H. R. W. Ansink, H. Cerfontain
Sep 2, 2010
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Influential Citations
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Journal
Recueil des Travaux Chimiques des Pays-Bas
Abstract
The sulfonation of 1, 2-(methylenedioxy)benzene (2), 1,2-(ethylenedioxy)benzene (3), benzo-15-crown-5 (4), 2-methylanisole (5), 2,3-dihydrobenzofuran (7), 2, 3-dihydrobenzopyran (chromane, 8) and dibenzo-30-crown-10 (9) in concentrated sulfuric acid and with sulfur trioxide mainly in nitromethane has been studied. Upon dissolution in sulfuric acid, 3 yields a mixture of 3-3-sulfonic acid (3-3-S) and 3–4-S in a ratio of 0.8, independent of the H2SO4 concentration. In sulfuric acid with a concentration greater than 83% H2SO4, the two monosulfonic acids both eventually yield 3-3,5-S2. The ratio of rate coefficients of sulfonation of 3-3-S and 3-4-S is approximately 70. The reaction of the crown ethers 4 and 9 in sulfuric acid leads to formation of 4-4-S and to an equimolar mixture of 9-4,4′-S2 and 9-4,5′-S2, respectively. Sulfonation of 5 in 85 and 98% H2SO4 yields a mixture of 5–4-S and 5-5-S in a ratio of approximately 7:1 and 11:1, respectively; in 98% H2SO4, these products are converted into 5-4,6-S2 and 5-3,5-S2, respectively. On dissolving 5 in 105% H2SO4, the initially observed product is 5–4,6-S2, which exhibits O demethylation. Sulfonation of both 7 and 8 in 85% H2SO4 yields a mixture of 4-S and 6-S in an initial ratio of 1.4. These acids eventually yield 7-4,6-S2 and 8-4,6-S2. The rate coefficients of sulfonation of 7-6-S and 8-6-S are both approximately 50 times those of the corresponding 4-sulfonic acid isomers. Upon sulfonation with 1.0 equiv of SO3 in nitromethane, all the substrates studied yield the corresponding 4-sulfonic acid. Upon reaction with 2.0-4.0 equiv of SO3, 2, 3, 7 and 8 all yield the 4,6-S2 almost quantitatively; 4 does not yield any disulfonic acid. Reaction of 9 with ≥2.0 equiv of SO3 yields a 1:1 mixture of 4,4′-S2 and 4,5′-S2. The routes of the sulfonation of 1,2-(methylenedioxy)- (2) and 1, 2-(ethylenedioxy)benzene (3) and their monosulfonic acids have been compared with those of 1,2-dimethoxybenzene (1) and its 4-sulfonic acid and the differences are discussed in terms of the Curtin-Hammett principle. The differences observed between the mono- and disulfonation of 2,3-dihydroxybenzofuran (7) and 2,3-dihydrobenzopyran (8) on the one hand and those of 2-methylanisole (5) on the other are discussed along similar lines.