The solubility of benzene and toluene in aqueous sulfuric acid 75 wt-% has been determined at 5, 25 and 45".Molar heats of solution have been calculated. The benzene to toluene activity coefficient ratio is slightly greater than unity. The relatively large difference in activation entropy for sulfonation of the para-position in toluene and a single position in benzene 1 is therefore attributed mainly to differences in solvation of the transition states.
IntroductionRecently a comparison was made between the sulfonation of toluene and benzene in aqueous sulfuric acid 1. It was observed that the difference in activation parameters for substitution of the para-position in toluene and one single position in benzene, as calculated from the partial rate factor, deviates from that commonly observed with electrophilic aromatic substitution. Tentatively this deviating behaviour was attributed to differences in the temperature dependence of the activity coefficient ratios of the two hydrocarbons and/or of the transition states.In order to obtain information on the variation of the activity coefficient ratio of benzene and toluene, we thought it of interest to determine for these two hydrocarbons the solubility in concentrated aqueous sulfuric acid as a function of acid concentration and temperature.