AbstractThe isomer distribution in the sulfonation of toluene with sulfur trioxide in nitromethane at ‐ 25.0° and 25.0° has been determined aso: 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 ofortho‐substitution is greater for the primary sulfonation than for the secondary sulfonation.The degree ofortho‐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