Aromatic isomerization reactions. Part III. Kinetics of the isomerization of the sulphonic acids of o- and m-xylene in aqueous sulphuric acid

Abstract

The kinetics of the isomerization of the monosulphonic acids of o-and m-xylene in concentrated aqueous sulphuric acid have been studied. Pseudo-first-order isomerization rate constants are reported.

At 141° and 74·0% H₂SO₄, the equilibrium composition of the o-xylenesulphonic acids contains 2·0 ± 0·4% of the 3- and 98·0 ± 0·4% of the 4-sulphonic acid. The equilibrium mixture of the m-xylenesulphonic acids under the same experimental conditions contains 0·0 ± 0·5% of the 2-, 17·5 ± 1·5% of the 4-, and 79 ± 2% of the 5-sulphonic acid, and 3·5 ± 1·5% of the 4,6-disulphonic acid.

Pseudo-first-order rate constants for protiodesulphonation and the corresponding partial rate factors have been calculated for most of the sulphonic acids from the isomerization rate constants.