield the 4,6‐disulfonic acid and the 4‐sulfonic acid of 3 mainly yields the 4,6‐ together with some 4,5‐disulfonic acid.
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