Aromatic sulphonation V: A kinetic study on the sulphonation of toluene, ethylbenzene and isopropylbenzene in aqueous sulphuric acid

Rate measurements have been made on the homogeneous sulphonation of toluene in aqueous sulphuric acid varying from 70.0 to 95.9 wt-% at 5.0°, 25.0° and 45.0°. In addition, rate constants have been determined for the homogeneous sulphonation of ethylbenzene and isopropylbenzene at 25.0° in aqueous sulphuric acid solutions varying from 72.4 to 89.1 wt-%. All reactions were found to be first order with respect to the aromatic compound. It is suggested that the differences in the overall rate constants for the sulphonation of toluene, ethylbenzene and isopropylbenzene originate predominantly from steric hindrance for ortho-substitution.