Kinetics of the isomerization of toluenesulfonic acids in aqueous sulfuric acid

The kinetics of the isomerization of the three isomeric toluenesulfonic acids have been studied at 140° in 68.7 and 74.0 wt-% sulfuric acid. The isomer distribution in the sulfonation of toluene at this temperature and acid concentrations, has also been determined. The equilibrium mixtures contain mainly the meta- and para- and only small amounts of ortho-isomer. The experimentally determined pseudo first-order isomerization rate constants compare satisfactorily with the rate constants calculated from desulfonation rate constants and sulfonation isomer distribution data. This result is discussed in terms of an intermolecular isomerization mechanism.