Aromatic sulfonation 31: (Isomer distribution in the homogeneous sulfonation of toluene with sulfur trioxide and some acidic sulfonating reagents)

The isomer distribution in the sulfonation of toluene with sulfur trioxide in nitromethane at - 25.0° and 25.0° has been determined as o: m: p = 13.6: 0.8: 85.4, and 12.2: 1.4: 86.4, respectively. These isomer distributions are overall data for the primary and secondary sulfonation. As indicated by flow system experiments, the degree of ortho-substitution is greater for the primary sulfonation than for the secondary sulfonation. The degree of ortho-substitution for the sulfonation of toluene in nitromethane as solvent is virtually the same for the protic reagents ClSO3H, FSO3H, H2S2O7, C6H5S2O6H and CH3S2O6H, viz. 6.0 ± 0.8%.