sium dihydrogen phosphate fixing solution to illustrate its applicability as an ammonia fixing agent, while the other distillations employed a 1000p.p.m. boric acid fixing solution. The per cent relative standard deviation decreases as the concentration of ammonia increases and indicates satisfactory reproducibility.
The kinetics of the isomerization of p -and rn-t-butylbenzenesulfonic acid have been studied in 74.0 wt-% sulfuric acid at elevated temperatures. The isomerization is accompanied by dealkylation. Evidence was obtained that the formation of benzenesulfonic acid from p-t-butylbenzenesulfonic acid proceeds mainly by a three-step process, viz., desulfonation, dealkylation and sulfonation of the benzene produced. With m-t-butylbenzenesulfonic acid, however, there is an indication of additional dealkylation of the sulfonic acid itself. Desulfonation rate constants were calculated. The activation energies for desulfonation are of the order of 27-30 kcal . mole-1.
IntroductionIn connection with our study on isomer distribution 1, it was thought of interest to investigate the kinetics of the isomerization of p -and m-tbutylbenzenesulfonic acids in aqueous sulfuric acid.The kinetics of the isomerization of the three isomeric toluenesulfonic acids in aqueous sulfuric acid were determined previously 2 .In that study it was observed that the apparent rate constants of isomerization can be correlated satisfactorily with desulfonation rate constants and sulfonation isomer distribution, thus allowing the isomerization to be described as an intermolecular process (viz., desulfonation followed by rapid sulfonation).
The isomer distribution in the homogeneous sulfonation of t-butylbenzene in 74.0-103.0 wt-% sulfuric acid has been determined at various temperatures.Orrho-substitution does not take place. The degree of meta-substitution is low under all conditions. The partial rate factors for para-and meta-substitution in 86.3 wt-% HzS04 at 25" are 53 =I= 6 and 3.0 * 0.3 respectively.Isomerization of p -and m-t-butylbenzenesulfonic acids is relatively insignificant at temperatures below 110".
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